include/gzip_helper.hpp

#pragma once

#include <zlib.h>
#include <cstring>
#include <string>

inline bool gzip_inflate(const std::string& compressedBytes,
                        std::string& uncompressedBytes) {
  if (compressedBytes.empty()) {
    uncompressedBytes = compressedBytes;
    return true;
  }

  uncompressedBytes.clear();

  unsigned half_length = compressedBytes.size() / 2;

  z_stream strm{};

  // The following line is nolint because we're declaring away constness.
  // It's not clear why the input buffers on zlib aren't const, so this is a
  // bit of a cheat for the moment
  strm.next_in = (Bytef*)compressedBytes.data();  // NOLINT
  strm.avail_in = compressedBytes.size();
  strm.total_out = 0;
  strm.zalloc = Z_NULL;
  strm.zfree = Z_NULL;

  bool done = false;

  if (inflateInit2(&strm, (16 + MAX_WBITS)) != Z_OK) {
    return false;
  }

  while (!done) {
    // If our output buffer is too small
    if (strm.total_out >= uncompressedBytes.size()) {
      uncompressedBytes.resize(uncompressedBytes.size() + half_length);
    }

    strm.next_out =
        (Bytef*)(uncompressedBytes.data() + strm.total_out);  // NOLINT
    strm.avail_out =
        ((uLong)uncompressedBytes.size() - strm.total_out);  // NOLINT

    // Inflate another chunk.
    int err = inflate(&strm, Z_SYNC_FLUSH);
    if (err == Z_STREAM_END) {
      done = true;
    } else if (err != Z_OK) {
      break;
    }
  }

  return inflateEnd(&strm) == Z_OK;
}