// Copyright (c) 2012-2013 The Cryptonote developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#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) << 3; 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], 2 * HASH_SIZE, 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], 2 * HASH_SIZE, root_hash);
  }
}

size_t tree_depth(size_t count)
{
  size_t i;
  size_t depth = 0;
  assert(count > 0);
  for (i = sizeof(size_t) << 2; i > 0; i >>= 1)
  {
    if (count >> i > 0)
    {
      count >>= i;
      depth += i;
    }
  }
  return depth;
}

void tree_branch(const char (*hashes)[HASH_SIZE], size_t count, char (*branch)[HASH_SIZE])
{
  size_t i, j;
  size_t cnt = 1;
  size_t depth = 0;
  char (*ints)[HASH_SIZE];
  assert(count > 0);
  for (i = sizeof(size_t) << 2; i > 0; i >>= 1)
  {
    if (cnt << i <= count)
    {
      cnt <<= i;
      depth += i;
    }
  }
  assert(cnt == 1ULL << depth);
  assert(depth == tree_depth(count));
  ints = alloca((cnt - 1) * HASH_SIZE);
  memcpy(ints, hashes + 1, (2 * cnt - count - 1) * HASH_SIZE);
  for (i = 2 * cnt - count, j = 2 * cnt - count - 1; j < cnt - 1; i += 2, ++j)
  {
    cn_fast_hash(hashes[i], 2 * HASH_SIZE, ints[j]);
  }
  assert(i == count);
  while (depth > 0)
  {
    assert(cnt == 1ULL << depth);
    cnt >>= 1;
    --depth;
    memcpy(branch[depth], ints[0], HASH_SIZE);
    for (i = 1, j = 0; j < cnt - 1; i += 2, ++j)
    {
      cn_fast_hash(ints[i], 2 * HASH_SIZE, ints[j]);
    }
  }
}

void tree_hash_from_branch(const char (*branch)[HASH_SIZE], size_t depth, const char* leaf, const void* path, char* root_hash)
{
  if (depth == 0)
  {
    memcpy(root_hash, leaf, HASH_SIZE);
  }
  else
  {
    char buffer[2][HASH_SIZE];
    int from_leaf = 1;
    char *leaf_path, *branch_path;
    while (depth > 0)
    {
      --depth;
      if (path && (((const char*) path)[depth >> 3] & (1 << (depth & 7))) != 0)
      {
        leaf_path = buffer[1];
        branch_path = buffer[0];
      }
      else
      {
        leaf_path = buffer[0];
        branch_path = buffer[1];
      }
      if (from_leaf)
      {
        memcpy(leaf_path, leaf, HASH_SIZE);
        from_leaf = 0;
      }
      else
      {
        cn_fast_hash(buffer, 2 * HASH_SIZE, leaf_path);
      }
      memcpy(branch_path, branch[depth], HASH_SIZE);
    }
    cn_fast_hash(buffer, 2 * HASH_SIZE, root_hash);
  }
}