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annotate zlib/crc32.c @ 1998:0740d90812ee

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Enter debugger when a VDP data port read would cause a CPU lockup
author Mike Pavone <pavone@retrodev.com>
date Sun, 28 Jun 2020 22:53:52 -0700
parents 00d788dac91a
children
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1 /* crc32.c -- compute the CRC-32 of a data stream
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2 * Copyright (C) 1995-2006, 2010, 2011, 2012, 2016 Mark Adler
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3 * For conditions of distribution and use, see copyright notice in zlib.h
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4 *
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5 * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
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6 * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
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7 * tables for updating the shift register in one step with three exclusive-ors
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8 * instead of four steps with four exclusive-ors. This results in about a
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9 * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
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10 */
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11
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12 /* @(#) $Id$ */
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13
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14 /*
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15 Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
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16 protection on the static variables used to control the first-use generation
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17 of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should
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18 first call get_crc_table() to initialize the tables before allowing more than
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19 one thread to use crc32().
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20
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21 DYNAMIC_CRC_TABLE and MAKECRCH can be #defined to write out crc32.h.
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22 */
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23
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24 #ifdef MAKECRCH
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25 # include <stdio.h>
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26 # ifndef DYNAMIC_CRC_TABLE
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27 # define DYNAMIC_CRC_TABLE
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28 # endif /* !DYNAMIC_CRC_TABLE */
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29 #endif /* MAKECRCH */
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30
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31 #include "zutil.h" /* for STDC and FAR definitions */
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32
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33 /* Definitions for doing the crc four data bytes at a time. */
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34 #if !defined(NOBYFOUR) && defined(Z_U4)
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35 # define BYFOUR
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36 #endif
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37 #ifdef BYFOUR
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38 local unsigned long crc32_little OF((unsigned long,
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39 const unsigned char FAR *, z_size_t));
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40 local unsigned long crc32_big OF((unsigned long,
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41 const unsigned char FAR *, z_size_t));
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42 # define TBLS 8
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43 #else
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44 # define TBLS 1
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45 #endif /* BYFOUR */
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46
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47 /* Local functions for crc concatenation */
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48 local unsigned long gf2_matrix_times OF((unsigned long *mat,
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49 unsigned long vec));
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50 local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
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51 local uLong crc32_combine_ OF((uLong crc1, uLong crc2, z_off64_t len2));
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52
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53
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54 #ifdef DYNAMIC_CRC_TABLE
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55
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56 local volatile int crc_table_empty = 1;
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57 local z_crc_t FAR crc_table[TBLS][256];
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58 local void make_crc_table OF((void));
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59 #ifdef MAKECRCH
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60 local void write_table OF((FILE *, const z_crc_t FAR *));
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61 #endif /* MAKECRCH */
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62 /*
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63 Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
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64 x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.
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65
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66 Polynomials over GF(2) are represented in binary, one bit per coefficient,
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67 with the lowest powers in the most significant bit. Then adding polynomials
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68 is just exclusive-or, and multiplying a polynomial by x is a right shift by
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69 one. If we call the above polynomial p, and represent a byte as the
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70 polynomial q, also with the lowest power in the most significant bit (so the
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71 byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
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72 where a mod b means the remainder after dividing a by b.
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73
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74 This calculation is done using the shift-register method of multiplying and
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75 taking the remainder. The register is initialized to zero, and for each
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76 incoming bit, x^32 is added mod p to the register if the bit is a one (where
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77 x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
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78 x (which is shifting right by one and adding x^32 mod p if the bit shifted
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79 out is a one). We start with the highest power (least significant bit) of
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80 q and repeat for all eight bits of q.
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81
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82 The first table is simply the CRC of all possible eight bit values. This is
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83 all the information needed to generate CRCs on data a byte at a time for all
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84 combinations of CRC register values and incoming bytes. The remaining tables
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85 allow for word-at-a-time CRC calculation for both big-endian and little-
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86 endian machines, where a word is four bytes.
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87 */
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88 local void make_crc_table()
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89 {
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90 z_crc_t c;
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91 int n, k;
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92 z_crc_t poly; /* polynomial exclusive-or pattern */
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93 /* terms of polynomial defining this crc (except x^32): */
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94 static volatile int first = 1; /* flag to limit concurrent making */
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95 static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
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96
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97 /* See if another task is already doing this (not thread-safe, but better
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98 than nothing -- significantly reduces duration of vulnerability in
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99 case the advice about DYNAMIC_CRC_TABLE is ignored) */
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100 if (first) {
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101 first = 0;
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102
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103 /* make exclusive-or pattern from polynomial (0xedb88320UL) */
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104 poly = 0;
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105 for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++)
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106 poly |= (z_crc_t)1 << (31 - p[n]);
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107
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108 /* generate a crc for every 8-bit value */
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109 for (n = 0; n < 256; n++) {
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110 c = (z_crc_t)n;
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111 for (k = 0; k < 8; k++)
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112 c = c & 1 ? poly ^ (c >> 1) : c >> 1;
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113 crc_table[0][n] = c;
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114 }
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115
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116 #ifdef BYFOUR
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117 /* generate crc for each value followed by one, two, and three zeros,
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118 and then the byte reversal of those as well as the first table */
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119 for (n = 0; n < 256; n++) {
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120 c = crc_table[0][n];
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121 crc_table[4][n] = ZSWAP32(c);
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122 for (k = 1; k < 4; k++) {
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123 c = crc_table[0][c & 0xff] ^ (c >> 8);
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124 crc_table[k][n] = c;
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125 crc_table[k + 4][n] = ZSWAP32(c);
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126 }
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127 }
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128 #endif /* BYFOUR */
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129
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130 crc_table_empty = 0;
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131 }
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132 else { /* not first */
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133 /* wait for the other guy to finish (not efficient, but rare) */
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134 while (crc_table_empty)
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135 ;
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136 }
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137
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138 #ifdef MAKECRCH
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139 /* write out CRC tables to crc32.h */
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140 {
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141 FILE *out;
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142
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143 out = fopen("crc32.h", "w");
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144 if (out == NULL) return;
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145 fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
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146 fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
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147 fprintf(out, "local const z_crc_t FAR ");
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148 fprintf(out, "crc_table[TBLS][256] =\n{\n {\n");
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149 write_table(out, crc_table[0]);
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150 # ifdef BYFOUR
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151 fprintf(out, "#ifdef BYFOUR\n");
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152 for (k = 1; k < 8; k++) {
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153 fprintf(out, " },\n {\n");
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154 write_table(out, crc_table[k]);
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155 }
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156 fprintf(out, "#endif\n");
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157 # endif /* BYFOUR */
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158 fprintf(out, " }\n};\n");
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159 fclose(out);
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160 }
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161 #endif /* MAKECRCH */
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162 }
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163
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164 #ifdef MAKECRCH
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165 local void write_table(out, table)
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166 FILE *out;
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167 const z_crc_t FAR *table;
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168 {
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169 int n;
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170
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171 for (n = 0; n < 256; n++)
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172 fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ",
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173 (unsigned long)(table[n]),
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174 n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
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175 }
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176 #endif /* MAKECRCH */
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177
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178 #else /* !DYNAMIC_CRC_TABLE */
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179 /* ========================================================================
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180 * Tables of CRC-32s of all single-byte values, made by make_crc_table().
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181 */
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182 #include "crc32.h"
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183 #endif /* DYNAMIC_CRC_TABLE */
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184
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185 /* =========================================================================
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186 * This function can be used by asm versions of crc32()
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187 */
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188 const z_crc_t FAR * ZEXPORT get_crc_table()
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189 {
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190 #ifdef DYNAMIC_CRC_TABLE
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191 if (crc_table_empty)
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192 make_crc_table();
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193 #endif /* DYNAMIC_CRC_TABLE */
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194 return (const z_crc_t FAR *)crc_table;
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195 }
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196
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diff changeset
197 /* ========================================================================= */
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198 #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
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199 #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
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200
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201 /* ========================================================================= */
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202 unsigned long ZEXPORT crc32_z(crc, buf, len)
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203 unsigned long crc;
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204 const unsigned char FAR *buf;
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205 z_size_t len;
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206 {
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207 if (buf == Z_NULL) return 0UL;
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208
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209 #ifdef DYNAMIC_CRC_TABLE
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210 if (crc_table_empty)
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211 make_crc_table();
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212 #endif /* DYNAMIC_CRC_TABLE */
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213
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214 #ifdef BYFOUR
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215 if (sizeof(void *) == sizeof(ptrdiff_t)) {
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216 z_crc_t endian;
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217
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218 endian = 1;
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219 if (*((unsigned char *)(&endian)))
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220 return crc32_little(crc, buf, len);
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221 else
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222 return crc32_big(crc, buf, len);
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223 }
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224 #endif /* BYFOUR */
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225 crc = crc ^ 0xffffffffUL;
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226 while (len >= 8) {
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227 DO8;
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228 len -= 8;
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229 }
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diff changeset
230 if (len) do {
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diff changeset
231 DO1;
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232 } while (--len);
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233 return crc ^ 0xffffffffUL;
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234 }
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235
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236 /* ========================================================================= */
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237 unsigned long ZEXPORT crc32(crc, buf, len)
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diff changeset
238 unsigned long crc;
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239 const unsigned char FAR *buf;
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240 uInt len;
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241 {
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242 return crc32_z(crc, buf, len);
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243 }
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244
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245 #ifdef BYFOUR
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246
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247 /*
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diff changeset
248 This BYFOUR code accesses the passed unsigned char * buffer with a 32-bit
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diff changeset
249 integer pointer type. This violates the strict aliasing rule, where a
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diff changeset
250 compiler can assume, for optimization purposes, that two pointers to
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diff changeset
251 fundamentally different types won't ever point to the same memory. This can
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diff changeset
252 manifest as a problem only if one of the pointers is written to. This code
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253 only reads from those pointers. So long as this code remains isolated in
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diff changeset
254 this compilation unit, there won't be a problem. For this reason, this code
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255 should not be copied and pasted into a compilation unit in which other code
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256 writes to the buffer that is passed to these routines.
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257 */
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258
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diff changeset
259 /* ========================================================================= */
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diff changeset
260 #define DOLIT4 c ^= *buf4++; \
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diff changeset
261 c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
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262 crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
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diff changeset
263 #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
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264
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diff changeset
265 /* ========================================================================= */
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266 local unsigned long crc32_little(crc, buf, len)
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diff changeset
267 unsigned long crc;
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268 const unsigned char FAR *buf;
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269 z_size_t len;
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270 {
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271 register z_crc_t c;
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272 register const z_crc_t FAR *buf4;
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273
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274 c = (z_crc_t)crc;
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275 c = ~c;
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276 while (len && ((ptrdiff_t)buf & 3)) {
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277 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
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278 len--;
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279 }
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280
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281 buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
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282 while (len >= 32) {
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283 DOLIT32;
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284 len -= 32;
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diff changeset
285 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
286 while (len >= 4) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
287 DOLIT4;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
288 len -= 4;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
289 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
290 buf = (const unsigned char FAR *)buf4;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
291
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
292 if (len) do {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
293 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
294 } while (--len);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
295 c = ~c;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
296 return (unsigned long)c;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
297 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
298
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
299 /* ========================================================================= */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
300 #define DOBIG4 c ^= *buf4++; \
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
301 c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
302 crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
303 #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
304
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
305 /* ========================================================================= */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
306 local unsigned long crc32_big(crc, buf, len)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
307 unsigned long crc;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
308 const unsigned char FAR *buf;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
309 z_size_t len;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
310 {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
311 register z_crc_t c;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
312 register const z_crc_t FAR *buf4;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
313
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
314 c = ZSWAP32((z_crc_t)crc);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
315 c = ~c;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
316 while (len && ((ptrdiff_t)buf & 3)) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
317 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
318 len--;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
319 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
320
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
321 buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
322 while (len >= 32) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
323 DOBIG32;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
324 len -= 32;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
325 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
326 while (len >= 4) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
327 DOBIG4;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
328 len -= 4;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
329 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
330 buf = (const unsigned char FAR *)buf4;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
331
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
332 if (len) do {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
333 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
334 } while (--len);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
335 c = ~c;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
336 return (unsigned long)(ZSWAP32(c));
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
337 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
338
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
339 #endif /* BYFOUR */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
340
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
341 #define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
342
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
343 /* ========================================================================= */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
344 local unsigned long gf2_matrix_times(mat, vec)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
345 unsigned long *mat;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
346 unsigned long vec;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
347 {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
348 unsigned long sum;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
349
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
350 sum = 0;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
351 while (vec) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
352 if (vec & 1)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
353 sum ^= *mat;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
354 vec >>= 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
355 mat++;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
356 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
357 return sum;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
358 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
359
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
360 /* ========================================================================= */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
361 local void gf2_matrix_square(square, mat)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
362 unsigned long *square;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
363 unsigned long *mat;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
364 {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
365 int n;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
366
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
367 for (n = 0; n < GF2_DIM; n++)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
368 square[n] = gf2_matrix_times(mat, mat[n]);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
369 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
370
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
371 /* ========================================================================= */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
372 local uLong crc32_combine_(crc1, crc2, len2)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
373 uLong crc1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
374 uLong crc2;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
375 z_off64_t len2;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
376 {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
377 int n;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
378 unsigned long row;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
379 unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
380 unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
381
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
382 /* degenerate case (also disallow negative lengths) */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
383 if (len2 <= 0)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
384 return crc1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
385
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
386 /* put operator for one zero bit in odd */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
387 odd[0] = 0xedb88320UL; /* CRC-32 polynomial */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
388 row = 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
389 for (n = 1; n < GF2_DIM; n++) {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
390 odd[n] = row;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
391 row <<= 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
392 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
393
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
394 /* put operator for two zero bits in even */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
395 gf2_matrix_square(even, odd);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
396
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
397 /* put operator for four zero bits in odd */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
398 gf2_matrix_square(odd, even);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
399
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
400 /* apply len2 zeros to crc1 (first square will put the operator for one
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
401 zero byte, eight zero bits, in even) */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
402 do {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
403 /* apply zeros operator for this bit of len2 */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
404 gf2_matrix_square(even, odd);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
405 if (len2 & 1)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
406 crc1 = gf2_matrix_times(even, crc1);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
407 len2 >>= 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
408
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
409 /* if no more bits set, then done */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
410 if (len2 == 0)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
411 break;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
412
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
413 /* another iteration of the loop with odd and even swapped */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
414 gf2_matrix_square(odd, even);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
415 if (len2 & 1)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
416 crc1 = gf2_matrix_times(odd, crc1);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
417 len2 >>= 1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
418
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
419 /* if no more bits set, then done */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
420 } while (len2 != 0);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
421
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
422 /* return combined crc */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
423 crc1 ^= crc2;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
424 return crc1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
425 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
426
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
427 /* ========================================================================= */
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
428 uLong ZEXPORT crc32_combine(crc1, crc2, len2)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
429 uLong crc1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
430 uLong crc2;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
431 z_off_t len2;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
432 {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
433 return crc32_combine_(crc1, crc2, len2);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
434 }
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
435
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
436 uLong ZEXPORT crc32_combine64(crc1, crc2, len2)
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
437 uLong crc1;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
438 uLong crc2;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
439 z_off64_t len2;
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
440 {
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
441 return crc32_combine_(crc1, crc2, len2);
00d788dac91a Added support for reading gzipped ROMs
Michael Pavone <pavone@retrodev.com>
parents:
diff changeset
442 }