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376 lines
9.0 KiB
JavaScript
376 lines
9.0 KiB
JavaScript
var TINF_OK = 0;
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var TINF_DATA_ERROR = -3;
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function Tree() {
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this.table = new Uint16Array(16); /* table of code length counts */
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this.trans = new Uint16Array(288); /* code -> symbol translation table */
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}
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function Data(source, dest) {
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this.source = source;
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this.sourceIndex = 0;
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this.tag = 0;
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this.bitcount = 0;
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this.dest = dest;
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this.destLen = 0;
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this.ltree = new Tree(); /* dynamic length/symbol tree */
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this.dtree = new Tree(); /* dynamic distance tree */
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}
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/* --------------------------------------------------- *
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* -- uninitialized global data (static structures) -- *
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* --------------------------------------------------- */
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var sltree = new Tree();
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var sdtree = new Tree();
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/* extra bits and base tables for length codes */
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var length_bits = new Uint8Array(30);
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var length_base = new Uint16Array(30);
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/* extra bits and base tables for distance codes */
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var dist_bits = new Uint8Array(30);
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var dist_base = new Uint16Array(30);
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/* special ordering of code length codes */
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var clcidx = new Uint8Array([
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16, 17, 18, 0, 8, 7, 9, 6,
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10, 5, 11, 4, 12, 3, 13, 2,
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14, 1, 15
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]);
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/* used by tinf_decode_trees, avoids allocations every call */
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var code_tree = new Tree();
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var lengths = new Uint8Array(288 + 32);
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/* ----------------------- *
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* -- utility functions -- *
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* ----------------------- */
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/* build extra bits and base tables */
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function tinf_build_bits_base(bits, base, delta, first) {
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var i, sum;
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/* build bits table */
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for (i = 0; i < delta; ++i) bits[i] = 0;
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for (i = 0; i < 30 - delta; ++i) bits[i + delta] = i / delta | 0;
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/* build base table */
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for (sum = first, i = 0; i < 30; ++i) {
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base[i] = sum;
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sum += 1 << bits[i];
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}
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}
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/* build the fixed huffman trees */
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function tinf_build_fixed_trees(lt, dt) {
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var i;
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/* build fixed length tree */
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for (i = 0; i < 7; ++i) lt.table[i] = 0;
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lt.table[7] = 24;
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lt.table[8] = 152;
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lt.table[9] = 112;
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for (i = 0; i < 24; ++i) lt.trans[i] = 256 + i;
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for (i = 0; i < 144; ++i) lt.trans[24 + i] = i;
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for (i = 0; i < 8; ++i) lt.trans[24 + 144 + i] = 280 + i;
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for (i = 0; i < 112; ++i) lt.trans[24 + 144 + 8 + i] = 144 + i;
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/* build fixed distance tree */
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for (i = 0; i < 5; ++i) dt.table[i] = 0;
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dt.table[5] = 32;
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for (i = 0; i < 32; ++i) dt.trans[i] = i;
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}
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/* given an array of code lengths, build a tree */
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var offs = new Uint16Array(16);
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function tinf_build_tree(t, lengths, off, num) {
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var i, sum;
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/* clear code length count table */
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for (i = 0; i < 16; ++i) t.table[i] = 0;
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/* scan symbol lengths, and sum code length counts */
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for (i = 0; i < num; ++i) t.table[lengths[off + i]]++;
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t.table[0] = 0;
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/* compute offset table for distribution sort */
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for (sum = 0, i = 0; i < 16; ++i) {
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offs[i] = sum;
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sum += t.table[i];
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}
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/* create code->symbol translation table (symbols sorted by code) */
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for (i = 0; i < num; ++i) {
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if (lengths[off + i]) t.trans[offs[lengths[off + i]]++] = i;
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}
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}
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/* ---------------------- *
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* -- decode functions -- *
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* ---------------------- */
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/* get one bit from source stream */
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function tinf_getbit(d) {
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/* check if tag is empty */
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if (!d.bitcount--) {
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/* load next tag */
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d.tag = d.source[d.sourceIndex++];
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d.bitcount = 7;
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}
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/* shift bit out of tag */
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var bit = d.tag & 1;
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d.tag >>>= 1;
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return bit;
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}
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/* read a num bit value from a stream and add base */
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function tinf_read_bits(d, num, base) {
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if (!num)
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return base;
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while (d.bitcount < 24) {
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d.tag |= d.source[d.sourceIndex++] << d.bitcount;
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d.bitcount += 8;
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}
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var val = d.tag & (0xffff >>> (16 - num));
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d.tag >>>= num;
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d.bitcount -= num;
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return val + base;
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}
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/* given a data stream and a tree, decode a symbol */
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function tinf_decode_symbol(d, t) {
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while (d.bitcount < 24) {
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d.tag |= d.source[d.sourceIndex++] << d.bitcount;
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d.bitcount += 8;
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}
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var sum = 0, cur = 0, len = 0;
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var tag = d.tag;
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/* get more bits while code value is above sum */
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do {
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cur = 2 * cur + (tag & 1);
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tag >>>= 1;
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++len;
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sum += t.table[len];
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cur -= t.table[len];
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} while (cur >= 0);
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d.tag = tag;
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d.bitcount -= len;
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return t.trans[sum + cur];
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}
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/* given a data stream, decode dynamic trees from it */
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function tinf_decode_trees(d, lt, dt) {
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var hlit, hdist, hclen;
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var i, num, length;
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/* get 5 bits HLIT (257-286) */
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hlit = tinf_read_bits(d, 5, 257);
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/* get 5 bits HDIST (1-32) */
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hdist = tinf_read_bits(d, 5, 1);
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/* get 4 bits HCLEN (4-19) */
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hclen = tinf_read_bits(d, 4, 4);
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for (i = 0; i < 19; ++i) lengths[i] = 0;
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/* read code lengths for code length alphabet */
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for (i = 0; i < hclen; ++i) {
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/* get 3 bits code length (0-7) */
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var clen = tinf_read_bits(d, 3, 0);
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lengths[clcidx[i]] = clen;
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}
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/* build code length tree */
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tinf_build_tree(code_tree, lengths, 0, 19);
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/* decode code lengths for the dynamic trees */
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for (num = 0; num < hlit + hdist;) {
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var sym = tinf_decode_symbol(d, code_tree);
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switch (sym) {
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case 16:
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/* copy previous code length 3-6 times (read 2 bits) */
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var prev = lengths[num - 1];
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for (length = tinf_read_bits(d, 2, 3); length; --length) {
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lengths[num++] = prev;
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}
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break;
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case 17:
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/* repeat code length 0 for 3-10 times (read 3 bits) */
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for (length = tinf_read_bits(d, 3, 3); length; --length) {
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lengths[num++] = 0;
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}
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break;
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case 18:
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/* repeat code length 0 for 11-138 times (read 7 bits) */
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for (length = tinf_read_bits(d, 7, 11); length; --length) {
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lengths[num++] = 0;
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}
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break;
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default:
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/* values 0-15 represent the actual code lengths */
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lengths[num++] = sym;
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break;
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}
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}
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/* build dynamic trees */
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tinf_build_tree(lt, lengths, 0, hlit);
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tinf_build_tree(dt, lengths, hlit, hdist);
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}
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/* ----------------------------- *
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* -- block inflate functions -- *
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* ----------------------------- */
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/* given a stream and two trees, inflate a block of data */
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function tinf_inflate_block_data(d, lt, dt) {
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while (1) {
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var sym = tinf_decode_symbol(d, lt);
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/* check for end of block */
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if (sym === 256) {
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return TINF_OK;
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}
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if (sym < 256) {
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d.dest[d.destLen++] = sym;
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} else {
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var length, dist, offs;
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var i;
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sym -= 257;
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/* possibly get more bits from length code */
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length = tinf_read_bits(d, length_bits[sym], length_base[sym]);
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dist = tinf_decode_symbol(d, dt);
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/* possibly get more bits from distance code */
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offs = d.destLen - tinf_read_bits(d, dist_bits[dist], dist_base[dist]);
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/* copy match */
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for (i = offs; i < offs + length; ++i) {
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d.dest[d.destLen++] = d.dest[i];
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}
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}
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}
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}
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/* inflate an uncompressed block of data */
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function tinf_inflate_uncompressed_block(d) {
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var length, invlength;
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var i;
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/* unread from bitbuffer */
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while (d.bitcount > 8) {
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d.sourceIndex--;
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d.bitcount -= 8;
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}
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/* get length */
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length = d.source[d.sourceIndex + 1];
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length = 256 * length + d.source[d.sourceIndex];
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/* get one's complement of length */
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invlength = d.source[d.sourceIndex + 3];
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invlength = 256 * invlength + d.source[d.sourceIndex + 2];
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/* check length */
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if (length !== (~invlength & 0x0000ffff))
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return TINF_DATA_ERROR;
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d.sourceIndex += 4;
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/* copy block */
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for (i = length; i; --i)
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d.dest[d.destLen++] = d.source[d.sourceIndex++];
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/* make sure we start next block on a byte boundary */
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d.bitcount = 0;
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return TINF_OK;
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}
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/* inflate stream from source to dest */
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function tinf_uncompress(source, dest) {
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var d = new Data(source, dest);
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var bfinal, btype, res;
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do {
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/* read final block flag */
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bfinal = tinf_getbit(d);
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/* read block type (2 bits) */
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btype = tinf_read_bits(d, 2, 0);
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/* decompress block */
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switch (btype) {
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case 0:
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/* decompress uncompressed block */
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res = tinf_inflate_uncompressed_block(d);
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break;
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case 1:
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/* decompress block with fixed huffman trees */
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res = tinf_inflate_block_data(d, sltree, sdtree);
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break;
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case 2:
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/* decompress block with dynamic huffman trees */
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tinf_decode_trees(d, d.ltree, d.dtree);
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res = tinf_inflate_block_data(d, d.ltree, d.dtree);
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break;
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default:
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res = TINF_DATA_ERROR;
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}
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if (res !== TINF_OK)
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throw new Error('Data error');
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} while (!bfinal);
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if (d.destLen < d.dest.length) {
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if (typeof d.dest.slice === 'function')
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return d.dest.slice(0, d.destLen);
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else
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return d.dest.subarray(0, d.destLen);
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}
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return d.dest;
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}
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/* -------------------- *
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* -- initialization -- *
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* -------------------- */
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/* build fixed huffman trees */
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tinf_build_fixed_trees(sltree, sdtree);
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/* build extra bits and base tables */
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tinf_build_bits_base(length_bits, length_base, 4, 3);
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tinf_build_bits_base(dist_bits, dist_base, 2, 1);
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/* fix a special case */
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length_bits[28] = 0;
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length_base[28] = 258;
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module.exports = tinf_uncompress;
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