Start on Issue #16. Make BitStream a module, but provide a Web Worker version of BitStream via a build step

archive/unrar.js

@@ -12,7 +12,7 @@
 // present.
 
 // This file expects to be invoked as a Worker (see onmessage below).
-importScripts('../io/bitstream.js');
+importScripts('../io/bitstream-worker.js');
 importScripts('../io/bytestream.js');
 importScripts('../io/bytebuffer.js');
 importScripts('archive.js');
@@ -40,13 +40,13 @@ let totalUncompressedBytesInArchive = 0;
 let totalFilesInArchive = 0;
 
 // Helper functions.
-const info = function(str) {
+const info = function (str) {
   postMessage(new bitjs.archive.UnarchiveInfoEvent(str));
 };
-const err = function(str) {
+const err = function (str) {
   postMessage(new bitjs.archive.UnarchiveErrorEvent(str));
 };
-const postProgress = function() {
+const postProgress = function () {
   postMessage(new bitjs.archive.UnarchiveProgressEvent(
     currentFilename,
     currentFileNumber,
@@ -60,11 +60,11 @@ const postProgress = function() {
 
 // shows a byte value as its hex representation
 const nibble = '0123456789ABCDEF';
-const byteValueToHexString = function(num) {
+const byteValueToHexString = function (num) {
-  return nibble[num>>4] + nibble[num&0xF];
+  return nibble[num >> 4] + nibble[num & 0xF];
 };
-const twoByteValueToHexString = function(num) {
+const twoByteValueToHexString = function (num) {
-  return nibble[(num>>12)&0xF] + nibble[(num>>8)&0xF] + nibble[(num>>4)&0xF] + nibble[num&0xF];
+  return nibble[(num >> 12) & 0xF] + nibble[(num >> 8) & 0xF] + nibble[(num >> 4) & 0xF] + nibble[num & 0xF];
 };
 
 
@@ -262,11 +262,11 @@ class RarVolumeHeader {
 const BLOCK_LZ = 0;
 const BLOCK_PPM = 1;
 
-const rLDecode = [0,1,2,3,4,5,6,7,8,10,12,14,16,20,24,28,32,40,48,56,64,80,96,112,128,160,192,224];
+const rLDecode = [0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 20, 24, 28, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224];
-const rLBits = [0,0,0,0,0,0,0,0,1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4,  4,  5,  5,  5,  5];
+const rLBits = [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5];
-const rDBitLengthCounts = [4,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,14,0,12];
+const rDBitLengthCounts = [4, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 14, 0, 12];
-const rSDDecode = [0,4,8,16,32,64,128,192];
+const rSDDecode = [0, 4, 8, 16, 32, 64, 128, 192];
-const rSDBits = [2,2,3, 4, 5, 6,  6,  6];
+const rSDBits = [2, 2, 3, 4, 5, 6, 6, 6];
 
 const rDDecode = [0, 1, 2, 3, 4, 6, 8, 12, 16, 24, 32,
   48, 64, 96, 128, 192, 256, 384, 512, 768, 1024, 1536, 2048, 3072,
@@ -285,7 +285,7 @@ const rDC = 60;
 const rLDC = 17;
 const rRC = 28;
 const rBC = 20;
-const rHUFF_TABLE_SIZE = (rNC+rDC+rRC+rLDC);
+const rHUFF_TABLE_SIZE = (rNC + rDC + rRC + rLDC);
 
 const UnpOldTable = new Array(rHUFF_TABLE_SIZE);
 
@@ -353,7 +353,7 @@ function RarReadTables(bstream) {
   const Table = new Array(rHUFF_TABLE_SIZE);
 
   // before we start anything we need to get byte-aligned
-  bstream.readBits( (8 - bstream.bitPtr) & 0x7 );
+  bstream.readBits((8 - bstream.bitPtr) & 0x7);
 
   if (bstream.readBits(1)) {
     info('Error!  PPM not implemented yet');
@@ -429,23 +429,23 @@ function RarDecodeNumber(bstream, dec) {
   const DecodeNum = dec.DecodeNum;
   const bitField = bstream.getBits() & 0xfffe;
   //some sort of rolled out binary search
-  const bits = ((bitField < DecodeLen[8])?
+  const bits = ((bitField < DecodeLen[8]) ?
-    ((bitField < DecodeLen[4])?
+    ((bitField < DecodeLen[4]) ?
-      ((bitField < DecodeLen[2])?
+      ((bitField < DecodeLen[2]) ?
-        ((bitField < DecodeLen[1])?1:2)
+        ((bitField < DecodeLen[1]) ? 1 : 2)
-       :((bitField < DecodeLen[3])?3:4))
+        : ((bitField < DecodeLen[3]) ? 3 : 4))
-     :(bitField < DecodeLen[6])?
+      : (bitField < DecodeLen[6]) ?
-        ((bitField < DecodeLen[5])?5:6)
+        ((bitField < DecodeLen[5]) ? 5 : 6)
-        :((bitField < DecodeLen[7])?7:8))
+        : ((bitField < DecodeLen[7]) ? 7 : 8))
-    :((bitField < DecodeLen[12])?
+    : ((bitField < DecodeLen[12]) ?
-      ((bitField < DecodeLen[10])?
+      ((bitField < DecodeLen[10]) ?
-        ((bitField < DecodeLen[9])?9:10)
+        ((bitField < DecodeLen[9]) ? 9 : 10)
-       :((bitField < DecodeLen[11])?11:12))
+        : ((bitField < DecodeLen[11]) ? 11 : 12))
-     :(bitField < DecodeLen[14])?
+      : (bitField < DecodeLen[14]) ?
-        ((bitField < DecodeLen[13])?13:14)
+        ((bitField < DecodeLen[13]) ? 13 : 14)
-        :15));
+        : 15));
   bstream.readBits(bits);
-  const N = DecodePos[bits] + ((bitField - DecodeLen[bits -1]) >>> (16 - bits));
+  const N = DecodePos[bits] + ((bitField - DecodeLen[bits - 1]) >>> (16 - bits));
 
   return DecodeNum[N];
 }
@@ -455,8 +455,8 @@ function RarMakeDecodeTables(BitLength, offset, dec, size) {
   const DecodeLen = dec.DecodeLen;
   const DecodePos = dec.DecodePos;
   const DecodeNum = dec.DecodeNum;
-  const LenCount = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0];
+  const LenCount = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
-  const TmpPos = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0];
+  const TmpPos = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
   let N = 0;
   let M = 0;
 
@@ -472,18 +472,18 @@ function RarMakeDecodeTables(BitLength, offset, dec, size) {
   DecodeLen[0] = 0;
 
   for (let I = 1; I < 16; ++I) {
-    N = 2 * (N+LenCount[I]);
+    N = 2 * (N + LenCount[I]);
-    M = (N << (15-I));
+    M = (N << (15 - I));
     if (M > 0xFFFF) {
       M = 0xFFFF;
     }
     DecodeLen[I] = M;
-    DecodePos[I] = DecodePos[I-1] + LenCount[I-1];
+    DecodePos[I] = DecodePos[I - 1] + LenCount[I - 1];
     TmpPos[I] = DecodePos[I];
   }
   for (let I = 0; I < size; ++I) {
     if (BitLength[I + offset] != 0) {
-      DecodeNum[ TmpPos[ BitLength[offset + I] & 0xF ]++] = I;
+      DecodeNum[TmpPos[BitLength[offset + I] & 0xF]++] = I;
     }
   }
 
@@ -550,7 +550,7 @@ function Unpack20(bstream, Solid) {
     if (num < 261) {
       const Distance = rOldDist[(oldDistPtr - (num - 256)) & 3];
       const LengthNumber = RarDecodeNumber(bstream, RD);
-      let Length = rLDecode[LengthNumber] +2;
+      let Length = rLDecode[LengthNumber] + 2;
       if ((Bits = rLBits[LengthNumber]) > 0) {
         Length += bstream.readBits(Bits);
       }
@@ -650,7 +650,7 @@ function RarReadTables20(bstream) {
 let lowDistRepCount = 0;
 let prevLowDist = 0;
 
-let rOldDist = [0,0,0,0];
+let rOldDist = [0, 0, 0, 0];
 let lastDist;
 let lastLength;
 
@@ -899,17 +899,17 @@ function Unpack29(bstream, Solid) {
   let BitLength = 0;
   let Slot = 0;
 
-  for (let I = 0; I < rDBitLengthCounts.length; I++,BitLength++) {
+  for (let I = 0; I < rDBitLengthCounts.length; I++, BitLength++) {
-    for (let J = 0; J < rDBitLengthCounts[I]; J++,Slot++,Dist+=(1<<BitLength)) {
+    for (let J = 0; J < rDBitLengthCounts[I]; J++, Slot++, Dist += (1 << BitLength)) {
-      DDecode[Slot]=Dist;
+      DDecode[Slot] = Dist;
-      DBits[Slot]=BitLength;
+      DBits[Slot] = BitLength;
     }
   }
 
   let Bits;
   //tablesRead = false;
 
-  rOldDist = [0,0,0,0]
+  rOldDist = [0, 0, 0, 0]
 
   lastDist = 0;
   lastLength = 0;
@@ -993,7 +993,7 @@ function Unpack29(bstream, Solid) {
       const Distance = rOldDist[DistNum];
 
       for (let I = DistNum; I > 0; I--) {
-        rOldDist[I] = rOldDist[I-1];
+        rOldDist[I] = rOldDist[I - 1];
       }
       rOldDist[0] = Distance;
 
@@ -1158,8 +1158,8 @@ function RarWriteBuf() {
 function RarWriteArea(startPtr, endPtr) {
   if (endPtr < startPtr) {
     console.error('endPtr < startPtr, endPtr=' + endPtr + ', startPtr=' + startPtr);
-//    RarWriteData(startPtr, -(int)StartPtr & MAXWINMASK);
+    //    RarWriteData(startPtr, -(int)StartPtr & MAXWINMASK);
-//    RarWriteData(0, endPtr);
+    //    RarWriteData(0, endPtr);
     return;
   } else if (startPtr < endPtr) {
     RarWriteData(startPtr, endPtr - startPtr);
@@ -1187,8 +1187,7 @@ function RarWriteData(offset, numBytes) {
 /**
  * @param {VM_PreparedProgram} prg
  */
-function RarExecuteCode(prg)
+function RarExecuteCode(prg) {
-{
   if (prg.GlobalData.length > 0) {
     const writtenFileSize = wBuffer.ptr;
     prg.InitR[6] = writtenFileSize;
@@ -1219,8 +1218,8 @@ function RarInsertLastMatch(length, distance) {
 }
 
 function RarInsertOldDist(distance) {
-  rOldDist.splice(3,1);
+  rOldDist.splice(3, 1);
-  rOldDist.splice(0,0,distance);
+  rOldDist.splice(0, 0, distance);
 }
 
 /**
@@ -1259,7 +1258,7 @@ function unpack(v) {
   // TODO: implement what happens when unpVer is < 15
   const Ver = v.header.unpVer <= 15 ? 15 : v.header.unpVer;
   const Solid = v.header.flags.LHD_SOLID;
-  const bstream = new bitjs.io.BitStream(v.fileData.buffer, true /* rtl */, v.fileData.byteOffset, v.fileData.byteLength );
+  const bstream = new bitjs.io.BitStream(v.fileData.buffer, true /* rtl */, v.fileData.byteOffset, v.fileData.byteLength);
 
   rBuffer = new bitjs.io.ByteBuffer(v.header.unpackedSize);
 
@@ -1396,7 +1395,7 @@ function unrar() {
 
 // event.data.file has the first ArrayBuffer.
 // event.data.bytes has all subsequent ArrayBuffers.
-onmessage = function(event) {
+onmessage = function (event) {
   const bytes = event.data.file || event.data.bytes;
   logToConsole = !!event.data.logToConsole;
 

archive/unzip.js

@@ -13,7 +13,7 @@
  */
 
 // This file expects to be invoked as a Worker (see onmessage below).
-importScripts('../io/bitstream.js');
+importScripts('../io/bitstream-worker.js');
 importScripts('../io/bytebuffer.js');
 importScripts('../io/bytestream.js');
 importScripts('archive.js');
@@ -40,13 +40,13 @@ let totalUncompressedBytesInArchive = 0;
 let totalFilesInArchive = 0;
 
 // Helper functions.
-const info = function(str) {
+const info = function (str) {
   postMessage(new bitjs.archive.UnarchiveInfoEvent(str));
 };
-const err = function(str) {
+const err = function (str) {
   postMessage(new bitjs.archive.UnarchiveErrorEvent(str));
 };
-const postProgress = function() {
+const postProgress = function () {
   postMessage(new bitjs.archive.UnarchiveProgressEvent(
     currentFilename,
     currentFileNumber,
@@ -66,7 +66,7 @@ const zEndOfCentralDirSignature = 0x06054b50;
 const zEndOfCentralDirLocatorSignature = 0x07064b50;
 
 // mask for getting the Nth bit (zero-based)
-const BIT = [ 0x01, 0x02, 0x04, 0x08,
+const BIT = [0x01, 0x02, 0x04, 0x08,
   0x10, 0x20, 0x40, 0x80,
   0x100, 0x200, 0x400, 0x800,
   0x1000, 0x2000, 0x4000, 0x8000];
@@ -75,7 +75,7 @@ const BIT = [ 0x01, 0x02, 0x04, 0x08,
 class ZipLocalFile {
   // takes a ByteStream and parses out the local file information
   constructor(bstream) {
-    if (typeof bstream != typeof {} || !bstream.readNumber || typeof bstream.readNumber != typeof function(){}) {
+    if (typeof bstream != typeof {} || !bstream.readNumber || typeof bstream.readNumber != typeof function () { }) {
       return null;
     }
 
@@ -138,9 +138,9 @@ class ZipLocalFile {
   // determine what kind of compressed data we have and decompress
   unzip() {
     // Zip Version 1.0, no compression (store only)
-    if (this.compressionMethod == 0 ) {
+    if (this.compressionMethod == 0) {
       if (logToConsole) {
-        info("ZIP v"+this.version+", store only: " + this.filename + " (" + this.compressedSize + " bytes)");
+        info("ZIP v" + this.version + ", store only: " + this.filename + " (" + this.compressedSize + " bytes)");
       }
       currentBytesUnarchivedInFile = this.compressedSize;
       currentBytesUnarchived += this.compressedSize;
@@ -193,10 +193,10 @@ function getHuffmanCodes(bitLengths) {
   const next_code = [];
   let code = 0;
   for (let bits = 1; bits <= MAX_BITS; ++bits) {
-    const length = bits-1;
+    const length = bits - 1;
     // ensure undefined lengths are zero
     if (bl_count[length] == undefined) bl_count[length] = 0;
-    code = (code + bl_count[bits-1]) << 1;
+    code = (code + bl_count[bits - 1]) << 1;
     next_code[bits] = code;
   }
 
@@ -270,10 +270,10 @@ function decodeSymbol(bstream, hcTable) {
   let match = false;
 
   // loop until we match
-  for (;;) {
+  for (; ;) {
     // read in next bit
     const bit = bstream.readBits(1);
-    code = (code<<1) | bit;
+    code = (code << 1) | bit;
     ++len;
 
     // check against Huffman Code table and break if found
@@ -308,14 +308,14 @@ Code Bits Length(s) Code Bits Lengths   Code Bits Length(s)
  266   1  13,14      276   3   59-66
 */
 const LengthLookupTable = [
-    [0,3], [0,4], [0,5], [0,6],
+  [0, 3], [0, 4], [0, 5], [0, 6],
-    [0,7], [0,8], [0,9], [0,10],
+  [0, 7], [0, 8], [0, 9], [0, 10],
-    [1,11], [1,13], [1,15], [1,17],
+  [1, 11], [1, 13], [1, 15], [1, 17],
-    [2,19], [2,23], [2,27], [2,31],
+  [2, 19], [2, 23], [2, 27], [2, 31],
-    [3,35], [3,43], [3,51], [3,59],
+  [3, 35], [3, 43], [3, 51], [3, 59],
-    [4,67], [4,83], [4,99], [4,115],
+  [4, 67], [4, 83], [4, 99], [4, 115],
-    [5,131], [5,163], [5,195], [5,227],
+  [5, 131], [5, 163], [5, 195], [5, 227],
-    [0,258]
+  [0, 258]
 ];
 
 /*
@@ -334,20 +334,20 @@ const LengthLookupTable = [
    9   3  25-32   19   8   769-1024   29   13 24577-32768
 */
 const DistLookupTable = [
-    [0,1], [0,2], [0,3], [0,4],
+  [0, 1], [0, 2], [0, 3], [0, 4],
-    [1,5], [1,7],
+  [1, 5], [1, 7],
-    [2,9], [2,13],
+  [2, 9], [2, 13],
-    [3,17], [3,25],
+  [3, 17], [3, 25],
-    [4,33], [4,49],
+  [4, 33], [4, 49],
-    [5,65], [5,97],
+  [5, 65], [5, 97],
-    [6,129], [6,193],
+  [6, 129], [6, 193],
-    [7,257], [7,385],
+  [7, 257], [7, 385],
-    [8,513], [8,769],
+  [8, 513], [8, 769],
-    [9,1025], [9,1537],
+  [9, 1025], [9, 1537],
-    [10,2049], [10,3073],
+  [10, 2049], [10, 3073],
-    [11,4097], [11,6145],
+  [11, 4097], [11, 6145],
-    [12,8193], [12,12289],
+  [12, 8193], [12, 12289],
-    [13,16385], [13,24577]
+  [13, 16385], [13, 24577]
 ];
 
 function inflateBlockData(bstream, hcLiteralTable, hcDistanceTable, buffer) {
@@ -368,7 +368,7 @@ function inflateBlockData(bstream, hcLiteralTable, hcDistanceTable, buffer) {
   */
   let numSymbols = 0;
   let blockSize = 0;
-  for (;;) {
+  for (; ;) {
     const symbol = decodeSymbol(bstream, hcLiteralTable);
     ++numSymbols;
     if (symbol < 256) {
@@ -398,7 +398,7 @@ function inflateBlockData(bstream, hcLiteralTable, hcDistanceTable, buffer) {
         // loop for each character
         let ch = buffer.ptr - distance;
         blockSize += length;
-        if(length > distance) {
+        if (length > distance) {
           const data = buffer.data;
           while (length--) {
             buffer.insertByte(data[ch++]);
@@ -451,9 +451,9 @@ function inflate(compressedData, numDecompressedBytes) {
       const numCodeLengthCodes = bstream.readBits(4) + 4;
 
       // populate the array of code length codes (first de-compaction)
-      const codeLengthsCodeLengths = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0];
+      const codeLengthsCodeLengths = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
       for (let i = 0; i < numCodeLengthCodes; ++i) {
-        codeLengthsCodeLengths[ CodeLengthCodeOrder[i] ] = bstream.readBits(3);
+        codeLengthsCodeLengths[CodeLengthCodeOrder[i]] = bstream.readBits(3);
       }
 
       // get the Huffman Codes for the code lengths
@@ -649,7 +649,7 @@ function unzip() {
 
 // event.data.file has the first ArrayBuffer.
 // event.data.bytes has all subsequent ArrayBuffers.
-onmessage = function(event) {
+onmessage = function (event) {
   const bytes = event.data.file || event.data.bytes;
   logToConsole = !!event.data.logToConsole;
 

build/Makefile

@@ -0,0 +1,13 @@
+
+all: bitjs-io bitjs-image-webp-shim
+
+clean:
+	$(MAKE) -C io clean
+	$(MAKE) -C image/webp-shim clean
+
+bitjs-io:
+	$(MAKE) -C io
+
+# Make webp-shim/
+bitjs-image-webp-shim:
+	$(MAKE) -C image/webp-shim

build/io/Makefile

@@ -0,0 +1,25 @@
+OUT_PATH=/out/io
+BITSTREAM_MODULE=${OUT_PATH}/bitstream.js
+BITSTREAM_WORKER=${OUT_PATH}/bitstream-worker.js
+
+BITSTREAM_DEF=bitstream-def.js
+
+DISCLAIMER="// THIS IS A GENERATED FILE!  DO NOT EDIT, INSTEAD EDIT THE FILE IN bitjs/build/io."
+
+all: ${BITSTREAM_MODULE} ${BITSTREAM_WORKER}
+
+${BITSTREAM_MODULE}: Makefile ${BITSTREAM_DEF}
+	echo ${DISCLAIMER} > ${BITSTREAM_MODULE}
+	echo "export const BitStream =" >> ${BITSTREAM_MODULE}
+	cat ${BITSTREAM_DEF} >> ${BITSTREAM_MODULE}
+
+${BITSTREAM_WORKER}: Makefile ${BITSTREAM_DEF}
+	echo ${DISCLAIMER} > ${BITSTREAM_WORKER}
+	echo "var bitjs = bitjs || {};" >> ${BITSTREAM_WORKER}
+	echo "bitjs.io = bitjs.io || {};" >> ${BITSTREAM_WORKER}
+	echo "bitjs.io.BitStream =" >> ${BITSTREAM_WORKER}
+	cat ${BITSTREAM_DEF} >> ${BITSTREAM_WORKER}
+
+clean:
+	rm -rf ${BITSTREAM_MODULE}
+	rm -rf ${BITSTREAM_WORKER}

build/io/bitstream-def.js

@@ -0,0 +1,287 @@
+/*
+ * bitstream-def.js
+ *
+ * Provides readers for bitstreams.
+ *
+ * Licensed under the MIT License
+ *
+ * Copyright(c) 2011 Google Inc.
+ * Copyright(c) 2011 antimatter15
+ */
+
+(function () {
+  // mask for getting N number of bits (0-8)
+  const BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF];
+
+  /**
+   * This object allows you to peek and consume bits and bytes out of a stream.
+   * Note that this stream is optimized, and thus, will *NOT* throw an error if
+   * the end of the stream is reached.  Only use this in scenarios where you
+   * already have all the bits you need.
+   */
+  class BitStream {
+    /**
+     * @param {ArrayBuffer} ab An ArrayBuffer object or a Uint8Array.
+     * @param {boolean} rtl Whether the stream reads bits from the byte starting
+     *     from bit 7 to 0 (true) or bit 0 to 7 (false).
+     * @param {Number} opt_offset The offset into the ArrayBuffer
+     * @param {Number} opt_length The length of this BitStream
+     */
+    constructor(ab, rtl, opt_offset, opt_length) {
+      if (!(ab instanceof ArrayBuffer)) {
+        throw 'Error! BitArray constructed with an invalid ArrayBuffer object';
+      }
+
+      const offset = opt_offset || 0;
+      const length = opt_length || ab.byteLength;
+
+      /**
+       * The bytes in the stream.
+       * @type {Uint8Array}
+       * @private
+       */
+      this.bytes = new Uint8Array(ab, offset, length);
+
+      /**
+       * The byte in the stream that we are currently on.
+       * @type {Number}
+       * @private
+       */
+      this.bytePtr = 0;
+
+      /**
+       * The bit in the current byte that we will read next (can have values 0 through 7).
+       * @type {Number}
+       * @private
+       */
+      this.bitPtr = 0; // tracks which bit we are on (can have values 0 through 7)
+
+      /**
+       * An ever-increasing number.
+       * @type {Number}
+       * @private
+       */
+      this.bitsRead_ = 0;
+
+      this.peekBits = rtl ? this.peekBits_rtl : this.peekBits_ltr;
+    }
+
+    /**
+     * Returns how many bites have been read in the stream since the beginning of time.
+     */
+    getNumBitsRead() {
+      return this.bitsRead_;
+    }
+
+    /**
+     * Returns how many bits are currently in the stream left to be read.
+     */
+    getNumBitsLeft() {
+      const bitsLeftInByte = 8 - this.bitPtr;
+      return (this.bytes.byteLength - this.bytePtr - 1) * 8 + bitsLeftInByte;
+    }
+
+    /**
+     *   byte0      byte1      byte2      byte3
+     * 7......0 | 7......0 | 7......0 | 7......0
+     *
+     * The bit pointer starts at bit0 of byte0 and moves left until it reaches
+     * bit7 of byte0, then jumps to bit0 of byte1, etc.
+     * @param {number} n The number of bits to peek, must be a positive integer.
+     * @param {boolean=} movePointers Whether to move the pointer, defaults false.
+     * @return {number} The peeked bits, as an unsigned number.
+     */
+    peekBits_ltr(n, opt_movePointers) {
+      const NUM = parseInt(n, 10);
+      let num = NUM;
+      if (n !== num || num <= 0) {
+        return 0;
+      }
+
+      const movePointers = opt_movePointers || false;
+      let bytes = this.bytes;
+      let bytePtr = this.bytePtr;
+      let bitPtr = this.bitPtr;
+      let result = 0;
+      let bitsIn = 0;
+
+      // keep going until we have no more bits left to peek at
+      while (num > 0) {
+        // We overflowed the stream, so just return what we got.
+        if (bytePtr >= bytes.length) {
+          break;
+        }
+
+        const numBitsLeftInThisByte = (8 - bitPtr);
+        if (num >= numBitsLeftInThisByte) {
+          const mask = (BITMASK[numBitsLeftInThisByte] << bitPtr);
+          result |= (((bytes[bytePtr] & mask) >> bitPtr) << bitsIn);
+
+          bytePtr++;
+          bitPtr = 0;
+          bitsIn += numBitsLeftInThisByte;
+          num -= numBitsLeftInThisByte;
+        } else {
+          const mask = (BITMASK[num] << bitPtr);
+          result |= (((bytes[bytePtr] & mask) >> bitPtr) << bitsIn);
+
+          bitPtr += num;
+          break;
+        }
+      }
+
+      if (movePointers) {
+        this.bitPtr = bitPtr;
+        this.bytePtr = bytePtr;
+        this.bitsRead_ += NUM;
+      }
+
+      return result;
+    }
+
+    /**
+     *   byte0      byte1      byte2      byte3
+     * 7......0 | 7......0 | 7......0 | 7......0
+     *
+     * The bit pointer starts at bit7 of byte0 and moves right until it reaches
+     * bit0 of byte0, then goes to bit7 of byte1, etc.
+     * @param {number} n The number of bits to peek.  Must be a positive integer.
+     * @param {boolean=} movePointers Whether to move the pointer, defaults false.
+     * @return {number} The peeked bits, as an unsigned number.
+     */
+    peekBits_rtl(n, opt_movePointers) {
+      const NUM = parseInt(n, 10);
+      let num = NUM;
+      if (n !== num || num <= 0) {
+        return 0;
+      }
+
+      const movePointers = opt_movePointers || false;
+      let bytes = this.bytes;
+      let bytePtr = this.bytePtr;
+      let bitPtr = this.bitPtr;
+      let result = 0;
+
+      // keep going until we have no more bits left to peek at
+      while (num > 0) {
+        // We overflowed the stream, so just return the bits we got.
+        if (bytePtr >= bytes.length) {
+          break;
+        }
+
+        const numBitsLeftInThisByte = (8 - bitPtr);
+        if (num >= numBitsLeftInThisByte) {
+          result <<= numBitsLeftInThisByte;
+          result |= (BITMASK[numBitsLeftInThisByte] & bytes[bytePtr]);
+          bytePtr++;
+          bitPtr = 0;
+          num -= numBitsLeftInThisByte;
+        } else {
+          result <<= num;
+          const numBits = 8 - num - bitPtr;
+          result |= ((bytes[bytePtr] & (BITMASK[num] << numBits)) >> numBits);
+
+          bitPtr += num;
+          break;
+        }
+      }
+
+      if (movePointers) {
+        this.bitPtr = bitPtr;
+        this.bytePtr = bytePtr;
+        this.bitsRead_ += NUM;
+      }
+
+      return result;
+    }
+
+    /**
+     * Peek at 16 bits from current position in the buffer.
+     * Bit at (bytePtr,bitPtr) has the highest position in returning data.
+     * Taken from getbits.hpp in unrar.
+     * TODO: Move this out of BitStream and into unrar.
+     */
+    getBits() {
+      return (((((this.bytes[this.bytePtr] & 0xff) << 16) +
+        ((this.bytes[this.bytePtr + 1] & 0xff) << 8) +
+        ((this.bytes[this.bytePtr + 2] & 0xff))) >>> (8 - this.bitPtr)) & 0xffff);
+    }
+
+    /**
+     * Reads n bits out of the stream, consuming them (moving the bit pointer).
+     * @param {number} n The number of bits to read.  Must be a positive integer.
+     * @return {number} The read bits, as an unsigned number.
+     */
+    readBits(n) {
+      return this.peekBits(n, true);
+    }
+
+    /**
+     * This returns n bytes as a sub-array, advancing the pointer if movePointers
+     * is true.  Only use this for uncompressed blocks as this throws away remaining
+     * bits in the current byte.
+     * @param {number} n The number of bytes to peek.  Must be a positive integer.
+     * @param {boolean=} movePointers Whether to move the pointer, defaults false.
+     * @return {Uint8Array} The subarray.
+     */
+    peekBytes(n, opt_movePointers) {
+      const num = parseInt(n, 10);
+      if (n !== num || num < 0) {
+        throw 'Error!  Called peekBytes() with a non-positive integer: ' + n;
+      } else if (num === 0) {
+        return new Uint8Array();
+      }
+
+      // Flush bits until we are byte-aligned.
+      // from http://tools.ietf.org/html/rfc1951#page-11
+      // "Any bits of input up to the next byte boundary are ignored."
+      while (this.bitPtr != 0) {
+        this.readBits(1);
+      }
+
+      const numBytesLeft = this.getNumBitsLeft() / 8;
+      if (num > numBytesLeft) {
+        throw 'Error!  Overflowed the bit stream! n=' + num + ', bytePtr=' + this.bytePtr +
+        ', bytes.length=' + this.bytes.length + ', bitPtr=' + this.bitPtr;
+      }
+
+      const movePointers = opt_movePointers || false;
+      const result = new Uint8Array(num);
+      let bytes = this.bytes;
+      let ptr = this.bytePtr;
+      let bytesLeftToCopy = num;
+      while (bytesLeftToCopy > 0) {
+        const bytesLeftInStream = bytes.length - ptr;
+        const sourceLength = Math.min(bytesLeftToCopy, bytesLeftInStream);
+
+        result.set(bytes.subarray(ptr, ptr + sourceLength), num - bytesLeftToCopy);
+
+        ptr += sourceLength;
+        // Overflowed the stream, just return what we got.
+        if (ptr >= bytes.length) {
+          break;
+        }
+
+        bytesLeftToCopy -= sourceLength;
+      }
+
+      if (movePointers) {
+        this.bytePtr += num;
+        this.bitsRead_ += (num * 8);
+      }
+
+      return result;
+    }
+
+    /**
+     * @param {number} n The number of bytes to read.
+     * @return {Uint8Array} The subarray.
+     */
+    readBytes(n) {
+      return this.peekBytes(n, true);
+    }
+  }
+
+  return BitStream;
+
+})();

io/bitstream-worker.js

@@ -0,0 +1,291 @@
+// THIS IS A GENERATED FILE!  DO NOT EDIT, INSTEAD EDIT THE FILE IN bitjs/build/io.
+var bitjs = bitjs || {};
+bitjs.io = bitjs.io || {};
+bitjs.io.BitStream =
+/*
+ * bitstream-def.js
+ *
+ * Provides readers for bitstreams.
+ *
+ * Licensed under the MIT License
+ *
+ * Copyright(c) 2011 Google Inc.
+ * Copyright(c) 2011 antimatter15
+ */
+
+(function () {
+  // mask for getting N number of bits (0-8)
+  const BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF];
+
+  /**
+   * This object allows you to peek and consume bits and bytes out of a stream.
+   * Note that this stream is optimized, and thus, will *NOT* throw an error if
+   * the end of the stream is reached.  Only use this in scenarios where you
+   * already have all the bits you need.
+   */
+  class BitStream {
+    /**
+     * @param {ArrayBuffer} ab An ArrayBuffer object or a Uint8Array.
+     * @param {boolean} rtl Whether the stream reads bits from the byte starting
+     *     from bit 7 to 0 (true) or bit 0 to 7 (false).
+     * @param {Number} opt_offset The offset into the ArrayBuffer
+     * @param {Number} opt_length The length of this BitStream
+     */
+    constructor(ab, rtl, opt_offset, opt_length) {
+      if (!(ab instanceof ArrayBuffer)) {
+        throw 'Error! BitArray constructed with an invalid ArrayBuffer object';
+      }
+
+      const offset = opt_offset || 0;
+      const length = opt_length || ab.byteLength;
+
+      /**
+       * The bytes in the stream.
+       * @type {Uint8Array}
+       * @private
+       */
+      this.bytes = new Uint8Array(ab, offset, length);
+
+      /**
+       * The byte in the stream that we are currently on.
+       * @type {Number}
+       * @private
+       */
+      this.bytePtr = 0;
+
+      /**
+       * The bit in the current byte that we will read next (can have values 0 through 7).
+       * @type {Number}
+       * @private
+       */
+      this.bitPtr = 0; // tracks which bit we are on (can have values 0 through 7)
+
+      /**
+       * An ever-increasing number.
+       * @type {Number}
+       * @private
+       */
+      this.bitsRead_ = 0;
+
+      this.peekBits = rtl ? this.peekBits_rtl : this.peekBits_ltr;
+    }
+
+    /**
+     * Returns how many bites have been read in the stream since the beginning of time.
+     */
+    getNumBitsRead() {
+      return this.bitsRead_;
+    }
+
+    /**
+     * Returns how many bits are currently in the stream left to be read.
+     */
+    getNumBitsLeft() {
+      const bitsLeftInByte = 8 - this.bitPtr;
+      return (this.bytes.byteLength - this.bytePtr - 1) * 8 + bitsLeftInByte;
+    }
+
+    /**
+     *   byte0      byte1      byte2      byte3
+     * 7......0 | 7......0 | 7......0 | 7......0
+     *
+     * The bit pointer starts at bit0 of byte0 and moves left until it reaches
+     * bit7 of byte0, then jumps to bit0 of byte1, etc.
+     * @param {number} n The number of bits to peek, must be a positive integer.
+     * @param {boolean=} movePointers Whether to move the pointer, defaults false.
+     * @return {number} The peeked bits, as an unsigned number.
+     */
+    peekBits_ltr(n, opt_movePointers) {
+      const NUM = parseInt(n, 10);
+      let num = NUM;
+      if (n !== num || num <= 0) {
+        return 0;
+      }
+
+      const movePointers = opt_movePointers || false;
+      let bytes = this.bytes;
+      let bytePtr = this.bytePtr;
+      let bitPtr = this.bitPtr;
+      let result = 0;
+      let bitsIn = 0;
+
+      // keep going until we have no more bits left to peek at
+      while (num > 0) {
+        // We overflowed the stream, so just return what we got.
+        if (bytePtr >= bytes.length) {
+          break;
+        }
+
+        const numBitsLeftInThisByte = (8 - bitPtr);
+        if (num >= numBitsLeftInThisByte) {
+          const mask = (BITMASK[numBitsLeftInThisByte] << bitPtr);
+          result |= (((bytes[bytePtr] & mask) >> bitPtr) << bitsIn);
+
+          bytePtr++;
+          bitPtr = 0;
+          bitsIn += numBitsLeftInThisByte;
+          num -= numBitsLeftInThisByte;
+        } else {
+          const mask = (BITMASK[num] << bitPtr);
+          result |= (((bytes[bytePtr] & mask) >> bitPtr) << bitsIn);
+
+          bitPtr += num;
+          break;
+        }
+      }
+
+      if (movePointers) {
+        this.bitPtr = bitPtr;
+        this.bytePtr = bytePtr;
+        this.bitsRead_ += NUM;
+      }
+
+      return result;
+    }
+
+    /**
+     *   byte0      byte1      byte2      byte3
+     * 7......0 | 7......0 | 7......0 | 7......0
+     *
+     * The bit pointer starts at bit7 of byte0 and moves right until it reaches
+     * bit0 of byte0, then goes to bit7 of byte1, etc.
+     * @param {number} n The number of bits to peek.  Must be a positive integer.
+     * @param {boolean=} movePointers Whether to move the pointer, defaults false.
+     * @return {number} The peeked bits, as an unsigned number.
+     */
+    peekBits_rtl(n, opt_movePointers) {
+      const NUM = parseInt(n, 10);
+      let num = NUM;
+      if (n !== num || num <= 0) {
+        return 0;
+      }
+
+      const movePointers = opt_movePointers || false;
+      let bytes = this.bytes;
+      let bytePtr = this.bytePtr;
+      let bitPtr = this.bitPtr;
+      let result = 0;
+
+      // keep going until we have no more bits left to peek at
+      while (num > 0) {
+        // We overflowed the stream, so just return the bits we got.
+        if (bytePtr >= bytes.length) {
+          break;
+        }
+
+        const numBitsLeftInThisByte = (8 - bitPtr);
+        if (num >= numBitsLeftInThisByte) {
+          result <<= numBitsLeftInThisByte;
+          result |= (BITMASK[numBitsLeftInThisByte] & bytes[bytePtr]);
+          bytePtr++;
+          bitPtr = 0;
+          num -= numBitsLeftInThisByte;
+        } else {
+          result <<= num;
+          const numBits = 8 - num - bitPtr;
+          result |= ((bytes[bytePtr] & (BITMASK[num] << numBits)) >> numBits);
+
+          bitPtr += num;
+          break;
+        }
+      }
+
+      if (movePointers) {
+        this.bitPtr = bitPtr;
+        this.bytePtr = bytePtr;
+        this.bitsRead_ += NUM;
+      }
+
+      return result;
+    }
+
+    /**
+     * Peek at 16 bits from current position in the buffer.
+     * Bit at (bytePtr,bitPtr) has the highest position in returning data.
+     * Taken from getbits.hpp in unrar.
+     * TODO: Move this out of BitStream and into unrar.
+     */
+    getBits() {
+      return (((((this.bytes[this.bytePtr] & 0xff) << 16) +
+        ((this.bytes[this.bytePtr + 1] & 0xff) << 8) +
+        ((this.bytes[this.bytePtr + 2] & 0xff))) >>> (8 - this.bitPtr)) & 0xffff);
+    }
+
+    /**
+     * Reads n bits out of the stream, consuming them (moving the bit pointer).
+     * @param {number} n The number of bits to read.  Must be a positive integer.
+     * @return {number} The read bits, as an unsigned number.
+     */
+    readBits(n) {
+      return this.peekBits(n, true);
+    }
+
+    /**
+     * This returns n bytes as a sub-array, advancing the pointer if movePointers
+     * is true.  Only use this for uncompressed blocks as this throws away remaining
+     * bits in the current byte.
+     * @param {number} n The number of bytes to peek.  Must be a positive integer.
+     * @param {boolean=} movePointers Whether to move the pointer, defaults false.
+     * @return {Uint8Array} The subarray.
+     */
+    peekBytes(n, opt_movePointers) {
+      const num = parseInt(n, 10);
+      if (n !== num || num < 0) {
+        throw 'Error!  Called peekBytes() with a non-positive integer: ' + n;
+      } else if (num === 0) {
+        return new Uint8Array();
+      }
+
+      // Flush bits until we are byte-aligned.
+      // from http://tools.ietf.org/html/rfc1951#page-11
+      // "Any bits of input up to the next byte boundary are ignored."
+      while (this.bitPtr != 0) {
+        this.readBits(1);
+      }
+
+      const numBytesLeft = this.getNumBitsLeft() / 8;
+      if (num > numBytesLeft) {
+        throw 'Error!  Overflowed the bit stream! n=' + num + ', bytePtr=' + this.bytePtr +
+        ', bytes.length=' + this.bytes.length + ', bitPtr=' + this.bitPtr;
+      }
+
+      const movePointers = opt_movePointers || false;
+      const result = new Uint8Array(num);
+      let bytes = this.bytes;
+      let ptr = this.bytePtr;
+      let bytesLeftToCopy = num;
+      while (bytesLeftToCopy > 0) {
+        const bytesLeftInStream = bytes.length - ptr;
+        const sourceLength = Math.min(bytesLeftToCopy, bytesLeftInStream);
+
+        result.set(bytes.subarray(ptr, ptr + sourceLength), num - bytesLeftToCopy);
+
+        ptr += sourceLength;
+        // Overflowed the stream, just return what we got.
+        if (ptr >= bytes.length) {
+          break;
+        }
+
+        bytesLeftToCopy -= sourceLength;
+      }
+
+      if (movePointers) {
+        this.bytePtr += num;
+        this.bitsRead_ += (num * 8);
+      }
+
+      return result;
+    }
+
+    /**
+     * @param {number} n The number of bytes to read.
+     * @return {Uint8Array} The subarray.
+     */
+    readBytes(n) {
+      return this.peekBytes(n, true);
+    }
+  }
+
+  return BitStream;
+
+})();

io/bitstream.js

@@ -1,5 +1,7 @@
+// THIS IS A GENERATED FILE!  DO NOT EDIT, INSTEAD EDIT THE FILE IN bitjs/build/io.
+export const BitStream =
 /*
- * bitstream.js
+ * bitstream-def.js
  *
  * Provides readers for bitstreams.
  *
@@ -9,17 +11,17 @@
  * Copyright(c) 2011 antimatter15
  */
 
-var bitjs = bitjs || {};
+(function () {
-bitjs.io = bitjs.io || {};
+  // mask for getting N number of bits (0-8)
+  const BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF];
 
-
+  /**
-/**
    * This object allows you to peek and consume bits and bytes out of a stream.
    * Note that this stream is optimized, and thus, will *NOT* throw an error if
    * the end of the stream is reached.  Only use this in scenarios where you
    * already have all the bits you need.
    */
-bitjs.io.BitStream = class {
+  class BitStream {
     /**
      * @param {ArrayBuffer} ab An ArrayBuffer object or a Uint8Array.
      * @param {boolean} rtl Whether the stream reads bits from the byte starting
@@ -98,7 +100,6 @@ bitjs.io.BitStream = class {
         return 0;
       }
 
-    const BITMASK = bitjs.io.BitStream.BITMASK;
       const movePointers = opt_movePointers || false;
       let bytes = this.bytes;
       let bytePtr = this.bytePtr;
@@ -157,7 +158,6 @@ bitjs.io.BitStream = class {
         return 0;
       }
 
-    const BITMASK = bitjs.io.BitStream.BITMASK;
       const movePointers = opt_movePointers || false;
       let bytes = this.bytes;
       let bytePtr = this.bytePtr;
@@ -205,8 +205,8 @@ bitjs.io.BitStream = class {
      */
     getBits() {
       return (((((this.bytes[this.bytePtr] & 0xff) << 16) +
-                ((this.bytes[this.bytePtr+1] & 0xff) << 8) +
+        ((this.bytes[this.bytePtr + 1] & 0xff) << 8) +
-                ((this.bytes[this.bytePtr+2] & 0xff))) >>> (8-this.bitPtr)) & 0xffff);
+        ((this.bytes[this.bytePtr + 2] & 0xff))) >>> (8 - this.bitPtr)) & 0xffff);
     }
 
     /**
@@ -282,7 +282,8 @@ bitjs.io.BitStream = class {
     readBytes(n) {
       return this.peekBytes(n, true);
     }
-}
+  }
 
-// mask for getting N number of bits (0-8)
+  return BitStream;
-bitjs.io.BitStream.BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF ];
+
+})();

tests/io-bitstream-test.html

@@ -3,7 +3,7 @@
 <head>
     <title>Unit tests for bitjs.io.BitStream</title>
     <script src="muther.js"></script>
-    <script src="../io/bitstream.js"></script>
+    <script src="../io/bitstream-worker.js"></script>
 </head>
 <body>
 <script>