import of BlockchainDB files

tried rebasing, tree-filter, and many other things.  at this point,
the history of these files previous to this can live on
in my bc2 branch, as I'm importing them as-is to here.

4 files changed, 3003 insertions, 0 deletions

diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
new file mode 100644
index 000000000..22ae7a39a
--- /dev/null
+++ b/src/cryptonote_core/blockchain.cpp
@@ -0,0 +1,2137 @@
+// Copyright (c) 2014, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+// 
+// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
+
+#include <algorithm>
+#include <cstdio>
+#include <boost/archive/binary_oarchive.hpp>
+#include <boost/archive/binary_iarchive.hpp>
+
+#include "include_base_utils.h"
+#include "cryptonote_basic_impl.h"
+#include "blockchain.h"
+#include "cryptonote_format_utils.h"
+#include "cryptonote_boost_serialization.h"
+#include "cryptonote_config.h"
+#include "miner.h"
+#include "misc_language.h"
+#include "profile_tools.h"
+#include "file_io_utils.h"
+#include "common/boost_serialization_helper.h"
+#include "warnings.h"
+#include "crypto/hash.h"
+//#include "serialization/json_archive.h"
+
+/* TODO:
+ *  Clean up code:
+ *    Possibly change how outputs are referred to/indexed in blockchain and wallets
+ *
+ */
+
+using namespace cryptonote;
+
+DISABLE_VS_WARNINGS(4267)
+
+//------------------------------------------------------------------
+// TODO: initialize m_db with a concrete implementation of BlockchainDB
+Blockchain::Blockchain(tx_memory_pool& tx_pool):m_db(), m_tx_pool(tx_pool), m_current_block_cumul_sz_limit(0), m_is_in_checkpoint_zone(false), m_is_blockchain_storing(false)
+{
+  if (m_db == NULL)
+  {
+    throw new DB_ERROR("database pointer null in blockchain init");
+  }
+}
+//------------------------------------------------------------------
+//TODO: is this still needed?  I don't think so - tewinget
+template<class archive_t>
+void Blockchain::serialize(archive_t & ar, const unsigned int version)
+{
+  if(version < 11)
+    return;
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  ar & m_blocks;
+  ar & m_blocks_index;
+  ar & m_transactions;
+  ar & m_spent_keys;
+  ar & m_alternative_chains;
+  ar & m_outputs;
+  ar & m_invalid_blocks;
+  ar & m_current_block_cumul_sz_limit;
+  /*serialization bug workaround*/
+  if(version > 11)
+  {
+    uint64_t total_check_count = m_db->height() + m_blocks_index.size() + m_transactions.size() + m_spent_keys.size() + m_alternative_chains.size() + m_outputs.size() + m_invalid_blocks.size() + m_current_block_cumul_sz_limit;
+    if(archive_t::is_saving::value)
+    {        
+      ar & total_check_count;
+    }else
+    {
+      uint64_t total_check_count_loaded = 0;
+      ar & total_check_count_loaded;
+      if(total_check_count != total_check_count_loaded)
+      {
+        LOG_ERROR("Blockchain storage data corruption detected. total_count loaded from file = " << total_check_count_loaded << ", expected = " << total_check_count);
+
+        LOG_PRINT_L0("Blockchain storage:" << std::endl << 
+          "m_blocks: " << m_db->height() << std::endl  << 
+          "m_blocks_index: " << m_blocks_index.size() << std::endl  << 
+          "m_transactions: " << m_transactions.size() << std::endl  << 
+          "m_spent_keys: " << m_spent_keys.size() << std::endl  << 
+          "m_alternative_chains: " << m_alternative_chains.size() << std::endl  << 
+          "m_outputs: " << m_outputs.size() << std::endl  << 
+          "m_invalid_blocks: " << m_invalid_blocks.size() << std::endl  << 
+          "m_current_block_cumul_sz_limit: " << m_current_block_cumul_sz_limit);
+
+        throw std::runtime_error("Blockchain data corruption");
+      }
+    }
+  }
+
+
+  LOG_PRINT_L2("Blockchain storage:" << std::endl << 
+      "m_blocks: " << m_db->height() << std::endl  << 
+      "m_blocks_index: " << m_blocks_index.size() << std::endl  << 
+      "m_transactions: " << m_transactions.size() << std::endl  << 
+      "m_spent_keys: " << m_spent_keys.size() << std::endl  << 
+      "m_alternative_chains: " << m_alternative_chains.size() << std::endl  << 
+      "m_outputs: " << m_outputs.size() << std::endl  << 
+      "m_invalid_blocks: " << m_invalid_blocks.size() << std::endl  << 
+      "m_current_block_cumul_sz_limit: " << m_current_block_cumul_sz_limit);
+}
+//------------------------------------------------------------------
+bool Blockchain::have_tx(const crypto::hash &id)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  return m_db->tx_exists(id);
+}
+//------------------------------------------------------------------
+bool Blockchain::have_tx_keyimg_as_spent(const crypto::key_image &key_im)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  return  m_db->has_key_image(key_im);
+}
+//------------------------------------------------------------------
+// This function makes sure that each "input" in an input (mixins) exists
+// and collects the public key for each from the transaction it was included in
+// via the visitor passed to it.
+template<class visitor_t>
+bool Blockchain::scan_outputkeys_for_indexes(const txin_to_key& tx_in_to_key, visitor_t& vis, uint64_t* pmax_related_block_height)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // verify that the input has key offsets (that it exists properly, really)
+  if(!tx_in_to_key.key_offsets.size())
+    return false;
+
+  // cryptonote_format_utils uses relative offsets for indexing to the global
+  // outputs list.  that is to say that absolute offset #2 is absolute offset
+  // #1 plus relative offset #2.
+  // TODO: Investigate if this is necessary / why this is done.
+  std::vector<uint64_t> absolute_offsets = relative_output_offsets_to_absolute(tx_in_to_key.key_offsets);
+
+
+  //std::vector<std::pair<crypto::hash, size_t> >& amount_outs_vec = it->second;
+  size_t count = 0;
+  for (const uint64_t& i : absolute_offsets)
+  {
+    try
+    {
+      // get tx hash and output index for output
+      auto output_index = m_db->get_output_tx_and_index(tx_in_to_key.amount, i);
+
+      // get tx that output is from
+      auto tx = m_db->get_tx(output_index.first);
+
+      // make sure output index is within range for the given transaction
+      if (output_index.second >= tx.vout.size())
+      {
+        LOG_PRINT_L0("Output does not exist.  tx = " << output_index.first << ", index = " << output_index.second);
+        return false;
+      }
+
+      // call to the passed boost visitor to grab the public key for the output
+      if(!vis.handle_output(tx, tx.vout[output_index.second]))
+      {
+        LOG_PRINT_L0("Failed to handle_output for output no = " << count << ", with absolute offset " << i);
+        return false;
+      }
+
+      // if on last output and pmax_related_block_height not null pointer
+      if(++count == absolute_offsets.size() && pmax_related_block_height)
+      {
+        // set *pmax_related_block_height to tx block height for this output
+        auto h = m_db->get_tx_block_height(output_index.first);
+        if(*pmax_related_block_height < h)
+        {
+          *pmax_related_block_height = h;
+        }
+      }
+
+    }
+    catch (const OUTPUT_DNE& e)
+    {
+      LOG_PRINT_L0("Output does not exist: " << e.what());
+      return false;
+    }
+    catch (const TX_DNE& e)
+    {
+      LOG_PRINT_L0("Transaction does not exist: " << e.what());
+      return false;
+    }
+
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+uint64_t Blockchain::get_current_blockchain_height()
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  return m_db->height();
+}
+//------------------------------------------------------------------
+//FIXME: possibly move this into the constructor, to avoid accidentally
+//       dereferencing a null BlockchainDB pointer
+bool Blockchain::init(const std::string& config_folder)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  m_config_folder = config_folder;
+  LOG_PRINT_L0("Loading blockchain...");
+
+  //FIXME: update filename for BlockchainDB
+  const std::string filename = m_config_folder + "/" CRYPTONOTE_BLOCKCHAINDATA_FILENAME;
+  try
+  {
+    m_db->open(filename);
+  }
+  catch (const DB_OPEN_FAILURE& e)
+  {
+    LOG_PRINT_L0("No blockchain file found, attempting to create one.");
+    try
+    {
+      m_db->create(filename);
+    }
+    catch (const DB_CREATE_FAILURE& db_create_error)
+    {
+      LOG_PRINT_L0("Unable to create BlockchainDB!  This is not good...");
+      //TODO: make sure whatever calls this handles the return value properly
+      return false;
+    }
+  }
+
+  // if the blockchain is new, add the genesis block
+  // this feels kinda kludgy to do it this way, but can be looked at later.
+  if(!m_db->height())
+  {
+    LOG_PRINT_L0("Blockchain not loaded, generating genesis block.");
+    block bl = boost::value_initialized<block>();
+    block_verification_context bvc = boost::value_initialized<block_verification_context>();
+    generate_genesis_block(bl);
+    add_new_block(bl, bvc);
+    CHECK_AND_ASSERT_MES(!bvc.m_verification_failed, false, "Failed to add genesis block to blockchain");
+  }
+
+  // check how far behind we are
+  uint64_t top_block_timestamp = m_db->get_top_block_timestamp();
+  uint64_t timestamp_diff = time(NULL) - top_block_timestamp;
+
+  // genesis block has no timestamp, could probably change it to have timestamp of 1341378000...
+  if(!top_block_timestamp)
+    timestamp_diff = time(NULL) - 1341378000;
+  LOG_PRINT_GREEN("Blockchain initialized. last block: " << m_db->height() - 1 << ", " << epee::misc_utils::get_time_interval_string(timestamp_diff) << " time ago, current difficulty: " << get_difficulty_for_next_block(), LOG_LEVEL_0);
+
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::store_blockchain()
+{
+  // TODO: make sure if this throws that it is not simply ignored higher
+  // up the call stack
+  try
+  {
+    m_db->sync();
+  }
+  catch (const std::exception& e)
+  {
+    LOG_PRINT_L0(std::string("Error syncing blockchain db: ") + e.what() + "-- shutting down now to prevent issues!");
+    throw;
+  }
+  catch (...)
+  {
+    LOG_PRINT_L0("There was an issue storing the blockchain, shutting down now to prevent issues!");
+    throw;
+  }
+  LOG_PRINT_L0("Blockchain stored OK.");
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::deinit()
+{
+  // as this should be called if handling a SIGSEGV, need to check
+  // if m_db is a NULL pointer (and thus may have caused the illegal
+  // memory operation), otherwise we may cause a loop.
+  if (m_db == NULL)
+  {
+    throw new DB_ERROR("The db pointer is null in Blockchain, the blockchain may be corrupt!");
+  }
+
+  try
+  {
+    m_db->close();
+  }
+  catch (const std::exception& e)
+  {
+    LOG_PRINT_L0(std::string("Error closing blockchain db: ") + e.what());
+  }
+  catch (...)
+  {
+    LOG_PRINT_L0("There was an issue closing/storing the blockchain, shutting down now to prevent issues!");
+  }
+  return true;
+}
+//------------------------------------------------------------------
+// This function tells BlockchainDB to remove the top block from the
+// blockchain and then returns all transactions (except the miner tx, of course)
+// from it to the tx_pool
+block Blockchain::pop_block_from_blockchain()
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  block popped_block;
+  std::vector<transaction> popped_txs;
+
+  try
+  {
+    m_db->pop_block(popped_block, popped_txs);
+  }
+  // anything that could cause this to throw is likely catastrophic,
+  // so we re-throw
+  catch (const std::exception& e)
+  {
+    LOG_ERROR("Error popping block from blockchain: " << e.what());
+    throw;
+  }
+  catch (...)
+  {
+    LOG_ERROR("Error popping block from blockchain, throwing!");
+    throw;
+  }
+
+  // return transactions from popped block to the tx_pool
+  for (transaction& tx : popped_txs)
+  {
+    if (!is_coinbase(tx))
+    {
+      cryptonote::tx_verification_context tvc = AUTO_VAL_INIT(tvc);
+      bool r = m_tx_pool.add_tx(tx, tvc, true);
+      if (!r)
+      {
+        LOG_ERROR("Error returning transaction to tx_pool");
+      }
+    }
+  }
+
+  return popped_block;
+}
+//------------------------------------------------------------------
+bool Blockchain::reset_and_set_genesis_block(const block& b)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  m_transactions.clear();
+  m_spent_keys.clear();
+  m_blocks.clear();
+  m_blocks_index.clear();
+  m_alternative_chains.clear();
+  m_outputs.clear();
+  m_db->reset();
+
+  block_verification_context bvc = boost::value_initialized<block_verification_context>();
+  add_new_block(b, bvc);
+  return bvc.m_added_to_main_chain && !bvc.m_verification_failed;
+}
+//------------------------------------------------------------------
+//TODO: move to BlockchainDB subclass
+bool Blockchain::purge_transaction_keyimages_from_blockchain(const transaction& tx, bool strict_check)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+    struct purge_transaction_visitor: public boost::static_visitor<bool>
+  {
+    key_images_container& m_spent_keys;
+    bool m_strict_check;
+    purge_transaction_visitor(key_images_container& spent_keys, bool strict_check):m_spent_keys(spent_keys), m_strict_check(strict_check){}
+
+    bool operator()(const txin_to_key& inp) const
+    {
+      //const crypto::key_image& ki = inp.k_image;
+      auto r = m_spent_keys.find(inp.k_image);
+      if(r != m_spent_keys.end())
+      {
+        m_spent_keys.erase(r);
+      }else
+      {
+        CHECK_AND_ASSERT_MES(!m_strict_check, false, "purge_block_data_from_blockchain: key image in transaction not found");
+      }
+      return true;
+    }
+    bool operator()(const txin_gen& inp) const
+    {
+      return true;
+    }
+    bool operator()(const txin_to_script& tx) const
+    {
+      return false;
+    }
+
+    bool operator()(const txin_to_scripthash& tx) const
+    {
+      return false;
+    }
+  };
+
+  BOOST_FOREACH(const txin_v& in, tx.vin)
+  {
+    bool r = boost::apply_visitor(purge_transaction_visitor(m_spent_keys, strict_check), in);
+    CHECK_AND_ASSERT_MES(!strict_check || r, false, "failed to process purge_transaction_visitor");
+  }
+  return true;
+}
+//------------------------------------------------------------------
+crypto::hash Blockchain::get_tail_id(uint64_t& height)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  height = m_db->height();
+  return get_tail_id();
+}
+//------------------------------------------------------------------
+crypto::hash Blockchain::get_tail_id()
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  return m_db->top_block_hash();
+}
+//------------------------------------------------------------------
+/*TODO: this function was...poorly written.  As such, I'm not entirely
+ *      certain on what it was supposed to be doing.  Need to look into this,
+ *      but it doesn't seem terribly important just yet.
+ *
+ * puts into list <ids> a list of hashes representing certain blocks
+ * from the blockchain in reverse chronological order
+ *
+ * the blocks chosen, at the time of this writing, are:
+ *   the most recent 11
+ *   powers of 2 less recent from there, so 13, 17, 25, etc...
+ *
+ */
+bool Blockchain::get_short_chain_history(std::list<crypto::hash>& ids)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  uint64_t i = 0;
+  uint64_t current_multiplier = 1;
+  uint64_t sz = m_db->height();
+
+  if(!sz)
+    return true;
+
+  uint64_t current_back_offset = 0;
+  while(current_back_offset < sz)
+  {
+    ids.push_back(m_db->get_block_hash_from_height(sz-current_back_offset));
+    if(i < 10)
+    {
+      ++current_back_offset;
+    }
+    else
+    {
+      current_multiplier *= 2;
+      current_back_offset += current_multiplier;
+    }
+    ++i;
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+crypto::hash Blockchain::get_block_id_by_height(uint64_t height)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  try
+  {
+    return m_db->get_block_hash_from_height(height);
+  }
+  catch (const BLOCK_DNE& e)
+  {
+  }
+  catch (const std::exception& e)
+  {
+    LOG_PRINT_L0(std::string("Something went wrong fetching block hash by height: ") + e.what());
+    throw;
+  }
+  catch (...)
+  {
+    LOG_PRINT_L0(std::string("Something went wrong fetching block hash by height"));
+    throw;
+  }
+  return null_hash;
+}
+//------------------------------------------------------------------
+bool Blockchain::get_block_by_hash(const crypto::hash &h, block &blk)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // try to find block in main chain
+  try
+  {
+    blk = m_db->get_block(h);
+    return true;
+  }
+  // try to find block in alternative chain
+  catch (const BLOCK_DNE& e)
+  {
+    blocks_ext_by_hash::const_iterator it_alt = m_alternative_chains.find(h);
+    if (m_alternative_chains.end() != it_alt) {
+      blk = it_alt->second.bl;
+      return true;
+    }
+  }
+  catch (const std::exception& e)
+  {
+    LOG_PRINT_L0(std::string("Something went wrong fetching block by hash: ") + e.what());
+    throw;
+  }
+  catch (...)
+  {
+    LOG_PRINT_L0(std::string("Something went wrong fetching block hash by hash"));
+    throw;
+  }
+
+  return false;
+}
+//------------------------------------------------------------------
+void Blockchain::get_all_known_block_ids(std::list<crypto::hash> &main, std::list<crypto::hash> &alt, std::list<crypto::hash> &invalid)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  main = m_db->get_hashes_range(0, m_db->height());
+
+  BOOST_FOREACH(blocks_ext_by_hash::value_type &v, m_alternative_chains)
+    alt.push_back(v.first);
+
+  BOOST_FOREACH(blocks_ext_by_hash::value_type &v, m_invalid_blocks)
+    invalid.push_back(v.first);
+}
+//------------------------------------------------------------------
+// This function aggregates the cumulative difficulties and timestamps of the
+// last DIFFICULTY_BLOCKS_COUNT blocks and passes them to next_difficulty,
+// returning the result of that call.  Ignores the genesis block, and can use
+// less blocks than desired if there aren't enough.
+difficulty_type Blockchain::get_difficulty_for_next_block()
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  std::vector<uint64_t> timestamps;
+  std::vector<difficulty_type> cumulative_difficulties;
+  auto h = m_db->height();
+
+  size_t offset = h - std::min(h, static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT));
+
+  // because BlockchainDB::height() returns the index of the top block, the
+  // first index we need to get needs to be one
+  // higher than height() - DIFFICULTY_BLOCKS_COUNT.  This also conveniently
+  // makes sure we don't use the genesis block.
+  ++offset;
+
+  for(; offset <= h; offset++)
+  {
+    timestamps.push_back(m_db->get_block_timestamp(offset));
+    cumulative_difficulties.push_back(m_db->get_block_cumulative_difficulty(offset));
+  }
+  return next_difficulty(timestamps, cumulative_difficulties);
+}
+//------------------------------------------------------------------
+// This function removes blocks from the blockchain until it gets to the
+// position where the blockchain switch started and then re-adds the blocks
+// that had been removed.
+bool Blockchain::rollback_blockchain_switching(std::list<block>& original_chain)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // remove blocks from blockchain until we get back to where we were.
+  // Conveniently, that's until our top block's hash == the parent block of
+  // the first block we need to add back.
+  while (m_db->top_block_hash() != original_chain.front().prev_id)
+  {
+    pop_block_from_blockchain();
+  }
+
+  //return back original chain
+  for (auto& bl : original_chain)
+  {
+    block_verification_context bvc = boost::value_initialized<block_verification_context>();
+    bool r = handle_block_to_main_chain(bl, bvc);
+    CHECK_AND_ASSERT_MES(r && bvc.m_added_to_main_chain, false, "PANIC!!! failed to add (again) block while chain switching during the rollback!");
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+// This function attempts to switch to an alternate chain, returning
+// boolean based on success therein.
+bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::iterator>& alt_chain, bool discard_disconnected_chain)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // if empty alt chain passed (not sure how that could happen), return false
+  CHECK_AND_ASSERT_MES(alt_chain.size(), false, "switch_to_alternative_blockchain: empty chain passed");
+
+  // verify that main chain has front of alt chain's parent block
+  if (!m_db->block_exists(alt_chain.front()->second.bl.prev_id))
+  {
+    LOG_ERROR("Attempting to move to an alternate chain, but it doesn't appear to connect to the main chain!");
+    return false;
+  }
+
+  // pop blocks from the blockchain until the top block is the parent
+  // of the front block of the alt chain.
+  std::list<block> disconnected_chain;
+  while (m_db->top_block_hash() != alt_chain.front()->second.bl.prev_id)
+  {
+    block b = pop_block_from_blockchain();
+    disconnected_chain.push_front(b);
+  }
+
+  auto split_height = m_db->height();
+
+  //connecting new alternative chain
+  for(auto alt_ch_iter = alt_chain.begin(); alt_ch_iter != alt_chain.end(); alt_ch_iter++)
+  {
+    auto ch_ent = *alt_ch_iter;
+    block_verification_context bvc = boost::value_initialized<block_verification_context>();
+
+    // add block to main chain
+    bool r = handle_block_to_main_chain(ch_ent->second.bl, bvc);
+
+    // if adding block to main chain failed, rollback to previous state and
+    // return false
+    if(!r || !bvc.m_added_to_main_chain)
+    {
+      LOG_PRINT_L0("Failed to switch to alternative blockchain");
+      rollback_blockchain_switching(disconnected_chain);
+
+      // FIXME: Why do we keep invalid blocks around?  Possibly in case we hear
+      // about them again so we can immediately dismiss them, but needs some
+      // looking into.
+      add_block_as_invalid(ch_ent->second, get_block_hash(ch_ent->second.bl));
+      LOG_PRINT_L0("The block was inserted as invalid while connecting new alternative chain,  block_id: " << get_block_hash(ch_ent->second.bl));
+      m_alternative_chains.erase(ch_ent);
+
+      for(auto alt_ch_to_orph_iter = ++alt_ch_iter; alt_ch_to_orph_iter != alt_chain.end(); alt_ch_to_orph_iter++)
+      {
+        add_block_as_invalid((*alt_ch_iter)->second, (*alt_ch_iter)->first);
+        m_alternative_chains.erase(*alt_ch_to_orph_iter);
+      }
+      return false;
+    }
+  }
+
+  // if we're to keep the disconnected blocks, add them as alternates
+  if(!discard_disconnected_chain)
+  {
+    //pushing old chain as alternative chain
+    for (auto& old_ch_ent : disconnected_chain)
+    {
+      block_verification_context bvc = boost::value_initialized<block_verification_context>();
+      bool r = handle_alternative_block(old_ch_ent, get_block_hash(old_ch_ent), bvc);
+      if(!r)
+      {
+        LOG_ERROR("Failed to push ex-main chain blocks to alternative chain ");
+        // previously this would fail the blockchain switching, but I don't
+        // think this is bad enough to warrant that.
+      }
+    }
+  }
+
+  //removing alt_chain entries from alternative chain
+  BOOST_FOREACH(auto ch_ent, alt_chain)
+  {
+    m_alternative_chains.erase(ch_ent);
+  }
+
+  LOG_PRINT_GREEN("REORGANIZE SUCCESS! on height: " << split_height << ", new blockchain size: " << m_db->height(), LOG_LEVEL_0);
+  return true;
+}
+//------------------------------------------------------------------
+// This function calculates the difficulty target for the block being added to
+// an alternate chain.
+difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std::list<blocks_ext_by_hash::iterator>& alt_chain, block_extended_info& bei)
+{
+  std::vector<uint64_t> timestamps;
+  std::vector<difficulty_type> cumulative_difficulties;
+
+  // if the alt chain isn't long enough to calculate the difficulty target
+  // based on its blocks alone, need to get more blocks from the main chain
+  if(alt_chain.size()< DIFFICULTY_BLOCKS_COUNT)
+  {
+    CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+    // Figure out start and stop offsets for main chain blocks
+    size_t main_chain_stop_offset = alt_chain.size() ? alt_chain.front()->second.height : bei.height;
+    size_t main_chain_count = DIFFICULTY_BLOCKS_COUNT - std::min(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT), alt_chain.size());
+    main_chain_count = std::min(main_chain_count, main_chain_stop_offset);
+    size_t main_chain_start_offset = main_chain_stop_offset - main_chain_count;
+
+    if(!main_chain_start_offset)
+      ++main_chain_start_offset; //skip genesis block
+
+    // get difficulties and timestamps from relevant main chain blocks
+    for(; main_chain_start_offset < main_chain_stop_offset; ++main_chain_start_offset)
+    {
+      timestamps.push_back(m_db->get_block_timestamp(main_chain_start_offset));
+      cumulative_difficulties.push_back(m_db->get_block_cumulative_difficulty(main_chain_start_offset));
+    }
+
+    // make sure we haven't accidentally grabbed too many blocks...maybe don't need this check?
+    CHECK_AND_ASSERT_MES((alt_chain.size() + timestamps.size()) <= DIFFICULTY_BLOCKS_COUNT, false,
+        "Internal error, alt_chain.size()[" << alt_chain.size()
+                                            << "] + vtimestampsec.size()[" << timestamps.size()
+                                            << "] NOT <= DIFFICULTY_WINDOW[]" << DIFFICULTY_BLOCKS_COUNT
+    );
+
+    for (auto it : alt_chain)
+    {
+      timestamps.push_back(it->second.bl.timestamp);
+      cumulative_difficulties.push_back(it->second.cumulative_difficulty);
+    }
+  }
+  // if the alt chain is long enough for the difficulty calc, grab difficulties
+  // and timestamps from it alone
+  else
+  {
+    timestamps.resize(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT));
+    cumulative_difficulties.resize(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT));
+    size_t count = 0;
+    size_t max_i = timestamps.size()-1;
+    // get difficulties and timestamps from most recent blocks in alt chain
+    BOOST_REVERSE_FOREACH(auto it, alt_chain)
+    {
+      timestamps[max_i - count] = it->second.bl.timestamp;
+      cumulative_difficulties[max_i - count] = it->second.cumulative_difficulty;
+      count++;
+      if(count >= DIFFICULTY_BLOCKS_COUNT)
+        break;
+    }
+  }
+
+  // calculate the difficulty target for the block and return it
+  return next_difficulty(timestamps, cumulative_difficulties);
+}
+//------------------------------------------------------------------
+// This function does a sanity check on basic things that all miner
+// transactions have in common, such as:
+//   one input, of type txin_gen, with height set to the block's height
+//   correct miner tx unlock time
+//   a non-overflowing tx amount (dubious necessity on this check)
+bool Blockchain::prevalidate_miner_transaction(const block& b, uint64_t height)
+{
+  CHECK_AND_ASSERT_MES(b.miner_tx.vin.size() == 1, false, "coinbase transaction in the block has no inputs");
+  CHECK_AND_ASSERT_MES(b.miner_tx.vin[0].type() == typeid(txin_gen), false, "coinbase transaction in the block has the wrong type");
+  if(boost::get<txin_gen>(b.miner_tx.vin[0]).height != height)
+  {
+    LOG_PRINT_RED_L0("The miner transaction in block has invalid height: " << boost::get<txin_gen>(b.miner_tx.vin[0]).height << ", expected: " << height);
+    return false;
+  }
+  CHECK_AND_ASSERT_MES(b.miner_tx.unlock_time == height + CRYPTONOTE_MINED_MONEY_UNLOCK_WINDOW,
+                  false,
+                  "coinbase transaction transaction have wrong unlock time=" << b.miner_tx.unlock_time << ", expected " << height + CRYPTONOTE_MINED_MONEY_UNLOCK_WINDOW);
+
+  //check outs overflow
+  //NOTE: not entirely sure this is necessary, given that this function is
+  //      designed simply to make sure the total amount for a transaction
+  //      does not overflow a uint64_t, and this transaction *is* a uint64_t...
+  if(!check_outs_overflow(b.miner_tx))
+  {
+    LOG_PRINT_RED_L0("miner transaction have money overflow in block " << get_block_hash(b));
+    return false;
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+// This function validates the miner transaction reward
+bool Blockchain::validate_miner_transaction(const block& b, size_t cumulative_block_size, uint64_t fee, uint64_t& base_reward, uint64_t already_generated_coins)
+{
+  //validate reward
+  uint64_t money_in_use = 0;
+  BOOST_FOREACH(auto& o, b.miner_tx.vout)
+    money_in_use += o.amount;
+
+  std::vector<size_t> last_blocks_sizes;
+  get_last_n_blocks_sizes(last_blocks_sizes, CRYPTONOTE_REWARD_BLOCKS_WINDOW);
+  if (!get_block_reward(epee::misc_utils::median(last_blocks_sizes), cumulative_block_size, already_generated_coins, base_reward)) {
+    LOG_PRINT_L0("block size " << cumulative_block_size << " is bigger than allowed for this blockchain");
+    return false;
+  }
+  if(base_reward + fee < money_in_use)
+  {
+    LOG_ERROR("coinbase transaction spend too much money (" << print_money(money_in_use) << "). Block reward is " << print_money(base_reward + fee) << "(" << print_money(base_reward) << "+" << print_money(fee) << ")");
+    return false;
+  }
+  if(base_reward + fee != money_in_use)
+  {
+    LOG_ERROR("coinbase transaction doesn't use full amount of block reward:  spent: "
+                            << print_money(money_in_use) << ",  block reward " << print_money(base_reward + fee) << "(" << print_money(base_reward) << "+" << print_money(fee) << ")");
+    return false;
+  }
+  return true;
+}
+//------------------------------------------------------------------
+// get the block sizes of the last <count> blocks, starting at <from_height>
+// and return by reference <sz>.
+void Blockchain::get_last_n_blocks_sizes(std::vector<size_t>& sz, size_t count)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  auto h = m_db->height();
+
+  // this function is meaningless for an empty blockchain...granted it should never be empty
+  if(h == 0)
+    return;
+
+  // add size of last <count> blocks to vector <sz> (or less, if blockchain size < count)
+  size_t start_offset = (h+1) - std::min((h+1), count);
+  for(size_t i = start_offset; i <= h; i++)
+  {
+    sz.push_back(m_db->get_block_size(i));
+  }
+}
+//------------------------------------------------------------------
+uint64_t Blockchain::get_current_cumulative_blocksize_limit()
+{
+  return m_current_block_cumul_sz_limit;
+}
+//------------------------------------------------------------------
+//TODO: This function only needed minor modification to work with BlockchainDB,
+//      and *works*.  As such, to reduce the number of things that might break
+//      in moving to BlockchainDB, this function will remain otherwise
+//      unchanged for the time being.
+//
+// This function makes a new block for a miner to mine the hash for
+//
+// FIXME: this codebase references #if defined(DEBUG_CREATE_BLOCK_TEMPLATE)
+// in a lot of places.  That flag is not referenced in any of the code
+// nor any of the makefiles, howeve.  Need to look into whether or not it's
+// necessary at all.
+bool Blockchain::create_block_template(block& b, const account_public_address& miner_address, difficulty_type& diffic, uint64_t& height, const blobdata& ex_nonce)
+{
+  size_t median_size;
+  uint64_t already_generated_coins;
+
+  CRITICAL_REGION_BEGIN(m_blockchain_lock);
+  b.major_version = CURRENT_BLOCK_MAJOR_VERSION;
+  b.minor_version = CURRENT_BLOCK_MINOR_VERSION;
+  b.prev_id = get_tail_id();
+  b.timestamp = time(NULL);
+
+  auto old_height = m_db->height();
+  height = old_height + 1;
+  diffic = get_difficulty_for_next_block();
+  CHECK_AND_ASSERT_MES(diffic, false, "difficulty owverhead.");
+
+  median_size = m_current_block_cumul_sz_limit / 2;
+  already_generated_coins = m_db->get_block_already_generated_coins(old_height);
+
+  CRITICAL_REGION_END();
+
+  size_t txs_size;
+  uint64_t fee;
+  if (!m_tx_pool.fill_block_template(b, median_size, already_generated_coins, txs_size, fee)) {
+    return false;
+  }
+#if defined(DEBUG_CREATE_BLOCK_TEMPLATE)
+  size_t real_txs_size = 0;
+  uint64_t real_fee = 0;
+  CRITICAL_REGION_BEGIN(m_tx_pool.m_transactions_lock);
+  BOOST_FOREACH(crypto::hash &cur_hash, b.tx_hashes) {
+    auto cur_res = m_tx_pool.m_transactions.find(cur_hash);
+    if (cur_res == m_tx_pool.m_transactions.end()) {
+      LOG_ERROR("Creating block template: error: transaction not found");
+      continue;
+    }
+    tx_memory_pool::tx_details &cur_tx = cur_res->second;
+    real_txs_size += cur_tx.blob_size;
+    real_fee += cur_tx.fee;
+    if (cur_tx.blob_size != get_object_blobsize(cur_tx.tx)) {
+      LOG_ERROR("Creating block template: error: invalid transaction size");
+    }
+    uint64_t inputs_amount;
+    if (!get_inputs_money_amount(cur_tx.tx, inputs_amount)) {
+      LOG_ERROR("Creating block template: error: cannot get inputs amount");
+    } else if (cur_tx.fee != inputs_amount - get_outs_money_amount(cur_tx.tx)) {
+      LOG_ERROR("Creating block template: error: invalid fee");
+    }
+  }
+  if (txs_size != real_txs_size) {
+    LOG_ERROR("Creating block template: error: wrongly calculated transaction size");
+  }
+  if (fee != real_fee) {
+    LOG_ERROR("Creating block template: error: wrongly calculated fee");
+  }
+  CRITICAL_REGION_END();
+  LOG_PRINT_L1("Creating block template: height " << height <<
+    ", median size " << median_size <<
+    ", already generated coins " << already_generated_coins <<
+    ", transaction size " << txs_size <<
+    ", fee " << fee);
+#endif
+
+  /*
+     two-phase miner transaction generation: we don't know exact block size until we prepare block, but we don't know reward until we know
+     block size, so first miner transaction generated with fake amount of money, and with phase we know think we know expected block size
+  */
+  //make blocks coin-base tx looks close to real coinbase tx to get truthful blob size
+  bool r = construct_miner_tx(height, median_size, already_generated_coins, txs_size, fee, miner_address, b.miner_tx, ex_nonce, 11);
+  CHECK_AND_ASSERT_MES(r, false, "Failed to construc miner tx, first chance");
+  size_t cumulative_size = txs_size + get_object_blobsize(b.miner_tx);
+#if defined(DEBUG_CREATE_BLOCK_TEMPLATE)
+  LOG_PRINT_L1("Creating block template: miner tx size " << get_object_blobsize(b.miner_tx) <<
+    ", cumulative size " << cumulative_size);
+#endif
+  for (size_t try_count = 0; try_count != 10; ++try_count) {
+    r = construct_miner_tx(height, median_size, already_generated_coins, cumulative_size, fee, miner_address, b.miner_tx, ex_nonce, 11);
+
+    CHECK_AND_ASSERT_MES(r, false, "Failed to construc miner tx, second chance");
+    size_t coinbase_blob_size = get_object_blobsize(b.miner_tx);
+    if (coinbase_blob_size > cumulative_size - txs_size) {
+      cumulative_size = txs_size + coinbase_blob_size;
+#if defined(DEBUG_CREATE_BLOCK_TEMPLATE)
+      LOG_PRINT_L1("Creating block template: miner tx size " << coinbase_blob_size <<
+        ", cumulative size " << cumulative_size << " is greater then before");
+#endif
+      continue;
+    }
+
+    if (coinbase_blob_size < cumulative_size - txs_size) {
+      size_t delta = cumulative_size - txs_size - coinbase_blob_size;
+#if defined(DEBUG_CREATE_BLOCK_TEMPLATE)
+      LOG_PRINT_L1("Creating block template: miner tx size " << coinbase_blob_size <<
+        ", cumulative size " << txs_size + coinbase_blob_size <<
+        " is less then before, adding " << delta << " zero bytes");
+#endif
+      b.miner_tx.extra.insert(b.miner_tx.extra.end(), delta, 0);
+      //here  could be 1 byte difference, because of extra field counter is varint, and it can become from 1-byte len to 2-bytes len.
+      if (cumulative_size != txs_size + get_object_blobsize(b.miner_tx)) {
+        CHECK_AND_ASSERT_MES(cumulative_size + 1 == txs_size + get_object_blobsize(b.miner_tx), false, "unexpected case: cumulative_size=" << cumulative_size << " + 1 is not equal txs_cumulative_size=" << txs_size << " + get_object_blobsize(b.miner_tx)=" << get_object_blobsize(b.miner_tx));
+        b.miner_tx.extra.resize(b.miner_tx.extra.size() - 1);
+        if (cumulative_size != txs_size + get_object_blobsize(b.miner_tx)) {
+          //fuck, not lucky, -1 makes varint-counter size smaller, in that case we continue to grow with cumulative_size
+          LOG_PRINT_RED("Miner tx creation have no luck with delta_extra size = " << delta << " and " << delta - 1 , LOG_LEVEL_2);
+          cumulative_size += delta - 1;
+          continue;
+        }
+        LOG_PRINT_GREEN("Setting extra for block: " << b.miner_tx.extra.size() << ", try_count=" << try_count, LOG_LEVEL_1);
+      }
+    }
+    CHECK_AND_ASSERT_MES(cumulative_size == txs_size + get_object_blobsize(b.miner_tx), false, "unexpected case: cumulative_size=" << cumulative_size << " is not equal txs_cumulative_size=" << txs_size << " + get_object_blobsize(b.miner_tx)=" << get_object_blobsize(b.miner_tx));
+#if defined(DEBUG_CREATE_BLOCK_TEMPLATE)
+    LOG_PRINT_L1("Creating block template: miner tx size " << coinbase_blob_size <<
+      ", cumulative size " << cumulative_size << " is now good");
+#endif
+    return true;
+  }
+  LOG_ERROR("Failed to create_block_template with " << 10 << " tries");
+  return false;
+}
+//------------------------------------------------------------------
+// for an alternate chain, get the timestamps from the main chain to complete
+// the needed number of timestamps for the BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW.
+bool Blockchain::complete_timestamps_vector(uint64_t start_top_height, std::vector<uint64_t>& timestamps)
+{
+
+  if(timestamps.size() >= BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW)
+    return true;
+
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  size_t need_elements = BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW - timestamps.size();
+  CHECK_AND_ASSERT_MES(start_top_height <= m_db->height(), false, "internal error: passed start_height > " << " m_db->height() -- " << start_top_height << " > " << m_db->height());
+  size_t stop_offset = start_top_height > need_elements ? start_top_height - need_elements : 0;
+  while (start_top_height != stop_offset);
+  {
+    timestamps.push_back(m_db->get_block_timestamp(start_top_height));
+    --start_top_height;
+  }
+  return true;
+}
+//------------------------------------------------------------------
+// If a block is to be added and its parent block is not the current
+// main chain top block, then we need to see if we know about its parent block.
+// If its parent block is part of a known forked chain, then we need to see
+// if that chain is long enough to become the main chain and re-org accordingly
+// if so.  If not, we need to hang on to the block in case it becomes part of
+// a long forked chain eventually.
+bool Blockchain::handle_alternative_block(const block& b, const crypto::hash& id, block_verification_context& bvc)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  uint64_t block_height = get_block_height(b);
+  if(0 == block_height)
+  {
+    LOG_ERROR("Block with id: " << epee::string_tools::pod_to_hex(id) << " (as alternative) have wrong miner transaction");
+    bvc.m_verification_failed = true;
+    return false;
+  }
+  // TODO: this basically says if the blockchain is smaller than the first
+  // checkpoint then alternate blocks are allowed...this seems backwards, but
+  // I'm not sure.  Needs further investigating.
+  if (!m_checkpoints.is_alternative_block_allowed(get_current_blockchain_height(), block_height))
+  {
+    LOG_PRINT_RED_L0("Block with id: " << id
+      << std::endl << " can't be accepted for alternative chain, block height: " << block_height
+      << std::endl << " blockchain height: " << get_current_blockchain_height());
+    bvc.m_verification_failed = true;
+    return false;
+  }
+
+  //block is not related with head of main chain
+  //first of all - look in alternative chains container
+  auto it_prev = m_alternative_chains.find(b.prev_id);
+  bool parent_in_main = m_db->block_exists(b.prev_id);
+  if(it_prev != m_alternative_chains.end() || parent_in_main)
+  {
+    //we have new block in alternative chain
+
+    //build alternative subchain, front -> mainchain, back -> alternative head
+    blocks_ext_by_hash::iterator alt_it = it_prev; //m_alternative_chains.find()
+    std::list<blocks_ext_by_hash::iterator> alt_chain;
+    std::vector<uint64_t> timestamps;
+    while(alt_it != m_alternative_chains.end())
+    {
+      alt_chain.push_front(alt_it);
+      timestamps.push_back(alt_it->second.bl.timestamp);
+      alt_it = m_alternative_chains.find(alt_it->second.bl.prev_id);
+    }
+
+    // if block to be added connects to known blocks that aren't part of the
+    // main chain -- that is, if we're adding on to an alternate chain
+    if(alt_chain.size())
+    {
+      // make sure alt chain doesn't somehow start past the end of the main chain
+      CHECK_AND_ASSERT_MES(m_db->height() > alt_chain.front()->second.height, false, "main blockchain wrong height");
+
+      // make sure that the blockchain contains the block that should connect
+      // this alternate chain with it.
+      if (!m_db->block_exists(alt_chain.front()->second.bl.prev_id))
+      {
+        LOG_PRINT_L1("alternate chain does not appear to connect to main chain...");
+        return false;
+      }
+
+      // make sure block connects correctly to the main chain
+      auto h = m_db->get_block_hash_from_height(alt_chain.front()->second.height - 1);
+      CHECK_AND_ASSERT_MES(h == alt_chain.front()->second.bl.prev_id, false, "alternative chain have wrong connection to main chain");
+      complete_timestamps_vector(m_db->get_block_height(alt_chain.front()->second.bl.prev_id), timestamps);
+    }
+    // if block not associated with known alternate chain
+    else
+    {
+      // if block parent is not part of main chain or an alternate chain,
+      // we ignore it
+      CHECK_AND_ASSERT_MES(parent_in_main, false, "internal error: broken imperative condition it_main_prev != m_blocks_index.end()");
+
+      complete_timestamps_vector(m_db->get_block_height(b.prev_id), timestamps);
+    }
+
+    // verify that the block's timestamp is within the acceptable range
+    // (not earlier than the median of the last X blocks)
+    if(!check_block_timestamp(timestamps, b))
+    {
+      LOG_PRINT_RED_L0("Block with id: " << id
+        << std::endl << " for alternative chain, have invalid timestamp: " << b.timestamp);
+      bvc.m_verification_failed = true;
+      return false;
+    }
+
+    // FIXME: consider moving away from block_extended_info at some point
+    block_extended_info bei = boost::value_initialized<block_extended_info>();
+    bei.bl = b;
+    bei.height = alt_chain.size() ? it_prev->second.height + 1 : m_db->get_block_height(b.prev_id) + 1;
+
+    bool is_a_checkpoint;
+    if(!m_checkpoints.check_block(bei.height, id, is_a_checkpoint))
+    {
+      LOG_ERROR("CHECKPOINT VALIDATION FAILED");
+      bvc.m_verification_failed = true;
+      return false;
+    }
+
+    // Check the block's hash against the difficulty target for its alt chain
+    m_is_in_checkpoint_zone = false;
+    difficulty_type current_diff = get_next_difficulty_for_alternative_chain(alt_chain, bei);
+    CHECK_AND_ASSERT_MES(current_diff, false, "!!!!!!! DIFFICULTY OVERHEAD !!!!!!!");
+    crypto::hash proof_of_work = null_hash;
+    get_block_longhash(bei.bl, proof_of_work, bei.height);
+    if(!check_hash(proof_of_work, current_diff))
+    {
+      LOG_PRINT_RED_L0("Block with id: " << id
+        << std::endl << " for alternative chain, have not enough proof of work: " << proof_of_work
+        << std::endl << " expected difficulty: " << current_diff);
+      bvc.m_verification_failed = true;
+      return false;
+    }
+
+    if(!prevalidate_miner_transaction(b, bei.height))
+    {
+      LOG_PRINT_RED_L0("Block with id: " << epee::string_tools::pod_to_hex(id)
+        << " (as alternative) have wrong miner transaction.");
+      bvc.m_verification_failed = true;
+      return false;
+
+    }
+
+    // FIXME:
+    // this brings up an interesting point: consider allowing to get block
+    // difficulty both by height OR by hash, not just height.
+    bei.cumulative_difficulty = alt_chain.size() ? it_prev->second.cumulative_difficulty : m_db->get_block_cumulative_difficulty(m_db->get_block_height(b.prev_id));
+    bei.cumulative_difficulty += current_diff;
+
+    // add block to alternate blocks storage,
+    // as well as the current "alt chain" container
+    auto i_res = m_alternative_chains.insert(blocks_ext_by_hash::value_type(id, bei));
+    CHECK_AND_ASSERT_MES(i_res.second, false, "insertion of new alternative block returned as it already exist");
+    alt_chain.push_back(i_res.first);
+
+    // FIXME: is it even possible for a checkpoint to show up not on the main chain?
+    if(is_a_checkpoint)
+    {
+      //do reorganize!
+      LOG_PRINT_GREEN("###### REORGANIZE on height: " << alt_chain.front()->second.height << " of " << m_db->height() - 1 <<
+        ", checkpoint is found in alternative chain on height " << bei.height, LOG_LEVEL_0);
+
+      bool r = switch_to_alternative_blockchain(alt_chain, true);
+
+      bvc.m_added_to_main_chain = r;
+      bvc.m_verification_failed = !r;
+
+      return r;
+    }
+    else if(m_blocks.back().cumulative_difficulty < bei.cumulative_difficulty) //check if difficulty bigger then in main chain
+    {
+      //do reorganize!
+      LOG_PRINT_GREEN("###### REORGANIZE on height: "
+          << alt_chain.front()->second.height << " of " << m_db->height()
+          << " with cum_difficulty " << m_db->get_block_cumulative_difficulty(m_db->height())
+          << std::endl << " alternative blockchain size: " << alt_chain.size()
+          << " with cum_difficulty " << bei.cumulative_difficulty, LOG_LEVEL_0
+      );
+
+      bool r = switch_to_alternative_blockchain(alt_chain, false);
+      if(r) bvc.m_added_to_main_chain = true;
+      else bvc.m_verification_failed = true;
+      return r;
+    }
+    else
+    {
+      LOG_PRINT_BLUE("----- BLOCK ADDED AS ALTERNATIVE ON HEIGHT " << bei.height
+        << std::endl << "id:\t" << id
+        << std::endl << "PoW:\t" << proof_of_work
+        << std::endl << "difficulty:\t" << current_diff, LOG_LEVEL_0);
+      return true;
+    }
+  }
+  else
+  {
+    //block orphaned
+    bvc.m_marked_as_orphaned = true;
+    LOG_PRINT_RED_L0("Block recognized as orphaned and rejected, id = " << id);
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks, std::list<transaction>& txs)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  if(start_offset > m_db->height())
+    return false;
+
+  if (!get_blocks(start_offset, count, blocks))
+  {
+    return false;
+  }
+
+  for(const block& blk : blocks)
+  {
+    std::list<crypto::hash> missed_ids;
+    get_transactions(blk.tx_hashes, txs, missed_ids);
+    CHECK_AND_ASSERT_MES(!missed_ids.size(), false, "have missed transactions in own block in main blockchain");
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  if(start_offset > m_db->height())
+    return false;
+
+  for(size_t i = start_offset; i < start_offset + count && i <= m_db->height();i++)
+  {
+    blocks.push_back(m_db->get_block_from_height(i));
+  }
+  return true;
+}
+//------------------------------------------------------------------
+//TODO: This function *looks* like it won't need to be rewritten
+//      to use BlockchainDB, as it calls other functions that were,
+//      but it warrants some looking into later.
+bool Blockchain::handle_get_objects(NOTIFY_REQUEST_GET_OBJECTS::request& arg, NOTIFY_RESPONSE_GET_OBJECTS::request& rsp)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  rsp.current_blockchain_height = get_current_blockchain_height();
+  std::list<block> blocks;
+  get_blocks(arg.blocks, blocks, rsp.missed_ids);
+
+  BOOST_FOREACH(const auto& bl, blocks)
+  {
+    std::list<crypto::hash> missed_tx_id;
+    std::list<transaction> txs;
+    get_transactions(bl.tx_hashes, txs, rsp.missed_ids);
+    CHECK_AND_ASSERT_MES(!missed_tx_id.size(), false, "Internal error: have missed missed_tx_id.size()=" << missed_tx_id.size()
+      << std::endl << "for block id = " << get_block_hash(bl));
+   rsp.blocks.push_back(block_complete_entry());
+   block_complete_entry& e = rsp.blocks.back();
+   //pack block
+   e.block = t_serializable_object_to_blob(bl);
+   //pack transactions
+   BOOST_FOREACH(transaction& tx, txs)
+     e.txs.push_back(t_serializable_object_to_blob(tx));
+
+  }
+  //get another transactions, if need
+  std::list<transaction> txs;
+  get_transactions(arg.txs, txs, rsp.missed_ids);
+  //pack aside transactions
+  BOOST_FOREACH(const auto& tx, txs)
+    rsp.txs.push_back(t_serializable_object_to_blob(tx));
+
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::get_alternative_blocks(std::list<block>& blocks)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  BOOST_FOREACH(const auto& alt_bl, m_alternative_chains)
+  {
+    blocks.push_back(alt_bl.second.bl);
+  }
+  return true;
+}
+//------------------------------------------------------------------
+size_t Blockchain::get_alternative_blocks_count()
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  return m_alternative_chains.size();
+}
+//------------------------------------------------------------------
+// This function adds the output specified by <amount, i> to the result_outs container
+// unlocked and other such checks should be done by here.
+void Blockchain::add_out_to_get_random_outs(COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::outs_for_amount& result_outs, uint64_t amount, size_t i)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::out_entry& oen = *result_outs.outs.insert(result_outs.outs.end(), COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::out_entry());
+  oen.global_amount_index = i;
+  oen.out_key = m_db->get_output_key(amount, i);
+}
+//------------------------------------------------------------------
+// This function takes an RPC request for mixins and creates an RPC response
+// with the requested mixins.
+// TODO: figure out why this returns boolean / if we should be returning false
+// in some cases
+bool Blockchain::get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res)
+{
+  srand(static_cast<unsigned int>(time(NULL)));
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // for each amount that we need to get mixins for, get <n> random outputs
+  // from BlockchainDB where <n> is req.outs_count (number of mixins).
+  for (uint64_t amount : req.amounts)
+  {
+    // create outs_for_amount struct and populate amount field
+    COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::outs_for_amount& result_outs = *res.outs.insert(res.outs.end(), COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::outs_for_amount());
+    result_outs.amount = amount;
+
+    std::unordered_set<uint64_t> seen_indices;
+
+    // if there aren't enough outputs to mix with (or just enough),
+    // use all of them.  Eventually this should become impossible.
+    if (m_db->get_num_outputs(amount) <= req.outs_count)
+    {
+      for (uint64_t i = 0; i < m_db->get_num_outputs(amount); i++)
+      {
+        // get tx_hash, tx_out_index from DB
+        tx_out_index toi = m_db->get_output_tx_and_index(amount, i);
+
+        // if tx is unlocked, add output to result_outs
+        if (is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first)))
+        {
+          add_out_to_get_random_outs(result_outs, amount, i);
+        }
+
+      }
+    }
+    else
+    {
+      // while we still need more mixins
+      auto num_outs = m_db->get_num_outputs(amount);
+      while (result_outs.outs.size() < req.outs_count)
+      {
+        // if we've gone through every possible output, we've gotten all we can
+        if (seen_indices.size() == num_outs)
+        {
+          break;
+        }
+
+        // get a random output index from the DB.  If we've already seen it,
+        // return to the top of the loop and try again, otherwise add it to the
+        // list of output indices we've seen.
+        uint64_t i = m_db->get_random_output(amount);
+        if (seen_indices.count(i))
+        {
+          continue;
+        }
+        seen_indices.emplace(i);
+
+        // get tx_hash, tx_out_index from DB
+        tx_out_index toi = m_db->get_output_tx_and_index(amount, i);
+
+        // if the output's transaction is unlocked, add the output's index to
+        // our list.
+        if (is_tx_spendtime_unlocked(m_db->get_tx_unlock_time(toi.first)))
+        {
+          add_out_to_get_random_outs(result_outs, amount, i);
+        }
+      }
+    }
+  }
+  return true;
+}
+//------------------------------------------------------------------
+// This function takes a list of block hashes from another node
+// on the network to find where the split point is between us and them.
+// This is used to see what to send another node that needs to sync.
+bool Blockchain::find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, uint64_t& starter_offset)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // make sure the request includes at least the genesis block, otherwise
+  // how can we expect to sync from the client that the block list came from?
+  if(!qblock_ids.size() /*|| !req.m_total_height*/)
+  {
+    LOG_ERROR("Client sent wrong NOTIFY_REQUEST_CHAIN: m_block_ids.size()=" << qblock_ids.size() << /*", m_height=" << req.m_total_height <<*/ ", dropping connection");
+    return false;
+  }
+
+  // make sure that the last block in the request's block list matches
+  // the genesis block
+  auto gen_hash = m_db->get_block_hash_from_height(0);
+  if(qblock_ids.back() != gen_hash)
+  {
+    LOG_ERROR("Client sent wrong NOTIFY_REQUEST_CHAIN: genesis block missmatch: " << std::endl << "id: "
+      << qblock_ids.back() << ", " << std::endl << "expected: " << gen_hash
+      << "," << std::endl << " dropping connection");
+    return false;
+  }
+
+  // Find the first block the foreign chain has that we also have.
+  // Assume qblock_ids is in reverse-chronological order.
+  auto bl_it = qblock_ids.begin();
+  uint64_t split_height = 0;
+  for(; bl_it != qblock_ids.end(); bl_it++)
+  {
+    try
+    {
+      split_height = m_db->get_block_height(*bl_it);
+      break;
+    }
+    catch (const BLOCK_DNE& e)
+    {
+      continue;
+    }
+    catch (const std::exception& e)
+    {
+      LOG_PRINT_L1("Non-critical error trying to find block by hash in BlockchainDB, hash: " << *bl_it);
+      return false;
+    }
+  }
+
+  // this should be impossible, as we checked that we share the genesis block,
+  // but just in case...
+  if(bl_it == qblock_ids.end())
+  {
+    LOG_ERROR("Internal error handling connection, can't find split point");
+    return false;
+  }
+
+  // if split_height remains 0, we didn't have any but the genesis block in common
+  if(split_height == 0)
+  {
+    LOG_ERROR("Ours and foreign blockchain have only genesis block in common... o.O");
+    return false;
+  }
+
+  //we start to put block ids INCLUDING last known id, just to make other side be sure
+  starter_offset = split_height;
+  return true;
+}
+//------------------------------------------------------------------
+uint64_t Blockchain::block_difficulty(uint64_t i)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  try
+  {
+    return m_db->get_block_difficulty(i);
+  }
+  catch (const BLOCK_DNE& e)
+  {
+    LOG_PRINT_L0("Attempted to get block difficulty for height above blockchain height");
+  }
+  return 0;
+}
+//------------------------------------------------------------------
+template<class t_ids_container, class t_blocks_container, class t_missed_container>
+void Blockchain::get_blocks(const t_ids_container& block_ids, t_blocks_container& blocks, t_missed_container& missed_bs)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  for (const auto& block_hash : block_ids)
+  {
+    try
+    {
+      blocks.push_back(m_db->get_block(block_hash));
+    }
+    catch (const BLOCK_DNE& e)
+    {
+      missed_bs.push_back(block_hash);
+    }
+  }
+}
+//------------------------------------------------------------------
+template<class t_ids_container, class t_tx_container, class t_missed_container>
+void Blockchain::get_transactions(const t_ids_container& txs_ids, t_tx_container& txs, t_missed_container& missed_txs)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  for (const auto& tx_hash : txs_ids)
+  {
+    try
+    {
+      txs.push_back(m_db->get_tx(tx_hash));
+    }
+    catch (const TX_DNE& e)
+    {
+      missed_txs.push_back(tx_hash);
+    }
+  }
+}
+//------------------------------------------------------------------
+void Blockchain::print_blockchain(uint64_t start_index, uint64_t end_index)
+{
+  std::stringstream ss;
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  auto h = m_db->height();
+  if(start_index > h)
+  {
+    LOG_PRINT_L0("Wrong starter index set: " << start_index << ", expected max index " << h);
+    return;
+  }
+
+  for(size_t i = start_index; i <= h && i != end_index; i++)
+  {
+    ss << "height " << i
+       << ", timestamp " << m_db->get_block_timestamp(i)
+       << ", cumul_dif " << m_db->get_block_cumulative_difficulty(i)
+       << ", size " << m_db->get_block_size(i)
+       << "\nid\t\t" <<  m_db->get_block_hash_from_height(i)
+       << "\ndifficulty\t\t" << m_db->get_block_difficulty(i)
+       << ", nonce " << m_db->get_block_from_height(i).nonce
+       << ", tx_count " << m_db->get_block_from_height(i).tx_hashes.size()
+       << std::endl;
+  }
+  LOG_PRINT_L1("Current blockchain:" << std::endl << ss.str());
+  LOG_PRINT_L0("Blockchain printed with log level 1");
+}
+//------------------------------------------------------------------
+void Blockchain::print_blockchain_index()
+{
+  std::stringstream ss;
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  for(uint64_t i = 0; i <= m_db->height(); i++)
+  {
+    ss << "height: " << i << ", hash: " << m_db->get_block_hash_from_height(i);
+  }
+
+  LOG_PRINT_L0("Current blockchain index:" << std::endl
+               << ss.str()
+              );
+}
+//------------------------------------------------------------------
+//TODO: remove this function and references to it
+void Blockchain::print_blockchain_outs(const std::string& file)
+{
+  return;
+}
+//------------------------------------------------------------------
+// Find the split point between us and foreign blockchain and return
+// (by reference) the most recent common block hash along with up to
+// BLOCKS_IDS_SYNCHRONIZING_DEFAULT_COUNT additional (more recent) hashes.
+bool Blockchain::find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, NOTIFY_RESPONSE_CHAIN_ENTRY::request& resp)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // if we can't find the split point, return false
+  if(!find_blockchain_supplement(qblock_ids, resp.start_height))
+  {
+    return false;
+  }
+
+  resp.total_height = get_current_blockchain_height();
+  size_t count = 0;
+  for(size_t i = resp.start_height; i <= m_db->height() && count < BLOCKS_IDS_SYNCHRONIZING_DEFAULT_COUNT; i++, count++)
+  {
+    resp.m_block_ids.push_back(m_db->get_block_hash_from_height(i));
+  }
+  return true;
+}
+//------------------------------------------------------------------
+//FIXME: change argument to std::vector, low priority
+// find split point between ours and foreign blockchain (or start at
+// blockchain height <req_start_block>), and return up to max_count FULL
+// blocks by reference.
+bool Blockchain::find_blockchain_supplement(const uint64_t req_start_block, const std::list<crypto::hash>& qblock_ids, std::list<std::pair<block, std::list<transaction> > >& blocks, uint64_t& total_height, uint64_t& start_height, size_t max_count)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  // if a specific start height has been requested
+  if(req_start_block > 0)
+  {
+    // if requested height is higher than our chain, return false -- we can't help
+    if (req_start_block > m_db->height())
+    {
+      return false;
+    }
+    start_height = req_start_block; 
+  }
+  else
+  {
+    if(!find_blockchain_supplement(qblock_ids, start_height))
+    {
+      return false;
+    }
+  }
+
+  total_height = get_current_blockchain_height();
+  size_t count = 0;
+  for(size_t i = start_height; i <= m_db->height() && count < max_count; i++, count++)
+  {
+    blocks.resize(blocks.size()+1);
+    blocks.back().first = m_db->get_block_from_height(i);
+    std::list<crypto::hash> mis;
+    get_transactions(m_blocks[i].bl.tx_hashes, blocks.back().second, mis);
+    CHECK_AND_ASSERT_MES(!mis.size(), false, "internal error, transaction from block not found");
+  }
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::add_block_as_invalid(const block& bl, const crypto::hash& h)
+{
+  block_extended_info bei = AUTO_VAL_INIT(bei);
+  bei.bl = bl;
+  return add_block_as_invalid(bei, h);
+}
+//------------------------------------------------------------------
+bool Blockchain::add_block_as_invalid(const block_extended_info& bei, const crypto::hash& h)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  auto i_res = m_invalid_blocks.insert(std::map<crypto::hash, block_extended_info>::value_type(h, bei));
+  CHECK_AND_ASSERT_MES(i_res.second, false, "at insertion invalid by tx returned status existed");
+  LOG_PRINT_L0("BLOCK ADDED AS INVALID: " << h << std::endl << ", prev_id=" << bei.bl.prev_id << ", m_invalid_blocks count=" << m_invalid_blocks.size());
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::have_block(const crypto::hash& id)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  if(m_db->block_exists(id))
+    return true;
+
+  if(m_alternative_chains.count(id))
+    return true;
+
+  if(m_invalid_blocks.count(id))
+    return true;
+
+  return false;
+}
+//------------------------------------------------------------------
+bool Blockchain::handle_block_to_main_chain(const block& bl, block_verification_context& bvc)
+{
+  crypto::hash id = get_block_hash(bl);
+  return handle_block_to_main_chain(bl, id, bvc);
+}
+//------------------------------------------------------------------
+size_t Blockchain::get_total_transactions()
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  return m_db->get_tx_count();
+}
+//------------------------------------------------------------------
+// This function checks each input in the transaction <tx> to make sure it
+// has not been used already, and adds its key to the container <keys_this_block>.
+//
+// This container should be managed by the code that validates blocks so we don't
+// have to store the used keys in a given block in the permanent storage only to
+// remove them later if the block fails validation.
+bool Blockchain::check_for_double_spend(const transaction& tx, key_images_container& keys_this_block)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  struct add_transaction_input_visitor: public boost::static_visitor<bool>
+  {
+    key_images_container& m_spent_keys;
+    BlockchainDB* m_db;
+    add_transaction_input_visitor(key_images_container& spent_keys, BlockchainDB* db):m_spent_keys(spent_keys), m_db(db)
+    {}
+    bool operator()(const txin_to_key& in) const
+    {
+      const crypto::key_image& ki = in.k_image;
+
+      // attempt to insert the newly-spent key into the container of
+      // keys spent this block.  If this fails, the key was spent already
+      // in this block, return false to flag that a double spend was detected.
+      //
+      // if the insert into the block-wide spent keys container succeeds,
+      // check the blockchain-wide spent keys container and make sure the
+      // key wasn't used in another block already.
+      auto r = m_spent_keys.insert(ki);
+      if(!r.second || m_db->has_key_image(ki))
+      {
+        //double spend detected
+        return false;
+      }
+
+      // if no double-spend detected, return true
+      return true;
+    }
+
+    bool operator()(const txin_gen& tx) const{return true;}
+    bool operator()(const txin_to_script& tx) const{return false;}
+    bool operator()(const txin_to_scripthash& tx) const{return false;}
+  };
+
+  for (const txin_v& in : tx.vin)
+  {
+    if(!boost::apply_visitor(add_transaction_input_visitor(keys_this_block, m_db), in))
+    {
+      LOG_ERROR("Double spend detected!");
+      return false;
+    }
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::get_tx_outputs_gindexs(const crypto::hash& tx_id, std::vector<uint64_t>& indexs)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  if (!m_db->tx_exists(tx_id))
+  {
+    LOG_PRINT_L0("warning: get_tx_outputs_gindexs failed to find transaction with id = " << tx_id);
+    return false;
+  }
+
+  indexs = m_db->get_tx_output_indices(tx_id);
+  return true;
+}
+//------------------------------------------------------------------
+// This function overloads its sister function with
+// an extra value (hash of highest block that holds an output used as input)
+// as a return-by-reference.
+bool Blockchain::check_tx_inputs(const transaction& tx, uint64_t& max_used_block_height, crypto::hash& max_used_block_id)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  bool res = check_tx_inputs(tx, &max_used_block_height);
+  if(!res) return false;
+  CHECK_AND_ASSERT_MES(max_used_block_height < m_db->height(), false,  "internal error: max used block index=" << max_used_block_height << " is not less then blockchain size = " << m_db->height());
+  max_used_block_id = m_db->get_block_hash_from_height(max_used_block_height);
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::have_tx_keyimges_as_spent(const transaction &tx)
+{
+  BOOST_FOREACH(const txin_v& in, tx.vin)
+  {
+    CHECKED_GET_SPECIFIC_VARIANT(in, const txin_to_key, in_to_key, true);
+    if(have_tx_keyimg_as_spent(in_to_key.k_image))
+      return true;
+  }
+  return false;
+}
+//------------------------------------------------------------------
+// This function validates transaction inputs and their keys.  Previously
+// it also performed double spend checking, but that has been moved to its
+// own function.
+bool Blockchain::check_tx_inputs(const transaction& tx, uint64_t* pmax_used_block_height)
+{
+  size_t sig_index = 0;
+  if(pmax_used_block_height)
+    *pmax_used_block_height = 0;
+
+  crypto::hash tx_prefix_hash = get_transaction_prefix_hash(tx);
+
+  for (const auto& txin : tx.vin)
+  {
+    // make sure output being spent is of type txin_to_key, rather than
+    // e.g. txin_gen, which is only used for miner transactions
+    CHECK_AND_ASSERT_MES(txin.type() == typeid(txin_to_key), false, "wrong type id in tx input at Blockchain::check_tx_inputs");
+    const txin_to_key& in_to_key = boost::get<txin_to_key>(txin);
+
+    // make sure tx output has key offset(s) (is signed to be used)
+    CHECK_AND_ASSERT_MES(in_to_key.key_offsets.size(), false, "empty in_to_key.key_offsets in transaction with id " << get_transaction_hash(tx));
+
+    // basically, make sure number of inputs == number of signatures
+    CHECK_AND_ASSERT_MES(sig_index < tx.signatures.size(), false, "wrong transaction: not signature entry for input with index= " << sig_index);
+
+    // make sure that output being spent matches up correctly with the
+    // signature spending it.
+    if(!check_tx_input(in_to_key, tx_prefix_hash, tx.signatures[sig_index], pmax_used_block_height))
+    {
+      LOG_PRINT_L0("Failed to check ring signature for tx " << get_transaction_hash(tx));
+      return false;
+    }
+
+    sig_index++;
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+// This function checks to see if a tx is unlocked.  unlock_time is either
+// a block index or a unix time.
+bool Blockchain::is_tx_spendtime_unlocked(uint64_t unlock_time)
+{
+  if(unlock_time < CRYPTONOTE_MAX_BLOCK_NUMBER)
+  {
+    //interpret as block index
+    if(get_current_blockchain_height() + CRYPTONOTE_LOCKED_TX_ALLOWED_DELTA_BLOCKS >= unlock_time)
+      return true;
+    else
+      return false;
+  }else
+  {
+    //interpret as time
+    uint64_t current_time = static_cast<uint64_t>(time(NULL));
+    if(current_time + CRYPTONOTE_LOCKED_TX_ALLOWED_DELTA_SECONDS >= unlock_time)
+      return true;
+    else
+      return false;
+  }
+  return false;
+}
+//------------------------------------------------------------------
+// This function locates all outputs associated with a given input (mixins)
+// and validates that they exist and are usable.  It also checks the ring
+// signature for each input.
+bool Blockchain::check_tx_input(const txin_to_key& txin, const crypto::hash& tx_prefix_hash, const std::vector<crypto::signature>& sig, uint64_t* pmax_related_block_height)
+{
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
+  struct outputs_visitor
+  {
+    std::vector<const crypto::public_key *>& m_results_collector;
+    Blockchain& m_bch;
+    outputs_visitor(std::vector<const crypto::public_key *>& results_collector, Blockchain& bch):m_results_collector(results_collector), m_bch(bch)
+    {}
+    bool handle_output(const transaction& tx, const tx_out& out)
+    {
+      //check tx unlock time
+      if(!m_bch.is_tx_spendtime_unlocked(tx.unlock_time))
+      {
+        LOG_PRINT_L0("One of outputs for one of inputs have wrong tx.unlock_time = " << tx.unlock_time);
+        return false;
+      }
+
+      if(out.target.type() != typeid(txout_to_key))
+      {
+        LOG_PRINT_L0("Output have wrong type id, which=" << out.target.which());
+        return false;
+      }
+
+      m_results_collector.push_back(&boost::get<txout_to_key>(out.target).key);
+      return true;
+    }
+  };
+
+  //check ring signature
+  std::vector<const crypto::public_key *> output_keys;
+  outputs_visitor vi(output_keys, *this);
+  if(!scan_outputkeys_for_indexes(txin, vi, pmax_related_block_height))
+  {
+    LOG_PRINT_L0("Failed to get output keys for tx with amount = " << print_money(txin.amount) << " and count indexes " << txin.key_offsets.size());
+    return false;
+  }
+
+  if(txin.key_offsets.size() != output_keys.size())
+  {
+    LOG_PRINT_L0("Output keys for tx with amount = " << txin.amount << " and count indexes " << txin.key_offsets.size() << " returned wrong keys count " << output_keys.size());
+    return false;
+  }
+  CHECK_AND_ASSERT_MES(sig.size() == output_keys.size(), false, "internal error: tx signatures count=" << sig.size() << " mismatch with outputs keys count for inputs=" << output_keys.size());
+  if(m_is_in_checkpoint_zone)
+    return true;
+  return crypto::check_ring_signature(tx_prefix_hash, txin.k_image, output_keys, sig.data());
+}
+//------------------------------------------------------------------
+//TODO: Is this intended to do something else?  Need to look into the todo there.
+uint64_t Blockchain::get_adjusted_time()
+{
+  //TODO: add collecting median time
+  return time(NULL);
+}
+//------------------------------------------------------------------
+bool Blockchain::check_block_timestamp(const std::vector<uint64_t>& timestamps, const block& b)
+{
+  uint64_t median_ts = epee::misc_utils::median(timestamps);
+
+  if(b.timestamp < median_ts)
+  {
+    LOG_PRINT_L0("Timestamp of block with id: " << get_block_hash(b) << ", " << b.timestamp << ", less than median of last " << BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW << " blocks, " << median_ts);
+    return false;
+  }
+
+  return true;
+}
+//------------------------------------------------------------------
+// This function grabs the timestamps from the most recent <n> blocks,
+// where n = BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW.  If there are not those many
+// blocks in the blockchain, the timestap is assumed to be valid.  If there
+// are, this function returns:
+//   true if the block's timestamp is not less than the timestamp of the
+//       median of the selected blocks
+//   false otherwise
+bool Blockchain::check_block_timestamp(const block& b)
+{
+  if(b.timestamp > get_adjusted_time() + CRYPTONOTE_BLOCK_FUTURE_TIME_LIMIT)
+  {
+    LOG_PRINT_L0("Timestamp of block with id: " << get_block_hash(b) << ", " << b.timestamp << ", bigger than adjusted time + 2 hours");
+    return false;
+  }
+
+  // if not enough blocks, no proper median yet, return true
+  if(m_db->height() < BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW + 1)
+  {
+    return true;
+  }
+
+  std::vector<uint64_t> timestamps;
+  auto h = m_db->height();
+
+  // need most recent 60 blocks, get index of first of those
+  // using +1 because BlockchainDB::height() returns the index of the top block,
+  // not the size of the blockchain (0-indexed)
+  size_t offset = h - BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW + 1;
+  for(;offset <= h; ++offset)
+  {
+    timestamps.push_back(m_db->get_block_timestamp(offset));
+  }
+
+  return check_block_timestamp(timestamps, b);
+}
+//------------------------------------------------------------------
+//      Needs to validate the block and acquire each transaction from the
+//      transaction mem_pool, then pass the block and transactions to
+//      m_db->add_block()
+bool Blockchain::handle_block_to_main_chain(const block& bl, const crypto::hash& id, block_verification_context& bvc)
+{
+  // if we already have the block, return false
+  if (have_block(id))
+  {
+    LOG_PRINT_L0("Attempting to add block to main chain, but it's already either there or in an alternate chain.  hash: " << id);
+    bvc.m_verification_failed = true;
+    return false;
+  }
+  
+  TIME_MEASURE_START(block_processing_time);
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+  if(bl.prev_id != get_tail_id())
+  {
+    LOG_PRINT_L0("Block with id: " << id << std::endl
+      << "have wrong prev_id: " << bl.prev_id << std::endl
+      << "expected: " << get_tail_id());
+    return false;
+  }
+
+  // make sure block timestamp is not less than the median timestamp
+  // of a set number of the most recent blocks.
+  if(!check_block_timestamp(bl))
+  {
+    LOG_PRINT_L0("Block with id: " << id << std::endl
+      << "have invalid timestamp: " << bl.timestamp);
+    bvc.m_verification_failed = true;
+    return false;
+  }
+
+  //check proof of work
+  TIME_MEASURE_START(target_calculating_time);
+
+  // get the target difficulty for the block.
+  // the calculation can overflow, among other failure cases,
+  // so we need to check the return type.
+  // FIXME: get_difficulty_for_next_block can also assert, look into
+  // changing this to throwing exceptions instead so we can clean up.
+  difficulty_type current_diffic = get_difficulty_for_next_block();
+  CHECK_AND_ASSERT_MES(current_diffic, false, "!!!!!!!!! difficulty overhead !!!!!!!!!");
+
+  TIME_MEASURE_FINISH(target_calculating_time);
+
+  TIME_MEASURE_START(longhash_calculating_time);
+
+  crypto::hash proof_of_work = null_hash;
+
+  // Formerly the code below contained an if loop with the following condition
+  // !m_checkpoints.is_in_checkpoint_zone(get_current_blockchain_height())
+  // however, this caused the daemon to not bother checking PoW for blocks
+  // before checkpoints, which is very dangerous behaviour. We moved the PoW
+  // validation out of the next chunk of code to make sure that we correctly
+  // check PoW now.
+  // FIXME: height parameter is not used...should it be used or should it not
+  // be a parameter?
+  proof_of_work = get_block_longhash(bl, m_db->height());
+
+  // validate proof_of_work versus difficulty target
+  if(!check_hash(proof_of_work, current_diffic))
+  {
+    LOG_PRINT_L0("Block with id: " << id << std::endl
+      << "have not enough proof of work: " << proof_of_work << std::endl
+      << "nexpected difficulty: " << current_diffic );
+    bvc.m_verification_failed = true;
+    return false;
+  }
+
+  // If we're at a checkpoint, ensure that our hardcoded checkpoint hash
+  // is correct.
+  if(m_checkpoints.is_in_checkpoint_zone(get_current_blockchain_height()))
+  {
+    if(!m_checkpoints.check_block(get_current_blockchain_height(), id))
+    {
+      LOG_ERROR("CHECKPOINT VALIDATION FAILED");
+      bvc.m_verification_failed = true;
+      return false;
+    }
+  }
+
+  TIME_MEASURE_FINISH(longhash_calculating_time);
+
+  // sanity check basic miner tx properties
+  if(!prevalidate_miner_transaction(bl, m_db->height()))
+  {
+    LOG_PRINT_L0("Block with id: " << id
+      << " failed to pass prevalidation");
+    bvc.m_verification_failed = true;
+    return false;
+  }
+
+  size_t coinbase_blob_size = get_object_blobsize(bl.miner_tx);
+  size_t cumulative_block_size = coinbase_blob_size;
+
+  std::vector<transaction> txs;
+  key_images_container keys;
+
+  // add miner transaction to list of block's transactions.
+  txs.push_back(bl.miner_tx);
+
+  uint64_t fee_summary = 0;
+
+  // Iterate over the block's transaction hashes, grabbing each
+  // from the tx_pool and validating them.  Each is then added
+  // to txs.  Keys spent in each are added to <keys> by the double spend check.
+  for (const crypto::hash& tx_id : bl.tx_hashes)
+  {
+    transaction tx;
+    size_t blob_size = 0;
+    uint64_t fee = 0;
+
+    if (m_db->tx_exists(tx_id))
+    {
+      LOG_PRINT_L0("Block with id: " << id << " attempting to add transaction already in blockchain with id: " << tx_id);
+      bvc.m_verification_failed = true;
+      break;
+    }
+
+    // get transaction with hash <tx_id> from tx_pool
+    if(!m_tx_pool.take_tx(tx_id, tx, blob_size, fee))
+    {
+      LOG_PRINT_L0("Block with id: " << id  << "have at least one unknown transaction with id: " << tx_id);
+      bvc.m_verification_failed = true;
+      break;
+    }
+
+    // add the transaction to the temp list of transactions, so we can either
+    // store the list of transactions all at once or return the ones we've
+    // taken from the tx_pool back to it if the block fails verification.
+    txs.push_back(tx);
+
+    // validate that transaction inputs and the keys spending them are correct.
+    if(!check_tx_inputs(tx))
+    {
+      LOG_PRINT_L0("Block with id: " << id  << "have at least one transaction (id: " << tx_id << ") with wrong inputs.");
+
+      //TODO: why is this done?  make sure that keeping invalid blocks makes sense.
+      add_block_as_invalid(bl, id);
+      LOG_PRINT_L0("Block with id " << id << " added as invalid becouse of wrong inputs in transactions");
+      bvc.m_verification_failed = true;
+      break;
+    }
+
+    if (!check_for_double_spend(tx, keys))
+    {
+      LOG_PRINT_L0("Double spend detected in transaction (id: " << tx_id);
+      bvc.m_verification_failed = true;
+      break;
+    }
+
+    fee_summary += fee;
+    cumulative_block_size += blob_size;
+  }
+
+  uint64_t base_reward = 0;
+  uint64_t already_generated_coins = m_db->height() ? m_db->get_block_already_generated_coins(m_db->height()) : 0;
+  if(!validate_miner_transaction(bl, cumulative_block_size, fee_summary, base_reward, already_generated_coins))
+  {
+    LOG_PRINT_L0("Block with id: " << id
+      << " have wrong miner transaction");
+    bvc.m_verification_failed = true;
+  }
+
+
+  block_extended_info bei = boost::value_initialized<block_extended_info>();
+  size_t block_size;
+  difficulty_type cumulative_difficulty;
+
+  // populate various metadata about the block to be stored alongside it.
+  block_size = cumulative_block_size;
+  cumulative_difficulty = current_diffic;
+  already_generated_coins = already_generated_coins + base_reward;
+  if(m_db->height())
+    cumulative_difficulty += m_db->get_block_cumulative_difficulty(m_db->height());
+
+  update_next_cumulative_size_limit();
+
+  TIME_MEASURE_FINISH(block_processing_time);
+
+  uint64_t new_height = 0;
+  bool add_success = true;
+  try
+  {
+    new_height = m_db->add_block(bl, block_size, cumulative_difficulty, already_generated_coins, txs);
+  }
+  catch (const std::exception& e)
+  {
+    //TODO: figure out the best way to deal with this failure
+    LOG_ERROR("Error adding block with hash: " << id << " to blockchain, what = " << e.what());
+    add_success = false;
+  }
+
+  // if we failed for any reason to verify the block, return taken
+  // transactions to the tx_pool.
+  if (bvc.m_verification_failed || !add_success)
+  {
+    // return taken transactions to transaction pool
+    for (auto& tx : txs)
+    {
+      cryptonote::tx_verification_context tvc = AUTO_VAL_INIT(tvc);
+      if (!m_tx_pool.add_tx(tx, tvc, true))
+      {
+        LOG_PRINT_L0("Failed to return taken transaction with hash: " << get_transaction_hash(tx) << " to tx_pool");
+      }
+    }
+    return false;
+  }
+
+  LOG_PRINT_L1("+++++ BLOCK SUCCESSFULLY ADDED" << std::endl << "id:\t" << id
+    << std::endl << "PoW:\t" << proof_of_work
+    << std::endl << "HEIGHT " << new_height << ", difficulty:\t" << current_diffic
+    << std::endl << "block reward: " << print_money(fee_summary + base_reward) << "(" << print_money(base_reward) << " + " << print_money(fee_summary)
+    << "), coinbase_blob_size: " << coinbase_blob_size << ", cumulative size: " << cumulative_block_size
+    << ", " << block_processing_time << "("<< target_calculating_time << "/" << longhash_calculating_time << ")ms");
+
+  bvc.m_added_to_main_chain = true;
+
+  // appears to be a NOP *and* is called elsewhere.  wat?
+  m_tx_pool.on_blockchain_inc(new_height, id);
+
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::update_next_cumulative_size_limit()
+{
+  std::vector<size_t> sz;
+  get_last_n_blocks_sizes(sz, CRYPTONOTE_REWARD_BLOCKS_WINDOW);
+
+  uint64_t median = epee::misc_utils::median(sz);
+  if(median <= CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE)
+    median = CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE;
+
+  m_current_block_cumul_sz_limit = median*2;
+  return true;
+}
+//------------------------------------------------------------------
+bool Blockchain::add_new_block(const block& bl_, block_verification_context& bvc)
+{
+  //copy block here to let modify block.target
+  block bl = bl_;
+  crypto::hash id = get_block_hash(bl);
+  CRITICAL_REGION_LOCAL(m_tx_pool);//to avoid deadlock lets lock tx_pool for whole add/reorganize process
+  CRITICAL_REGION_LOCAL1(m_blockchain_lock);
+  if(have_block(id))
+  {
+    LOG_PRINT_L3("block with id = " << id << " already exists");
+    bvc.m_already_exists = true;
+    return false;
+  }
+
+  //check that block refers to chain tail
+  if(!(bl.prev_id == get_tail_id()))
+  {
+    //chain switching or wrong block
+    bvc.m_added_to_main_chain = false;
+    return handle_alternative_block(bl, id, bvc);
+    //never relay alternative blocks
+  }
+
+  return handle_block_to_main_chain(bl, id, bvc);
+}
diff --git a/src/cryptonote_core/blockchain.h b/src/cryptonote_core/blockchain.h
new file mode 100644
index 000000000..27e5cde8c
--- /dev/null
+++ b/src/cryptonote_core/blockchain.h
@@ -0,0 +1,221 @@
+// Copyright (c) 2014, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+// 
+// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
+
+#pragma once
+#include <boost/serialization/serialization.hpp>
+#include <boost/serialization/version.hpp>
+#include <boost/serialization/list.hpp>
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/global_fun.hpp>
+#include <boost/multi_index/hashed_index.hpp>
+#include <boost/multi_index/member.hpp>
+#include <boost/foreach.hpp>
+#include <atomic>
+
+#include "syncobj.h"
+#include "string_tools.h"
+#include "tx_pool.h"
+#include "cryptonote_basic.h"
+#include "common/util.h"
+#include "cryptonote_protocol/cryptonote_protocol_defs.h"
+#include "rpc/core_rpc_server_commands_defs.h"
+#include "difficulty.h"
+#include "cryptonote_core/cryptonote_format_utils.h"
+#include "verification_context.h"
+#include "crypto/hash.h"
+#include "checkpoints.h"
+#include "blockchain_db.h"
+
+namespace cryptonote
+{
+
+  /************************************************************************/
+  /*                                                                      */
+  /************************************************************************/
+  class Blockchain
+  {
+  public:
+    struct transaction_chain_entry
+    {
+      transaction tx;
+      uint64_t m_keeper_block_height;
+      size_t m_blob_size;
+      std::vector<uint64_t> m_global_output_indexes;
+    };
+
+    struct block_extended_info
+    {
+      block   bl;
+      uint64_t height;
+      size_t block_cumulative_size;
+      difficulty_type cumulative_difficulty;
+      uint64_t already_generated_coins;
+    };
+
+    Blockchain(tx_memory_pool& tx_pool);
+
+    bool init() { return init(tools::get_default_data_dir()); }
+    bool init(const std::string& config_folder);
+    bool deinit();
+
+    void set_checkpoints(checkpoints&& chk_pts) { m_checkpoints = chk_pts; }
+
+    //bool push_new_block();
+    bool get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks, std::list<transaction>& txs);
+    bool get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks);
+    bool get_alternative_blocks(std::list<block>& blocks);
+    size_t get_alternative_blocks_count();
+    crypto::hash get_block_id_by_height(uint64_t height);
+    bool get_block_by_hash(const crypto::hash &h, block &blk);
+    void get_all_known_block_ids(std::list<crypto::hash> &main, std::list<crypto::hash> &alt, std::list<crypto::hash> &invalid);
+
+    template<class archive_t>
+    void serialize(archive_t & ar, const unsigned int version);
+
+    bool have_tx(const crypto::hash &id);
+    bool have_tx_keyimges_as_spent(const transaction &tx);
+    bool have_tx_keyimg_as_spent(const crypto::key_image &key_im);
+
+    template<class visitor_t>
+    bool scan_outputkeys_for_indexes(const txin_to_key& tx_in_to_key, visitor_t& vis, uint64_t* pmax_related_block_height = NULL);
+
+    uint64_t get_current_blockchain_height();
+    crypto::hash get_tail_id();
+    crypto::hash get_tail_id(uint64_t& height);
+    difficulty_type get_difficulty_for_next_block();
+    bool add_new_block(const block& bl_, block_verification_context& bvc);
+    bool reset_and_set_genesis_block(const block& b);
+    bool create_block_template(block& b, const account_public_address& miner_address, difficulty_type& di, uint64_t& height, const blobdata& ex_nonce);
+    bool have_block(const crypto::hash& id);
+    size_t get_total_transactions();
+    bool get_short_chain_history(std::list<crypto::hash>& ids);
+    bool find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, NOTIFY_RESPONSE_CHAIN_ENTRY::request& resp);
+    bool find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, uint64_t& starter_offset);
+    bool find_blockchain_supplement(const uint64_t req_start_block, const std::list<crypto::hash>& qblock_ids, std::list<std::pair<block, std::list<transaction> > >& blocks, uint64_t& total_height, uint64_t& start_height, size_t max_count);
+    bool handle_get_objects(NOTIFY_REQUEST_GET_OBJECTS::request& arg, NOTIFY_RESPONSE_GET_OBJECTS::request& rsp);
+    bool handle_get_objects(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res);
+    bool get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res);
+    bool get_tx_outputs_gindexs(const crypto::hash& tx_id, std::vector<uint64_t>& indexs);
+    bool store_blockchain();
+    bool check_tx_input(const txin_to_key& txin, const crypto::hash& tx_prefix_hash, const std::vector<crypto::signature>& sig, uint64_t* pmax_related_block_height = NULL);
+    bool check_tx_inputs(const transaction& tx, uint64_t* pmax_used_block_height = NULL);
+    bool check_tx_inputs(const transaction& tx, uint64_t& pmax_used_block_height, crypto::hash& max_used_block_id);
+    uint64_t get_current_cumulative_blocksize_limit();
+    bool is_storing_blockchain(){return m_is_blockchain_storing;}
+    uint64_t block_difficulty(uint64_t i);
+
+    template<class t_ids_container, class t_blocks_container, class t_missed_container>
+    void get_blocks(const t_ids_container& block_ids, t_blocks_container& blocks, t_missed_container& missed_bs);
+
+    template<class t_ids_container, class t_tx_container, class t_missed_container>
+    void get_transactions(const t_ids_container& txs_ids, t_tx_container& txs, t_missed_container& missed_txs);
+
+    //debug functions
+    void print_blockchain(uint64_t start_index, uint64_t end_index);
+    void print_blockchain_index();
+    void print_blockchain_outs(const std::string& file);
+
+  private:
+    typedef std::unordered_map<crypto::hash, size_t> blocks_by_id_index;
+    typedef std::unordered_map<crypto::hash, transaction_chain_entry> transactions_container;
+    typedef std::unordered_set<crypto::key_image> key_images_container;
+    typedef std::vector<block_extended_info> blocks_container;
+    typedef std::unordered_map<crypto::hash, block_extended_info> blocks_ext_by_hash;
+    typedef std::unordered_map<crypto::hash, block> blocks_by_hash;
+    typedef std::map<uint64_t, std::vector<std::pair<crypto::hash, size_t>>> outputs_container; //crypto::hash - tx hash, size_t - index of out in transaction
+
+    BlockchainDB* m_db;
+
+    tx_memory_pool& m_tx_pool;
+    epee::critical_section m_blockchain_lock; // TODO: add here reader/writer lock
+
+    // main chain
+    blocks_container m_blocks;               // height  -> block_extended_info
+    blocks_by_id_index m_blocks_index;       // crypto::hash -> height
+    transactions_container m_transactions;
+    key_images_container m_spent_keys;
+    size_t m_current_block_cumul_sz_limit;
+
+
+    // all alternative chains
+    blocks_ext_by_hash m_alternative_chains; // crypto::hash -> block_extended_info
+
+    // some invalid blocks
+    blocks_ext_by_hash m_invalid_blocks;     // crypto::hash -> block_extended_info
+    outputs_container m_outputs;
+
+
+    std::string m_config_folder;
+    checkpoints m_checkpoints;
+    std::atomic<bool> m_is_in_checkpoint_zone;
+    std::atomic<bool> m_is_blockchain_storing;
+
+    bool switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::iterator>& alt_chain, bool discard_disconnected_chain);
+    block pop_block_from_blockchain();
+    bool purge_transaction_from_blockchain(const crypto::hash& tx_id);
+    bool purge_transaction_keyimages_from_blockchain(const transaction& tx, bool strict_check);
+
+    bool handle_block_to_main_chain(const block& bl, block_verification_context& bvc);
+    bool handle_block_to_main_chain(const block& bl, const crypto::hash& id, block_verification_context& bvc);
+    bool handle_alternative_block(const block& b, const crypto::hash& id, block_verification_context& bvc);
+    difficulty_type get_next_difficulty_for_alternative_chain(const std::list<blocks_ext_by_hash::iterator>& alt_chain, block_extended_info& bei);
+    bool prevalidate_miner_transaction(const block& b, uint64_t height);
+    bool validate_miner_transaction(const block& b, size_t cumulative_block_size, uint64_t fee, uint64_t& base_reward, uint64_t already_generated_coins);
+    bool validate_transaction(const block& b, uint64_t height, const transaction& tx);
+    bool rollback_blockchain_switching(std::list<block>& original_chain);
+    bool add_transaction_from_block(const transaction& tx, const crypto::hash& tx_id, const crypto::hash& bl_id, uint64_t bl_height);
+    bool push_transaction_to_global_outs_index(const transaction& tx, const crypto::hash& tx_id, std::vector<uint64_t>& global_indexes);
+    bool pop_transaction_from_global_index(const transaction& tx, const crypto::hash& tx_id);
+    void get_last_n_blocks_sizes(std::vector<size_t>& sz, size_t count);
+    void add_out_to_get_random_outs(COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::outs_for_amount& result_outs, uint64_t amount, size_t i);
+    bool is_tx_spendtime_unlocked(uint64_t unlock_time);
+    bool add_block_as_invalid(const block& bl, const crypto::hash& h);
+    bool add_block_as_invalid(const block_extended_info& bei, const crypto::hash& h);
+    bool check_block_timestamp(const block& b);
+    bool check_block_timestamp(const std::vector<uint64_t>& timestamps, const block& b);
+    uint64_t get_adjusted_time();
+    bool complete_timestamps_vector(uint64_t start_height, std::vector<uint64_t>& timestamps);
+    bool update_next_cumulative_size_limit();
+
+    bool check_for_double_spend(const transaction& tx, key_images_container& keys_this_block);
+  };
+
+
+  /************************************************************************/
+  /*                                                                      */
+  /************************************************************************/
+
+  #define CURRENT_BLOCKCHAIN_STORAGE_ARCHIVE_VER    12
+
+  //------------------------------------------------------------------
+
+}  // namespace cryptonote
+
+BOOST_CLASS_VERSION(cryptonote::Blockchain, CURRENT_BLOCKCHAIN_STORAGE_ARCHIVE_VER)
diff --git a/src/cryptonote_core/blockchain_db.cpp b/src/cryptonote_core/blockchain_db.cpp
new file mode 100644
index 000000000..606b34310
--- /dev/null
+++ b/src/cryptonote_core/blockchain_db.cpp
@@ -0,0 +1,135 @@
+// Copyright (c) 2014, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "cryptonote_core/blockchain_db.h"
+#include "cryptonote_format_utils.h"
+
+namespace cryptonote
+{
+
+void BlockchainDB::pop_block()
+{
+  block blk;
+  std::vector<transaction> txs;
+  pop_block(blk, txs);
+}
+
+void BlockchainDB::add_transaction(const crypto::hash& blk_hash, const transaction& tx)
+{
+  crypto::hash tx_hash = get_transaction_hash(tx);
+
+  add_transaction_data(blk_hash, tx);
+
+  // iterate tx.vout using indices instead of C++11 foreach syntax because
+  // we need the index
+  for (uint64_t i = 0; i < tx.vout.size(); ++i)
+  {
+    add_output(tx_hash, tx.vout[i], i);
+  }
+
+  for (const txin_v& tx_input : tx.vin)
+  {
+    if (tx_input.type() == typeid(txin_to_key))
+    {
+      add_spent_key(boost::get<txin_to_key>(tx_input).k_image);
+    }
+  }
+}
+
+uint64_t BlockchainDB::add_block( const block& blk
+                  , const size_t& block_size
+                  , const difficulty_type& cumulative_difficulty
+                  , const uint64_t& coins_generated
+                  , const std::vector<transaction>& txs
+                  )
+{
+  try
+  {
+    // call out to subclass implementation to add the block & metadata
+    add_block(blk, block_size, cumulative_difficulty, coins_generated);
+
+    crypto::hash blk_hash = get_block_hash(blk);
+    // call out to add the transactions
+    for (const transaction& tx : txs)
+    {
+      add_transaction(blk_hash, tx);
+    }
+  }
+  // in case any of the add_block process goes awry, undo
+  catch (const std::exception& e)
+  {
+    LOG_ERROR("Error adding block to db: " << e.what());
+    try
+    {
+      pop_block();
+    }
+    // if undoing goes wrong as well, we need to throw, as blockchain
+    // will be in a bad state
+    catch (const std::exception& e)
+    {
+      LOG_ERROR("Error undoing partially added block: " << e.what());
+      throw;
+    }
+    throw;
+  }
+
+  return height();
+}
+
+void BlockchainDB::pop_block(block& blk, std::vector<transaction>& txs)
+{
+  blk = get_top_block();
+  
+  for (const auto& h : blk.tx_hashes)
+  {
+    txs.push_back(get_tx(h));
+    remove_transaction(h);
+  }
+}
+
+void BlockchainDB::remove_transaction(const crypto::hash& tx_hash)
+{
+  transaction tx = get_tx(tx_hash);
+
+  for (const tx_out& tx_output : tx.vout)
+  {
+    remove_output(tx_output);
+  }
+
+  for (const txin_v& tx_input : tx.vin)
+  {
+    if (tx_input.type() == typeid(txin_to_key))
+    {
+      remove_spent_key(boost::get<txin_to_key>(tx_input).k_image);
+    }
+  }
+
+  remove_transaction_data(tx_hash);
+}
+
+}  // namespace cryptonote
diff --git a/src/cryptonote_core/blockchain_db.h b/src/cryptonote_core/blockchain_db.h
new file mode 100644
index 000000000..5728f7065
--- /dev/null
+++ b/src/cryptonote_core/blockchain_db.h
@@ -0,0 +1,510 @@
+// Copyright (c) 2014, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <list>
+#include <string>
+#include <exception>
+#include "crypto/hash.h"
+#include "cryptonote_core/cryptonote_basic.h"
+#include "cryptonote_core/difficulty.h"
+
+/* DB Driver Interface
+ *
+ * The DB interface is a store for the canonical block chain.
+ * It serves as a persistent storage for the blockchain.
+ *
+ * For the sake of efficiency, the reference implementation will also
+ * store some blockchain data outside of the blocks, such as spent
+ * transfer key images, unspent transaction outputs, etc.
+ *
+ * Transactions are duplicated so that we don't have to fetch a whole block
+ * in order to fetch a transaction from that block.  If this is deemed
+ * unnecessary later, this can change.
+ *
+ * Spent key images are duplicated outside of the blocks so it is quick
+ * to verify an output hasn't already been spent
+ *
+ * Unspent transaction outputs are duplicated to quickly gather random
+ * outputs to use for mixins
+ *
+ * IMPORTANT:
+ * A concrete implementation of this interface should populate these
+ * duplicated members!  It is possible to have a partial implementation
+ * of this interface call to private members of the interface to be added
+ * later that will then populate as needed.
+ *
+ * General:
+ *   open()
+ *   close()
+ *   sync()
+ *   reset()
+ *
+ *   Lock and unlock provided for reorg externally, and for block
+ *   additions internally, this way threaded reads are completely fine
+ *   unless the blockchain is changing.
+ *   bool lock()
+ *   unlock()
+ *
+ * Blocks:
+ *   bool        block_exists(hash)
+ *   height      add_block(block, block_size, cumulative_difficulty, coins_generated, transactions)
+ *   block       get_block(hash)
+ *   height      get_block_height(hash)
+ *   header      get_block_header(hash)
+ *   block       get_block_from_height(height)
+ *   size_t      get_block_size(height)
+ *   difficulty  get_block_cumulative_difficulty(height)
+ *   uint64_t    get_block_already_generated_coins(height)
+ *   uint64_t    get_block_timestamp(height) 
+ *   uint64_t    get_top_block_timestamp()
+ *   hash        get_block_hash_from_height(height)
+ *   blocks      get_blocks_range(height1, height2)
+ *   hashes      get_hashes_range(height1, height2)
+ *   hash        top_block_hash()
+ *   block       get_top_block()
+ *   height      height()
+ *   void        pop_block(block&, tx_list&)
+ *
+ * Transactions:
+ *   bool        tx_exists(hash)
+ *   uint64_t    get_tx_unlock_time(hash)
+ *   tx          get_tx(hash)
+ *   uint64_t    get_tx_count()
+ *   tx_list     get_tx_list(hash_list)
+ *   height      get_tx_block_height(hash)
+ *
+ * Outputs:
+ *   index       get_random_output(amount)
+ *   uint64_t    get_num_outputs(amount)
+ *   pub_key     get_output_key(amount, index)
+ *   tx_out      get_output(tx_hash, index)
+ *   hash,index  get_output_tx_and_index(amount, index)
+ *   vec<uint64> get_tx_output_indices(tx_hash)
+ *
+ *
+ * Spent Output Key Images:
+ *   bool        has_key_image(key_image)
+ *
+ * Exceptions:
+ *   DB_ERROR -- generic
+ *   DB_OPEN_FAILURE
+ *   DB_CREATE_FAILURE
+ *   DB_SYNC_FAILURE
+ *   BLOCK_DNE
+ *   BLOCK_PARENT_DNE
+ *   BLOCK_EXISTS
+ *   BLOCK_INVALID -- considering making this multiple errors
+ *   TX_DNE
+ *   TX_EXISTS
+ *   OUTPUT_DNE
+ */
+
+namespace cryptonote
+{
+
+/***********************************
+ * Exception Definitions
+ ***********************************/
+class DB_ERROR : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    DB_ERROR() : m("Generic DB Error") { }
+    DB_ERROR(const char* s) : m(s) { }
+
+    virtual ~DB_ERROR() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class DB_OPEN_FAILURE : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    DB_OPEN_FAILURE() : m("Failed to open the db") { }
+    DB_OPEN_FAILURE(const char* s) : m(s) { }
+
+    virtual ~DB_OPEN_FAILURE() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class DB_CREATE_FAILURE : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    DB_CREATE_FAILURE() : m("Failed to create the db") { }
+    DB_CREATE_FAILURE(const char* s) : m(s) { }
+
+    virtual ~DB_CREATE_FAILURE() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class DB_SYNC_FAILURE : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    DB_SYNC_FAILURE() : m("Failed to sync the db") { }
+    DB_SYNC_FAILURE(const char* s) : m(s) { }
+
+    virtual ~DB_SYNC_FAILURE() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class BLOCK_DNE : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    BLOCK_DNE() : m("The block requested does not exist") { }
+    BLOCK_DNE(const char* s) : m(s) { }
+
+    virtual ~BLOCK_DNE() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class BLOCK_PARENT_DNE : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    BLOCK_PARENT_DNE() : m("The parent of the block does not exist") { }
+    BLOCK_PARENT_DNE(const char* s) : m(s) { }
+
+    virtual ~BLOCK_PARENT_DNE() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class BLOCK_EXISTS : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    BLOCK_EXISTS() : m("The block to be added already exists!") { }
+    BLOCK_EXISTS(const char* s) : m(s) { }
+
+    virtual ~BLOCK_EXISTS() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class BLOCK_INVALID : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    BLOCK_INVALID() : m("The block to be added did not pass validation!") { }
+    BLOCK_INVALID(const char* s) : m(s) { }
+
+    virtual ~BLOCK_INVALID() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class TX_DNE : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    TX_DNE() : m("The transaction requested does not exist") { }
+    TX_DNE(const char* s) : m(s) { }
+
+    virtual ~TX_DNE() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class TX_EXISTS : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    TX_EXISTS() : m("The transaction to be added already exists!") { }
+    TX_EXISTS(const char* s) : m(s) { }
+
+    virtual ~TX_EXISTS() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+class OUTPUT_DNE : public std::exception
+{
+  private:
+    std::string m;
+  public:
+    OUTPUT_DNE() : m("The transaction requested does not exist") { }
+    OUTPUT_DNE(const char* s) : m(s) { }
+
+    virtual ~OUTPUT_DNE() { }
+
+    const char* what() const throw()
+    {
+      return m.c_str();
+    }
+};
+
+/***********************************
+ * End of Exception Definitions
+ ***********************************/
+
+
+class BlockchainDB
+{
+private:
+  /*********************************************************************
+   * private virtual members
+   *********************************************************************/
+
+  // tells the subclass to add the block and metadata to storage
+  virtual void add_block( const block& blk
+                , const size_t& block_size
+                , const difficulty_type& cumulative_difficulty
+                , const uint64_t& coins_generated
+                ) = 0;
+
+  // tells the subclass to remove data about a block
+  virtual void remove_block(const crypto::hash& blk_hash) = 0;
+
+  // tells the subclass to store the transaction and its metadata
+  virtual void add_transaction_data(const crypto::hash& blk_hash, const transaction& tx) = 0;
+
+  // tells the subclass to remove data about a transaction
+  virtual void remove_transaction_data(const crypto::hash& tx_hash) = 0;
+
+  // tells the subclass to store an output
+  virtual void add_output(const crypto::hash& tx_hash, const tx_out& tx_output, const uint64_t& local_index) = 0;
+
+  // tells the subclass to remove an output
+  virtual void remove_output(const tx_out& tx_output) = 0;
+
+  // tells the subclass to store a spent key
+  virtual void add_spent_key(const crypto::key_image& k_image) = 0;
+
+  // tells the subclass to remove a spent key
+  virtual void remove_spent_key(const crypto::key_image& k_image) = 0;
+
+
+  /*********************************************************************
+   * private concrete members
+   *********************************************************************/ 
+  // private version of pop_block, for undoing if an add_block goes tits up
+  void pop_block();
+
+  // helper function for add_transactions, to add each individual tx
+  void add_transaction(const crypto::hash& blk_hash, const transaction& tx);
+
+  // helper function to remove transaction from blockchain
+  void remove_transaction(const crypto::hash& tx_hash);
+
+
+public:
+  // open the db at location <filename>, or create it if there isn't one.
+  virtual void open(const std::string& filename) = 0;
+
+  // make sure implementation has a create function as well
+  virtual void create(const std::string& filename) = 0;
+
+  // close and sync the db
+  virtual void close() = 0;
+
+  // sync the db
+  virtual void sync() = 0;
+
+  // reset the db -- USE WITH CARE
+  virtual void reset() = 0;
+
+
+  // FIXME: these are just for functionality mocking, need to implement
+  // RAII-friendly and multi-read one-write friendly locking mechanism
+  //
+  // acquire db lock
+  virtual bool lock() = 0;
+
+  // release db lock
+  virtual void unlock() = 0;
+
+
+  // adds a block with the given metadata to the top of the blockchain, returns the new height
+  uint64_t add_block( const block& blk
+                    , const size_t& block_size
+                    , const difficulty_type& cumulative_difficulty
+                    , const uint64_t& coins_generated
+                    , const std::vector<transaction>& txs
+                    );
+
+  // return true if a block with hash <h> exists in the blockchain
+  virtual bool block_exists(const crypto::hash& h) = 0;
+
+  // return block with hash <h>
+  virtual block get_block(const crypto::hash& h) = 0;
+
+  // return the height of the block with hash <h> on the blockchain,
+  // throw if it doesn't exist
+  virtual uint64_t get_block_height(const crypto::hash& h) = 0;
+
+  // return header for block with hash <h>
+  virtual block_header get_block_header(const crypto::hash& h) = 0;
+
+  // return block at height <height>
+  virtual block get_block_from_height(const uint64_t& height) = 0;
+
+  // return timestamp of block at height <height>
+  virtual uint64_t get_block_timestamp(const uint64_t& height)  = 0;
+
+  // return timestamp of most recent block
+  virtual uint64_t get_top_block_timestamp() = 0;
+
+  // return block size of block at height <height>
+  virtual size_t get_block_size(const uint64_t& height) = 0;
+
+  // return cumulative difficulty up to and including block at height <height>
+  virtual difficulty_type get_block_cumulative_difficulty(const uint64_t& height) = 0;
+
+  // return difficulty of block at height <height>
+  virtual difficulty_type get_block_difficulty(const uint64_t& height) = 0;
+
+  // return number of coins generated up to and including block at height <height>
+  virtual uint64_t get_block_already_generated_coins(const uint64_t& height) = 0;
+
+  // return hash of block at height <height>
+  virtual crypto::hash get_block_hash_from_height(const uint64_t& height) = 0;
+
+  // return list of blocks in range <h1,h2> of height.
+  virtual std::list<block> get_blocks_range(const uint64_t& h1, const uint64_t& h2) = 0;
+
+  // return list of block hashes in range <h1, h2> of height
+  virtual std::list<crypto::hash> get_hashes_range(const uint64_t& h1, const uint64_t& h2) = 0;
+
+  // return the hash of the top block on the chain
+  virtual crypto::hash top_block_hash() = 0;
+
+  // return the block at the top of the blockchain
+  virtual block get_top_block() = 0;
+
+  // return the index of the top block on the chain
+  // NOTE: for convenience using heights as indices, this is not the total
+  // size of the blockchain, but rather the index of the top block.  As the
+  // chain is 0-indexed, the total size will be height() + 1.
+  virtual uint64_t height() = 0;
+
+  // pops the top block off the blockchain.
+  // Returns by reference the popped block and its associated transactions
+  //
+  // IMPORTANT:
+  // When a block is popped, the transactions associated with it need to be
+  // removed, as well as outputs and spent key images associated with
+  // those transactions.
+  void pop_block(block& blk, std::vector<transaction>& txs);
+
+
+  // return true if a transaction with hash <h> exists
+  virtual bool tx_exists(const crypto::hash& h) = 0;
+
+  // return unlock time of tx with hash <h>
+  virtual uint64_t get_tx_unlock_time(const crypto::hash& h) = 0;
+
+  // return tx with hash <h>
+  // throw if no such tx exists
+  virtual transaction get_tx(const crypto::hash& h) = 0;
+
+  // returns the total number of transactions in all blocks
+  virtual uint64_t get_tx_count() = 0;
+
+  // return list of tx with hashes <hlist>.
+  // TODO: decide if a missing hash means return empty list
+  // or just skip that hash
+  virtual std::list<transaction> get_tx_list(const std::vector<crypto::hash>& hlist) = 0;
+
+  // returns height of block that contains transaction with hash <h>
+  virtual uint64_t get_tx_block_height(const crypto::hash& h) = 0;
+
+  // return global output index of a random output of amount <amount>
+  virtual uint64_t get_random_output(const uint64_t& amount) = 0;
+
+  // returns the total number of outputs of amount <amount>
+  virtual uint64_t get_num_outputs(const uint64_t& amount) = 0;
+
+  // return public key for output with global output amount <amount> and index <index>
+  virtual crypto::public_key get_output_key(const uint64_t& amount, const uint64_t& index) = 0;
+
+  // returns the output indexed by <index> in the transaction with hash <h>
+  virtual tx_out get_output(const crypto::hash& h, const uint64_t& index) = 0;
+
+  // returns the transaction-local reference for the output with <amount> at <index>
+  // return type is pair of tx hash and index
+  virtual tx_out_index get_output_tx_and_index(const uint64_t& amount, const uint64_t& index) = 0;
+
+  // return a vector of indices corresponding to the global output index for
+  // each output in the transaction with hash <h>
+  virtual std::vector<uint64_t> get_tx_output_indices(const crypto::hash& h) = 0;
+
+  // returns true if key image <img> is present in spent key images storage
+  virtual bool has_key_image(const crypto::key_image& img) = 0;
+
+};  // class BlockchainDB
+
+
+}  // namespace cryptonote