zlib.js/src/inflate.js at develop · imaya/zlib.js · GitHub

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goog.provide('Zlib.Inflate');

goog.require('USE_TYPEDARRAY');
goog.require('Zlib.Adler32');
goog.require('Zlib.RawInflate');

goog.scope(function() {

/**
 * @constructor
 * @param {!(Uint8Array|Array)} input deflated buffer.
 * @param {Object=} opt_params option parameters.
 *
 * opt_params は以下のプロパティを指定する事ができます。
 *   - index: input buffer の deflate コンテナの開始位置.
 *   - blockSize: バッファのブロックサイズ.
 *   - verify: 伸張が終わった後 adler-32 checksum の検証を行うか.
 *   - bufferType: Zlib.Inflate.BufferType の値によってバッファの管理方法を指定する.
 *       Zlib.Inflate.BufferType は Zlib.RawInflate.BufferType のエイリアス.
 */
Zlib.Inflate = function(input, opt_params) {
  /** @type {number} */
  var bufferSize;
  /** @type {Zlib.Inflate.BufferType} */
  var bufferType;
  /** @type {number} */
  var cmf;
  /** @type {number} */
  var flg;

  /** @type {!(Uint8Array|Array)} */
  this.input = input;
  /** @type {number} */
  this.ip = 0;
  /** @type {Zlib.RawInflate} */
  this.rawinflate;
  /** @type {(boolean|undefined)} verify flag. */
  this.verify;

  // option parameters
  if (opt_params || !(opt_params = {})) {
    if (opt_params['index']) {
      this.ip = opt_params['index'];
    }
    if (opt_params['verify']) {
      this.verify = opt_params['verify'];
    }
  }

  // Compression Method and Flags
  cmf = input[this.ip++];
  flg = input[this.ip++];

  // compression method
  switch (cmf & 0x0f) {
    case Zlib.CompressionMethod.DEFLATE:
      this.method = Zlib.CompressionMethod.DEFLATE;
      break;
    default:
      throw new Error('unsupported compression method');
  }

  // fcheck
  if (((cmf << 8) + flg) % 31 !== 0) {
    throw new Error('invalid fcheck flag:' + ((cmf << 8) + flg) % 31);
  }

  // fdict (not supported)
  if (flg & 0x20) {
    throw new Error('fdict flag is not supported');
  }

  // RawInflate
  this.rawinflate = new Zlib.RawInflate(input, {
    'index': this.ip,
    'bufferSize': opt_params['bufferSize'],
    'bufferType': opt_params['bufferType'],
    'resize': opt_params['resize']
  });
}

/**
 * @enum {number}
 */
Zlib.Inflate.BufferType = Zlib.RawInflate.BufferType;

/**
 * decompress.
 * @return {!(Uint8Array|Array)} inflated buffer.
 */
Zlib.Inflate.prototype.decompress = function() {
  /** @type {!(Array|Uint8Array)} input buffer. */
  var input = this.input;
  /** @type {!(Uint8Array|Array)} inflated buffer. */
  var buffer;
  /** @type {number} adler-32 checksum */
  var adler32;

  buffer = this.rawinflate.decompress();
  this.ip = this.rawinflate.ip;

  // verify adler-32
  if (this.verify) {
    adler32 = (
      input[this.ip++] << 24 | input[this.ip++] << 16 |
      input[this.ip++] << 8 | input[this.ip++]
    ) >>> 0;

    if (adler32 !== Zlib.Adler32(buffer)) {
      throw new Error('invalid adler-32 checksum');
    }
  }

  return buffer;
};

// end of scope
});

/* vim:set expandtab ts=2 sw=2 tw=80: */