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diff --git a/src/cryptonote_basic/hardfork.cpp b/src/cryptonote_basic/hardfork.cpp
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+++ b/src/cryptonote_basic/hardfork.cpp
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+// Copyright (c) 2014-2017, 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 <algorithm>
+#include <cstdio>
+
+#include "cryptonote_basic/cryptonote_basic.h"
+#include "blockchain_db/blockchain_db.h"
+#include "hardfork.h"
+
+#undef MONERO_DEFAULT_LOG_CATEGORY
+#define MONERO_DEFAULT_LOG_CATEGORY "hardfork"
+
+using namespace cryptonote;
+
+static uint8_t get_block_vote(const cryptonote::block &b)
+{
+  // Pre-hardfork blocks have a minor version hardcoded to 0.
+  // For the purposes of voting, we consider 0 to refer to
+  // version number 1, which is what all blocks from the genesis
+  // block are. It makes things simpler.
+  if (b.minor_version == 0)
+    return 1;
+  return b.minor_version;
+}
+
+static uint8_t get_block_version(const cryptonote::block &b)
+{
+  return b.major_version;
+}
+
+HardFork::HardFork(cryptonote::BlockchainDB &db, uint8_t original_version, uint64_t original_version_till_height, time_t forked_time, time_t update_time, uint64_t window_size, uint8_t default_threshold_percent):
+  db(db),
+  original_version(original_version),
+  original_version_till_height(original_version_till_height),
+  forked_time(forked_time),
+  update_time(update_time),
+  window_size(window_size),
+  default_threshold_percent(default_threshold_percent)
+{
+  if (window_size == 0)
+    throw "window_size needs to be strictly positive";
+  if (default_threshold_percent > 100)
+    throw "default_threshold_percent needs to be between 0 and 100";
+}
+
+bool HardFork::add_fork(uint8_t version, uint64_t height, uint8_t threshold, time_t time)
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  // add in order
+  if (version == 0)
+    return false;
+  if (!heights.empty()) {
+    if (version <= heights.back().version)
+      return false;
+    if (height <= heights.back().height)
+      return false;
+    if (time <= heights.back().time)
+      return false;
+  }
+  if (threshold > 100)
+    return false;
+  heights.push_back(Params(version, height, threshold, time));
+  return true;
+}
+
+bool HardFork::add_fork(uint8_t version, uint64_t height, time_t time)
+{
+  return add_fork(version, height, default_threshold_percent, time);
+}
+
+uint8_t HardFork::get_effective_version(uint8_t voting_version) const
+{
+  if (!heights.empty()) {
+    uint8_t max_version = heights.back().version;
+    if (voting_version > max_version)
+      voting_version = max_version;
+  }
+  return voting_version;
+}
+
+bool HardFork::do_check(uint8_t block_version, uint8_t voting_version) const
+{
+  return block_version == heights[current_fork_index].version
+      && voting_version >= heights[current_fork_index].version;
+}
+
+bool HardFork::check(const cryptonote::block &block) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  return do_check(::get_block_version(block), ::get_block_vote(block));
+}
+
+bool HardFork::do_check_for_height(uint8_t block_version, uint8_t voting_version, uint64_t height) const
+{
+  int fork_index = get_voted_fork_index(height);
+  return block_version == heights[fork_index].version
+      && voting_version >= heights[fork_index].version;
+}
+
+bool HardFork::check_for_height(const cryptonote::block &block, uint64_t height) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  return do_check_for_height(::get_block_version(block), ::get_block_vote(block), height);
+}
+
+bool HardFork::add(uint8_t block_version, uint8_t voting_version, uint64_t height)
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  if (!do_check(block_version, voting_version))
+    return false;
+
+  db.set_hard_fork_version(height, heights[current_fork_index].version);
+
+  voting_version = get_effective_version(voting_version);
+
+  while (versions.size() >= window_size) {
+    const uint8_t old_version = versions.front();
+    assert(last_versions[old_version] >= 1);
+    last_versions[old_version]--;
+    versions.pop_front();
+  }
+
+  last_versions[voting_version]++;
+  versions.push_back(voting_version);
+
+  uint8_t voted = get_voted_fork_index(height + 1);
+  if (voted > current_fork_index) {
+    current_fork_index = voted;
+  }
+
+  return true;
+}
+
+bool HardFork::add(const cryptonote::block &block, uint64_t height)
+{
+  return add(::get_block_version(block), ::get_block_vote(block), height);
+}
+
+void HardFork::init()
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  // add a placeholder for the default version, to avoid special cases
+  if (heights.empty())
+    heights.push_back(Params(original_version, 0, 0, 0));
+
+  versions.clear();
+  for (size_t n = 0; n < 256; ++n)
+    last_versions[n] = 0;
+  current_fork_index = 0;
+
+  // restore state from DB
+  uint64_t height = db.height();
+  if (height > window_size)
+    height -= window_size - 1;
+  else
+    height = 1;
+
+  bool populate = false;
+  try
+  {
+    db.get_hard_fork_version(0);
+  }
+  catch (...) { populate = true; }
+  if (populate) {
+    MINFO("The DB has no hard fork info, reparsing from start");
+    height = 1;
+  }
+  MDEBUG("reorganizing from " << height);
+  if (populate) {
+    reorganize_from_chain_height(height);
+    // reorg will not touch the genesis block, use this as a flag for populating done
+    db.set_hard_fork_version(0, original_version);
+  }
+  else {
+    rescan_from_chain_height(height);
+  }
+  MDEBUG("reorganization done");
+}
+
+uint8_t HardFork::get_block_version(uint64_t height) const
+{
+  if (height <= original_version_till_height)
+    return original_version;
+
+  const cryptonote::block &block = db.get_block_from_height(height);
+  return ::get_block_version(block);
+}
+
+bool HardFork::reorganize_from_block_height(uint64_t height)
+{
+  CRITICAL_REGION_LOCAL(lock);
+  if (height >= db.height())
+    return false;
+
+  db.set_batch_transactions(true);
+  bool stop_batch = db.batch_start();
+
+  versions.clear();
+
+  for (size_t n = 0; n < 256; ++n)
+    last_versions[n] = 0;
+  const uint64_t rescan_height = height >= (window_size - 1) ? height - (window_size  -1) : 0;
+  const uint8_t start_version = height == 0 ? original_version : db.get_hard_fork_version(height);
+  while (current_fork_index > 0 && heights[current_fork_index].version > start_version) {
+    --current_fork_index;
+  }
+  for (uint64_t h = rescan_height; h <= height; ++h) {
+    cryptonote::block b = db.get_block_from_height(h);
+    const uint8_t v = get_effective_version(get_block_vote(b));
+    last_versions[v]++;
+    versions.push_back(v);
+  }
+
+  uint8_t voted = get_voted_fork_index(height + 1);
+  if (voted > current_fork_index) {
+    current_fork_index = voted;
+  }
+
+  const uint64_t bc_height = db.height();
+  for (uint64_t h = height + 1; h < bc_height; ++h) {
+    add(db.get_block_from_height(h), h);
+  }
+
+  if (stop_batch)
+    db.batch_stop();
+
+  return true;
+}
+
+bool HardFork::reorganize_from_chain_height(uint64_t height)
+{
+  if (height == 0)
+    return false;
+  return reorganize_from_block_height(height - 1);
+}
+
+bool HardFork::rescan_from_block_height(uint64_t height)
+{
+  CRITICAL_REGION_LOCAL(lock);
+  db.block_txn_start(true);
+  if (height >= db.height()) {
+    db.block_txn_stop();
+    return false;
+  }
+
+  versions.clear();
+
+  for (size_t n = 0; n < 256; ++n)
+    last_versions[n] = 0;
+  for (uint64_t h = height; h < db.height(); ++h) {
+    cryptonote::block b = db.get_block_from_height(h);
+    const uint8_t v = get_effective_version(get_block_vote(b));
+    last_versions[v]++;
+    versions.push_back(v);
+  }
+
+  uint8_t lastv = db.get_hard_fork_version(db.height() - 1);
+  current_fork_index = 0;
+  while (current_fork_index + 1 < heights.size() && heights[current_fork_index].version != lastv)
+    ++current_fork_index;
+
+  uint8_t voted = get_voted_fork_index(db.height());
+  if (voted > current_fork_index) {
+    current_fork_index = voted;
+  }
+
+  db.block_txn_stop();
+
+  return true;
+}
+
+bool HardFork::rescan_from_chain_height(uint64_t height)
+{
+  if (height == 0)
+    return false;
+  return rescan_from_block_height(height - 1);
+}
+
+int HardFork::get_voted_fork_index(uint64_t height) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  uint32_t accumulated_votes = 0;
+  for (unsigned int n = heights.size() - 1; n > current_fork_index; --n) {
+    uint8_t v = heights[n].version;
+    accumulated_votes += last_versions[v];
+    uint32_t threshold = (window_size * heights[n].threshold + 99) / 100;
+    if (height >= heights[n].height && accumulated_votes >= threshold) {
+      return n;
+    }
+  }
+  return current_fork_index;
+}
+
+HardFork::State HardFork::get_state(time_t t) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  // no hard forks setup yet
+  if (heights.size() <= 1)
+    return Ready;
+
+  time_t t_last_fork = heights.back().time;
+  if (t >= t_last_fork + forked_time)
+    return LikelyForked;
+  if (t >= t_last_fork + update_time)
+    return UpdateNeeded;
+  return Ready;
+}
+
+HardFork::State HardFork::get_state() const
+{
+  return get_state(time(NULL));
+}
+
+uint8_t HardFork::get(uint64_t height) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  if (height > db.height()) {
+    assert(false);
+    return 255;
+  }
+  if (height == db.height()) {
+    return get_current_version();
+  }
+  return db.get_hard_fork_version(height);
+}
+
+uint8_t HardFork::get_current_version() const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  return heights[current_fork_index].version;
+}
+
+uint8_t HardFork::get_ideal_version() const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  return heights.back().version;
+}
+
+uint8_t HardFork::get_ideal_version(uint64_t height) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  for (unsigned int n = heights.size() - 1; n > 0; --n) {
+    if (height >= heights[n].height) {
+      return heights[n].version;
+    }
+  }
+  return original_version;
+}
+
+uint64_t HardFork::get_earliest_ideal_height_for_version(uint8_t version) const
+{
+  for (unsigned int n = heights.size() - 1; n > 0; --n) {
+    if (heights[n].version <= version)
+      return heights[n].height;
+  }
+  return 0;
+}
+
+uint8_t HardFork::get_next_version() const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  uint64_t height = db.height();
+  for (unsigned int n = heights.size() - 1; n > 0; --n) {
+    if (height >= heights[n].height) {
+      return heights[n < heights.size() - 1 ? n + 1 : n].version;
+    }
+  }
+  return original_version;
+}
+
+bool HardFork::get_voting_info(uint8_t version, uint32_t &window, uint32_t &votes, uint32_t &threshold, uint64_t &earliest_height, uint8_t &voting) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  const uint8_t current_version = heights[current_fork_index].version;
+  const bool enabled = current_version >= version;
+  window = versions.size();
+  votes = 0;
+  for (size_t n = version; n < 256; ++n)
+      votes += last_versions[n];
+  threshold = (window * heights[current_fork_index].threshold + 99) / 100;
+  //assert((votes >= threshold) == enabled);
+  earliest_height = get_earliest_ideal_height_for_version(version);
+  voting = heights.back().version;
+  return enabled;
+}
+