deflate.js

/**
 * @fileoverview Deflate (RFC1951) 実装.
 * Deflateアルゴリズム本体は Zlib.RawDeflate で実装されている.
 */
goog.provide('Zlib.Deflate');

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

goog.scope(function() {

/**
 * Zlib Deflate
 * @constructor
 * @param {!(Array|Uint8Array)} input 符号化する対象の byte array.
 * @param {Object=} opt_params option parameters.
 */
Zlib.Deflate = function(input, opt_params) {
  /** @type {!(Array|Uint8Array)} */
  this.input = input;
  /** @type {!(Array|Uint8Array)} */
  this.output =
    new (USE_TYPEDARRAY ? Uint8Array : Array)(Zlib.Deflate.DefaultBufferSize);
  /** @type {Zlib.Deflate.CompressionType} */
  this.compressionType = Zlib.Deflate.CompressionType.DYNAMIC;
  /** @type {Zlib.RawDeflate} */
  this.rawDeflate;
  /** @type {Object} */
  var rawDeflateOption = {};
  /** @type {string} */
  var prop;

  // option parameters
  if (opt_params || !(opt_params = {})) {
    if (typeof opt_params['compressionType'] === 'number') {
      this.compressionType = opt_params['compressionType'];
    }
  }

  // copy options
  for (prop in opt_params) {
    rawDeflateOption[prop] = opt_params[prop];
  }

  // set raw-deflate output buffer
  rawDeflateOption['outputBuffer'] = this.output;

  this.rawDeflate = new Zlib.RawDeflate(this.input, rawDeflateOption);
};

/**
 * @const
 * @type {number} デフォルトバッファサイズ.
 */
Zlib.Deflate.DefaultBufferSize = 0x8000;

/**
 * @enum {number}
 */
Zlib.Deflate.CompressionType = Zlib.RawDeflate.CompressionType;

/**
 * 直接圧縮に掛ける.
 * @param {!(Array|Uint8Array)} input target buffer.
 * @param {Object=} opt_params option parameters.
 * @return {!(Array|Uint8Array)} compressed data byte array.
 */
Zlib.Deflate.compress = function(input, opt_params) {
  return (new Zlib.Deflate(input, opt_params)).compress();
};

/**
 * Deflate Compression.
 * @return {!(Array|Uint8Array)} compressed data byte array.
 */
Zlib.Deflate.prototype.compress = function() {
  /** @type {Zlib.CompressionMethod} */
  var cm;
  /** @type {number} */
  var cinfo;
  /** @type {number} */
  var cmf;
  /** @type {number} */
  var flg;
  /** @type {number} */
  var fcheck;
  /** @type {number} */
  var fdict;
  /** @type {number} */
  var flevel;
  /** @type {number} */
  var clevel;
  /** @type {number} */
  var adler;
  /** @type {boolean} */
  var error = false;
  /** @type {!(Array|Uint8Array)} */
  var output;
  /** @type {number} */
  var pos = 0;

  output = this.output;

  // Compression Method and Flags
  cm = Zlib.CompressionMethod.DEFLATE;
  switch (cm) {
    case Zlib.CompressionMethod.DEFLATE:
      cinfo = Math.LOG2E * Math.log(Zlib.RawDeflate.WindowSize) - 8;
      break;
    default:
      throw new Error('invalid compression method');
  }
  cmf = (cinfo << 4) | cm;
  output[pos++] = cmf;

  // Flags
  fdict = 0;
  switch (cm) {
    case Zlib.CompressionMethod.DEFLATE:
      switch (this.compressionType) {
        case Zlib.Deflate.CompressionType.NONE: flevel = 0; break;
        case Zlib.Deflate.CompressionType.FIXED: flevel = 1; break;
        case Zlib.Deflate.CompressionType.DYNAMIC: flevel = 2; break;
        default: throw new Error('unsupported compression type');
      }
      break;
    default:
      throw new Error('invalid compression method');
  }
  flg = (flevel << 6) | (fdict << 5);
  fcheck = 31 - (cmf * 256 + flg) % 31;
  flg |= fcheck;
  output[pos++] = flg;

  // Adler-32 checksum
  adler = Zlib.Adler32(this.input);

  this.rawDeflate.op = pos;
  output = this.rawDeflate.compress();
  pos = output.length;

  if (USE_TYPEDARRAY) {
    // subarray 分を元にもどす
    output = new Uint8Array(output.buffer);
    // expand buffer
    if (output.length <= pos + 4) {
      this.output = new Uint8Array(output.length + 4);
      this.output.set(output);
      output = this.output;
    }
    output = output.subarray(0, pos + 4);
  }

  // adler32
  output[pos++] = (adler >> 24) & 0xff;
  output[pos++] = (adler >> 16) & 0xff;
  output[pos++] = (adler >>  8) & 0xff;
  output[pos++] = (adler      ) & 0xff;

  return output;
};

// end of scope
});

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