Method CompressBuffer

cpp/src/arrow/ipc/writer.cc:196–236

  }

  Status CompressBuffer(const Buffer& buffer, util::Codec* codec,
                        std::shared_ptr<Buffer>* out) {
    // Convert buffer to uncompressed-length-prefixed buffer. The actual body may or may
    // not be compressed, depending on user-preference and projected size reduction.
    int64_t maximum_length = codec->MaxCompressedLen(buffer.size(), buffer.data());
    int64_t prefixed_length = buffer.size();

    ARROW_ASSIGN_OR_RAISE(
        auto result,
        AllocateResizableBuffer(maximum_length + sizeof(int64_t), options_.memory_pool));
    ARROW_ASSIGN_OR_RAISE(auto actual_length,
                          codec->Compress(buffer.size(), buffer.data(), maximum_length,
                                          result->mutable_data() + sizeof(int64_t)));
    // FIXME: Not the most sophisticated way to handle this. Ideally, you'd want to avoid
    // pre-compressing the entire buffer via some kind of sampling method. As the feature
    // gains adoption, this may become a worthwhile optimization.
    //
    // See: GH-33885
    if (!ShouldCompress(buffer.size(), actual_length)) {
      if (buffer.size() < actual_length || buffer.size() > maximum_length) {
        RETURN_NOT_OK(
            result->Resize(buffer.size() + sizeof(int64_t), /*shrink_to_fit=*/false));
        result->ZeroPadding();
      }
      std::memcpy(result->mutable_data() + sizeof(int64_t), buffer.data(),
                  static_cast<size_t>(buffer.size()));
      actual_length = buffer.size();
      // Size of -1 indicates to the reader that the body doesn't need to be decompressed
      prefixed_length = -1;
    } else {
      // Shrink compressed buffer
      RETURN_NOT_OK(
          result->Resize(actual_length + sizeof(int64_t), /* shrink_to_fit= */ true));
    }
    int64_t prefixed_length_little_endian = bit_util::ToLittleEndian(prefixed_length);
    util::SafeStore(result->mutable_data(), prefixed_length_little_endian);

    *out = SliceBuffer(std::move(result), /*offset=*/0, actual_length + sizeof(int64_t));

    return Status::OK();
  }

  Status CompressBodyBuffers() {
    RETURN_NOT_OK(