ZLIB inflate give 'data error' in PHP

Question

I've got a file that has zlib deflated blocks of 4096 bytes. I'm able to inflate at least 1 block of 4096 bytes with C++, using Minzip's inflate implementation, without garbled text or data error.

I'm using the following C++ implementation to inflate the data:

#define DEC_BUFFER_LEN 20000
int main(int argc, char* argv[]) {
    FILE *file = fopen("unpackme.3di", "rb");

    char *buffer = new char[4096];

    std::fstream outputFile;
    outputFile.open("output.txt", std::ios_base::out | std::ios_base::trunc | std::ios_base::binary);


    // Data zit nu in de buffer
    char *decbuffer = new char[DEC_BUFFER_LEN];

    mz_streamp streampie = new mz_stream();

    streampie->zalloc = Z_NULL;
    streampie->zfree = Z_NULL;
    streampie->opaque = Z_NULL;
    streampie->avail_in = Z_NULL;
    streampie->next_in = Z_NULL;

    if (inflateInit(streampie) != Z_OK)
        return -1;

    fread(buffer, 1, 4096, file);

    streampie->next_in = (Byte *)&buffer[0];
    streampie->avail_in = 4096;

    streampie->next_out = (Byte *)&decbuffer[0];
    streampie->avail_out = DEC_BUFFER_LEN;

    streampie->total_out = 0;

    int res = inflate(streampie, Z_NO_FLUSH);

    if (res != Z_OK && res != Z_STREAM_END) {
        std::cout << "Error: " << streampie->msg << std::endl;
        return;
    }
    outputFile.write(decbuffer, streampie->total_out); // Write data to file

    fclose(file);

    inflateEnd(streampie);

    outputFile.flush();
    outputFile.close();

    getchar();

    return 0;
}

and I'm using the following PHP implementation:

function Unpack3DI($inputFilename) {
    $handle = fopen($inputFilename, 'rb');
    if ($handle === false) return null;

    $data = gzinflate(fread($handle, 4096));
    return $data;
}


var_dump(Unpack3DI('unpackme.3di'));

Result:

Warning: gzinflate() [function.gzinflate]: data error in /var/www/html/3di.php on line 9
bool(false)

Answer 1

The issue was that I used the wrong function. I had to use gzuncompress instead of gzinflate. Also, pushing the whole file in gzuncompress did the job very well actually, as zlib checks if there are remaining blocks to be uncompressed.

More information about the Zlib methods in PHP are answered in this answer to "Which compression method to use in PHP?".