monero/src/crypto/tree-hash.c

// 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 <alloca.h>
#include <assert.h>
#include <stddef.h>
#include <string.h>

#include "hash-ops.h"

void tree_hash(const char (*hashes)[HASH_SIZE], size_t count, char *root_hash) {
  assert(count > 0);
  if (count == 1) {
    memcpy(root_hash, hashes, HASH_SIZE);
  } else if (count == 2) {
    cn_fast_hash(hashes, 2 * HASH_SIZE, root_hash);
  } else {
    size_t i, j;
    size_t cnt = count - 1;
    char (*ints)[HASH_SIZE];
    for (i = 1; i < sizeof(size_t); i <<= 1) {
      cnt |= cnt >> i;
    }
    cnt &= ~(cnt >> 1);
    ints = alloca(cnt * HASH_SIZE);
    memcpy(ints, hashes, (2 * cnt - count) * HASH_SIZE);
    for (i = 2 * cnt - count, j = 2 * cnt - count; j < cnt; i += 2, ++j) {
      cn_fast_hash(hashes[i], 64, ints[j]);
    }
    assert(i == count);
    while (cnt > 2) {
      cnt >>= 1;
      for (i = 0, j = 0; j < cnt; i += 2, ++j) {
        cn_fast_hash(ints[i], 64, ints[j]);
      }
    }
    cn_fast_hash(ints[0], 64, root_hash);
  }
}