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Function tr_static_init

zlib/trees.c:295–374  ·  view source on GitHub ↗

=========================================================================== * Initialize the various 'constant' tables. */

Source from the content-addressed store, hash-verified

293 * Initialize the various 'constant' tables.
294 */
295local void tr_static_init(void) {
296#if defined(GEN_TREES_H) || !defined(STDC)
297 static int static_init_done = 0;
298 int n; /* iterates over tree elements */
299 int bits; /* bit counter */
300 int length; /* length value */
301 int code; /* code value */
302 int dist; /* distance index */
303 ush bl_count[MAX_BITS+1];
304 /* number of codes at each bit length for an optimal tree */
305
306 if (static_init_done) return;
307
308 /* For some embedded targets, global variables are not initialized: */
309#ifdef NO_INIT_GLOBAL_POINTERS
310 static_l_desc.static_tree = static_ltree;
311 static_l_desc.extra_bits = extra_lbits;
312 static_d_desc.static_tree = static_dtree;
313 static_d_desc.extra_bits = extra_dbits;
314 static_bl_desc.extra_bits = extra_blbits;
315#endif
316
317 /* Initialize the mapping length (0..255) -> length code (0..28) */
318 length = 0;
319 for (code = 0; code < LENGTH_CODES-1; code++) {
320 base_length[code] = length;
321 for (n = 0; n < (1 << extra_lbits[code]); n++) {
322 _length_code[length++] = (uch)code;
323 }
324 }
325 Assert (length == 256, "tr_static_init: length != 256");
326 /* Note that the length 255 (match length 258) can be represented
327 * in two different ways: code 284 + 5 bits or code 285, so we
328 * overwrite length_code[255] to use the best encoding:
329 */
330 _length_code[length - 1] = (uch)code;
331
332 /* Initialize the mapping dist (0..32K) -> dist code (0..29) */
333 dist = 0;
334 for (code = 0 ; code < 16; code++) {
335 base_dist[code] = dist;
336 for (n = 0; n < (1 << extra_dbits[code]); n++) {
337 _dist_code[dist++] = (uch)code;
338 }
339 }
340 Assert (dist == 256, "tr_static_init: dist != 256");
341 dist >>= 7; /* from now on, all distances are divided by 128 */
342 for ( ; code < D_CODES; code++) {
343 base_dist[code] = dist << 7;
344 for (n = 0; n < (1 << (extra_dbits[code] - 7)); n++) {
345 _dist_code[256 + dist++] = (uch)code;
346 }
347 }
348 Assert (dist == 256, "tr_static_init: 256 + dist != 512");
349
350 /* Construct the codes of the static literal tree */
351 for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;
352 n = 0;

Callers 1

_tr_initFunction · 0.85

Calls 3

gen_codesFunction · 0.85
bi_reverseFunction · 0.85
gen_trees_headerFunction · 0.85

Tested by

no test coverage detected