zipfile.js

/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */

'use strict';

function error(s) {
  console.trace(s);
  throw new Error(s);
}

var codeLenCodeMap = new Uint32Array([
  16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
]);

var lengthDecode = new Uint32Array([
  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
]);

var distDecode = new Uint32Array([
  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
]);

var fixedLitCodeTab = [new Uint32Array([
  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];

var fixedDistCodeTab = [new Uint32Array([
  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 inflate(bytes) {
  var bytesPos = 0;

  var codeSize = 0;
  var codeBuf = 0;

  function getBits(bits) {
    var b;
    while (codeSize < bits) {
      b = bytes[bytesPos++] | 0;
      codeBuf |= b << codeSize;
      codeSize += 8;
    }
    b = codeBuf & ((1 << bits) - 1);
    codeBuf >>= bits;
    codeSize -= bits;
    return b;
  }

  function getCode(table) {
    var codes = table[0];
    var maxLen = table[1];

    while (codeSize < maxLen) {
      var b = bytes[bytesPos++] | 0;
      codeBuf |= (b << codeSize);
      codeSize += 8;
    }
    var code = codes[codeBuf & ((1 << maxLen) - 1)];
    var codeLen = code >> 16;
    var codeVal = code & 0xffff;
    if (codeSize == 0 || codeSize < codeLen || codeLen == 0)
      error('Bad encoding in flate stream');
    codeBuf >>= codeLen;
    codeSize -= codeLen;
    return codeVal;
  }

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

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

    // build the table
    var size = 1 << maxLen;
    var codes = new Uint32Array(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 (var i = 0; i < len; ++i) {
            code2 = (code2 << 1) | (t & 1);
            t >>= 1;
          }

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

          ++code;
        }
      }
    }

    return [codes, maxLen];
  };

  var buffer;
  var bufferLength = 0;

  function ensureBuffer(requested) {
    var current = buffer ? buffer.byteLength : 0;
    if (requested < current)
      return;
    var size = 512;
    while (size < requested)
      size <<= 1;
    var buffer2 = new Uint8Array(size);
    for (var i = 0; i < current; ++i)
      buffer2[i] = buffer[i];
    buffer = buffer2;
  }

  function readBlock() {
    var eof = false;

    // read block header
    var hdr = getBits(3);
    if (hdr & 1)
      eof = true;
    hdr >>= 1;

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

      if (typeof (b = bytes[bytesPos++]) == 'undefined')
        error('Bad block header in flate stream');
      var blockLen = b;
      if (typeof (b = bytes[bytesPos++]) == 'undefined')
        error('Bad block header in flate stream');
      blockLen |= (b << 8);
      if (typeof (b = bytes[bytesPos++]) == 'undefined')
        error('Bad block header in flate stream');
      var check = b;
      if (typeof (b = bytes[bytesPos++]) == 'undefined')
        error('Bad block header in flate stream');
      check |= (b << 8);
      if (check != (~blockLen & 0xffff))
        error('Bad uncompressed block length in flate stream');

      codeBuf = 0;
      codeSize = 0;

      ensureBuffer(bufferLength + blockLen);
      var end = bufferLength + blockLen;
      for (var n = bufferLength; n < end; ++n) {
        if (typeof (b = bytes[bytesPos++]) == 'undefined') {
          eof = true;
          break;
        }
        buffer[n] = b;
      }
      bufferLength = end;
      return eof;
    }

    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 = getBits(5) + 257;
      var numDistCodes = getBits(5) + 1;
      var numCodeLenCodes = getBits(4) + 4;

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

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

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

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

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

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

  while (!readBlock())
    ;

  // shrink the buffer to the actual data size
  return new Uint8Array(buffer.buffer, 0, bufferLength);
}

function ZipFile(buffer) {
  var bytes = new Uint8Array(buffer);
  var view = new DataView(buffer);

  // check for magic signature
  if (view.getInt32(0, true) != 0x04034b50)
    return;

  // scan backwards to locate the central directory record
  var pos = bytes.length - 22;
  while (true) {
    if (pos < 0)
      return;
    if (bytes[pos] != 0x50) {
      --pos;
      continue;
    }
    if (view.getInt32(pos, true) == 0x06054b50)
      break;
    pos -= 4;
  }

  // read the central directory
  var directory = Object.create(null);
  var entries = view.getInt16(pos + 8, true);
  var pos = view.getInt32(pos + 16, true);
  while (entries--) {
    // check for directory entry signature
    if (view.getInt32(pos, true) != 0x02014b50)
      return;
    var compression_method = view.getInt16(pos + 10, true);
    var compressed_len = view.getInt32(pos + 20, true);
    var uncompressed_len = view.getInt32(pos + 24, true);
    var filename_len = view.getInt16(pos + 28, true);
    var extra_len = view.getInt16(pos + 30, true);
    var comment_len = view.getInt16(pos + 32, true);
    var local_header_offset = view.getInt32(pos + 42, true);
    // read the filename
    pos += 46;
    var filename = "";
    for (var n = 0; n < filename_len; ++n)
      filename += String.fromCharCode(bytes[pos++]);
    // locate the compressed data
    var local_extra_len = view.getInt16(local_header_offset + 28, true);
    var data_offset = local_header_offset + 30 + filename_len + local_extra_len;
    // add the entry to the directory
    directory[filename] = {
      compression_method: compression_method,
      compressed_data: new Uint8Array(buffer, data_offset, compressed_len)
    };
    // advance to the next entry
    pos += extra_len + comment_len;
  }

  this.directory = directory;
}

ZipFile.prototype = {
  read: function(filename) {
    if (!this.directory)
      return null;
    var entry = this.directory[filename];
    if (!entry)
      return null;
    var data = entry.compressed_data;
    switch (entry.compression_method) {
    case 0: // stored
      return data;
    case 8: // deflated
      return inflate(data);
    }
    return null;
  }
};

if (typeof module === 'object') {
  module.exports.ZipFile = ZipFile;
}