From 275894cdefeb80095b4b3463ec732c6e728f91b9 Mon Sep 17 00:00:00 2001 From: moneromooo-monero Date: Sun, 9 Aug 2015 18:07:44 +0100 Subject: [PATCH] blockchain: always select random outs using triangular distribution It was only used by the older blockchain_storage. We also move the code to the calling blockchain level, to avoid replicating the code in every DB implementation. This also makes the get_random_out method obsolete, and we delete it. --- src/blockchain_db/berkeleydb/db_bdb.cpp | 13 ------------- src/blockchain_db/berkeleydb/db_bdb.h | 2 -- src/blockchain_db/blockchain_db.h | 4 ---- src/blockchain_db/lmdb/db_lmdb.cpp | 13 ------------- src/blockchain_db/lmdb/db_lmdb.h | 2 -- src/cryptonote_core/blockchain.cpp | 10 +++++++++- 6 files changed, 9 insertions(+), 35 deletions(-) diff --git a/src/blockchain_db/berkeleydb/db_bdb.cpp b/src/blockchain_db/berkeleydb/db_bdb.cpp index ad3febbd1..a990d7aaf 100644 --- a/src/blockchain_db/berkeleydb/db_bdb.cpp +++ b/src/blockchain_db/berkeleydb/db_bdb.cpp @@ -1264,19 +1264,6 @@ uint64_t BlockchainBDB::get_tx_block_height(const crypto::hash& h) const return (uint64_t)result - 1; } -//FIXME: make sure the random method used here is appropriate -uint64_t BlockchainBDB::get_random_output(const uint64_t& amount) const -{ - LOG_PRINT_L3("BlockchainBDB::" << __func__); - check_open(); - - uint64_t num_outputs = get_num_outputs(amount); - if (num_outputs == 0) - throw1(OUTPUT_DNE("Attempting to get a random output for an amount, but none exist")); - - return crypto::rand() % num_outputs; -} - uint64_t BlockchainBDB::get_num_outputs(const uint64_t& amount) const { LOG_PRINT_L3("BlockchainBDB::" << __func__); diff --git a/src/blockchain_db/berkeleydb/db_bdb.h b/src/blockchain_db/berkeleydb/db_bdb.h index 41f4bcb78..f92bbef68 100644 --- a/src/blockchain_db/berkeleydb/db_bdb.h +++ b/src/blockchain_db/berkeleydb/db_bdb.h @@ -295,8 +295,6 @@ public: virtual uint64_t get_tx_block_height(const crypto::hash& h) const; - virtual uint64_t get_random_output(const uint64_t& amount) const; - virtual uint64_t get_num_outputs(const uint64_t& amount) const; virtual output_data_t get_output_key(const uint64_t& amount, const uint64_t& index); diff --git a/src/blockchain_db/blockchain_db.h b/src/blockchain_db/blockchain_db.h index ff15109b0..25a34fc09 100644 --- a/src/blockchain_db/blockchain_db.h +++ b/src/blockchain_db/blockchain_db.h @@ -104,7 +104,6 @@ * 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) @@ -463,9 +462,6 @@ public: // returns height of block that contains transaction with hash virtual uint64_t get_tx_block_height(const crypto::hash& h) const = 0; - // return global output index of a random output of amount - virtual uint64_t get_random_output(const uint64_t& amount) const = 0; - // returns the total number of outputs of amount virtual uint64_t get_num_outputs(const uint64_t& amount) const = 0; diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp index dd829f3b0..d231322f6 100644 --- a/src/blockchain_db/lmdb/db_lmdb.cpp +++ b/src/blockchain_db/lmdb/db_lmdb.cpp @@ -1620,19 +1620,6 @@ uint64_t BlockchainLMDB::get_tx_block_height(const crypto::hash& h) const return *(const uint64_t*)result.mv_data; } -//FIXME: make sure the random method used here is appropriate -uint64_t BlockchainLMDB::get_random_output(const uint64_t& amount) const -{ - LOG_PRINT_L3("BlockchainLMDB::" << __func__); - check_open(); - - uint64_t num_outputs = get_num_outputs(amount); - if (num_outputs == 0) - throw1(OUTPUT_DNE("Attempting to get a random output for an amount, but none exist")); - - return crypto::rand() % num_outputs; -} - uint64_t BlockchainLMDB::get_num_outputs(const uint64_t& amount) const { LOG_PRINT_L3("BlockchainLMDB::" << __func__); diff --git a/src/blockchain_db/lmdb/db_lmdb.h b/src/blockchain_db/lmdb/db_lmdb.h index 0facb8713..b4c197803 100644 --- a/src/blockchain_db/lmdb/db_lmdb.h +++ b/src/blockchain_db/lmdb/db_lmdb.h @@ -157,8 +157,6 @@ public: virtual uint64_t get_tx_block_height(const crypto::hash& h) const; - virtual uint64_t get_random_output(const uint64_t& amount) const; - virtual uint64_t get_num_outputs(const uint64_t& amount) const; virtual output_data_t get_output_key(const uint64_t& amount, const uint64_t& index); diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp index cc2d6f821..8a81268ab 100644 --- a/src/cryptonote_core/blockchain.cpp +++ b/src/cryptonote_core/blockchain.cpp @@ -1511,7 +1511,15 @@ bool Blockchain::get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUT // 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); + + // triangular distribution over [a,b) with a=0, mode c=b=up_index_limit + uint64_t r = crypto::rand() % ((uint64_t)1 << 53); + double frac = std::sqrt((double)r / ((uint64_t)1 << 53)); + uint64_t i = (uint64_t)(frac*num_outs); + // just in case rounding up to 1 occurs after sqrt + if (i == num_outs) + --i; + if (seen_indices.count(i)) { continue;