1 /* crc32.cpp -- compute the CRC-32 of a data stream |
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2 * Copyright (C) 1995-2005 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: crc32.cpp,v 1.1.2.1 2008/08/14 15:26:57 e0222316 Exp $ */ |
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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 |
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22 #ifdef MAKECRCH |
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23 # include <stdio.h> |
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24 # ifndef DYNAMIC_CRC_TABLE |
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25 # define DYNAMIC_CRC_TABLE |
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26 # endif /* !DYNAMIC_CRC_TABLE */ |
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27 #endif /* MAKECRCH */ |
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28 |
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29 /* These defines are usually taken from limits.h, however this file is not supported in Symbian. */ |
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30 #if (defined(__SYMBIAN32__) && !defined(__TOOLS2__) && !defined(__TOOLS__)) |
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31 #define UINT_MAX 0xffffffffU /* Values taken from _limits.h:from PIPS */ |
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32 #define ULONG_MAX 0xffffffffUL /* Removing may slow down the crc operation */ |
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33 typedef int ptrdiff_t; |
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34 #endif /* __SYMBIAN32__ && !__TOOLS2__) && !__TOOLS__ */ |
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35 |
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36 #include "zutil.h" /* for STDC and FAR definitions */ |
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37 |
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38 |
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39 /* Find a four-byte integer type for crc32_little() and crc32_big(). */ |
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40 #ifndef NOBYFOUR |
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41 # ifdef STDC /* need ANSI C limits.h to determine sizes */ |
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42 # if (!defined(__SYMBIAN32__) || defined(__TOOLS2__) || defined(__TOOLS__)) /* only include for Tools builds */ |
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43 # include <limits.h> |
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44 # endif /* !__SYMBIAN32__ || __TOOLS2__) || __TOOLS__ */ |
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45 # define BYFOUR |
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46 # if (UINT_MAX == 0xffffffffUL) |
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47 typedef unsigned int u4; |
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48 # else |
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49 # if (ULONG_MAX == 0xffffffffUL) |
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50 typedef unsigned long u4; |
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51 # else |
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52 # if (USHRT_MAX == 0xffffffffUL) |
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53 typedef unsigned short u4; |
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54 # else |
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55 # undef BYFOUR /* can't find a four-byte integer type! */ |
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56 # endif |
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57 # endif |
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58 # endif |
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59 # endif /* STDC */ |
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60 #endif /* !NOBYFOUR */ |
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61 |
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62 /* Definitions for doing the crc four data bytes at a time. */ |
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63 #ifdef BYFOUR |
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64 # define REV(w) (((w)>>24)+(((w)>>8)&0xff00)+ \ |
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65 (((w)&0xff00)<<8)+(((w)&0xff)<<24)) |
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66 local unsigned long crc32_little OF((unsigned long, |
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67 const unsigned char FAR *, unsigned)); |
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68 local unsigned long crc32_big OF((unsigned long, |
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69 const unsigned char FAR *, unsigned)); |
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70 # define TBLS 8 |
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71 #else |
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72 # define TBLS 1 |
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73 #endif /* BYFOUR */ |
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74 |
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75 /* Local functions for crc concatenation */ |
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76 local unsigned long gf2_matrix_times OF((unsigned long *mat, |
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77 unsigned long vec)); |
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78 local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat)); |
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79 |
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80 #ifdef DYNAMIC_CRC_TABLE |
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81 |
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82 local volatile int crc_table_empty = 1; |
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83 local unsigned long FAR crc_table[TBLS][256]; |
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84 local void make_crc_table OF((void)); |
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85 #ifdef MAKECRCH |
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86 local void write_table OF((FILE *, const unsigned long FAR *)); |
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87 #endif /* MAKECRCH */ |
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88 /* |
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89 Generate tables for a byte-wise 32-bit CRC calculation on the polynomial: |
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90 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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91 |
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92 Polynomials over GF(2) are represented in binary, one bit per coefficient, |
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93 with the lowest powers in the most significant bit. Then adding polynomials |
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94 is just exclusive-or, and multiplying a polynomial by x is a right shift by |
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95 one. If we call the above polynomial p, and represent a byte as the |
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96 polynomial q, also with the lowest power in the most significant bit (so the |
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97 byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p, |
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98 where a mod b means the remainder after dividing a by b. |
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99 |
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100 This calculation is done using the shift-register method of multiplying and |
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101 taking the remainder. The register is initialized to zero, and for each |
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102 incoming bit, x^32 is added mod p to the register if the bit is a one (where |
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103 x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by |
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104 x (which is shifting right by one and adding x^32 mod p if the bit shifted |
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105 out is a one). We start with the highest power (least significant bit) of |
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106 q and repeat for all eight bits of q. |
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107 |
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108 The first table is simply the CRC of all possible eight bit values. This is |
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109 all the information needed to generate CRCs on data a byte at a time for all |
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110 combinations of CRC register values and incoming bytes. The remaining tables |
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111 allow for word-at-a-time CRC calculation for both big-endian and little- |
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112 endian machines, where a word is four bytes. |
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113 */ |
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114 local void make_crc_table() |
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115 { |
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116 unsigned long c; |
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117 int n, k; |
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118 unsigned long poly; /* polynomial exclusive-or pattern */ |
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119 /* terms of polynomial defining this crc (except x^32): */ |
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120 static volatile int first = 1; /* flag to limit concurrent making */ |
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121 static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26}; |
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122 |
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123 /* See if another task is already doing this (not thread-safe, but better |
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124 than nothing -- significantly reduces duration of vulnerability in |
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125 case the advice about DYNAMIC_CRC_TABLE is ignored) */ |
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126 if (first) { |
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127 first = 0; |
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128 |
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129 /* make exclusive-or pattern from polynomial (0xedb88320UL) */ |
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130 poly = 0UL; |
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131 for (n = 0; n < sizeof(p)/sizeof(unsigned char); n++) |
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132 poly |= 1UL << (31 - p[n]); |
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133 |
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134 /* generate a crc for every 8-bit value */ |
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135 for (n = 0; n < 256; n++) { |
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136 c = (unsigned long)n; |
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137 for (k = 0; k < 8; k++) |
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138 c = c & 1 ? poly ^ (c >> 1) : c >> 1; |
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139 crc_table[0][n] = c; |
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140 } |
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141 |
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142 #ifdef BYFOUR |
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143 /* generate crc for each value followed by one, two, and three zeros, |
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144 and then the byte reversal of those as well as the first table */ |
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145 for (n = 0; n < 256; n++) { |
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146 c = crc_table[0][n]; |
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147 crc_table[4][n] = REV(c); |
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148 for (k = 1; k < 4; k++) { |
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149 c = crc_table[0][c & 0xff] ^ (c >> 8); |
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150 crc_table[k][n] = c; |
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151 crc_table[k + 4][n] = REV(c); |
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152 } |
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153 } |
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154 #endif /* BYFOUR */ |
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155 |
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156 crc_table_empty = 0; |
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157 } |
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158 else { /* not first */ |
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159 /* wait for the other guy to finish (not efficient, but rare) */ |
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160 while (crc_table_empty) |
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161 ; |
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162 } |
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163 |
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164 #ifdef MAKECRCH |
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165 /* write out CRC tables to crc32.h */ |
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166 { |
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167 FILE *out; |
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168 |
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169 out = fopen("crc32.h", "w"); |
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170 if (out == NULL) return; |
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171 fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n"); |
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172 fprintf(out, " * Generated automatically by crc32.c\n */\n\n"); |
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173 fprintf(out, "local const unsigned long FAR "); |
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174 fprintf(out, "crc_table[TBLS][256] =\n{\n {\n"); |
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175 write_table(out, crc_table[0]); |
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176 # ifdef BYFOUR |
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177 fprintf(out, "#ifdef BYFOUR\n"); |
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178 for (k = 1; k < 8; k++) { |
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179 fprintf(out, " },\n {\n"); |
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180 write_table(out, crc_table[k]); |
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181 } |
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182 fprintf(out, "#endif\n"); |
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183 # endif /* BYFOUR */ |
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184 fprintf(out, " }\n};\n"); |
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185 fclose(out); |
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186 } |
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187 #endif /* MAKECRCH */ |
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188 } |
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189 |
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190 #ifdef MAKECRCH |
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191 #ifdef __SYMBIAN32__ |
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192 local void write_table(FILE * out, const unsigned long FAR * table) |
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193 #else |
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194 local void write_table(out, table) |
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195 FILE *out; |
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196 const unsigned long FAR *table; |
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197 #endif //__SYMBIAN32__ |
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198 { |
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199 int n; |
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200 |
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201 for (n = 0; n < 256; n++) |
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202 fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ", table[n], |
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203 n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", ")); |
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204 } |
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205 #endif /* MAKECRCH */ |
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206 |
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207 #else /* !DYNAMIC_CRC_TABLE */ |
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208 /* ======================================================================== |
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209 * Tables of CRC-32s of all single-byte values, made by make_crc_table(). |
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210 */ |
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211 #include "crc32.h" |
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212 #endif /* DYNAMIC_CRC_TABLE */ |
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213 |
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214 /* ========================================================================= |
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215 * This function can be used by asm versions of crc32() |
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216 */ |
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217 #ifdef __SYMBIAN32__ |
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218 EXPORT_C const unsigned long FAR * get_crc_table_r() |
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219 #else |
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220 const unsigned long FAR * ZEXPORT get_crc_table() |
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221 #endif //__SYMBIAN32__ |
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222 { |
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223 #ifdef DYNAMIC_CRC_TABLE |
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224 if (crc_table_empty) |
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225 make_crc_table(); |
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226 #endif /* DYNAMIC_CRC_TABLE */ |
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227 return (const unsigned long FAR *)crc_table; |
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228 } |
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229 |
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230 /* ========================================================================= */ |
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231 #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8) |
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232 #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1 |
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233 |
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234 /* ========================================================================= */ |
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235 |
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236 #ifdef __SYMBIAN32__ |
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237 EXPORT_C unsigned long crc32_r( unsigned long crc, const unsigned char FAR * buf,unsigned len) |
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238 #else |
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239 unsigned long ZEXPORT crc32(crc, buf, len) |
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240 unsigned long crc; |
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241 const unsigned char FAR *buf; |
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242 unsigned len; |
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243 #endif //__SYMBIAN32__ |
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244 { |
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245 if (buf == Z_NULL) return 0UL; |
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246 |
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247 #ifdef DYNAMIC_CRC_TABLE |
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248 if (crc_table_empty) |
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249 make_crc_table(); |
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250 #endif /* DYNAMIC_CRC_TABLE */ |
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251 |
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252 #ifdef BYFOUR |
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253 if (sizeof(void *) == sizeof(ptrdiff_t)) { |
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254 u4 endian; |
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255 |
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256 endian = 1; |
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257 if (*((unsigned char *)(&endian))) |
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258 return crc32_little(crc, buf, len); |
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259 else |
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260 return crc32_big(crc, buf, len); |
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261 } |
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262 else |
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263 { |
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264 #endif /* BYFOUR */ |
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265 crc = crc ^ 0xffffffffUL; |
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266 while (len >= 8) { |
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267 DO8; |
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268 len -= 8; |
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269 } |
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270 if (len) do { |
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271 DO1; |
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272 } while (--len); |
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273 return crc ^ 0xffffffffUL; |
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274 #ifdef BYFOUR |
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275 } |
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276 #endif |
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277 } |
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278 |
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279 |
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280 #ifdef BYFOUR |
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281 |
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282 /* ========================================================================= */ |
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283 #define DOLIT4 c ^= *buf4++; \ |
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284 c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \ |
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285 crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24] |
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286 #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4 |
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287 |
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288 /* ========================================================================= */ |
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289 #ifdef __SYMBIAN32__ |
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290 local unsigned long crc32_little( unsigned long crc,const unsigned char FAR * buf,unsigned len) |
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291 #else |
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292 local unsigned long crc32_little(crc, buf, len) |
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293 unsigned long crc; |
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294 const unsigned char FAR *buf; |
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295 unsigned len; |
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296 #endif //__SYMBIAN32__ |
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297 { |
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298 register u4 c; |
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299 register const u4 FAR *buf4; |
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300 |
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301 c = (u4)crc; |
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302 c = ~c; |
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303 while (len && ((ptrdiff_t)buf & 3)) { |
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304 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8); |
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305 len--; |
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306 } |
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307 |
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308 buf4 = (const u4 FAR *)(const void FAR *)buf; |
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309 while (len >= 32) { |
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310 DOLIT32; |
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311 len -= 32; |
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312 } |
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313 while (len >= 4) { |
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314 DOLIT4; |
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315 len -= 4; |
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316 } |
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317 buf = (const unsigned char FAR *)buf4; |
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318 |
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319 if (len) do { |
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320 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8); |
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321 } while (--len); |
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322 c = ~c; |
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323 return (unsigned long)c; |
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324 } |
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325 |
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326 /* ========================================================================= */ |
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327 #define DOBIG4 c ^= *++buf4; \ |
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328 c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \ |
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329 crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24] |
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330 #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4 |
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331 |
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332 /* ========================================================================= */ |
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333 #ifdef __SYMBIAN32__ |
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334 local unsigned long crc32_big( unsigned long crc, const unsigned char FAR * buf,unsigned len) |
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335 #else |
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336 local unsigned long crc32_big(crc, buf, len) |
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337 unsigned long crc; |
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338 const unsigned char FAR *buf; |
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339 unsigned len; |
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340 #endif //__SYMBIAN32__ |
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341 { |
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342 register u4 c; |
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343 register const u4 FAR *buf4; |
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344 |
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345 c = REV((u4)crc); |
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346 c = ~c; |
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347 while (len && ((ptrdiff_t)buf & 3)) { |
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348 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8); |
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349 len--; |
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350 } |
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351 |
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352 buf4 = (const u4 FAR *)(const void FAR *)buf; |
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353 buf4--; |
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354 while (len >= 32) { |
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355 DOBIG32; |
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356 len -= 32; |
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357 } |
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358 while (len >= 4) { |
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359 DOBIG4; |
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360 len -= 4; |
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361 } |
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362 buf4++; |
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363 buf = (const unsigned char FAR *)buf4; |
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364 |
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365 if (len) do { |
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366 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8); |
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367 } while (--len); |
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368 c = ~c; |
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369 return (unsigned long)(REV(c)); |
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370 } |
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371 |
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372 #endif /* BYFOUR */ |
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373 |
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374 #define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */ |
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375 |
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376 /* ========================================================================= */ |
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377 |
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378 #ifdef __SYMBIAN32__ |
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379 local unsigned long gf2_matrix_times( unsigned long * mat, unsigned long vec) |
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380 #else |
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381 local unsigned long gf2_matrix_times(mat, vec) |
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382 unsigned long *mat; |
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383 unsigned long vec; |
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384 #endif //__SYMBIAN32__ |
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385 { |
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386 unsigned long sum; |
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387 |
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388 sum = 0; |
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389 while (vec) { |
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390 if (vec & 1) |
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391 sum ^= *mat; |
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392 vec >>= 1; |
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393 mat++; |
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394 } |
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395 return sum; |
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396 } |
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397 |
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398 /* ========================================================================= */ |
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399 |
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400 #ifdef __SYMBIAN32__ |
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401 local void gf2_matrix_square( unsigned long * square,unsigned long * mat) |
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402 #else |
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403 local void gf2_matrix_square(square, mat) |
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404 unsigned long *square; |
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405 unsigned long *mat; |
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406 #endif //__SYMBIAN32__ |
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407 { |
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408 int n; |
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409 |
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410 for (n = 0; n < GF2_DIM; n++) |
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411 square[n] = gf2_matrix_times(mat, mat[n]); |
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412 } |
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413 |
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414 /* ========================================================================= */ |
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415 |
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416 |
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417 #ifdef __SYMBIAN32__ |
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418 EXPORT_C uLong crc32_combine_r(uLong crc1,uLong crc2,z_off_t len2) |
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419 #else |
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420 uLong ZEXPORT crc32_combine(crc1, crc2, len2) |
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421 uLong crc1; |
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422 uLong crc2; |
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423 z_off_t len2; |
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424 #endif //__SYMBIAN32__ |
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425 { |
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426 int n; |
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427 unsigned long row; |
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428 unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */ |
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429 unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */ |
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430 |
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431 /* degenerate case */ |
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432 if (len2 == 0) |
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433 return crc1; |
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434 |
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435 /* put operator for one zero bit in odd */ |
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436 odd[0] = 0xedb88320L; /* CRC-32 polynomial */ |
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437 row = 1; |
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438 for (n = 1; n < GF2_DIM; n++) { |
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439 odd[n] = row; |
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440 row <<= 1; |
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441 } |
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442 |
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443 /* put operator for two zero bits in even */ |
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444 gf2_matrix_square(even, odd); |
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445 |
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446 /* put operator for four zero bits in odd */ |
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447 gf2_matrix_square(odd, even); |
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448 |
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449 /* apply len2 zeros to crc1 (first square will put the operator for one |
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450 zero byte, eight zero bits, in even) */ |
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451 do { |
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452 /* apply zeros operator for this bit of len2 */ |
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453 gf2_matrix_square(even, odd); |
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454 if (len2 & 1) |
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455 crc1 = gf2_matrix_times(even, crc1); |
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456 len2 >>= 1; |
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457 |
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458 /* if no more bits set, then done */ |
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459 if (len2 == 0) |
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460 break; |
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461 |
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462 /* another iteration of the loop with odd and even swapped */ |
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463 gf2_matrix_square(odd, even); |
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464 if (len2 & 1) |
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465 crc1 = gf2_matrix_times(odd, crc1); |
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466 len2 >>= 1; |
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467 |
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468 /* if no more bits set, then done */ |
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469 } while (len2 != 0); |
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470 |
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471 /* return combined crc */ |
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472 crc1 ^= crc2; |
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473 return crc1; |
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474 } |
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475 |
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476 |
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