Protobuf with GZIP compression - c++

Question

I am having a problem in trying to serialize an array of unsigned char into file with GZIP compression using protobuf while playing with the library.
I think the problem might have to do with some of my syntax or misuse of API.
I have also tried std::fstream.
FYI, Windows 8.1 & VS2013 is the building environment.
scene.proto
syntax = "proto3";
package Recipe;
message Scene
{
repeated int32 imageData = 1 [packed=true];
}
source.cpp
#include <iostream>
#include <fstream>
#include <ostream>
#include <istream>
#include <string>
#include <cstdint>
#include "Scene.pb.h"
#include <google\protobuf\io\zero_copy_stream_impl.h>
#include <google\protobuf\io\gzip_stream.h>
int const _MIN = 0;
int const _MAX = 255;
unsigned int const _SIZE = 65200000;
unsigned int const _COMPRESSION_LEVEL = 10;
void randWithinUnsignedCharSize(uint8_t * buffer, unsigned int size)
{
for (size_t i = 0; i < size; ++i)
{
buffer[i] = _MIN + (rand() % static_cast<int>(_MAX - _MIN + 1));
}
}
using namespace google::protobuf::io;
int main()
{
GOOGLE_PROTOBUF_VERIFY_VERSION;
Recipe::Scene * scene = new Recipe::Scene();
uint8_t * imageData = new uint8_t[_SIZE];
randWithinUnsignedCharSize(imageData, _SIZE);
for (size_t i = 0; i < _SIZE; i++)
{
scene->add_imagedata(imageData[i]);
}
std::cout << "scene->imagedata_size() " << scene->imagedata_size() << std::endl;
{
std::ofstream output("scene.art", std::ofstream::out | std::ofstream::trunc | std::ofstream::binary);
OstreamOutputStream outputFileStream(&output);
GzipOutputStream::Options options;
options.format = GzipOutputStream::GZIP;
options.compression_level = _COMPRESSION_LEVEL;
GzipOutputStream gzipOutputStream(&outputFileStream, options);
if (!scene->SerializeToZeroCopyStream(&gzipOutputStream)) {
std::cerr << "Failed to write scene." << std::endl;
return -1;
}
}
Recipe::Scene * scene1 = new Recipe::Scene();
{
std::ifstream input("scene.art", std::ifstream::in | std::ifstream::binary);
IstreamInputStream inputFileStream(&input);
GzipInputStream gzipInputStream(&inputFileStream);
if (!scene1->ParseFromZeroCopyStream(&gzipInputStream)) {
std::cerr << "Failed to parse scene." << std::endl;
return -1;
}
}
std::cout << "scene1->imagedata_size() " << scene1->imagedata_size() <<std::endl;
google::protobuf::ShutdownProtobufLibrary();
return 0;
}

Answer 1

You seem to have a typo in your code. Compression level is according to documentation in range 0-9. You set incorrectly compression level to 10.
Your example is working for me when corrected to:
unsigned int const _COMPRESSION_LEVEL = 9;