// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <string.h>

#include "base/numerics/safe_math.h"
#include "third_party/hunspell/google/bdict.h"

// static
bool hunspell::BDict::Verify(const char* bdict_data, size_t bdict_length) {
  if (bdict_length <= sizeof(hunspell::BDict::Header))
    return false;

  const BDict::Header* header =
      reinterpret_cast<const hunspell::BDict::Header*>(bdict_data);
  if (header->signature != hunspell::BDict::SIGNATURE ||
      header->major_version > hunspell::BDict::MAJOR_VERSION ||
      header->aff_offset > bdict_length ||
      header->dic_offset > bdict_length) {
    return false;
  }

  {
    // Make sure there is enough room for the affix header.
    base::CheckedNumeric<uint32_t> aff_offset(header->aff_offset);
    aff_offset += sizeof(hunspell::BDict::AffHeader);
    if (!aff_offset.IsValid() || aff_offset.ValueOrDie() > bdict_length)
      return false;
  }

  const hunspell::BDict::AffHeader* aff_header =
      reinterpret_cast<const hunspell::BDict::AffHeader*>(
          &bdict_data[header->aff_offset]);

  // Make sure there is enough room for the affix group count dword.
  {
    base::CheckedNumeric<uint32_t> affix_group_offset(
        aff_header->affix_group_offset);
    affix_group_offset += sizeof(uint32_t);
    if (!affix_group_offset.IsValid() ||
        affix_group_offset.ValueOrDie() > bdict_length) {
      return false;
    }
  }

  // The new BDICT header has a MD5 digest of the dictionary data. Compare the
  // MD5 digest of the data with the one in the BDICT header.
  if (header->major_version >= 2) {
    base::MD5Digest digest;
    base::MD5Sum(aff_header, bdict_length - header->aff_offset, &digest);
    if (memcmp(&digest, &header->digest, sizeof(digest)))
      return false;
  }

  return true;
}