Method GetString

src/types/redis_bitmap.cc:139–180

Use this function after careful estimation, and reserve enough memory according to the max size of the bitmap string to prevent OOM.

// Use this function after careful estimation, and reserve enough memory
// according to the max size of the bitmap string to prevent OOM.
rocksdb::Status Bitmap::GetString(engine::Context &ctx, const Slice &user_key, const uint32_t max_btos_size,
                                  std::string *value) {
  value->clear();
  std::string raw_value;
  std::string ns_key = AppendNamespacePrefix(user_key);

  BitmapMetadata metadata(false);
  rocksdb::Status s = GetMetadata(ctx, ns_key, &metadata, &raw_value);
  if (!s.ok()) return s;
  if (metadata.size > max_btos_size) {
    return rocksdb::Status::Aborted(kErrBitmapStringOutOfRange);
  }
  value->assign(metadata.size, 0);

  std::string prefix_key = InternalKey(ns_key, "", metadata.version, storage_->IsSlotIdEncoded()).Encode();

  rocksdb::ReadOptions read_options = ctx.DefaultScanOptions();
  Slice prefix_key_slice(prefix_key);
  read_options.iterate_lower_bound = &prefix_key_slice;

  auto iter = util::UniqueIterator(ctx, read_options);
  for (iter->Seek(prefix_key); iter->Valid() && iter->key().starts_with(prefix_key); iter->Next()) {
    InternalKey ikey(iter->key(), storage_->IsSlotIdEncoded());
    auto parse_result = ParseInt<uint32_t>(ikey.GetSubKey().ToString(), 10);
    if (!parse_result) {
      return rocksdb::Status::InvalidArgument(parse_result.Msg());
    }
    uint32_t frag_index = *parse_result;
    std::string fragment = iter->value().ToString();
    // To be compatible with data written before the commit d603b0e(#338)
    // and avoid returning extra null char after expansion.
    uint32_t valid_size = std::min(
        {fragment.size(), static_cast<size_t>(kBitmapSegmentBytes), static_cast<size_t>(metadata.size - frag_index)});

    for (uint32_t i = 0; i < valid_size; i++) {
      if (!fragment[i]) continue;
      fragment[i] = static_cast<char>(kBitSwapTable[static_cast<uint8_t>(fragment[i])]);
    }
    value->replace(frag_index, valid_size, fragment.data(), valid_size);
  }
  return rocksdb::Status::OK();
}

rocksdb::Status Bitmap::SetBit(engine::Context &ctx, const Slice &user_key, uint32_t bit_offset, bool new_bit,
                               bool *old_bit) {