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c++binaryprotocol-bufferstcpclientfile-transfer

Sending Binary File Data via Google Protobuf

I have my protobuf-message set up fine it seems, all other fields I have transmit correctly across the network and do not truncate. I only have one problem, when I read the binary data of a picture or file then send it through google protobuf as bytes array type, on the other side it only contains the first 4 elements of the array. If the picture is say 200kb, on the other end it comes out as 1kb(Basically only contains a header or identifier). This problem is kinda complex so I will try to give a run down. Sorry if I make this impossible to understand. I may be going about this completely the wrong way.

  1. Example below contains conceptual work, and was written in class. It very well could contain small errors. The code compiles at home, and if it is a typo let me know and I can fix it.

        FILE* file;
    FILE* ofile;
    file = fopen("red.png", "rb");
    fseek(file, 0, SEEK_END);
    long fSize = ftell(file);
    rewind(file);
    BYTE* ret = new BYTE[fSize];
    fread(ret, 1, fSize, file);
    fclose(file);

    char dataStream[1024] //yes it is large enough
    myPacket.set_file(ret);
    //set other fields here
    myPacket.SerializeToArray(dataStream,sizeof(dataStream));
    //send through sockets below, works for all but file field.

    I can include more when I get back home to my main work computer, sorry, was just hoping I could let this stew while at class. If this is not enough info feel free to give me the smack down, it's alright just looking for advice. I also know that certain image formats can be read certain ways, but I was able to copy a png and rewrite it through binary locally, just not over protobuf

Thanks for reading my pseudo book guys, I am finally trying to leap into improving my knowledge.

Edited quickly typed pointer error(&ret) to (ret). Also then should size of be sizeof(myPacket) rather.

Solution

  • You have written this:

    char dataStream[1024] //yes it is large enough

    But how could 1024 bytes buffer be large enough if you want to store 200 000 bytes into it?

    Better allocate a bigger buffer on the heap, e.g.:

    std::vector<char> dataStream(500000);
myPacket.SerializeToArray(&dataStream[0], dataStream.size());