nginx/src/core/ngx_crc32.c

   1
   2 /*
   3  * Copyright (C) Igor Sysoev
   4  */
   5
   6
   7 #include <ngx_config.h>
   8 #include <ngx_core.h>
   9
  10
  11 /*
  12  * The code and lookup tables are based on the algorithm
  13  * described at http://www.w3.org/TR/PNG/
  14  *
  15  * The 256 element lookup table takes 1024 bytes, and it may be completely
  16  * cached after processing about 30-60 bytes of data.  So for short data
  17  * we use the 16 element lookup table that takes only 64 bytes and align it
  18  * to CPU cache line size.  Of course, the small table adds code inside
  19  * CRC32 loop, but the cache misses overhead is bigger than overhead of
  20  * the additional code.  For example, ngx_crc32_short() of 16 bytes of data
  21  * takes half as much CPU clocks than ngx_crc32_long().
  22  */
  23
  24
  25 static uint32_t  ngx_crc32_table16[] = {
  26     0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
  27     0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
  28     0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
  29     0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
  30 };
  31
  32
  33 uint32_t  ngx_crc32_table256[] = {
  34     0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
  35     0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
  36     0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
  37     0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
  38     0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
  39     0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
  40     0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
  41     0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
  42     0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
  43     0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
  44     0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
  45     0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
  46     0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
  47     0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
  48     0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
  49     0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
  50     0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
  51     0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
  52     0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
  53     0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
  54     0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
  55     0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
  56     0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
  57     0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
  58     0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
  59     0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
  60     0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
  61     0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
  62     0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
  63     0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
  64     0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
  65     0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
  66     0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
  67     0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
  68     0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
  69     0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
  70     0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
  71     0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
  72     0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
  73     0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
  74     0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
  75     0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
  76     0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
  77     0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
  78     0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
  79     0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
  80     0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
  81     0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
  82     0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
  83     0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
  84     0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
  85     0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
  86     0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
  87     0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
  88     0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
  89     0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
  90     0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
  91     0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
  92     0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
  93     0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
  94     0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
  95     0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
  96     0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
  97     0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
  98 };
  99
 100
 101 uint32_t *ngx_crc32_table_short = ngx_crc32_table16;
 102
 103
 104 ngx_int_t
 105 ngx_crc32_table_init(void)
 106 {
 107     void  *p;
 108
 109     if (((uintptr_t) ngx_crc32_table_short
 110           & ~((uintptr_t) ngx_cacheline_size - 1))
 111         == (uintptr_t) ngx_crc32_table_short)
 112     {
 113         return NGX_OK;
 114     }
 115
 116     p = ngx_alloc(16 * sizeof(uint32_t) + ngx_cacheline_size, ngx_cycle->log);
 117     if (p == NULL) {
 118         return NGX_ERROR;
 119     }
 120
 121     p = ngx_align_ptr(p, ngx_cacheline_size);
 122
 123     ngx_memcpy(p, ngx_crc32_table16, 16 * sizeof(uint32_t));
 124
 125     ngx_crc32_table_short = p;
 126
 127     return NGX_OK;
 128 }