pako/lib/deflate.js

'use strict';


var zlib_deflate = require('./zlib/deflate.js');
var utils = require('./zlib/utils');
var c = require('./zlib/constants');
var msg = require('./zlib/messages');
var zstream = require('./zlib/zstream');

// return sliced buffer, trying to avoid new objects creation and mem copy
function sliceBuf(buf, size) {
  if (buf.length === size) { return buf; }

  return utils.typedOk() ? buf.subarray(0, size) : buf.slice(0, size);
}

/**
 * class Deflate
 *
 * Generic JS-style wrapper for zlib calls. If you don't need
 * streaming behaviour - use more simple functions: [[deflate]],
 * [[deflateRaw]] and [[gzip]].
 **/

/* internal
 * Deflate.chunks -> Array
 *
 * Chunks of output data, if [[Deflate#onData]] not overriden.
 **/

/**
 * Deflate.result -> Uint8Array|Array
 *
 * Compressed result, generated by default [[Deflate#onData]]
 * and [[Deflate#onEnd]] handlers. Filled after you push last chunk
 * (call [[Deflate#push]] with `Z_FINISH` / `true` param).
 **/

/**
 * Deflate.err -> Number
 *
 * Error code after deflate finished. 0 (Z_OK) on success.
 * You will not need it in real life, because deflate errors
 * are possible only on wrong options or bad `onData` / `onEnd`
 * custom handlers.
 **/


/**
 * new Deflate(options)
 * - options (Object): zlib deflate options.
 *
 * Creates new deflator instance with specified params. Supported options:
 *
 * - `level`
 * - `windowBits`
 * - `memLevel`
 * - `strategy`
 *
 * [http://zlib.net/manual.html#Advanced](http://zlib.net/manual.html#Advanced)
 * for more information on these.
 *
 * Additional options, for internal needs:
 *
 * - `chunkSize` - size of generated data chunks (16K by default)
 * - `raw` (boolean) - do raw deflate
 * - `gzip` (boolean) - create gzip wrapper
 **/
var Deflate = function(options) {

  this.options = utils.assign({
    level: 6,
    method: c.Z_DEFLATED,
    chunkSize: 16384,
    windowBits: 15,
    memLevel: 8,
    strategy: c.Z_DEFAULT_STRATEGY
  }, options || {});

  var opt = this.options;

  if (opt.raw && (opt.windowBits > 0)) {
    opt.windowBits = -opt.windowBits;
  }

  else if (opt.gzip && (opt.windowBits > 0) && (opt.windowBits < 16)) {
    opt.windowBits += 16;
  }

  this.ended = false; // used to avoid multiple onEnd() calls
  this.chunks = [];   // chunks of compressed data

  this.strm = new zstream();

  var status = zlib_deflate.deflateInit2(
    this.strm,
    opt.level,
    opt.method,
    opt.windowBits,
    opt.memLevel,
    opt.strategy
  );

  if (status !== c.Z_OK) {
    throw new Error(msg[status]);
  }
};

/**
 * Deflate#push(data[, mode]) -> Boolean
 * - data (Uint8Array|Array): input data
 * - mode (Number|Boolean): 0..6 for corresponding Z_NO_FLUSH..Z_TREE modes.
 *   See constants. Skipped or `false` means Z_NO_FLUSH, `true` meansh Z_FINISH.
 *
 * Sends input data to deflate pipe, generating [[Deflate#onData]] calls with
 * new compressed chunks. Returns `true` on success. The last data block must have
 * mode Z_FINISH (or `true`). That flush internal pending buffers and call
 * [[Deflate#onEnd]].
 *
 * On fail call [[Deflate#onEnd]] with error code and return false.
 **/
Deflate.prototype.push = function(data, mode) {
  var strm = this.strm;
  var chunkSize = this.options.chunkSize;
  var status, _mode;

  if (this.ended) { return false; }

  _mode = (mode === ~~mode) ? mode : ((mode === true) ? c.Z_FINISH : c.Z_NO_FLUSH);

  strm.next_in = data;
  strm.next_in_index = 0;
  strm.avail_in = strm.next_in.length;
  strm.next_out = utils.arrayCreate(chunkSize);

  do {
    strm.avail_out = this.options.chunkSize;
    strm.next_out_index = 0;
    status = zlib_deflate.deflate(strm, _mode);    /* no bad return value */

    if (status !== c.Z_STREAM_END && status !== c.Z_OK) {
      this.onEnd(status);
      this.ended = true;
      return false;
    }
    if(strm.next_out_index) {
      this.onData(sliceBuf(strm.next_out, strm.next_out_index));
      // Allocate buffer for next chunk, if not last
      if (strm.avail_in > 0 || strm.avail_out === 0) {
        strm.next_out = utils.arrayCreate(this.options.chunkSize);
      }
    }
  } while (strm.avail_in > 0 || strm.avail_out === 0);

  // Finalize on the last chunk.
  if (_mode === c.Z_FINISH) {
    status = zlib_deflate.deflateEnd(this.strm);
    this.onEnd(status);
    this.ended = true;
    return status === c.Z_OK;
  }

  return true;
};


/**
 * Deflate#onData(chunk) -> Void
 * - chunk (Uint8Array|Array): ouput data. Type of array depends
 *   on js engine support.
 *
 * By default, stores data blocks in `chunks[]` property and glue
 * those in `onEnd`. Override this handler, if you need another behaviour.
 **/
Deflate.prototype.onData = function(chunk) {
  this.chunks.push(chunk);
};


/**
 * Deflate#onEnd(status) -> Void
 * - status (Number): deflate status. 0 (Z_OK) on success,
 *   other if not.
 *
 * Called once after you tell deflate that input stream complete.
 * By default - join collected chunks, free memory and fill
 * `results` / `err` properties.
 **/
Deflate.prototype.onEnd = function(status) {
  // On success - join
  if (status === c.Z_OK) {
    this.result = utils.flattenChunks(this.chunks);
  }
  this.chunks = [];
  this.err = status;
  // TODO: detect message by status, if not set in zstream
  this.msg = this.strm.msg || msg[status];
  this.ended = true;
};


/**
 * deflate(data[, options]) -> Uint8Array|Array
 * - data (Uint8Array|Array): input data to compress.
 * - options (Object): zlib deflate options.
 *
 * Compress `data` with deflate alrorythm and `options`.
 *
 * Supported options are:
 *
 * - level
 * - windowBits
 * - memLevel
 * - strategy
 *
 * [http://zlib.net/manual.html#Advanced](http://zlib.net/manual.html#Advanced)
 * for more information on these.
 **/
function deflate(input, options) {
  var deflator = new Deflate(options);

  deflator.push(input, true);

  // That will never happens, if you don't cheat with options :)
  if (deflator.err) { throw msg[deflator.err]; }

  return deflator.result;
}


/**
 * deflateRaw(data[, options]) -> Uint8Array|Array
 * - data (Uint8Array|Array): input data to compress.
 * - options (Object): zlib deflate options.
 *
 * The same as [[deflate]], but creates raw data, without wrapper
 * (header and adler32 crc).
 **/
function deflateRaw(input, options) {
  options = options || {};
  options.raw = true;
  return deflate(input, options);
}


/**
 * gzip(data[, options]) -> Uint8Array|Array
 * - data (Uint8Array|Array): input data to compress.
 * - options (Object): zlib deflate options.
 *
 * The same as [[deflate]], but create gzip wrapper instead of
 * deflate one.
 **/
function gzip(input, options) {
  options = options || {};
  options.gzip = true;
  return deflate(input, options);
}


exports.Deflate = Deflate;
exports.deflate = deflate;
exports.deflateRaw = deflateRaw;
exports.gzip = gzip;