328 lines
11 KiB
JavaScript
328 lines
11 KiB
JavaScript
'use strict';
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var utils = require('../utils/common');
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var MAXBITS = 15;
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var ENOUGH_LENS = 852;
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var ENOUGH_DISTS = 592;
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//var ENOUGH = (ENOUGH_LENS+ENOUGH_DISTS);
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var CODES = 0;
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var LENS = 1;
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var DISTS = 2;
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var lbase = [ /* Length codes 257..285 base */
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3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
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35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0
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];
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var lext = [ /* Length codes 257..285 extra */
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16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
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19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 72, 78
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];
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var dbase = [ /* Distance codes 0..29 base */
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1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
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257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
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8193, 12289, 16385, 24577, 0, 0
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];
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var dext = [ /* Distance codes 0..29 extra */
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16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
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23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
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28, 28, 29, 29, 64, 64
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];
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module.exports = function inflate_table(type, lens, lens_index, codes, table, table_index, work, opts)
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{
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var bits = opts.bits;
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//here = opts.here; /* table entry for duplication */
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var len = 0; /* a code's length in bits */
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var sym = 0; /* index of code symbols */
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var min = 0, max = 0; /* minimum and maximum code lengths */
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var root = 0; /* number of index bits for root table */
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var curr = 0; /* number of index bits for current table */
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var drop = 0; /* code bits to drop for sub-table */
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var left = 0; /* number of prefix codes available */
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var used = 0; /* code entries in table used */
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var huff = 0; /* Huffman code */
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var incr; /* for incrementing code, index */
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var fill; /* index for replicating entries */
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var low; /* low bits for current root entry */
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var mask; /* mask for low root bits */
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var next; /* next available space in table */
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var base = null; /* base value table to use */
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var base_index = 0;
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// var shoextra; /* extra bits table to use */
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var end; /* use base and extra for symbol > end */
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var count = new utils.Buf16(MAXBITS + 1); //[MAXBITS+1]; /* number of codes of each length */
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var offs = new utils.Buf16(MAXBITS + 1); //[MAXBITS+1]; /* offsets in table for each length */
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var extra = null;
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var extra_index = 0;
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var here_bits, here_op, here_val;
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/*
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Process a set of code lengths to create a canonical Huffman code. The
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code lengths are lens[0..codes-1]. Each length corresponds to the
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symbols 0..codes-1. The Huffman code is generated by first sorting the
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symbols by length from short to long, and retaining the symbol order
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for codes with equal lengths. Then the code starts with all zero bits
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for the first code of the shortest length, and the codes are integer
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increments for the same length, and zeros are appended as the length
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increases. For the deflate format, these bits are stored backwards
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from their more natural integer increment ordering, and so when the
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decoding tables are built in the large loop below, the integer codes
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are incremented backwards.
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This routine assumes, but does not check, that all of the entries in
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lens[] are in the range 0..MAXBITS. The caller must assure this.
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1..MAXBITS is interpreted as that code length. zero means that that
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symbol does not occur in this code.
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The codes are sorted by computing a count of codes for each length,
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creating from that a table of starting indices for each length in the
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sorted table, and then entering the symbols in order in the sorted
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table. The sorted table is work[], with that space being provided by
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the caller.
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The length counts are used for other purposes as well, i.e. finding
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the minimum and maximum length codes, determining if there are any
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codes at all, checking for a valid set of lengths, and looking ahead
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at length counts to determine sub-table sizes when building the
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decoding tables.
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*/
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/* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */
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for (len = 0; len <= MAXBITS; len++) {
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count[len] = 0;
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}
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for (sym = 0; sym < codes; sym++) {
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count[lens[lens_index + sym]]++;
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}
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/* bound code lengths, force root to be within code lengths */
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root = bits;
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for (max = MAXBITS; max >= 1; max--) {
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if (count[max] !== 0) { break; }
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}
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if (root > max) {
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root = max;
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}
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if (max === 0) { /* no symbols to code at all */
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//table.op[opts.table_index] = 64; //here.op = (var char)64; /* invalid code marker */
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//table.bits[opts.table_index] = 1; //here.bits = (var char)1;
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//table.val[opts.table_index++] = 0; //here.val = (var short)0;
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table[table_index++] = (1 << 24) | (64 << 16) | 0;
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//table.op[opts.table_index] = 64;
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//table.bits[opts.table_index] = 1;
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//table.val[opts.table_index++] = 0;
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table[table_index++] = (1 << 24) | (64 << 16) | 0;
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opts.bits = 1;
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return 0; /* no symbols, but wait for decoding to report error */
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}
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for (min = 1; min < max; min++) {
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if (count[min] !== 0) { break; }
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}
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if (root < min) {
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root = min;
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}
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/* check for an over-subscribed or incomplete set of lengths */
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left = 1;
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for (len = 1; len <= MAXBITS; len++) {
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left <<= 1;
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left -= count[len];
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if (left < 0) {
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return -1;
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} /* over-subscribed */
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}
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if (left > 0 && (type === CODES || max !== 1)) {
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return -1; /* incomplete set */
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}
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/* generate offsets into symbol table for each length for sorting */
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offs[1] = 0;
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for (len = 1; len < MAXBITS; len++) {
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offs[len + 1] = offs[len] + count[len];
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}
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/* sort symbols by length, by symbol order within each length */
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for (sym = 0; sym < codes; sym++) {
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if (lens[lens_index + sym] !== 0) {
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work[offs[lens[lens_index + sym]]++] = sym;
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}
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}
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/*
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Create and fill in decoding tables. In this loop, the table being
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filled is at next and has curr index bits. The code being used is huff
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with length len. That code is converted to an index by dropping drop
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bits off of the bottom. For codes where len is less than drop + curr,
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those top drop + curr - len bits are incremented through all values to
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fill the table with replicated entries.
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root is the number of index bits for the root table. When len exceeds
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root, sub-tables are created pointed to by the root entry with an index
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of the low root bits of huff. This is saved in low to check for when a
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new sub-table should be started. drop is zero when the root table is
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being filled, and drop is root when sub-tables are being filled.
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When a new sub-table is needed, it is necessary to look ahead in the
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code lengths to determine what size sub-table is needed. The length
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counts are used for this, and so count[] is decremented as codes are
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entered in the tables.
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used keeps track of how many table entries have been allocated from the
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provided *table space. It is checked for LENS and DIST tables against
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the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in
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the initial root table size constants. See the comments in inftrees.h
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for more information.
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sym increments through all symbols, and the loop terminates when
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all codes of length max, i.e. all codes, have been processed. This
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routine permits incomplete codes, so another loop after this one fills
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in the rest of the decoding tables with invalid code markers.
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*/
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/* set up for code type */
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// poor man optimization - use if-else instead of switch,
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// to avoid deopts in old v8
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if (type === CODES) {
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base = extra = work; /* dummy value--not used */
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end = 19;
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} else if (type === LENS) {
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base = lbase;
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base_index -= 257;
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extra = lext;
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extra_index -= 257;
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end = 256;
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} else { /* DISTS */
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base = dbase;
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extra = dext;
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end = -1;
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}
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/* initialize opts for loop */
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huff = 0; /* starting code */
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sym = 0; /* starting code symbol */
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len = min; /* starting code length */
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next = table_index; /* current table to fill in */
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curr = root; /* current table index bits */
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drop = 0; /* current bits to drop from code for index */
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low = -1; /* trigger new sub-table when len > root */
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used = 1 << root; /* use root table entries */
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mask = used - 1; /* mask for comparing low */
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/* check available table space */
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if ((type === LENS && used > ENOUGH_LENS) ||
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(type === DISTS && used > ENOUGH_DISTS)) {
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return 1;
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}
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var i = 0;
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/* process all codes and make table entries */
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for (;;) {
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i++;
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/* create table entry */
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here_bits = len - drop;
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if (work[sym] < end) {
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here_op = 0;
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here_val = work[sym];
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}
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else if (work[sym] > end) {
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here_op = extra[extra_index + work[sym]];
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here_val = base[base_index + work[sym]];
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}
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else {
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here_op = 32 + 64; /* end of block */
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here_val = 0;
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}
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/* replicate for those indices with low len bits equal to huff */
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incr = 1 << (len - drop);
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fill = 1 << curr;
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min = fill; /* save offset to next table */
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do {
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fill -= incr;
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table[next + (huff >> drop) + fill] = (here_bits << 24) | (here_op << 16) | here_val |0;
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} while (fill !== 0);
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/* backwards increment the len-bit code huff */
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incr = 1 << (len - 1);
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while (huff & incr) {
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incr >>= 1;
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}
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if (incr !== 0) {
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huff &= incr - 1;
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huff += incr;
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} else {
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huff = 0;
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}
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/* go to next symbol, update count, len */
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sym++;
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if (--count[len] === 0) {
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if (len === max) { break; }
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len = lens[lens_index + work[sym]];
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}
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/* create new sub-table if needed */
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if (len > root && (huff & mask) !== low) {
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/* if first time, transition to sub-tables */
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if (drop === 0) {
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drop = root;
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}
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/* increment past last table */
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next += min; /* here min is 1 << curr */
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/* determine length of next table */
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curr = len - drop;
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left = 1 << curr;
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while (curr + drop < max) {
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left -= count[curr + drop];
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if (left <= 0) { break; }
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curr++;
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left <<= 1;
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}
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/* check for enough space */
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used += 1 << curr;
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if ((type === LENS && used > ENOUGH_LENS) ||
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(type === DISTS && used > ENOUGH_DISTS)) {
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return 1;
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}
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/* point entry in root table to sub-table */
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low = huff & mask;
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/*table.op[low] = curr;
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table.bits[low] = root;
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table.val[low] = next - opts.table_index;*/
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table[low] = (root << 24) | (curr << 16) | (next - table_index) |0;
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}
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}
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/* fill in remaining table entry if code is incomplete (guaranteed to have
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at most one remaining entry, since if the code is incomplete, the
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maximum code length that was allowed to get this far is one bit) */
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if (huff !== 0) {
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//table.op[next + huff] = 64; /* invalid code marker */
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//table.bits[next + huff] = len - drop;
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//table.val[next + huff] = 0;
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table[next + huff] = ((len - drop) << 24) | (64 << 16) |0;
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}
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/* set return parameters */
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//opts.table_index += used;
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opts.bits = root;
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return 0;
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};
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