crc32.js

   crc32Blob: function (blob, cb){
            var fr = new FileReader();
            fr.onload = function(e){
                cb(CRC32.buf(new Uint8Array(this.result)).toString(16));
            };
            fr.readAsArrayBuffer(blob);
        }

 post.filesize = chunk.size;
                    upload.crc32Blob(file.getNative(), function(crc32){
                       console.log(crc32);
                       post.crc32 = crc32;
                   });