pdf.js/src/core/stream.js

/* Copyright 2012 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/* Copyright 1996-2003 Glyph & Cog, LLC
 *
 * The flate stream implementation contained in this file is a JavaScript port
 * of XPDF's implementation, made available under the Apache 2.0 open source
 * license.
 */

import {
  FormatError, isSpace, stringToBytes, unreachable
} from '../shared/util';
import { isDict } from './primitives';

var Stream = (function StreamClosure() {
  function Stream(arrayBuffer, start, length, dict) {
    this.bytes = (arrayBuffer instanceof Uint8Array ?
                  arrayBuffer : new Uint8Array(arrayBuffer));
    this.start = start || 0;
    this.pos = this.start;
    this.end = (start + length) || this.bytes.length;
    this.dict = dict;
  }

  // required methods for a stream. if a particular stream does not
  // implement these, an error should be thrown
  Stream.prototype = {
    get length() {
      return this.end - this.start;
    },
    get isEmpty() {
      return this.length === 0;
    },
    getByte: function Stream_getByte() {
      if (this.pos >= this.end) {
        return -1;
      }
      return this.bytes[this.pos++];
    },
    getUint16: function Stream_getUint16() {
      var b0 = this.getByte();
      var b1 = this.getByte();
      if (b0 === -1 || b1 === -1) {
        return -1;
      }
      return (b0 << 8) + b1;
    },
    getInt32: function Stream_getInt32() {
      var b0 = this.getByte();
      var b1 = this.getByte();
      var b2 = this.getByte();
      var b3 = this.getByte();
      return (b0 << 24) + (b1 << 16) + (b2 << 8) + b3;
    },
    // Returns subarray of original buffer, should only be read.
    getBytes(length, forceClamped = false) {
      var bytes = this.bytes;
      var pos = this.pos;
      var strEnd = this.end;

      if (!length) {
        let subarray = bytes.subarray(pos, strEnd);
        // `this.bytes` is always a `Uint8Array` here.
        return (forceClamped ? new Uint8ClampedArray(subarray) : subarray);
      }
      var end = pos + length;
      if (end > strEnd) {
        end = strEnd;
      }
      this.pos = end;
      let subarray = bytes.subarray(pos, end);
      // `this.bytes` is always a `Uint8Array` here.
      return (forceClamped ? new Uint8ClampedArray(subarray) : subarray);
    },
    peekByte: function Stream_peekByte() {
      var peekedByte = this.getByte();
      if (peekedByte !== -1) {
        this.pos--;
      }
      return peekedByte;
    },
    peekBytes(length, forceClamped = false) {
      var bytes = this.getBytes(length, forceClamped);
      this.pos -= bytes.length;
      return bytes;
    },

    getByteRange(begin, end) {
      if (begin < 0) {
        begin = 0;
      }
      if (end > this.end) {
        end = this.end;
      }
      return this.bytes.subarray(begin, end);
    },

    skip: function Stream_skip(n) {
      if (!n) {
        n = 1;
      }
      this.pos += n;
    },
    reset: function Stream_reset() {
      this.pos = this.start;
    },
    moveStart: function Stream_moveStart() {
      this.start = this.pos;
    },
    makeSubStream: function Stream_makeSubStream(start, length, dict) {
      return new Stream(this.bytes.buffer, start, length, dict);
    },
  };

  return Stream;
})();

var StringStream = (function StringStreamClosure() {
  function StringStream(str) {
    let bytes = stringToBytes(str);
    Stream.call(this, bytes);
  }

  StringStream.prototype = Stream.prototype;

  return StringStream;
})();

// super class for the decoding streams
var DecodeStream = (function DecodeStreamClosure() {
  // Lots of DecodeStreams are created whose buffers are never used.  For these
  // we share a single empty buffer. This is (a) space-efficient and (b) avoids
  // having special cases that would be required if we used |null| for an empty
  // buffer.
  var emptyBuffer = new Uint8Array(0);

  function DecodeStream(maybeMinBufferLength) {
    this._rawMinBufferLength = maybeMinBufferLength || 0;

    this.pos = 0;
    this.bufferLength = 0;
    this.eof = false;
    this.buffer = emptyBuffer;
    this.minBufferLength = 512;
    if (maybeMinBufferLength) {
      // Compute the first power of two that is as big as maybeMinBufferLength.
      while (this.minBufferLength < maybeMinBufferLength) {
        this.minBufferLength *= 2;
      }
    }
  }

  DecodeStream.prototype = {
    get isEmpty() {
      while (!this.eof && this.bufferLength === 0) {
        this.readBlock();
      }
      return this.bufferLength === 0;
    },
    ensureBuffer: function DecodeStream_ensureBuffer(requested) {
      var buffer = this.buffer;
      if (requested <= buffer.byteLength) {
        return buffer;
      }
      var size = this.minBufferLength;
      while (size < requested) {
        size *= 2;
      }
      var buffer2 = new Uint8Array(size);
      buffer2.set(buffer);
      return (this.buffer = buffer2);
    },
    getByte: function DecodeStream_getByte() {
      var pos = this.pos;
      while (this.bufferLength <= pos) {
        if (this.eof) {
          return -1;
        }
        this.readBlock();
      }
      return this.buffer[this.pos++];
    },
    getUint16: function DecodeStream_getUint16() {
      var b0 = this.getByte();
      var b1 = this.getByte();
      if (b0 === -1 || b1 === -1) {
        return -1;
      }
      return (b0 << 8) + b1;
    },
    getInt32: function DecodeStream_getInt32() {
      var b0 = this.getByte();
      var b1 = this.getByte();
      var b2 = this.getByte();
      var b3 = this.getByte();
      return (b0 << 24) + (b1 << 16) + (b2 << 8) + b3;
    },
    getBytes(length, forceClamped = false) {
      var end, pos = this.pos;

      if (length) {
        this.ensureBuffer(pos + length);
        end = pos + length;

        while (!this.eof && this.bufferLength < end) {
          this.readBlock();
        }
        var bufEnd = this.bufferLength;
        if (end > bufEnd) {
          end = bufEnd;
        }
      } else {
        while (!this.eof) {
          this.readBlock();
        }
        end = this.bufferLength;
      }

      this.pos = end;
      let subarray = this.buffer.subarray(pos, end);
      // `this.buffer` is either a `Uint8Array` or `Uint8ClampedArray` here.
      return (forceClamped && !(subarray instanceof Uint8ClampedArray) ?
              new Uint8ClampedArray(subarray) : subarray);
    },
    peekByte: function DecodeStream_peekByte() {
      var peekedByte = this.getByte();
      if (peekedByte !== -1) {
        this.pos--;
      }
      return peekedByte;
    },
    peekBytes(length, forceClamped = false) {
      var bytes = this.getBytes(length, forceClamped);
      this.pos -= bytes.length;
      return bytes;
    },
    makeSubStream: function DecodeStream_makeSubStream(start, length, dict) {
      var end = start + length;
      while (this.bufferLength <= end && !this.eof) {
        this.readBlock();
      }
      return new Stream(this.buffer, start, length, dict);
    },

    getByteRange(begin, end) {
      unreachable('Should not call DecodeStream.getByteRange');
    },

    skip: function DecodeStream_skip(n) {
      if (!n) {
        n = 1;
      }
      this.pos += n;
    },
    reset: function DecodeStream_reset() {
      this.pos = 0;
    },
    getBaseStreams: function DecodeStream_getBaseStreams() {
      if (this.str && this.str.getBaseStreams) {
        return this.str.getBaseStreams();
      }
      return [];
    },
  };

  return DecodeStream;
})();

var StreamsSequenceStream = (function StreamsSequenceStreamClosure() {
  function StreamsSequenceStream(streams) {
    this.streams = streams;

    let maybeLength = 0;
    for (let i = 0, ii = streams.length; i < ii; i++) {
      const stream = streams[i];
      if (stream instanceof DecodeStream) {
        maybeLength += stream._rawMinBufferLength;
      } else {
        maybeLength += stream.length;
      }
    }
    DecodeStream.call(this, maybeLength);
  }

  StreamsSequenceStream.prototype = Object.create(DecodeStream.prototype);

  StreamsSequenceStream.prototype.readBlock =
      function streamSequenceStreamReadBlock() {

    var streams = this.streams;
    if (streams.length === 0) {
      this.eof = true;
      return;
    }
    var stream = streams.shift();
    var chunk = stream.getBytes();
    var bufferLength = this.bufferLength;
    var newLength = bufferLength + chunk.length;
    var buffer = this.ensureBuffer(newLength);
    buffer.set(chunk, bufferLength);
    this.bufferLength = newLength;
  };

  StreamsSequenceStream.prototype.getBaseStreams =
    function StreamsSequenceStream_getBaseStreams() {

    var baseStreams = [];
    for (var i = 0, ii = this.streams.length; i < ii; i++) {
      var stream = this.streams[i];
      if (stream.getBaseStreams) {
        baseStreams.push(...stream.getBaseStreams());
      }
    }
    return baseStreams;
  };

  return StreamsSequenceStream;
})();

var FlateStream = (function FlateStreamClosure() {
  // prettier-ignore
  var codeLenCodeMap = new Int32Array([
    16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
  ]);

  // prettier-ignore
  var lengthDecode = new Int32Array([
    0x00003, 0x00004, 0x00005, 0x00006, 0x00007, 0x00008, 0x00009, 0x0000a,
    0x1000b, 0x1000d, 0x1000f, 0x10011, 0x20013, 0x20017, 0x2001b, 0x2001f,
    0x30023, 0x3002b, 0x30033, 0x3003b, 0x40043, 0x40053, 0x40063, 0x40073,
    0x50083, 0x500a3, 0x500c3, 0x500e3, 0x00102, 0x00102, 0x00102
  ]);

  // prettier-ignore
  var distDecode = new Int32Array([
    0x00001, 0x00002, 0x00003, 0x00004, 0x10005, 0x10007, 0x20009, 0x2000d,
    0x30011, 0x30019, 0x40021, 0x40031, 0x50041, 0x50061, 0x60081, 0x600c1,
    0x70101, 0x70181, 0x80201, 0x80301, 0x90401, 0x90601, 0xa0801, 0xa0c01,
    0xb1001, 0xb1801, 0xc2001, 0xc3001, 0xd4001, 0xd6001
  ]);

  // prettier-ignore
  var fixedLitCodeTab = [new Int32Array([
    0x70100, 0x80050, 0x80010, 0x80118, 0x70110, 0x80070, 0x80030, 0x900c0,
    0x70108, 0x80060, 0x80020, 0x900a0, 0x80000, 0x80080, 0x80040, 0x900e0,
    0x70104, 0x80058, 0x80018, 0x90090, 0x70114, 0x80078, 0x80038, 0x900d0,
    0x7010c, 0x80068, 0x80028, 0x900b0, 0x80008, 0x80088, 0x80048, 0x900f0,
    0x70102, 0x80054, 0x80014, 0x8011c, 0x70112, 0x80074, 0x80034, 0x900c8,
    0x7010a, 0x80064, 0x80024, 0x900a8, 0x80004, 0x80084, 0x80044, 0x900e8,
    0x70106, 0x8005c, 0x8001c, 0x90098, 0x70116, 0x8007c, 0x8003c, 0x900d8,
    0x7010e, 0x8006c, 0x8002c, 0x900b8, 0x8000c, 0x8008c, 0x8004c, 0x900f8,
    0x70101, 0x80052, 0x80012, 0x8011a, 0x70111, 0x80072, 0x80032, 0x900c4,
    0x70109, 0x80062, 0x80022, 0x900a4, 0x80002, 0x80082, 0x80042, 0x900e4,
    0x70105, 0x8005a, 0x8001a, 0x90094, 0x70115, 0x8007a, 0x8003a, 0x900d4,
    0x7010d, 0x8006a, 0x8002a, 0x900b4, 0x8000a, 0x8008a, 0x8004a, 0x900f4,
    0x70103, 0x80056, 0x80016, 0x8011e, 0x70113, 0x80076, 0x80036, 0x900cc,
    0x7010b, 0x80066, 0x80026, 0x900ac, 0x80006, 0x80086, 0x80046, 0x900ec,
    0x70107, 0x8005e, 0x8001e, 0x9009c, 0x70117, 0x8007e, 0x8003e, 0x900dc,
    0x7010f, 0x8006e, 0x8002e, 0x900bc, 0x8000e, 0x8008e, 0x8004e, 0x900fc,
    0x70100, 0x80051, 0x80011, 0x80119, 0x70110, 0x80071, 0x80031, 0x900c2,
    0x70108, 0x80061, 0x80021, 0x900a2, 0x80001, 0x80081, 0x80041, 0x900e2,
    0x70104, 0x80059, 0x80019, 0x90092, 0x70114, 0x80079, 0x80039, 0x900d2,
    0x7010c, 0x80069, 0x80029, 0x900b2, 0x80009, 0x80089, 0x80049, 0x900f2,
    0x70102, 0x80055, 0x80015, 0x8011d, 0x70112, 0x80075, 0x80035, 0x900ca,
    0x7010a, 0x80065, 0x80025, 0x900aa, 0x80005, 0x80085, 0x80045, 0x900ea,
    0x70106, 0x8005d, 0x8001d, 0x9009a, 0x70116, 0x8007d, 0x8003d, 0x900da,
    0x7010e, 0x8006d, 0x8002d, 0x900ba, 0x8000d, 0x8008d, 0x8004d, 0x900fa,
    0x70101, 0x80053, 0x80013, 0x8011b, 0x70111, 0x80073, 0x80033, 0x900c6,
    0x70109, 0x80063, 0x80023, 0x900a6, 0x80003, 0x80083, 0x80043, 0x900e6,
    0x70105, 0x8005b, 0x8001b, 0x90096, 0x70115, 0x8007b, 0x8003b, 0x900d6,
    0x7010d, 0x8006b, 0x8002b, 0x900b6, 0x8000b, 0x8008b, 0x8004b, 0x900f6,
    0x70103, 0x80057, 0x80017, 0x8011f, 0x70113, 0x80077, 0x80037, 0x900ce,
    0x7010b, 0x80067, 0x80027, 0x900ae, 0x80007, 0x80087, 0x80047, 0x900ee,
    0x70107, 0x8005f, 0x8001f, 0x9009e, 0x70117, 0x8007f, 0x8003f, 0x900de,
    0x7010f, 0x8006f, 0x8002f, 0x900be, 0x8000f, 0x8008f, 0x8004f, 0x900fe,
    0x70100, 0x80050, 0x80010, 0x80118, 0x70110, 0x80070, 0x80030, 0x900c1,
    0x70108, 0x80060, 0x80020, 0x900a1, 0x80000, 0x80080, 0x80040, 0x900e1,
    0x70104, 0x80058, 0x80018, 0x90091, 0x70114, 0x80078, 0x80038, 0x900d1,
    0x7010c, 0x80068, 0x80028, 0x900b1, 0x80008, 0x80088, 0x80048, 0x900f1,
    0x70102, 0x80054, 0x80014, 0x8011c, 0x70112, 0x80074, 0x80034, 0x900c9,
    0x7010a, 0x80064, 0x80024, 0x900a9, 0x80004, 0x80084, 0x80044, 0x900e9,
    0x70106, 0x8005c, 0x8001c, 0x90099, 0x70116, 0x8007c, 0x8003c, 0x900d9,
    0x7010e, 0x8006c, 0x8002c, 0x900b9, 0x8000c, 0x8008c, 0x8004c, 0x900f9,
    0x70101, 0x80052, 0x80012, 0x8011a, 0x70111, 0x80072, 0x80032, 0x900c5,
    0x70109, 0x80062, 0x80022, 0x900a5, 0x80002, 0x80082, 0x80042, 0x900e5,
    0x70105, 0x8005a, 0x8001a, 0x90095, 0x70115, 0x8007a, 0x8003a, 0x900d5,
    0x7010d, 0x8006a, 0x8002a, 0x900b5, 0x8000a, 0x8008a, 0x8004a, 0x900f5,
    0x70103, 0x80056, 0x80016, 0x8011e, 0x70113, 0x80076, 0x80036, 0x900cd,
    0x7010b, 0x80066, 0x80026, 0x900ad, 0x80006, 0x80086, 0x80046, 0x900ed,
    0x70107, 0x8005e, 0x8001e, 0x9009d, 0x70117, 0x8007e, 0x8003e, 0x900dd,
    0x7010f, 0x8006e, 0x8002e, 0x900bd, 0x8000e, 0x8008e, 0x8004e, 0x900fd,
    0x70100, 0x80051, 0x80011, 0x80119, 0x70110, 0x80071, 0x80031, 0x900c3,
    0x70108, 0x80061, 0x80021, 0x900a3, 0x80001, 0x80081, 0x80041, 0x900e3,
    0x70104, 0x80059, 0x80019, 0x90093, 0x70114, 0x80079, 0x80039, 0x900d3,
    0x7010c, 0x80069, 0x80029, 0x900b3, 0x80009, 0x80089, 0x80049, 0x900f3,
    0x70102, 0x80055, 0x80015, 0x8011d, 0x70112, 0x80075, 0x80035, 0x900cb,
    0x7010a, 0x80065, 0x80025, 0x900ab, 0x80005, 0x80085, 0x80045, 0x900eb,
    0x70106, 0x8005d, 0x8001d, 0x9009b, 0x70116, 0x8007d, 0x8003d, 0x900db,
    0x7010e, 0x8006d, 0x8002d, 0x900bb, 0x8000d, 0x8008d, 0x8004d, 0x900fb,
    0x70101, 0x80053, 0x80013, 0x8011b, 0x70111, 0x80073, 0x80033, 0x900c7,
    0x70109, 0x80063, 0x80023, 0x900a7, 0x80003, 0x80083, 0x80043, 0x900e7,
    0x70105, 0x8005b, 0x8001b, 0x90097, 0x70115, 0x8007b, 0x8003b, 0x900d7,
    0x7010d, 0x8006b, 0x8002b, 0x900b7, 0x8000b, 0x8008b, 0x8004b, 0x900f7,
    0x70103, 0x80057, 0x80017, 0x8011f, 0x70113, 0x80077, 0x80037, 0x900cf,
    0x7010b, 0x80067, 0x80027, 0x900af, 0x80007, 0x80087, 0x80047, 0x900ef,
    0x70107, 0x8005f, 0x8001f, 0x9009f, 0x70117, 0x8007f, 0x8003f, 0x900df,
    0x7010f, 0x8006f, 0x8002f, 0x900bf, 0x8000f, 0x8008f, 0x8004f, 0x900ff
  ]), 9];

  // prettier-ignore
  var fixedDistCodeTab = [new Int32Array([
    0x50000, 0x50010, 0x50008, 0x50018, 0x50004, 0x50014, 0x5000c, 0x5001c,
    0x50002, 0x50012, 0x5000a, 0x5001a, 0x50006, 0x50016, 0x5000e, 0x00000,
    0x50001, 0x50011, 0x50009, 0x50019, 0x50005, 0x50015, 0x5000d, 0x5001d,
    0x50003, 0x50013, 0x5000b, 0x5001b, 0x50007, 0x50017, 0x5000f, 0x00000
  ]), 5];

  function FlateStream(str, maybeLength) {
    this.str = str;
    this.dict = str.dict;

    var cmf = str.getByte();
    var flg = str.getByte();
    if (cmf === -1 || flg === -1) {
      throw new FormatError(
        `Invalid header in flate stream: ${cmf}, ${flg}`);
    }
    if ((cmf & 0x0f) !== 0x08) {
      throw new FormatError(
        `Unknown compression method in flate stream: ${cmf}, ${flg}`);
    }
    if ((((cmf << 8) + flg) % 31) !== 0) {
      throw new FormatError(`Bad FCHECK in flate stream: ${cmf}, ${flg}`);
    }
    if (flg & 0x20) {
      throw new FormatError(
        `FDICT bit set in flate stream: ${cmf}, ${flg}`);
    }

    this.codeSize = 0;
    this.codeBuf = 0;

    DecodeStream.call(this, maybeLength);
  }

  FlateStream.prototype = Object.create(DecodeStream.prototype);

  FlateStream.prototype.getBits = function FlateStream_getBits(bits) {
    var str = this.str;
    var codeSize = this.codeSize;
    var codeBuf = this.codeBuf;

    var b;
    while (codeSize < bits) {
      if ((b = str.getByte()) === -1) {
        throw new FormatError('Bad encoding in flate stream');
      }
      codeBuf |= b << codeSize;
      codeSize += 8;
    }
    b = codeBuf & ((1 << bits) - 1);
    this.codeBuf = codeBuf >> bits;
    this.codeSize = codeSize -= bits;

    return b;
  };

  FlateStream.prototype.getCode = function FlateStream_getCode(table) {
    var str = this.str;
    var codes = table[0];
    var maxLen = table[1];
    var codeSize = this.codeSize;
    var codeBuf = this.codeBuf;

    var b;
    while (codeSize < maxLen) {
      if ((b = str.getByte()) === -1) {
        // premature end of stream. code might however still be valid.
        // codeSize < codeLen check below guards against incomplete codeVal.
        break;
      }
      codeBuf |= (b << codeSize);
      codeSize += 8;
    }
    var code = codes[codeBuf & ((1 << maxLen) - 1)];
    var codeLen = code >> 16;
    var codeVal = code & 0xffff;
    if (codeLen < 1 || codeSize < codeLen) {
      throw new FormatError('Bad encoding in flate stream');
    }
    this.codeBuf = (codeBuf >> codeLen);
    this.codeSize = (codeSize - codeLen);
    return codeVal;
  };

  FlateStream.prototype.generateHuffmanTable =
      function flateStreamGenerateHuffmanTable(lengths) {
    var n = lengths.length;

    // find max code length
    var maxLen = 0;
    var i;
    for (i = 0; i < n; ++i) {
      if (lengths[i] > maxLen) {
        maxLen = lengths[i];
      }
    }

    // build the table
    var size = 1 << maxLen;
    var codes = new Int32Array(size);
    for (var len = 1, code = 0, skip = 2;
         len <= maxLen;
         ++len, code <<= 1, skip <<= 1) {
      for (var val = 0; val < n; ++val) {
        if (lengths[val] === len) {
          // bit-reverse the code
          var code2 = 0;
          var t = code;
          for (i = 0; i < len; ++i) {
            code2 = (code2 << 1) | (t & 1);
            t >>= 1;
          }

          // fill the table entries
          for (i = code2; i < size; i += skip) {
            codes[i] = (len << 16) | val;
          }
          ++code;
        }
      }
    }

    return [codes, maxLen];
  };

  FlateStream.prototype.readBlock = function FlateStream_readBlock() {
    var buffer, len;
    var str = this.str;
    // read block header
    var hdr = this.getBits(3);
    if (hdr & 1) {
      this.eof = true;
    }
    hdr >>= 1;

    if (hdr === 0) { // uncompressed block
      var b;

      if ((b = str.getByte()) === -1) {
        throw new FormatError('Bad block header in flate stream');
      }
      var blockLen = b;
      if ((b = str.getByte()) === -1) {
        throw new FormatError('Bad block header in flate stream');
      }
      blockLen |= (b << 8);
      if ((b = str.getByte()) === -1) {
        throw new FormatError('Bad block header in flate stream');
      }
      var check = b;
      if ((b = str.getByte()) === -1) {
        throw new FormatError('Bad block header in flate stream');
      }
      check |= (b << 8);
      if (check !== (~blockLen & 0xffff) &&
          (blockLen !== 0 || check !== 0)) {
        // Ignoring error for bad "empty" block (see issue 1277)
        throw new FormatError(
          'Bad uncompressed block length in flate stream');
      }

      this.codeBuf = 0;
      this.codeSize = 0;

      const bufferLength = this.bufferLength, end = bufferLength + blockLen;
      buffer = this.ensureBuffer(end);
      this.bufferLength = end;

      if (blockLen === 0) {
        if (str.peekByte() === -1) {
          this.eof = true;
        }
      } else {
        const block = str.getBytes(blockLen);
        buffer.set(block, bufferLength);
        if (block.length < blockLen) {
          this.eof = true;
        }
      }
      return;
    }

    var litCodeTable;
    var distCodeTable;
    if (hdr === 1) { // compressed block, fixed codes
      litCodeTable = fixedLitCodeTab;
      distCodeTable = fixedDistCodeTab;
    } else if (hdr === 2) { // compressed block, dynamic codes
      var numLitCodes = this.getBits(5) + 257;
      var numDistCodes = this.getBits(5) + 1;
      var numCodeLenCodes = this.getBits(4) + 4;

      // build the code lengths code table
      var codeLenCodeLengths = new Uint8Array(codeLenCodeMap.length);

      var i;
      for (i = 0; i < numCodeLenCodes; ++i) {
        codeLenCodeLengths[codeLenCodeMap[i]] = this.getBits(3);
      }
      var codeLenCodeTab = this.generateHuffmanTable(codeLenCodeLengths);

      // build the literal and distance code tables
      len = 0;
      i = 0;
      var codes = numLitCodes + numDistCodes;
      var codeLengths = new Uint8Array(codes);
      var bitsLength, bitsOffset, what;
      while (i < codes) {
        var code = this.getCode(codeLenCodeTab);
        if (code === 16) {
          bitsLength = 2; bitsOffset = 3; what = len;
        } else if (code === 17) {
          bitsLength = 3; bitsOffset = 3; what = (len = 0);
        } else if (code === 18) {
          bitsLength = 7; bitsOffset = 11; what = (len = 0);
        } else {
          codeLengths[i++] = len = code;
          continue;
        }

        var repeatLength = this.getBits(bitsLength) + bitsOffset;
        while (repeatLength-- > 0) {
          codeLengths[i++] = what;
        }
      }

      litCodeTable =
        this.generateHuffmanTable(codeLengths.subarray(0, numLitCodes));
      distCodeTable =
        this.generateHuffmanTable(codeLengths.subarray(numLitCodes, codes));
    } else {
      throw new FormatError('Unknown block type in flate stream');
    }

    buffer = this.buffer;
    var limit = buffer ? buffer.length : 0;
    var pos = this.bufferLength;
    while (true) {
      var code1 = this.getCode(litCodeTable);
      if (code1 < 256) {
        if (pos + 1 >= limit) {
          buffer = this.ensureBuffer(pos + 1);
          limit = buffer.length;
        }
        buffer[pos++] = code1;
        continue;
      }
      if (code1 === 256) {
        this.bufferLength = pos;
        return;
      }
      code1 -= 257;
      code1 = lengthDecode[code1];
      var code2 = code1 >> 16;
      if (code2 > 0) {
        code2 = this.getBits(code2);
      }
      len = (code1 & 0xffff) + code2;
      code1 = this.getCode(distCodeTable);
      code1 = distDecode[code1];
      code2 = code1 >> 16;
      if (code2 > 0) {
        code2 = this.getBits(code2);
      }
      var dist = (code1 & 0xffff) + code2;
      if (pos + len >= limit) {
        buffer = this.ensureBuffer(pos + len);
        limit = buffer.length;
      }
      for (var k = 0; k < len; ++k, ++pos) {
        buffer[pos] = buffer[pos - dist];
      }
    }
  };

  return FlateStream;
})();

var PredictorStream = (function PredictorStreamClosure() {
  function PredictorStream(str, maybeLength, params) {
    if (!isDict(params)) {
      return str; // no prediction
    }
    var predictor = this.predictor = params.get('Predictor') || 1;

    if (predictor <= 1) {
      return str; // no prediction
    }
    if (predictor !== 2 && (predictor < 10 || predictor > 15)) {
      throw new FormatError(`Unsupported predictor: ${predictor}`);
    }

    if (predictor === 2) {
      this.readBlock = this.readBlockTiff;
    } else {
      this.readBlock = this.readBlockPng;
    }

    this.str = str;
    this.dict = str.dict;

    var colors = this.colors = params.get('Colors') || 1;
    var bits = this.bits = params.get('BitsPerComponent') || 8;
    var columns = this.columns = params.get('Columns') || 1;

    this.pixBytes = (colors * bits + 7) >> 3;
    this.rowBytes = (columns * colors * bits + 7) >> 3;

    DecodeStream.call(this, maybeLength);
    return this;
  }

  PredictorStream.prototype = Object.create(DecodeStream.prototype);

  PredictorStream.prototype.readBlockTiff =
      function predictorStreamReadBlockTiff() {
    var rowBytes = this.rowBytes;

    var bufferLength = this.bufferLength;
    var buffer = this.ensureBuffer(bufferLength + rowBytes);

    var bits = this.bits;
    var colors = this.colors;

    var rawBytes = this.str.getBytes(rowBytes);
    this.eof = !rawBytes.length;
    if (this.eof) {
      return;
    }

    var inbuf = 0, outbuf = 0;
    var inbits = 0, outbits = 0;
    var pos = bufferLength;
    var i;

    if (bits === 1 && colors === 1) {
      // Optimized version of the loop in the "else"-branch
      // for 1 bit-per-component and 1 color TIFF images.
      for (i = 0; i < rowBytes; ++i) {
        var c = rawBytes[i] ^ inbuf;
        c ^= c >> 1;
        c ^= c >> 2;
        c ^= c >> 4;
        inbuf = (c & 1) << 7;
        buffer[pos++] = c;
      }
    } else if (bits === 8) {
      for (i = 0; i < colors; ++i) {
        buffer[pos++] = rawBytes[i];
      }
      for (; i < rowBytes; ++i) {
        buffer[pos] = buffer[pos - colors] + rawBytes[i];
        pos++;
      }
    } else if (bits === 16) {
      var bytesPerPixel = colors * 2;
      for (i = 0; i < bytesPerPixel; ++i) {
        buffer[pos++] = rawBytes[i];
      }
      for (; i < rowBytes; i += 2) {
        var sum = ((rawBytes[i] & 0xFF) << 8) +
                  (rawBytes[i + 1] & 0xFF) +
                  ((buffer[pos - bytesPerPixel] & 0xFF) << 8) +
                  (buffer[pos - bytesPerPixel + 1] & 0xFF);
        buffer[pos++] = ((sum >> 8) & 0xFF);
        buffer[pos++] = (sum & 0xFF);
      }
    } else {
      var compArray = new Uint8Array(colors + 1);
      var bitMask = (1 << bits) - 1;
      var j = 0, k = bufferLength;
      var columns = this.columns;
      for (i = 0; i < columns; ++i) {
        for (var kk = 0; kk < colors; ++kk) {
          if (inbits < bits) {
            inbuf = (inbuf << 8) | (rawBytes[j++] & 0xFF);
            inbits += 8;
          }
          compArray[kk] = (compArray[kk] +
                           (inbuf >> (inbits - bits))) & bitMask;
          inbits -= bits;
          outbuf = (outbuf << bits) | compArray[kk];
          outbits += bits;
          if (outbits >= 8) {
            buffer[k++] = (outbuf >> (outbits - 8)) & 0xFF;
            outbits -= 8;
          }
        }
      }
      if (outbits > 0) {
        buffer[k++] = (outbuf << (8 - outbits)) +
                      (inbuf & ((1 << (8 - outbits)) - 1));
      }
    }
    this.bufferLength += rowBytes;
  };

  PredictorStream.prototype.readBlockPng =
      function predictorStreamReadBlockPng() {

    var rowBytes = this.rowBytes;
    var pixBytes = this.pixBytes;

    var predictor = this.str.getByte();
    var rawBytes = this.str.getBytes(rowBytes);
    this.eof = !rawBytes.length;
    if (this.eof) {
      return;
    }

    var bufferLength = this.bufferLength;
    var buffer = this.ensureBuffer(bufferLength + rowBytes);

    var prevRow = buffer.subarray(bufferLength - rowBytes, bufferLength);
    if (prevRow.length === 0) {
      prevRow = new Uint8Array(rowBytes);
    }

    var i, j = bufferLength, up, c;
    switch (predictor) {
      case 0:
        for (i = 0; i < rowBytes; ++i) {
          buffer[j++] = rawBytes[i];
        }
        break;
      case 1:
        for (i = 0; i < pixBytes; ++i) {
          buffer[j++] = rawBytes[i];
        }
        for (; i < rowBytes; ++i) {
          buffer[j] = (buffer[j - pixBytes] + rawBytes[i]) & 0xFF;
          j++;
        }
        break;
      case 2:
        for (i = 0; i < rowBytes; ++i) {
          buffer[j++] = (prevRow[i] + rawBytes[i]) & 0xFF;
        }
        break;
      case 3:
        for (i = 0; i < pixBytes; ++i) {
          buffer[j++] = (prevRow[i] >> 1) + rawBytes[i];
        }
        for (; i < rowBytes; ++i) {
          buffer[j] = (((prevRow[i] + buffer[j - pixBytes]) >> 1) +
                           rawBytes[i]) & 0xFF;
          j++;
        }
        break;
      case 4:
        // we need to save the up left pixels values. the simplest way
        // is to create a new buffer
        for (i = 0; i < pixBytes; ++i) {
          up = prevRow[i];
          c = rawBytes[i];
          buffer[j++] = up + c;
        }
        for (; i < rowBytes; ++i) {
          up = prevRow[i];
          var upLeft = prevRow[i - pixBytes];
          var left = buffer[j - pixBytes];
          var p = left + up - upLeft;

          var pa = p - left;
          if (pa < 0) {
            pa = -pa;
          }
          var pb = p - up;
          if (pb < 0) {
            pb = -pb;
          }
          var pc = p - upLeft;
          if (pc < 0) {
            pc = -pc;
          }

          c = rawBytes[i];
          if (pa <= pb && pa <= pc) {
            buffer[j++] = left + c;
          } else if (pb <= pc) {
            buffer[j++] = up + c;
          } else {
            buffer[j++] = upLeft + c;
          }
        }
        break;
      default:
        throw new FormatError(`Unsupported predictor: ${predictor}`);
    }
    this.bufferLength += rowBytes;
  };

  return PredictorStream;
})();

var DecryptStream = (function DecryptStreamClosure() {
  function DecryptStream(str, maybeLength, decrypt) {
    this.str = str;
    this.dict = str.dict;
    this.decrypt = decrypt;
    this.nextChunk = null;
    this.initialized = false;

    DecodeStream.call(this, maybeLength);
  }

  var chunkSize = 512;

  DecryptStream.prototype = Object.create(DecodeStream.prototype);

  DecryptStream.prototype.readBlock = function DecryptStream_readBlock() {
    var chunk;
    if (this.initialized) {
      chunk = this.nextChunk;
    } else {
      chunk = this.str.getBytes(chunkSize);
      this.initialized = true;
    }
    if (!chunk || chunk.length === 0) {
      this.eof = true;
      return;
    }
    this.nextChunk = this.str.getBytes(chunkSize);
    var hasMoreData = this.nextChunk && this.nextChunk.length > 0;

    var decrypt = this.decrypt;
    chunk = decrypt(chunk, !hasMoreData);

    var bufferLength = this.bufferLength;
    var i, n = chunk.length;
    var buffer = this.ensureBuffer(bufferLength + n);
    for (i = 0; i < n; i++) {
      buffer[bufferLength++] = chunk[i];
    }
    this.bufferLength = bufferLength;
  };

  return DecryptStream;
})();

var Ascii85Stream = (function Ascii85StreamClosure() {
  function Ascii85Stream(str, maybeLength) {
    this.str = str;
    this.dict = str.dict;
    this.input = new Uint8Array(5);

    // Most streams increase in size when decoded, but Ascii85 streams
    // typically shrink by ~20%.
    if (maybeLength) {
      maybeLength = 0.8 * maybeLength;
    }
    DecodeStream.call(this, maybeLength);
  }

  Ascii85Stream.prototype = Object.create(DecodeStream.prototype);

  Ascii85Stream.prototype.readBlock = function Ascii85Stream_readBlock() {
    var TILDA_CHAR = 0x7E; // '~'
    var Z_LOWER_CHAR = 0x7A; // 'z'
    var EOF = -1;

    var str = this.str;

    var c = str.getByte();
    while (isSpace(c)) {
      c = str.getByte();
    }

    if (c === EOF || c === TILDA_CHAR) {
      this.eof = true;
      return;
    }

    var bufferLength = this.bufferLength, buffer;
    var i;

    // special code for z
    if (c === Z_LOWER_CHAR) {
      buffer = this.ensureBuffer(bufferLength + 4);
      for (i = 0; i < 4; ++i) {
        buffer[bufferLength + i] = 0;
      }
      this.bufferLength += 4;
    } else {
      var input = this.input;
      input[0] = c;
      for (i = 1; i < 5; ++i) {
        c = str.getByte();
        while (isSpace(c)) {
          c = str.getByte();
        }

        input[i] = c;

        if (c === EOF || c === TILDA_CHAR) {
          break;
        }
      }
      buffer = this.ensureBuffer(bufferLength + i - 1);
      this.bufferLength += i - 1;

      // partial ending;
      if (i < 5) {
        for (; i < 5; ++i) {
          input[i] = 0x21 + 84;
        }
        this.eof = true;
      }
      var t = 0;
      for (i = 0; i < 5; ++i) {
        t = t * 85 + (input[i] - 0x21);
      }

      for (i = 3; i >= 0; --i) {
        buffer[bufferLength + i] = t & 0xFF;
        t >>= 8;
      }
    }
  };

  return Ascii85Stream;
})();

var AsciiHexStream = (function AsciiHexStreamClosure() {
  function AsciiHexStream(str, maybeLength) {
    this.str = str;
    this.dict = str.dict;

    this.firstDigit = -1;

    // Most streams increase in size when decoded, but AsciiHex streams shrink
    // by 50%.
    if (maybeLength) {
      maybeLength = 0.5 * maybeLength;
    }
    DecodeStream.call(this, maybeLength);
  }

  AsciiHexStream.prototype = Object.create(DecodeStream.prototype);

  AsciiHexStream.prototype.readBlock = function AsciiHexStream_readBlock() {
    var UPSTREAM_BLOCK_SIZE = 8000;
    var bytes = this.str.getBytes(UPSTREAM_BLOCK_SIZE);
    if (!bytes.length) {
      this.eof = true;
      return;
    }

    var maxDecodeLength = (bytes.length + 1) >> 1;
    var buffer = this.ensureBuffer(this.bufferLength + maxDecodeLength);
    var bufferLength = this.bufferLength;

    var firstDigit = this.firstDigit;
    for (var i = 0, ii = bytes.length; i < ii; i++) {
      var ch = bytes[i], digit;
      if (ch >= 0x30 && ch <= 0x39) { // '0'-'9'
        digit = ch & 0x0F;
      } else if ((ch >= 0x41 && ch <= 0x46) || (ch >= 0x61 && ch <= 0x66)) {
        // 'A'-'Z', 'a'-'z'
        digit = (ch & 0x0F) + 9;
      } else if (ch === 0x3E) { // '>'
        this.eof = true;
        break;
      } else { // probably whitespace
        continue; // ignoring
      }
      if (firstDigit < 0) {
        firstDigit = digit;
      } else {
        buffer[bufferLength++] = (firstDigit << 4) | digit;
        firstDigit = -1;
      }
    }
    if (firstDigit >= 0 && this.eof) {
      // incomplete byte
      buffer[bufferLength++] = (firstDigit << 4);
      firstDigit = -1;
    }
    this.firstDigit = firstDigit;
    this.bufferLength = bufferLength;
  };

  return AsciiHexStream;
})();

var RunLengthStream = (function RunLengthStreamClosure() {
  function RunLengthStream(str, maybeLength) {
    this.str = str;
    this.dict = str.dict;

    DecodeStream.call(this, maybeLength);
  }

  RunLengthStream.prototype = Object.create(DecodeStream.prototype);

  RunLengthStream.prototype.readBlock = function RunLengthStream_readBlock() {
    // The repeatHeader has following format. The first byte defines type of run
    // and amount of bytes to repeat/copy: n = 0 through 127 - copy next n bytes
    // (in addition to the second byte from the header), n = 129 through 255 -
    // duplicate the second byte from the header (257 - n) times, n = 128 - end.
    var repeatHeader = this.str.getBytes(2);
    if (!repeatHeader || repeatHeader.length < 2 || repeatHeader[0] === 128) {
      this.eof = true;
      return;
    }

    var buffer;
    var bufferLength = this.bufferLength;
    var n = repeatHeader[0];
    if (n < 128) {
      // copy n bytes
      buffer = this.ensureBuffer(bufferLength + n + 1);
      buffer[bufferLength++] = repeatHeader[1];
      if (n > 0) {
        var source = this.str.getBytes(n);
        buffer.set(source, bufferLength);
        bufferLength += n;
      }
    } else {
      n = 257 - n;
      var b = repeatHeader[1];
      buffer = this.ensureBuffer(bufferLength + n + 1);
      for (var i = 0; i < n; i++) {
        buffer[bufferLength++] = b;
      }
    }
    this.bufferLength = bufferLength;
  };

  return RunLengthStream;
})();

var LZWStream = (function LZWStreamClosure() {
  function LZWStream(str, maybeLength, earlyChange) {
    this.str = str;
    this.dict = str.dict;
    this.cachedData = 0;
    this.bitsCached = 0;

    var maxLzwDictionarySize = 4096;
    var lzwState = {
      earlyChange,
      codeLength: 9,
      nextCode: 258,
      dictionaryValues: new Uint8Array(maxLzwDictionarySize),
      dictionaryLengths: new Uint16Array(maxLzwDictionarySize),
      dictionaryPrevCodes: new Uint16Array(maxLzwDictionarySize),
      currentSequence: new Uint8Array(maxLzwDictionarySize),
      currentSequenceLength: 0,
    };
    for (var i = 0; i < 256; ++i) {
      lzwState.dictionaryValues[i] = i;
      lzwState.dictionaryLengths[i] = 1;
    }
    this.lzwState = lzwState;

    DecodeStream.call(this, maybeLength);
  }

  LZWStream.prototype = Object.create(DecodeStream.prototype);

  LZWStream.prototype.readBits = function LZWStream_readBits(n) {
    var bitsCached = this.bitsCached;
    var cachedData = this.cachedData;
    while (bitsCached < n) {
      var c = this.str.getByte();
      if (c === -1) {
        this.eof = true;
        return null;
      }
      cachedData = (cachedData << 8) | c;
      bitsCached += 8;
    }
    this.bitsCached = (bitsCached -= n);
    this.cachedData = cachedData;
    this.lastCode = null;
    return (cachedData >>> bitsCached) & ((1 << n) - 1);
  };

  LZWStream.prototype.readBlock = function LZWStream_readBlock() {
    var blockSize = 512;
    var estimatedDecodedSize = blockSize * 2, decodedSizeDelta = blockSize;
    var i, j, q;

    var lzwState = this.lzwState;
    if (!lzwState) {
      return; // eof was found
    }

    var earlyChange = lzwState.earlyChange;
    var nextCode = lzwState.nextCode;
    var dictionaryValues = lzwState.dictionaryValues;
    var dictionaryLengths = lzwState.dictionaryLengths;
    var dictionaryPrevCodes = lzwState.dictionaryPrevCodes;
    var codeLength = lzwState.codeLength;
    var prevCode = lzwState.prevCode;
    var currentSequence = lzwState.currentSequence;
    var currentSequenceLength = lzwState.currentSequenceLength;

    var decodedLength = 0;
    var currentBufferLength = this.bufferLength;
    var buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize);

    for (i = 0; i < blockSize; i++) {
      var code = this.readBits(codeLength);
      var hasPrev = currentSequenceLength > 0;
      if (code < 256) {
        currentSequence[0] = code;
        currentSequenceLength = 1;
      } else if (code >= 258) {
        if (code < nextCode) {
          currentSequenceLength = dictionaryLengths[code];
          for (j = currentSequenceLength - 1, q = code; j >= 0; j--) {
            currentSequence[j] = dictionaryValues[q];
            q = dictionaryPrevCodes[q];
          }
        } else {
          currentSequence[currentSequenceLength++] = currentSequence[0];
        }
      } else if (code === 256) {
        codeLength = 9;
        nextCode = 258;
        currentSequenceLength = 0;
        continue;
      } else {
        this.eof = true;
        delete this.lzwState;
        break;
      }

      if (hasPrev) {
        dictionaryPrevCodes[nextCode] = prevCode;
        dictionaryLengths[nextCode] = dictionaryLengths[prevCode] + 1;
        dictionaryValues[nextCode] = currentSequence[0];
        nextCode++;
        codeLength = (nextCode + earlyChange) & (nextCode + earlyChange - 1) ?
          codeLength : Math.min(Math.log(nextCode + earlyChange) /
          0.6931471805599453 + 1, 12) | 0;
      }
      prevCode = code;

      decodedLength += currentSequenceLength;
      if (estimatedDecodedSize < decodedLength) {
        do {
          estimatedDecodedSize += decodedSizeDelta;
        } while (estimatedDecodedSize < decodedLength);
        buffer = this.ensureBuffer(this.bufferLength + estimatedDecodedSize);
      }
      for (j = 0; j < currentSequenceLength; j++) {
        buffer[currentBufferLength++] = currentSequence[j];
      }
    }
    lzwState.nextCode = nextCode;
    lzwState.codeLength = codeLength;
    lzwState.prevCode = prevCode;
    lzwState.currentSequenceLength = currentSequenceLength;

    this.bufferLength = currentBufferLength;
  };

  return LZWStream;
})();

var NullStream = (function NullStreamClosure() {
  function NullStream() {
    Stream.call(this, new Uint8Array(0));
  }

  NullStream.prototype = Stream.prototype;

  return NullStream;
})();

export {
  Ascii85Stream,
  AsciiHexStream,
  DecryptStream,
  DecodeStream,
  FlateStream,
  NullStream,
  PredictorStream,
  RunLengthStream,
  Stream,
  StreamsSequenceStream,
  StringStream,
  LZWStream,
};