inflate.js

'use strict';


const zlib_inflate = require('./zlib/inflate');
const utils        = require('./utils/common');
const strings      = require('./utils/strings');
const msg          = require('./zlib/messages');
const ZStream      = require('./zlib/zstream');
const GZheader     = require('./zlib/gzheader');

const toString = Object.prototype.toString;

/* Public constants ==========================================================*/
/* ===========================================================================*/

const {
  Z_NO_FLUSH, Z_FINISH,
  Z_OK, Z_STREAM_END, Z_NEED_DICT, Z_STREAM_ERROR, Z_DATA_ERROR, Z_MEM_ERROR
} = require('./zlib/constants');

/* ===========================================================================*/


/**
 * class Inflate
 *
 * Generic JS-style wrapper for zlib calls. If you don't need
 * streaming behaviour - use more simple functions: [[inflate]]
 * and [[inflateRaw]].
 **/

/* internal
 * inflate.chunks -> Array
 *
 * Chunks of output data, if [[Inflate#onData]] not overridden.
 **/

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

/**
 * Inflate.err -> Number
 *
 * Error code after inflate finished. 0 (Z_OK) on success.
 * Should be checked if broken data possible.
 **/

/**
 * Inflate.msg -> String
 *
 * Error message, if [[Inflate.err]] != 0
 **/


/**
 * new Inflate(options)
 * - options (Object): zlib inflate options.
 *
 * Creates new inflator instance with specified params. Throws exception
 * on bad params. Supported options:
 *
 * - `windowBits`
 * - `dictionary`
 *
 * [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 inflate
 * - `to` (String) - if equal to 'string', then result will be converted
 *   from utf8 to utf16 (javascript) string. When string output requested,
 *   chunk length can differ from `chunkSize`, depending on content.
 *
 * By default, when no options set, autodetect deflate/gzip data format via
 * wrapper header.
 *
 * ##### Example:
 *
 * ```javascript
 * const pako = require('pako')
 * const chunk1 = new Uint8Array([1,2,3,4,5,6,7,8,9])
 * const chunk2 = new Uint8Array([10,11,12,13,14,15,16,17,18,19]);
 *
 * const inflate = new pako.Inflate({ level: 3});
 *
 * inflate.push(chunk1, false);
 * inflate.push(chunk2, true);  // true -> last chunk
 *
 * if (inflate.err) { throw new Error(inflate.err); }
 *
 * console.log(inflate.result);
 * ```
 **/
function Inflate(options) {
  this.options = utils.assign({
    chunkSize: 1024 * 64,
    windowBits: 15,
    to: ''
  }, options || {});

  const opt = this.options;

  // Force window size for `raw` data, if not set directly,
  // because we have no header for autodetect.
  if (opt.raw && (opt.windowBits >= 0) && (opt.windowBits < 16)) {
    opt.windowBits = -opt.windowBits;
    if (opt.windowBits === 0) { opt.windowBits = -15; }
  }

  // If `windowBits` not defined (and mode not raw) - set autodetect flag for gzip/deflate
  if ((opt.windowBits >= 0) && (opt.windowBits < 16) &&
      !(options && options.windowBits)) {
    opt.windowBits += 32;
  }

  // Gzip header has no info about windows size, we can do autodetect only
  // for deflate. So, if window size not set, force it to max when gzip possible
  if ((opt.windowBits > 15) && (opt.windowBits < 48)) {
    // bit 3 (16) -> gzipped data
    // bit 4 (32) -> autodetect gzip/deflate
    if ((opt.windowBits & 15) === 0) {
      opt.windowBits |= 15;
    }
  }

  this.err    = 0;      // error code, if happens (0 = Z_OK)
  this.msg    = '';     // error message
  this.ended  = false;  // used to avoid multiple onEnd() calls
  this.chunks = [];     // chunks of compressed data

  this.strm   = new ZStream();
  this.strm.avail_out = 0;

  let status  = zlib_inflate.inflateInit2(
    this.strm,
    opt.windowBits
  );

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

  this.header = new GZheader();

  zlib_inflate.inflateGetHeader(this.strm, this.header);

  // Setup dictionary
  if (opt.dictionary) {
    // Convert data if needed
    if (typeof opt.dictionary === 'string') {
      opt.dictionary = strings.string2buf(opt.dictionary);
    } else if (toString.call(opt.dictionary) === '[object ArrayBuffer]') {
      opt.dictionary = new Uint8Array(opt.dictionary);
    }
    if (opt.raw) { //In raw mode we need to set the dictionary early
      status = zlib_inflate.inflateSetDictionary(this.strm, opt.dictionary);
      if (status !== Z_OK) {
        throw new Error(msg[status]);
      }
    }
  }
}

/**
 * Inflate#push(data[, flush_mode]) -> Boolean
 * - data (Uint8Array|ArrayBuffer): input data
 * - flush_mode (Number|Boolean): 0..6 for corresponding Z_NO_FLUSH..Z_TREE
 *   flush modes. See constants. Skipped or `false` means Z_NO_FLUSH,
 *   `true` means Z_FINISH.
 *
 * Sends input data to inflate pipe, generating [[Inflate#onData]] calls with
 * new output chunks. Returns `true` on success. If end of stream detected,
 * [[Inflate#onEnd]] will be called.
 *
 * `flush_mode` is not needed for normal operation, because end of stream
 * detected automatically. You may try to use it for advanced things, but
 * this functionality was not tested.
 *
 * On fail call [[Inflate#onEnd]] with error code and return false.
 *
 * ##### Example
 *
 * ```javascript
 * push(chunk, false); // push one of data chunks
 * ...
 * push(chunk, true);  // push last chunk
 * ```
 **/
Inflate.prototype.push = function (data, flush_mode) {
  const strm = this.strm;
  const chunkSize = this.options.chunkSize;
  const dictionary = this.options.dictionary;
  let status, _flush_mode, last_avail_out;

  if (this.ended) return false;

  if (flush_mode === ~~flush_mode) _flush_mode = flush_mode;
  else _flush_mode = flush_mode === true ? Z_FINISH : Z_NO_FLUSH;

  // Convert data if needed
  if (toString.call(data) === '[object ArrayBuffer]') {
    strm.input = new Uint8Array(data);
  } else {
    strm.input = data;
  }

  strm.next_in = 0;
  strm.avail_in = strm.input.length;

  for (;;) {
    if (strm.avail_out === 0) {
      strm.output = new Uint8Array(chunkSize);
      strm.next_out = 0;
      strm.avail_out = chunkSize;
    }

    status = zlib_inflate.inflate(strm, _flush_mode);

    if (status === Z_NEED_DICT && dictionary) {
      status = zlib_inflate.inflateSetDictionary(strm, dictionary);

      if (status === Z_OK) {
        status = zlib_inflate.inflate(strm, _flush_mode);
      } else if (status === Z_DATA_ERROR) {
        // Replace code with more verbose
        status = Z_NEED_DICT;
      }
    }

    // Skip snyc markers if more data follows and not raw mode
    while (strm.avail_in > 0 &&
           status === Z_STREAM_END &&
           strm.state.wrap > 0 &&
           data[strm.next_in] !== 0)
    {
      zlib_inflate.inflateReset(strm);
      status = zlib_inflate.inflate(strm, _flush_mode);
    }

    switch (status) {
      case Z_STREAM_ERROR:
      case Z_DATA_ERROR:
      case Z_NEED_DICT:
      case Z_MEM_ERROR:
        this.onEnd(status);
        this.ended = true;
        return false;
    }

    // Remember real `avail_out` value, because we may patch out buffer content
    // to align utf8 strings boundaries.
    last_avail_out = strm.avail_out;

    if (strm.next_out) {
      if (strm.avail_out === 0 || status === Z_STREAM_END) {

        if (this.options.to === 'string') {

          let next_out_utf8 = strings.utf8border(strm.output, strm.next_out);

          let tail = strm.next_out - next_out_utf8;
          let utf8str = strings.buf2string(strm.output, next_out_utf8);

          // move tail & realign counters
          strm.next_out = tail;
          strm.avail_out = chunkSize - tail;
          if (tail) strm.output.set(strm.output.subarray(next_out_utf8, next_out_utf8 + tail), 0);

          this.onData(utf8str);

        } else {
          this.onData(strm.output.length === strm.next_out ? strm.output : strm.output.subarray(0, strm.next_out));
        }
      }
    }

    // Must repeat iteration if out buffer is full
    if (status === Z_OK && last_avail_out === 0) continue;

    // Finalize if end of stream reached.
    if (status === Z_STREAM_END) {
      status = zlib_inflate.inflateEnd(this.strm);
      this.onEnd(status);
      this.ended = true;
      return true;
    }

    if (strm.avail_in === 0) break;
  }

  return true;
};


/**
 * Inflate#onData(chunk) -> Void
 * - chunk (Uint8Array|String): output data. When string output requested,
 *   each chunk will be string.
 *
 * By default, stores data blocks in `chunks[]` property and glue
 * those in `onEnd`. Override this handler, if you need another behaviour.
 **/
Inflate.prototype.onData = function (chunk) {
  this.chunks.push(chunk);
};


/**
 * Inflate#onEnd(status) -> Void
 * - status (Number): inflate status. 0 (Z_OK) on success,
 *   other if not.
 *
 * Called either after you tell inflate that the input stream is
 * complete (Z_FINISH). By default - join collected chunks,
 * free memory and fill `results` / `err` properties.
 **/
Inflate.prototype.onEnd = function (status) {
  // On success - join
  if (status === Z_OK) {
    if (this.options.to === 'string') {
      this.result = this.chunks.join('');
    } else {
      this.result = utils.flattenChunks(this.chunks);
    }
  }
  this.chunks = [];
  this.err = status;
  this.msg = this.strm.msg;
};


/**
 * inflate(data[, options]) -> Uint8Array|String
 * - data (Uint8Array): input data to decompress.
 * - options (Object): zlib inflate options.
 *
 * Decompress `data` with inflate/ungzip and `options`. Autodetect
 * format via wrapper header by default. That's why we don't provide
 * separate `ungzip` method.
 *
 * Supported options are:
 *
 * - windowBits
 *
 * [http://zlib.net/manual.html#Advanced](http://zlib.net/manual.html#Advanced)
 * for more information.
 *
 * Sugar (options):
 *
 * - `raw` (Boolean) - say that we work with raw stream, if you don't wish to specify
 *   negative windowBits implicitly.
 * - `to` (String) - if equal to 'string', then result will be converted
 *   from utf8 to utf16 (javascript) string. When string output requested,
 *   chunk length can differ from `chunkSize`, depending on content.
 *
 *
 * ##### Example:
 *
 * ```javascript
 * const pako = require('pako');
 * const input = pako.deflate(new Uint8Array([1,2,3,4,5,6,7,8,9]));
 * let output;
 *
 * try {
 *   output = pako.inflate(input);
 * } catch (err)
 *   console.log(err);
 * }
 * ```
 **/
function inflate(input, options) {
  const inflator = new Inflate(options);

  inflator.push(input);

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

  return inflator.result;
}


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


/**
 * ungzip(data[, options]) -> Uint8Array|String
 * - data (Uint8Array): input data to decompress.
 * - options (Object): zlib inflate options.
 *
 * Just shortcut to [[inflate]], because it autodetects format
 * by header.content. Done for convenience.
 **/


module.exports.Inflate = Inflate;
module.exports.inflate = inflate;
module.exports.inflateRaw = inflateRaw;
module.exports.ungzip = inflate;
module.exports.constants = require('./zlib/constants');