buffer-utils v1.1.0

Buffer utils that allow you to read and write bytes, strings, ints and floats sequentially.

BufferWriter

var BufferWriter = require('buffer-utils').BufferWriter;

var bw = new BufferWriter();

// Writes sequentially.
bw.writeInt8(0x12)
  .writeInt16LE(0x1234); // chaining allowed.

// Writes a buffer
bw.writeBytes(someBuffer);

// Writes a string
bw.writeString("hello world", "utf8");

// Gets the number of bytes written.
var bytesWritten = bw.size();

// Gets the contents and resets to empty.
var contents = bw.getContents();

// now bw.size() === 0

BufferReader

var BufferReader = require('buffer-utils').BufferReader;

// Wrapper over the buffer that keeps track of the current offset.
var br = new BufferReader(contents);

// Read integers sequentially.
// Supports all readInt*, readUInt*, readFloat*, readDouble* from Buffer.
var i8 = br.readInt8();     // 0x12
var i16 = br.readInt16LE(); // 0x1234

// Reads a chunk of bytes.
// Modifying `buf` will modify `contents` since it is a `slice` of
// `contents`.
var buf = br.readBytes();

// Reads a string
var str = br.readString('utf8'); // hello world

// Gets the number of bytes left.
var bytesLeft = br.bytesLeft(); // 0

RetainedBuffer

This is useful for reading a stream of data that is non-seekable and you do not want to store the entire stream in memory (e.g., when the data is huge). This util always retains the last X number of bytes read as you feed data into it, useful for reading variable-sized data followed by a fix-sized footer structure.

var retainedBuf = new RetainedBuffer(16); // retain 16 bytes

file.on('data', function(incomingChunk){
    // `chunks` is an array of Buffer's. Could be empty if all bytes read are
    // retained.
    var chunks = retainedBuf.read(incomingChunk);

    chunks.forEach(function(chunk){
        // do something with `chunk`...
        // the individual chunks will ultimately piece up to the
        // data read, minus the retained last 16 bytes.
    });
})
.on('end', function(){
    // `retained` is a buffer of 16 bytes if we have read at least 16 bytes
    // so far.
    var retained = retainedBuf.getRetained();
});