Invalid magic number

[miqmago]

Hi, I'm using lz4 c library to compress a string in a c++ project, send it to a nodejs server in b64 and decompress there. To compress the string (buffer is comming from rapidjson: GetString() is a well formed json char * and Size() is the correct size):

  int safeSize = LZ4_compressBound(buffer.Size());
  char *compressed = new char[safeSize];
  int compressedBytes = LZ4_compress(buffer.GetString(), compressed, buffer.Size());
  string ret(BASE64::base64_encode((unsigned char *) compressed, compressedBytes));
  delete [] compressed;

The b64 string received in server perfectly matches the sended b64 string. To decompress the string in nodejs:

  var compressedData = new Buffer(req.query.d, 'base64');
  var decompressedData = LZ4.decode(compressedData);

I'm always getting Error: Invalid magic number: 7B5B74F1

I've been investigating c library and there is nothing similar to a magic number. Is there something to do with versions? I've seen that lz4.cli.c (used in node.js) has LZ4S_MAGICNUMBER defined and some other differences to lz4.c. In that case, would it work if I compile the library with c files from node.js to use it in c++? OTW how should I proceed?

Please any help is really appreciated.

Regards, Miguel

[miqmago]

Ok, I've seen, correct me if I'm wrong, that this is to decode files.

If it can help anyone, I've managed to decode strings:

var LZ4Lib = require('lz4/build/Release/lz4');
exports.LZ4_uncompress = function(input, outputSize) {
  var output;
  if (typeof outputSize !== 'undefined') {
    output = new Buffer(outputSize);
    LZ4Lib.uncompress(input, output);
  } else {
    outputSize = input.length * 2; // TODO: calculate a safe outputSize form input size
    output = new Buffer(outputSize);
    LZ4Lib.uncompress_unknownOutputSize(input, output);
  }
  return output;
};

[pierrec]

Hello,

Indeed the exposed function decode() is to decode a file. What you are trying to do is to decode a chunk of compressed data. The function does exist but it is not exposed. I may do so in the future though.

For now, you could do something like what you suggested:

var uncompress = require('lz4').createDecoderStream.prototype.uncompressBlock

where uncompress() expects an input and output buffer.

HTH