int ZLib::CompressAtMostOrAll()

in tensorflow_serving/util/net_http/compression/gzip_zlib.cc [368:420]
35 lines of code
17 McCabe index (conditional complexity)

int ZLib::CompressAtMostOrAll(Bytef *dest, uLongf *destLen, const Bytef *source,
                              uLong *sourceLen,
                              int flush_mode) {  // Z_FULL_FLUSH or Z_FINISH
  int err;

  if ((err = CompressInit(dest, destLen, source, sourceLen)) != Z_OK)
    return err;

  // This is used to figure out how many bytes we wrote *this chunk*
  uint64_t compressed_size = comp_stream_.total_out;

  // Some setup happens only for the first chunk we compress in a run
  if (first_chunk_) {
    if ((err = WriteGzipHeader()) != Z_OK) return err;
    compressed_size -= sizeof(GZIP_HEADER) - 1;  // -= is right: adds to size
    crc_ = crc32(0, nullptr, 0);                 // initialize

    uncompressed_size_ = 0;
    first_chunk_ = false;  // so we don't do this again
  }

  // flush_mode is Z_FINISH for all mode, Z_SYNC_FLUSH for incremental
  // compression.
  err = deflate(&comp_stream_, flush_mode);

  const uLong source_bytes_consumed = *sourceLen - comp_stream_.avail_in;
  *sourceLen = comp_stream_.avail_in;

  if ((err == Z_STREAM_END || err == Z_OK) && comp_stream_.avail_in == 0 &&
      comp_stream_.avail_out != 0) {
    // we processed everything ok and the output buffer was large enough.
  } else if (err == Z_STREAM_END && comp_stream_.avail_in > 0) {
    return Z_BUF_ERROR;  // should never happen
  } else if (err != Z_OK && err != Z_STREAM_END && err != Z_BUF_ERROR) {
    // an error happened
    CompressErrorInit();
    return err;
  } else if (comp_stream_.avail_out == 0) {  // not enough space
    err = Z_BUF_ERROR;
  }

  assert(err == Z_OK || err == Z_STREAM_END || err == Z_BUF_ERROR);
  if (err == Z_STREAM_END) err = Z_OK;

  // update the crc and other metadata
  uncompressed_size_ += source_bytes_consumed;
  compressed_size = comp_stream_.total_out - compressed_size;  // delta
  *destLen = compressed_size;

  crc_ = crc32(crc_, source, source_bytes_consumed);

  return err;
}