lib/zlib.js

// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

var Transform = require('_stream_transform');

var binding = process.binding('zlib');
var util = require('util');
var assert = require('assert').ok;

// zlib doesn't provide these, so kludge them in following the same
// const naming scheme zlib uses.
binding.Z_MIN_WINDOWBITS = 8;
binding.Z_MAX_WINDOWBITS = 15;
binding.Z_DEFAULT_WINDOWBITS = 15;

// fewer than 64 bytes per chunk is stupid.
// technically it could work with as few as 8, but even 64 bytes
// is absurdly low.  Usually a MB or more is best.
binding.Z_MIN_CHUNK = 64;
binding.Z_MAX_CHUNK = Infinity;
binding.Z_DEFAULT_CHUNK = (16 * 1024);

binding.Z_MIN_MEMLEVEL = 1;
binding.Z_MAX_MEMLEVEL = 9;
binding.Z_DEFAULT_MEMLEVEL = 8;

binding.Z_MIN_LEVEL = -1;
binding.Z_MAX_LEVEL = 9;
binding.Z_DEFAULT_LEVEL = binding.Z_DEFAULT_COMPRESSION;

// expose all the zlib constants
Object.keys(binding).forEach(function(k) {
  if (k.match(/^Z/)) exports[k] = binding[k];
});

// translation table for return codes.
exports.codes = {
  Z_OK: binding.Z_OK,
  Z_STREAM_END: binding.Z_STREAM_END,
  Z_NEED_DICT: binding.Z_NEED_DICT,
  Z_ERRNO: binding.Z_ERRNO,
  Z_STREAM_ERROR: binding.Z_STREAM_ERROR,
  Z_DATA_ERROR: binding.Z_DATA_ERROR,
  Z_MEM_ERROR: binding.Z_MEM_ERROR,
  Z_BUF_ERROR: binding.Z_BUF_ERROR,
  Z_VERSION_ERROR: binding.Z_VERSION_ERROR
};

Object.keys(exports.codes).forEach(function(k) {
  exports.codes[exports.codes[k]] = k;
});

exports.Deflate = Deflate;
exports.Inflate = Inflate;
exports.Gzip = Gzip;
exports.Gunzip = Gunzip;
exports.DeflateRaw = DeflateRaw;
exports.InflateRaw = InflateRaw;
exports.Unzip = Unzip;

exports.createDeflate = function(o) {
  return new Deflate(o);
};

exports.createInflate = function(o) {
  return new Inflate(o);
};

exports.createDeflateRaw = function(o) {
  return new DeflateRaw(o);
};

exports.createInflateRaw = function(o) {
  return new InflateRaw(o);
};

exports.createGzip = function(o) {
  return new Gzip(o);
};

exports.createGunzip = function(o) {
  return new Gunzip(o);
};

exports.createUnzip = function(o) {
  return new Unzip(o);
};


// Convenience methods.
// compress/decompress a string or buffer in one step.
exports.deflate = function(buffer, callback) {
  zlibBuffer(new Deflate(), buffer, callback);
};

exports.gzip = function(buffer, callback) {
  zlibBuffer(new Gzip(), buffer, callback);
};

exports.deflateRaw = function(buffer, callback) {
  zlibBuffer(new DeflateRaw(), buffer, callback);
};

exports.unzip = function(buffer, callback) {
  zlibBuffer(new Unzip(), buffer, callback);
};

exports.inflate = function(buffer, callback) {
  zlibBuffer(new Inflate(), buffer, callback);
};

exports.gunzip = function(buffer, callback) {
  zlibBuffer(new Gunzip(), buffer, callback);
};

exports.inflateRaw = function(buffer, callback) {
  zlibBuffer(new InflateRaw(), buffer, callback);
};

function zlibBuffer(engine, buffer, callback) {
  var buffers = [];
  var nread = 0;

  engine.on('error', onError);
  engine.on('end', onEnd);

  engine.end(buffer);
  flow();

  function flow() {
    var chunk;
    while (null !== (chunk = engine.read())) {
      buffers.push(chunk);
      nread += chunk.length;
    }
    engine.once('readable', flow);
  }

  function onError(err) {
    engine.removeListener('end', onEnd);
    engine.removeListener('readable', flow);
    callback(err);
  }

  function onEnd() {
    var buf = Buffer.concat(buffers, nread);
    buffers = [];
    callback(null, buf);
    engine.close();
  }
}


// generic zlib
// minimal 2-byte header
function Deflate(opts) {
  if (!(this instanceof Deflate)) return new Deflate(opts);
  Zlib.call(this, opts, binding.DEFLATE);
}

function Inflate(opts) {
  if (!(this instanceof Inflate)) return new Inflate(opts);
  Zlib.call(this, opts, binding.INFLATE);
}


// gzip - bigger header, same deflate compression
function Gzip(opts) {
  if (!(this instanceof Gzip)) return new Gzip(opts);
  Zlib.call(this, opts, binding.GZIP);
}

function Gunzip(opts) {
  if (!(this instanceof Gunzip)) return new Gunzip(opts);
  Zlib.call(this, opts, binding.GUNZIP);
}


// raw - no header
function DeflateRaw(opts) {
  if (!(this instanceof DeflateRaw)) return new DeflateRaw(opts);
  Zlib.call(this, opts, binding.DEFLATERAW);
}

function InflateRaw(opts) {
  if (!(this instanceof InflateRaw)) return new InflateRaw(opts);
  Zlib.call(this, opts, binding.INFLATERAW);
}


// auto-detect header.
function Unzip(opts) {
  if (!(this instanceof Unzip)) return new Unzip(opts);
  Zlib.call(this, opts, binding.UNZIP);
}


// the Zlib class they all inherit from
// This thing manages the queue of requests, and returns
// true or false if there is anything in the queue when
// you call the .write() method.

function Zlib(opts, mode) {
  this._opts = opts = opts || {};
  this._chunkSize = opts.chunkSize || exports.Z_DEFAULT_CHUNK;

  Transform.call(this, opts);

  if (opts.flush) {
    if (opts.flush !== binding.Z_NO_FLUSH &&
        opts.flush !== binding.Z_PARTIAL_FLUSH &&
        opts.flush !== binding.Z_SYNC_FLUSH &&
        opts.flush !== binding.Z_FULL_FLUSH &&
        opts.flush !== binding.Z_FINISH &&
        opts.flush !== binding.Z_BLOCK) {
      throw new Error('Invalid flush flag: ' + opts.flush);
    }
  }
  this._flushFlag = opts.flush || binding.Z_NO_FLUSH;

  if (opts.chunkSize) {
    if (opts.chunkSize < exports.Z_MIN_CHUNK ||
        opts.chunkSize > exports.Z_MAX_CHUNK) {
      throw new Error('Invalid chunk size: ' + opts.chunkSize);
    }
  }

  if (opts.windowBits) {
    if (opts.windowBits < exports.Z_MIN_WINDOWBITS ||
        opts.windowBits > exports.Z_MAX_WINDOWBITS) {
      throw new Error('Invalid windowBits: ' + opts.windowBits);
    }
  }

  if (opts.level) {
    if (opts.level < exports.Z_MIN_LEVEL ||
        opts.level > exports.Z_MAX_LEVEL) {
      throw new Error('Invalid compression level: ' + opts.level);
    }
  }

  if (opts.memLevel) {
    if (opts.memLevel < exports.Z_MIN_MEMLEVEL ||
        opts.memLevel > exports.Z_MAX_MEMLEVEL) {
      throw new Error('Invalid memLevel: ' + opts.memLevel);
    }
  }

  if (opts.strategy) {
    if (opts.strategy != exports.Z_FILTERED &&
        opts.strategy != exports.Z_HUFFMAN_ONLY &&
        opts.strategy != exports.Z_RLE &&
        opts.strategy != exports.Z_FIXED &&
        opts.strategy != exports.Z_DEFAULT_STRATEGY) {
      throw new Error('Invalid strategy: ' + opts.strategy);
    }
  }

  if (opts.dictionary) {
    if (!Buffer.isBuffer(opts.dictionary)) {
      throw new Error('Invalid dictionary: it should be a Buffer instance');
    }
  }

  this._binding = new binding.Zlib(mode);

  var self = this;
  this._hadError = false;
  this._binding.onerror = function(message, errno) {
    // there is no way to cleanly recover.
    // continuing only obscures problems.
    self._binding = null;
    self._hadError = true;

    var error = new Error(message);
    error.errno = errno;
    error.code = exports.codes[errno];
    self.emit('error', error);
  };

  var level = exports.Z_DEFAULT_COMPRESSION;
  if (typeof opts.level === 'number') level = opts.level;

  var strategy = exports.Z_DEFAULT_STRATEGY;
  if (typeof opts.strategy === 'number') strategy = opts.strategy;

  this._binding.init(opts.windowBits || exports.Z_DEFAULT_WINDOWBITS,
                     level,
                     opts.memLevel || exports.Z_DEFAULT_MEMLEVEL,
                     strategy,
                     opts.dictionary);

  this._buffer = new Buffer(this._chunkSize);
  this._offset = 0;
  this._closed = false;

  this.once('end', this.close);
}

util.inherits(Zlib, Transform);

Zlib.prototype.reset = function reset() {
  return this._binding.reset();
};

// This is the _flush function called by the transform class,
// internally, when the last chunk has been written.
Zlib.prototype._flush = function(callback) {
  this._transform(new Buffer(0), '', callback);
};

Zlib.prototype.flush = function(callback) {
  var ws = this._writableState;

  if (ws.ended) {
    if (callback)
      process.nextTick(callback);
  } else if (ws.ending) {
    if (callback)
      this.once('end', callback);
  } else if (ws.needDrain) {
    var self = this;
    this.once('drain', function() {
      self.flush(callback);
    });
  } else {
    this._flushFlag = binding.Z_FULL_FLUSH;
    this.write(new Buffer(0), '', callback);
  }
};

Zlib.prototype.close = function(callback) {
  if (callback)
    process.nextTick(callback);

  if (this._closed)
    return;

  this._closed = true;

  this._binding.close();

  var self = this;
  process.nextTick(function() {
    self.emit('close');
  });
};

Zlib.prototype._transform = function(chunk, encoding, cb) {
  var flushFlag;
  var ws = this._writableState;
  var ending = ws.ending || ws.ended;
  var last = ending && (!chunk || ws.length === chunk.length);

  if (chunk !== null && !Buffer.isBuffer(chunk))
    return cb(new Error('invalid input'));

  // If it's the last chunk, or a final flush, we use the Z_FINISH flush flag.
  // If it's explicitly flushing at some other time, then we use
  // Z_FULL_FLUSH. Otherwise, use Z_NO_FLUSH for maximum compression
  // goodness.
  if (last)
    flushFlag = binding.Z_FINISH;
  else {
    flushFlag = this._flushFlag;
    // once we've flushed the last of the queue, stop flushing and
    // go back to the normal behavior.
    if (chunk.length >= ws.length) {
      this._flushFlag = this._opts.flush || binding.Z_NO_FLUSH;
    }
  }

  var availInBefore = chunk && chunk.length;
  var availOutBefore = this._chunkSize - this._offset;
  var inOff = 0;

  var req = this._binding.write(flushFlag,
                                chunk, // in
                                inOff, // in_off
                                availInBefore, // in_len
                                this._buffer, // out
                                this._offset, //out_off
                                availOutBefore); // out_len

  req.buffer = chunk;
  req.callback = callback;

  var self = this;
  function callback(availInAfter, availOutAfter, buffer) {
    if (self._hadError)
      return;

    var have = availOutBefore - availOutAfter;
    assert(have >= 0, 'have should not go down');

    if (have > 0) {
      var out = self._buffer.slice(self._offset, self._offset + have);
      self._offset += have;
      // serve some output to the consumer.
      self.push(out);
    }

    // exhausted the output buffer, or used all the input create a new one.
    if (availOutAfter === 0 || self._offset >= self._chunkSize) {
      availOutBefore = self._chunkSize;
      self._offset = 0;
      self._buffer = new Buffer(self._chunkSize);
    }

    if (availOutAfter === 0) {
      // Not actually done.  Need to reprocess.
      // Also, update the availInBefore to the availInAfter value,
      // so that if we have to hit it a third (fourth, etc.) time,
      // it'll have the correct byte counts.
      inOff += (availInBefore - availInAfter);
      availInBefore = availInAfter;

      var newReq = self._binding.write(flushFlag,
                                       chunk,
                                       inOff,
                                       availInBefore,
                                       self._buffer,
                                       self._offset,
                                       self._chunkSize);
      newReq.callback = callback; // this same function
      newReq.buffer = chunk;
      return;
    }

    // finished with the chunk.
    cb();
  }
};

util.inherits(Deflate, Zlib);
util.inherits(Inflate, Zlib);
util.inherits(Gzip, Zlib);
util.inherits(Gunzip, Zlib);
util.inherits(DeflateRaw, Zlib);
util.inherits(InflateRaw, Zlib);
util.inherits(Unzip, Zlib);