Pruning

The blockchain prunes seven eighths of prunable tx data.
This saves about two thirds of the blockchain size, while
keeping the node useful as a sync source for an eighth
of the blockchain.

No other data is currently pruned.

There are three ways to prune a blockchain:

- run monerod with --prune-blockchain
- run "prune_blockchain" in the monerod console
- run the monero-blockchain-prune utility

The first two will prune in place. Due to how LMDB works, this
will not reduce the blockchain size on disk. Instead, it will
mark parts of the file as free, so that future data will use
that free space, causing the file to not grow until free space
grows scarce.

The third way will create a second database, a pruned copy of
the original one. Since this is a new file, this one will be
smaller than the original one.

Once the database is pruned, it will stay pruned as it syncs.
That is, there is no need to use --prune-blockchain again, etc.

4 files changed, 171 insertions, 1 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 3b1eb6d23..212a1891e 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -40,6 +40,7 @@ set(common_sources
   notify.cpp
   password.cpp
   perf_timer.cpp
+  pruning.cpp
   spawn.cpp
   threadpool.cpp
   updates.cpp
@@ -69,6 +70,7 @@ set(common_private_headers
   http_connection.h
   notify.h
   pod-class.h
+  pruning.h
   rpc_client.h
   scoped_message_writer.h
   unordered_containers_boost_serialization.h
diff --git a/src/common/pruning.cpp b/src/common/pruning.cpp
new file mode 100644
index 000000000..442b24e4e
--- /dev/null
+++ b/src/common/pruning.cpp
@@ -0,0 +1,116 @@
+// Copyright (c) 2018, 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_config.h"
+#include "misc_log_ex.h"
+#include "crypto/crypto.h"
+#include "pruning.h"
+
+namespace tools
+{
+
+uint32_t make_pruning_seed(uint32_t stripe, uint32_t log_stripes)
+{
+  CHECK_AND_ASSERT_THROW_MES(log_stripes <= PRUNING_SEED_LOG_STRIPES_MASK, "log_stripes out of range");
+  CHECK_AND_ASSERT_THROW_MES(stripe > 0 && stripe <= (1ul << log_stripes), "stripe out of range");
+  return (log_stripes << PRUNING_SEED_LOG_STRIPES_SHIFT) | ((stripe - 1) << PRUNING_SEED_STRIPE_SHIFT);
+}
+
+bool has_unpruned_block(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed)
+{
+  const uint32_t stripe = get_pruning_stripe(pruning_seed);
+  if (stripe == 0)
+    return true;
+  const uint32_t log_stripes = get_pruning_log_stripes(pruning_seed);
+  uint32_t block_stripe = get_pruning_stripe(block_height, blockchain_height, log_stripes);
+  return block_stripe == 0 || block_stripe == stripe;
+}
+
+uint32_t get_pruning_stripe(uint64_t block_height, uint64_t blockchain_height, uint32_t log_stripes)
+{
+  if (block_height + CRYPTONOTE_PRUNING_TIP_BLOCKS >= blockchain_height)
+    return 0;
+  return ((block_height / CRYPTONOTE_PRUNING_STRIPE_SIZE) & (uint64_t)((1ul << log_stripes) - 1)) + 1;
+}
+
+uint32_t get_pruning_seed(uint64_t block_height, uint64_t blockchain_height, uint32_t log_stripes)
+{
+  const uint32_t stripe = get_pruning_stripe(block_height, blockchain_height, log_stripes);
+  if (stripe == 0)
+    return 0;
+  return make_pruning_seed(stripe, log_stripes);
+}
+
+uint64_t get_next_unpruned_block_height(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed)
+{
+  CHECK_AND_ASSERT_MES(block_height <= CRYPTONOTE_MAX_BLOCK_NUMBER+1, block_height, "block_height too large");
+  CHECK_AND_ASSERT_MES(blockchain_height <= CRYPTONOTE_MAX_BLOCK_NUMBER+1, block_height, "blockchain_height too large");
+  const uint32_t stripe = get_pruning_stripe(pruning_seed);
+  if (stripe == 0)
+    return block_height;
+  if (block_height + CRYPTONOTE_PRUNING_TIP_BLOCKS >= blockchain_height)
+    return block_height;
+  const uint32_t seed_log_stripes = get_pruning_log_stripes(pruning_seed);
+  const uint64_t log_stripes = seed_log_stripes ? seed_log_stripes : CRYPTONOTE_PRUNING_LOG_STRIPES;
+  const uint64_t mask = (1ul << log_stripes) - 1;
+  const uint32_t block_pruning_stripe = ((block_height / CRYPTONOTE_PRUNING_STRIPE_SIZE) & mask) + 1;
+  if (block_pruning_stripe == stripe)
+    return block_height;
+  const uint64_t cycles = ((block_height / CRYPTONOTE_PRUNING_STRIPE_SIZE) >> log_stripes);
+  const uint64_t cycle_start = cycles + ((stripe > block_pruning_stripe) ? 0 : 1);
+  const uint64_t h = cycle_start * (CRYPTONOTE_PRUNING_STRIPE_SIZE << log_stripes) + (stripe - 1) * CRYPTONOTE_PRUNING_STRIPE_SIZE;
+  if (h + CRYPTONOTE_PRUNING_TIP_BLOCKS > blockchain_height)
+    return blockchain_height < CRYPTONOTE_PRUNING_TIP_BLOCKS ? 0 : blockchain_height - CRYPTONOTE_PRUNING_TIP_BLOCKS;
+  CHECK_AND_ASSERT_MES(h >= block_height, block_height, "h < block_height, unexpected");
+  return h;
+}
+
+uint64_t get_next_pruned_block_height(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed)
+{
+  const uint32_t stripe = get_pruning_stripe(pruning_seed);
+  if (stripe == 0)
+    return blockchain_height;
+  if (block_height + CRYPTONOTE_PRUNING_TIP_BLOCKS >= blockchain_height)
+    return blockchain_height;
+  const uint32_t seed_log_stripes = get_pruning_log_stripes(pruning_seed);
+  const uint64_t log_stripes = seed_log_stripes ? seed_log_stripes : CRYPTONOTE_PRUNING_LOG_STRIPES;
+  const uint64_t mask = (1ul << log_stripes) - 1;
+  const uint32_t block_pruning_seed = ((block_height / CRYPTONOTE_PRUNING_STRIPE_SIZE) & mask) + 1;
+  if (block_pruning_seed != stripe)
+    return block_height;
+  const uint32_t next_stripe = 1 + (block_pruning_seed & mask);
+  return get_next_unpruned_block_height(block_height, blockchain_height, tools::make_pruning_seed(next_stripe, log_stripes));
+}
+
+uint32_t get_random_stripe()
+{
+  return 1 + crypto::rand<uint8_t>() % (1ul << CRYPTONOTE_PRUNING_LOG_STRIPES);
+}
+
+}
+
diff --git a/src/common/pruning.h b/src/common/pruning.h
new file mode 100644
index 000000000..3fac3c0fa
--- /dev/null
+++ b/src/common/pruning.h
@@ -0,0 +1,52 @@
+// Copyright (c) 2018, 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.
+
+#pragma once
+
+#include <stdint.h>
+
+namespace tools
+{
+  static constexpr uint32_t PRUNING_SEED_LOG_STRIPES_SHIFT = 7;
+  static constexpr uint32_t PRUNING_SEED_LOG_STRIPES_MASK = 0x7;
+  static constexpr uint32_t PRUNING_SEED_STRIPE_SHIFT = 0;
+  static constexpr uint32_t PRUNING_SEED_STRIPE_MASK = 0x7f;
+
+  constexpr inline uint32_t get_pruning_log_stripes(uint32_t pruning_seed) { return (pruning_seed >> PRUNING_SEED_LOG_STRIPES_SHIFT) & PRUNING_SEED_LOG_STRIPES_MASK; }
+  inline uint32_t get_pruning_stripe(uint32_t pruning_seed) { if (pruning_seed == 0) return 0; return 1 + ((pruning_seed >> PRUNING_SEED_STRIPE_SHIFT) & PRUNING_SEED_STRIPE_MASK); }
+
+  uint32_t make_pruning_seed(uint32_t stripe, uint32_t log_stripes);
+
+  bool has_unpruned_block(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed);
+  uint32_t get_pruning_stripe(uint64_t block_height, uint64_t blockchain_height, uint32_t log_stripes);
+  uint32_t get_pruning_seed(uint64_t block_height, uint64_t blockchain_height, uint32_t log_stripes);
+  uint64_t get_next_unpruned_block_height(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed);
+  uint64_t get_next_pruned_block_height(uint64_t block_height, uint64_t blockchain_height, uint32_t pruning_seed);
+  uint32_t get_random_stripe();
+}
+
diff --git a/src/common/varint.h b/src/common/varint.h
index 151d13dbf..904255afc 100644
--- a/src/common/varint.h
+++ b/src/common/varint.h
@@ -123,6 +123,6 @@ namespace tools {
    */
   template<typename InputIt, typename T>
     int read_varint(InputIt &&first, InputIt &&last, T &i) {
-    return read_varint<std::numeric_limits<T>::digits, InputIt, T>(std::move(first), std::move(last), i);
+    return read_varint<std::numeric_limits<T>::digits>(std::forward<InputIt>(first), std::forward<InputIt>(last), i);
   }
 }