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328 lines
9.3 KiB
JavaScript
328 lines
9.3 KiB
JavaScript
/**
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* this is a port of pyflate
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* @url http://www.paul.sladen.org/projects/pyflate/
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* @author kirilloid
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* @license CC-SA 3.0
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* @usage ArchUtils.bz2.decode(str)
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* @example ArchUtils.bz2.decode(
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* "BZh91AY&SYN\xEC\xE86\0\0\2Q\x80\0\x10@\0\6D\x90\x80 " +
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* "\x001\6LA\1\xA7\xA9\xA5\x80\xBB\x941\xF8\xBB\x92)\xC2\x84\x82wgA\xB0"
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* ) == "hello world\n";
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*/
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var ArchUtils = (function(){
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'use strict';
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// python functions eliminated, Gonzalo
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/**
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* bwt_reverse code from wikipedia (slightly modified)
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* @url http://en.wikipedia.org/wiki/Burrows%E2%80%93Wheeler_transform
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* @license: CC-SA 3.0
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*/
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function bwt_reverse(src, primary) {
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var len = src.length;
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if (primary >= len) throw RangeError("Out of bound");
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if (primary < 0) throw RangeError("Out of bound");
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//only used on arrays, optimized, Gonzalo
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var A = src;
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src = src.join('');
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A.sort();
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var start = {};
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for (var i = len-1; i >= 0; i--) start[A[i]] = i;
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var links = [];
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for (i = 0; i < len; i++) links.push(start[src[i]]++);
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var i, first = A[i = primary], ret = [];
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for (var j = 1; j < len; j++) {
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ret.push(A[i = links[i]]);
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}
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return first + ret.reverse().join('');
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}
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//move_to_front is always used to store reslt in array, optimized, Gonzalo
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function move_to_front_and_store(a, c, buff) {
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var v = a[c];
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for (var i = c; i > 0; a[i] = a[--i]);
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buff.push(a[0] = v);
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}
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// BitfieldBase never used directly, optimized, Gonzalo
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/**
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* @class RBitfield
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* right-sided bitfield for reading bits in byte from right to left
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*/
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var RBitfield = function() {
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this.init = function(x) {
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this.masks = [];
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for (var i = 0; i < 31; i++) this.masks[i] = (1 << i) - 1;
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this.masks[31] = -0x80000000;
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//eliminated support for RBitfield.init( RBitfield ), never used, Gonzalo
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this.f = x;
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this.bits = 0;
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this.bitfield = 0x0;
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this.count = 0;
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}
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//_read not used, optimized, Gonzalo
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//readByte inlined, Gonzalo
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//needbits inlined, Gonzalo
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//align inlined, Gonzalo
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//toskip inlined, Gonzalo
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// this.dropbytes not used, eliminated, Gonzalo
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// this.tell not used, eliminated, Gonzalo
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// since js truncate args to int32 with bit operators
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// we need to specific processing for n >= 32 bits reading
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// separate function is created for optimization purposes
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//readbits2 always called ith constants >=32, check removed, Gonzalo
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this.readbits2 = function readbits2(n) {
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//only for n>=32!!!, check removed
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var n2 = n >> 1;
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return this.readbits(n2) * (1 << n2) + this.readbits(n - n2);
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}
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this.readbits = function readbits(n) {
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//if (n > this.bits) this.needbits(n);
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// INLINED: needbits, readByte
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while (this.bits < n) {
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this.bitfield = (this.bitfield << 8) + this.f.charCodeAt(this.count++);
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this.bits += 8;
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}
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var m = this.masks[n];
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var r = (this.bitfield >> (this.bits - n)) & m;
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this.bits -= n;
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this.bitfield &= ~(m << this.bits);
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return r;
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}
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}
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/**
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* @class HuffmanLength
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* utility class, used for comparison of huffman codes
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*/
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var HuffmanLength = function(code, bits) {
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this.code = code;
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this.bits = bits;
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this.symbol = undefined;
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} //cropped unused functions and needless checks, Gonzalo
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//class HuffmanTable never used directly..., optimized, Gonzalo
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/**
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* @class OrderedHuffmanTable
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* utility class for working with huffman table
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*/
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var OrderedHuffmanTable = function() {
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this.process = function(lengths) {
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var len = lengths.length;
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var z = [];
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for (var i = 0; i < len; i++) {
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z.push([i, lengths[i]]);
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}
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z.push([len, -1]);
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var l = [];
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var b = z[0];
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var start = b[0], bits = b[1];
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for (var p = 1; p < z.length; p++) {
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var finish = z[p][0], endbits = z[p][1];
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if (bits)
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for (var code = start; code < finish; code++)
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l.push(new HuffmanLength(code, bits));
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start = finish;
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bits = endbits;
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if (endbits == -1) break;
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}
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l.sort(function (a, b) { //function cmpHuffmanTable(a, b), can be anonymous, optimized, Gonzalo
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return (a.bits - b.bits) || (a.code - b.code);
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});
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this.table = l;
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//inlined populate_huffman_symbols, Gonzalo
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var temp_bits = 0;
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var symbol = -1;
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// faht = Fast Access Huffman Table
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this.faht = [];
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var cb = null;
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for (var i = 0; i < this.table.length; i++) {
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var x = this.table[i];
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symbol += 1;
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if (x.bits != temp_bits ) {
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symbol <<= x.bits - temp_bits ;
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cb = this.faht[temp_bits = x.bits] = {};
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}
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cb[x.symbol = symbol] = x;
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}
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//inlined min_max_bits
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this.min_bits = 16;
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this.max_bits = -1;
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this.table.forEach(function(x){
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if (x.bits < this.min_bits) this.min_bits = x.bits;
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if (x.bits > this.max_bits) this.max_bits = x.bits;
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}, this);
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}
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}
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return ({ bz2: { decode: function(input) { //eliminated unused unpackSize, Gonzalo
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var b = new RBitfield();
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b.init(input);
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b.readbits(16);
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var method = b.readbits(8);
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if (method != 104) { //char 'h'
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throw "Unknown (not type 'h'uffman Bzip2) compression method";
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}
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var blocksize = b.readbits(8);
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if ( 49 <= blocksize && blocksize <= 57) { //char '1' && char '9'
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blocksize -= 48; //char 0
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} else {
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throw "Unknown (not size '1'-'9') Bzip2 blocksize";
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}
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function getUsedCharTable(b) {
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var a = [];
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var used_groups = b.readbits(16);
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for (var m1 = 1 << 15; m1 > 0; m1 >>= 1) {
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if (!(used_groups & m1)) {
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for (var i = 0; i < 16; i++) a.push(false);
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continue;
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}
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var used_chars = b.readbits(16);
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for (var m2 = 1 << 15; m2 > 0; m2 >>= 1) {
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a.push( Boolean(used_chars & m2) );
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}
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}
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return a;
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}
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var out = [];
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function main_loop() { while (true) {
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var blocktype = b.readbits2(48);
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var crc = b.readbits2(32);
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if (blocktype == 0x314159265359) { // (pi)
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if (b.readbits(1)) throw "Bzip2 randomised support not implemented";
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var pointer = b.readbits(24);
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var used = getUsedCharTable(b);
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var huffman_groups = b.readbits(3);
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if (2 > huffman_groups || huffman_groups > 6)
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throw RangeError("Bzip2: Number of Huffman groups not in range 2..6");
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var mtf = [0,1,2,3,4,5,6].slice(0,huffman_groups); //eliminate use of range, Gonzalo
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var selectors_list = [];
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for (var i = 0, selectors_used = b.readbits(15); i < selectors_used; i++) {
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// zero-terminated bit runs (0..62) of MTF'ed huffman table
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var c = 0;
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while (b.readbits(1)) {
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if (c++ >= huffman_groups)
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throw RangeError("More than max ("+huffman_groups+") groups");
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}
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move_to_front_and_store(mtf, c, selectors_list); //optimized to single function, Gonzalo
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}
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var groups_lengths = [];
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// INLINE: sum used only once, Gonzalo
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var symbols_in_use = used.reduce( function(a, b) {return a + b}, 0 ) + 2; //sum(used) + 2 // remember RUN[AB] RLE symbols
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for (var j = 0; j < huffman_groups; j++) {
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var length = b.readbits(5);
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var lengths = [];
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for (var i = 0; i < symbols_in_use; i++) {
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if (length < 0 || length > 20)
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throw RangeError("Bzip2 Huffman length code outside range 0..20");
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while (b.readbits(1)) length -= (b.readbits(1) * 2) - 1;
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lengths.push(length);
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}
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groups_lengths.push(lengths);
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}
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var tables = [];
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for (var g = 0; g < groups_lengths.length; g++) {
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var codes = new OrderedHuffmanTable();
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codes.process(groups_lengths[g]); //consolidated function calls
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tables.push(codes);
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}
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var favourites = [];
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for (var c = used.length - 1; c >= 0; c--) {
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if (used[c]) favourites.push(String.fromCharCode(c)); //inlined chr, used once, Gonzalo
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}
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favourites.reverse();
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var selector_pointer = 0;
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var decoded = 0;
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var t;
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// Main Huffman loop
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var repeat = 0;
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var repeat_power = 0;
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var buffer = [], r;
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while (true) {
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if (--decoded <= 0) {
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decoded = 50;
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if (selector_pointer <= selectors_list.length)
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t = tables[selectors_list[selector_pointer++]];
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}
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// INLINED: find_next_symbol
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for (var bb in t.faht) {
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if (b.bits < bb) {
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b.bitfield = (b.bitfield << 8) + b.f.charCodeAt(b.count++);
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b.bits += 8;
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}
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if (r = t.faht[bb][ b.bitfield >> (b.bits - bb) ]) {
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b.bitfield &= b.masks[b.bits -= bb];
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r = r.code;
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break;
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}
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}
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if (0 <= r && r <= 1) {
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if (repeat == 0) repeat_power = 1;
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repeat += repeat_power << r;
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repeat_power <<= 1;
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continue;
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} else {
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var v = favourites[0];
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for ( ; repeat > 0; repeat--) buffer.push(v);
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}
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if (r == symbols_in_use - 1) { // eof symbol
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break;
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} else {
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move_to_front_and_store(favourites,r-1,buffer); //Uninlined, size efficiency, Gonzalo
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}
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}
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var nt = bwt_reverse(buffer, pointer);
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var done = [];
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var i = 0;
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var len = nt.length;
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// RLE decoding
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while (i < len) {
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var c = nt.charCodeAt(i);
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if ((i < len - 4)
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&& nt.charCodeAt(i+1) == c
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&& nt.charCodeAt(i+2) == c
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&& nt.charCodeAt(i+3) == c) {
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var c = nt.charAt(i);
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var rep = nt.charCodeAt(i+4)+4;
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for (; rep > 0; rep--) done.push(c);
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i += 5;
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} else {
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done.push(nt[i++]);
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}
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}
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out.push(done.join(''));
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} else if (blocktype == 0x177245385090) { // sqrt(pi)
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b.readbits(b.bits & 0x7); //align
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break;
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} else {
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throw "Illegal Bzip2 blocktype = 0x" + blocktype.toString(16);
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}
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} }
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main_loop();
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return out.join('');
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} } });
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})(); |