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.

'use strict';

const Buffer = require('buffer').Buffer;
const Transform = require('_stream_transform');
const binding = process.binding('zlib');
const assert = require('assert').ok;
const kMaxLength = require('buffer').kMaxLength;
const kRangeErrorMessage = 'Cannot create final Buffer. It would be larger ' +
                           `than 0x${kMaxLength.toString(16)} bytes`;

const constants = process.binding('constants').zlib;
const { inherits } = require('util');
const { isArrayBufferView } = require('internal/util/types');

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

const ckeys = Object.keys(codes);
for (var ck = 0; ck < ckeys.length; ck++) {
  var ckey = ckeys[ck];
  codes[codes[ckey]] = ckey;
}

function isInvalidFlushFlag(flag) {
  return typeof flag !== 'number' ||
         flag < constants.Z_NO_FLUSH ||
         flag > constants.Z_BLOCK;

  // Covers: constants.Z_NO_FLUSH (0),
  //         constants.Z_PARTIAL_FLUSH (1),
  //         constants.Z_SYNC_FLUSH (2),
  //         constants.Z_FULL_FLUSH (3),
  //         constants.Z_FINISH (4), and
  //         constants.Z_BLOCK (5)
}

function isInvalidStrategy(strategy) {
  return typeof strategy !== 'number' ||
         strategy < constants.Z_DEFAULT_STRATEGY ||
         strategy > constants.Z_FIXED;

  // Covers: constants.Z_FILTERED, (1)
  //         constants.Z_HUFFMAN_ONLY (2),
  //         constants.Z_RLE (3),
  //         constants.Z_FIXED (4), and
  //         constants.Z_DEFAULT_STRATEGY (0)
}

function responseData(engine, buffer) {
  if (engine._opts.info) {
    return { buffer, engine };
  }
  return buffer;
}

function zlibBuffer(engine, buffer, callback) {
  // Streams do not support non-Buffer ArrayBufferViews yet. Convert it to a
  // Buffer without copying.
  if (isArrayBufferView(buffer) &&
      Object.getPrototypeOf(buffer) !== Buffer.prototype) {
    buffer = Buffer.from(buffer.buffer, buffer.byteOffset, buffer.byteLength);
  }

  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.byteLength;
    }
    engine.once('readable', flow);
  }

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

  function onEnd() {
    var buf;
    var err = null;

    if (nread >= kMaxLength) {
      err = new RangeError(kRangeErrorMessage);
    } else {
      buf = Buffer.concat(buffers, nread);
    }

    buffers = [];
    engine.close();
    callback(err, responseData(engine, buf));
  }
}

function zlibBufferSync(engine, buffer) {
  if (typeof buffer === 'string')
    buffer = Buffer.from(buffer);
  else if (!isArrayBufferView(buffer))
    throw new TypeError('"buffer" argument must be a string, Buffer, ' +
                        'TypedArray, or DataView');

  var flushFlag = engine._finishFlushFlag;

  return responseData(engine, engine._processChunk(buffer, flushFlag));
}

function zlibOnError(message, errno) {
  // there is no way to cleanly recover.
  // continuing only obscures problems.
  _close(this);
  this._hadError = true;

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

function flushCallback(level, strategy, callback) {
  assert(this._handle, 'zlib binding closed');
  this._handle.params(level, strategy);
  if (!this._hadError) {
    this._level = level;
    this._strategy = strategy;
    if (callback) callback();
  }
}

// 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) {
  opts = opts || {};
  Transform.call(this, opts);

  this.bytesRead = 0;

  this._opts = opts;
  this._chunkSize = opts.chunkSize || constants.Z_DEFAULT_CHUNK;

  if (opts.flush && isInvalidFlushFlag(opts.flush)) {
    throw new RangeError('Invalid flush flag: ' + opts.flush);
  }
  if (opts.finishFlush && isInvalidFlushFlag(opts.finishFlush)) {
    throw new RangeError('Invalid flush flag: ' + opts.finishFlush);
  }

  this._flushFlag = opts.flush || constants.Z_NO_FLUSH;
  this._finishFlushFlag = opts.finishFlush !== undefined ?
    opts.finishFlush : constants.Z_FINISH;
  this._scheduledFlushFlag = constants.Z_NO_FLUSH;

  if (opts.chunkSize !== undefined) {
    if (opts.chunkSize < constants.Z_MIN_CHUNK) {
      throw new RangeError('Invalid chunk size: ' + opts.chunkSize);
    }
  }

  if (opts.windowBits !== undefined) {
    if (opts.windowBits < constants.Z_MIN_WINDOWBITS ||
        opts.windowBits > constants.Z_MAX_WINDOWBITS) {
      throw new RangeError('Invalid windowBits: ' + opts.windowBits);
    }
  }

  if (opts.level !== undefined) {
    if (opts.level < constants.Z_MIN_LEVEL ||
        opts.level > constants.Z_MAX_LEVEL) {
      throw new RangeError('Invalid compression level: ' + opts.level);
    }
  }

  if (opts.memLevel !== undefined) {
    if (opts.memLevel < constants.Z_MIN_MEMLEVEL ||
        opts.memLevel > constants.Z_MAX_MEMLEVEL) {
      throw new RangeError('Invalid memLevel: ' + opts.memLevel);
    }
  }

  if (opts.strategy !== undefined && isInvalidStrategy(opts.strategy))
    throw new TypeError('Invalid strategy: ' + opts.strategy);

  if (opts.dictionary !== undefined) {
    if (!isArrayBufferView(opts.dictionary)) {
      throw new TypeError(
        'Invalid dictionary: it should be a Buffer, TypedArray, or DataView');
    }
  }

  this._handle = new binding.Zlib(mode);
  this._handle.onerror = zlibOnError.bind(this);
  this._hadError = false;

  var level = constants.Z_DEFAULT_COMPRESSION;
  if (Number.isFinite(opts.level)) {
    level = opts.level;
  }

  var strategy = constants.Z_DEFAULT_STRATEGY;
  if (Number.isFinite(opts.strategy)) {
    strategy = opts.strategy;
  }

  var windowBits = constants.Z_DEFAULT_WINDOWBITS;
  if (Number.isFinite(opts.windowBits)) {
    windowBits = opts.windowBits;
  }

  var memLevel = constants.Z_DEFAULT_MEMLEVEL;
  if (Number.isFinite(opts.memLevel)) {
    memLevel = opts.memLevel;
  }

  this._handle.init(windowBits,
                    level,
                    memLevel,
                    strategy,
                    opts.dictionary);

  this._buffer = Buffer.allocUnsafe(this._chunkSize);
  this._offset = 0;
  this._level = level;
  this._strategy = strategy;

  this.once('end', this.close);
}
inherits(Zlib, Transform);

Object.defineProperty(Zlib.prototype, '_closed', {
  configurable: true,
  enumerable: true,
  get() {
    return !this._handle;
  }
});

Zlib.prototype.params = function params(level, strategy, callback) {
  if (level < constants.Z_MIN_LEVEL ||
      level > constants.Z_MAX_LEVEL) {
    throw new RangeError('Invalid compression level: ' + level);
  }
  if (isInvalidStrategy(strategy))
    throw new TypeError('Invalid strategy: ' + strategy);

  if (this._level !== level || this._strategy !== strategy) {
    this.flush(constants.Z_SYNC_FLUSH,
               flushCallback.bind(this, level, strategy, callback));
  } else {
    process.nextTick(callback);
  }
};

Zlib.prototype.reset = function reset() {
  assert(this._handle, 'zlib binding closed');
  return this._handle.reset();
};

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

// If a flush is scheduled while another flush is still pending, a way to figure
// out which one is the "stronger" flush is needed.
// Roughly, the following holds:
// Z_NO_FLUSH (< Z_TREES) < Z_BLOCK < Z_PARTIAL_FLUSH <
//     Z_SYNC_FLUSH < Z_FULL_FLUSH < Z_FINISH
const flushiness = [];
let i = 0;
for (const flushFlag of [constants.Z_NO_FLUSH, constants.Z_BLOCK,
                         constants.Z_PARTIAL_FLUSH, constants.Z_SYNC_FLUSH,
                         constants.Z_FULL_FLUSH, constants.Z_FINISH]) {
  flushiness[flushFlag] = i++;
}

function maxFlush(a, b) {
  return flushiness[a] > flushiness[b] ? a : b;
}

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

  if (typeof kind === 'function' || (kind === undefined && !callback)) {
    callback = kind;
    kind = constants.Z_FULL_FLUSH;
  }

  if (ws.ended) {
    if (callback)
      process.nextTick(callback);
  } else if (ws.ending) {
    if (callback)
      this.once('end', callback);
  } else if (ws.needDrain) {
    const alreadyHadFlushScheduled =
        this._scheduledFlushFlag !== constants.Z_NO_FLUSH;
    this._scheduledFlushFlag = maxFlush(kind, this._scheduledFlushFlag);

    // If a callback was passed, always register a new `drain` + flush handler,
    // mostly because that's simpler and flush callbacks piling up is a rare
    // thing anyway.
    if (!alreadyHadFlushScheduled || callback) {
      const drainHandler = () => this.flush(this._scheduledFlushFlag, callback);
      this.once('drain', drainHandler);
    }
  } else {
    this._flushFlag = kind;
    this.write(Buffer.alloc(0), '', callback);
    this._scheduledFlushFlag = constants.Z_NO_FLUSH;
  }
};

Zlib.prototype.close = function close(callback) {
  _close(this, callback);
  process.nextTick(emitCloseNT, this);
};

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

  if (chunk !== null && !isArrayBufferView(chunk))
    return cb(new TypeError('invalid input'));

  if (!this._handle)
    return cb(new Error('zlib binding closed'));

  // If it's the last chunk, or a final flush, we use the Z_FINISH flush flag
  // (or whatever flag was provided using opts.finishFlush).
  // 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 = this._finishFlushFlag;
  else {
    flushFlag = this._flushFlag;
    // once we've flushed the last of the queue, stop flushing and
    // go back to the normal behavior.
    if (chunk.byteLength >= ws.length) {
      this._flushFlag = this._opts.flush || constants.Z_NO_FLUSH;
    }
  }

  this._processChunk(chunk, flushFlag, cb);
};

Zlib.prototype._processChunk = function _processChunk(chunk, flushFlag, cb) {
  var availInBefore = chunk && chunk.byteLength;
  var availOutBefore = this._chunkSize - this._offset;
  var inOff = 0;

  var self = this;

  var async = typeof cb === 'function';

  if (!async) {
    var buffers = [];
    var nread = 0;

    var error;
    this.on('error', function(er) {
      error = er;
    });

    assert(this._handle, 'zlib binding closed');
    do {
      var res = this._handle.writeSync(flushFlag,
                                       chunk, // in
                                       inOff, // in_off
                                       availInBefore, // in_len
                                       this._buffer, // out
                                       this._offset, //out_off
                                       availOutBefore); // out_len
    } while (!this._hadError && callback(res[0], res[1]));

    if (this._hadError) {
      throw error;
    }

    if (nread >= kMaxLength) {
      _close(this);
      throw new RangeError(kRangeErrorMessage);
    }

    var buf = Buffer.concat(buffers, nread);
    _close(this);

    return buf;
  }

  assert(this._handle, 'zlib binding closed');
  var req = this._handle.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;

  function callback(availInAfter, availOutAfter) {
    // When the callback is used in an async write, the callback's
    // context is the `req` object that was created. The req object
    // is === this._handle, and that's why it's important to null
    // out the values after they are done being used. `this._handle`
    // can stay in memory longer than the callback and buffer are needed.
    if (this) {
      this.buffer = null;
      this.callback = null;
    }

    if (self._hadError)
      return;

    if (self.destroyed)
      return;

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

    self.bytesRead += availInBefore - availInAfter;

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

    // 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 = Buffer.allocUnsafe(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;

      if (!async)
        return true;

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

    if (!async)
      return false;

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

function _close(engine, callback) {
  if (callback)
    process.nextTick(callback);

  // Caller may invoke .close after a zlib error (which will null _handle).
  if (!engine._handle)
    return;

  engine._handle.close();
  engine._handle = null;
}

function emitCloseNT(self) {
  self.emit('close');
}

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

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

function Gzip(opts) {
  if (!(this instanceof Gzip))
    return new Gzip(opts);
  Zlib.call(this, opts, constants.GZIP);
}
inherits(Gzip, Zlib);

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

function DeflateRaw(opts) {
  if (opts && opts.windowBits === 8) opts.windowBits = 9;
  if (!(this instanceof DeflateRaw))
    return new DeflateRaw(opts);
  Zlib.call(this, opts, constants.DEFLATERAW);
}
inherits(DeflateRaw, Zlib);

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

function Unzip(opts) {
  if (!(this instanceof Unzip))
    return new Unzip(opts);
  Zlib.call(this, opts, constants.UNZIP);
}
inherits(Unzip, Zlib);

function createConvenienceMethod(type, sync) {
  if (sync) {
    return function(buffer, opts) {
      return zlibBufferSync(new type(opts), buffer);
    };
  } else {
    return function(buffer, opts, callback) {
      if (typeof opts === 'function') {
        callback = opts;
        opts = {};
      }
      return zlibBuffer(new type(opts), buffer, callback);
    };
  }
}

function createProperty(type) {
  return {
    configurable: true,
    enumerable: true,
    value: type
  };
}

module.exports = {
  Deflate,
  Inflate,
  Gzip,
  Gunzip,
  DeflateRaw,
  InflateRaw,
  Unzip,

  // Convenience methods.
  // compress/decompress a string or buffer in one step.
  deflate: createConvenienceMethod(Deflate, false),
  deflateSync: createConvenienceMethod(Deflate, true),
  gzip: createConvenienceMethod(Gzip, false),
  gzipSync: createConvenienceMethod(Gzip, true),
  deflateRaw: createConvenienceMethod(DeflateRaw, false),
  deflateRawSync: createConvenienceMethod(DeflateRaw, true),
  unzip: createConvenienceMethod(Unzip, false),
  unzipSync: createConvenienceMethod(Unzip, true),
  inflate: createConvenienceMethod(Inflate, false),
  inflateSync: createConvenienceMethod(Inflate, true),
  gunzip: createConvenienceMethod(Gunzip, false),
  gunzipSync: createConvenienceMethod(Gunzip, true),
  inflateRaw: createConvenienceMethod(InflateRaw, false),
  inflateRawSync: createConvenienceMethod(InflateRaw, true)
};

Object.defineProperties(module.exports, {
  createDeflate: createProperty(module.exports.Deflate),
  createInflate: createProperty(module.exports.Inflate),
  createDeflateRaw: createProperty(module.exports.DeflateRaw),
  createInflateRaw: createProperty(module.exports.InflateRaw),
  createGzip: createProperty(module.exports.Gzip),
  createGunzip: createProperty(module.exports.Gunzip),
  createUnzip: createProperty(module.exports.Unzip),
  constants: {
    configurable: false,
    enumerable: true,
    value: constants
  },
  codes: {
    enumerable: true,
    writable: false,
    value: Object.freeze(codes)
  }
});

// These should be considered deprecated
// expose all the zlib constants
const bkeys = Object.keys(constants);
for (var bk = 0; bk < bkeys.length; bk++) {
  var bkey = bkeys[bk];
  Object.defineProperty(module.exports, bkey, {
    enumerable: true, value: constants[bkey], writable: false
  });
}