Annotation of embedaddon/nginx/src/core/ngx_crc32.c, revision 1.1.1.1

1.1       misho       1: 
                      2: /*
                      3:  * Copyright (C) Igor Sysoev
                      4:  * Copyright (C) Nginx, Inc.
                      5:  */
                      6: 
                      7: 
                      8: #include <ngx_config.h>
                      9: #include <ngx_core.h>
                     10: 
                     11: 
                     12: /*
                     13:  * The code and lookup tables are based on the algorithm
                     14:  * described at http://www.w3.org/TR/PNG/
                     15:  *
                     16:  * The 256 element lookup table takes 1024 bytes, and it may be completely
                     17:  * cached after processing about 30-60 bytes of data.  So for short data
                     18:  * we use the 16 element lookup table that takes only 64 bytes and align it
                     19:  * to CPU cache line size.  Of course, the small table adds code inside
                     20:  * CRC32 loop, but the cache misses overhead is bigger than overhead of
                     21:  * the additional code.  For example, ngx_crc32_short() of 16 bytes of data
                     22:  * takes half as much CPU clocks than ngx_crc32_long().
                     23:  */
                     24: 
                     25: 
                     26: static uint32_t  ngx_crc32_table16[] = {
                     27:     0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
                     28:     0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
                     29:     0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
                     30:     0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
                     31: };
                     32: 
                     33: 
                     34: uint32_t  ngx_crc32_table256[] = {
                     35:     0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
                     36:     0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
                     37:     0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
                     38:     0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
                     39:     0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
                     40:     0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
                     41:     0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
                     42:     0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
                     43:     0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
                     44:     0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
                     45:     0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
                     46:     0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
                     47:     0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
                     48:     0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
                     49:     0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
                     50:     0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
                     51:     0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
                     52:     0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
                     53:     0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
                     54:     0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
                     55:     0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
                     56:     0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
                     57:     0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
                     58:     0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
                     59:     0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
                     60:     0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
                     61:     0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
                     62:     0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
                     63:     0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
                     64:     0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
                     65:     0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
                     66:     0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
                     67:     0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
                     68:     0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
                     69:     0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
                     70:     0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
                     71:     0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
                     72:     0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
                     73:     0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
                     74:     0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
                     75:     0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
                     76:     0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
                     77:     0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
                     78:     0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
                     79:     0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
                     80:     0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
                     81:     0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
                     82:     0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
                     83:     0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
                     84:     0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
                     85:     0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
                     86:     0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
                     87:     0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
                     88:     0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
                     89:     0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
                     90:     0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
                     91:     0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
                     92:     0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
                     93:     0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
                     94:     0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
                     95:     0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
                     96:     0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
                     97:     0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
                     98:     0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
                     99: };
                    100: 
                    101: 
                    102: uint32_t *ngx_crc32_table_short = ngx_crc32_table16;
                    103: 
                    104: 
                    105: ngx_int_t
                    106: ngx_crc32_table_init(void)
                    107: {
                    108:     void  *p;
                    109: 
                    110:     if (((uintptr_t) ngx_crc32_table_short
                    111:           & ~((uintptr_t) ngx_cacheline_size - 1))
                    112:         == (uintptr_t) ngx_crc32_table_short)
                    113:     {
                    114:         return NGX_OK;
                    115:     }
                    116: 
                    117:     p = ngx_alloc(16 * sizeof(uint32_t) + ngx_cacheline_size, ngx_cycle->log);
                    118:     if (p == NULL) {
                    119:         return NGX_ERROR;
                    120:     }
                    121: 
                    122:     p = ngx_align_ptr(p, ngx_cacheline_size);
                    123: 
                    124:     ngx_memcpy(p, ngx_crc32_table16, 16 * sizeof(uint32_t));
                    125: 
                    126:     ngx_crc32_table_short = p;
                    127: 
                    128:     return NGX_OK;
                    129: }

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