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2957f5084d
* Update zlibng * Set cmake path more directly in zlibng to hopefully fix an issue with the build on drone * I'm dumb, missing / in path * Mackal helps with a dumb gitignore issue * Adding all the files, not sure what's ignoring them and im tired of looking * Some tweaks to zlibng build to hopefully get it to build properly. works on msvc now
109 lines
3.5 KiB
C
109 lines
3.5 KiB
C
/* crc32_comb.c -- compute the CRC-32 of a data stream
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* Copyright (C) 1995-2006, 2010, 2011, 2012, 2016, 2018 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*
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* Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
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* CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
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* tables for updating the shift register in one step with three exclusive-ors
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* instead of four steps with four exclusive-ors. This results in about a
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* factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
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*/
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#include "zbuild.h"
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#include <inttypes.h>
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#include "deflate.h"
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#include "crc32_p.h"
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#include "crc32_comb_tbl.h"
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/* Local functions for crc concatenation */
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static uint32_t crc32_combine_(uint32_t crc1, uint32_t crc2, z_off64_t len2);
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static void crc32_combine_gen_(uint32_t *op, z_off64_t len2);
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/* ========================================================================= */
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static uint32_t crc32_combine_(uint32_t crc1, uint32_t crc2, z_off64_t len2) {
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int n;
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if (len2 > 0)
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/* operator for 2^n zeros repeats every GF2_DIM n values */
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for (n = 0; len2; n = (n + 1) % GF2_DIM, len2 >>= 1)
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if (len2 & 1)
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crc1 = gf2_matrix_times(crc_comb[n], crc1);
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return crc1 ^ crc2;
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}
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/* ========================================================================= */
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#ifdef ZLIB_COMPAT
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unsigned long Z_EXPORT PREFIX(crc32_combine)(unsigned long crc1, unsigned long crc2, z_off_t len2) {
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return (unsigned long)crc32_combine_((uint32_t)crc1, (uint32_t)crc2, len2);
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}
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unsigned long Z_EXPORT PREFIX4(crc32_combine)(unsigned long crc1, unsigned long crc2, z_off64_t len2) {
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return (unsigned long)crc32_combine_((uint32_t)crc1, (uint32_t)crc2, len2);
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}
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#else
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uint32_t Z_EXPORT PREFIX4(crc32_combine)(uint32_t crc1, uint32_t crc2, z_off64_t len2) {
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return crc32_combine_(crc1, crc2, len2);
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}
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#endif
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/* ========================================================================= */
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static void crc32_combine_gen_(uint32_t *op, z_off64_t len2) {
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uint32_t row;
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int j;
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unsigned i;
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/* if len2 is zero or negative, return the identity matrix */
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if (len2 <= 0) {
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row = 1;
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for (j = 0; j < GF2_DIM; j++) {
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op[j] = row;
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row <<= 1;
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}
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return;
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}
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/* at least one bit in len2 is set -- find it, and copy the operator
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corresponding to that position into op */
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i = 0;
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for (;;) {
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if (len2 & 1) {
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for (j = 0; j < GF2_DIM; j++)
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op[j] = crc_comb[i][j];
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break;
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}
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len2 >>= 1;
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i = (i + 1) % GF2_DIM;
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}
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/* for each remaining bit set in len2 (if any), multiply op by the operator
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corresponding to that position */
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for (;;) {
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len2 >>= 1;
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i = (i + 1) % GF2_DIM;
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if (len2 == 0)
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break;
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if (len2 & 1)
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for (j = 0; j < GF2_DIM; j++)
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op[j] = gf2_matrix_times(crc_comb[i], op[j]);
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}
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}
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/* ========================================================================= */
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#ifdef ZLIB_COMPAT
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void Z_EXPORT PREFIX(crc32_combine_gen)(uint32_t *op, z_off_t len2) {
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crc32_combine_gen_(op, len2);
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}
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#endif
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void Z_EXPORT PREFIX4(crc32_combine_gen)(uint32_t *op, z_off64_t len2) {
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crc32_combine_gen_(op, len2);
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}
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/* ========================================================================= */
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uint32_t Z_EXPORT PREFIX(crc32_combine_op)(uint32_t crc1, uint32_t crc2, const uint32_t *op) {
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return gf2_matrix_times(op, crc1) ^ crc2;
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}
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