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comparison src/core/ngx_crc32.c @ 1021:8902a211b00e

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fix comment
author Igor Sysoev <igor@sysoev.ru>
date Fri, 12 Jan 2007 18:05:41 +0000
parents 45df22906c12
children 8c696afe46b3
comparison
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1020:c95800738d2c 1021:8902a211b00e
11 /* 11 /*
12 * The code and lookup tables are based on the algorithm 12 * The code and lookup tables are based on the algorithm
13 * described at http://www.w3.org/TR/PNG/ 13 * described at http://www.w3.org/TR/PNG/
14 * 14 *
15 * The 256 element lookup table takes 1024 bytes, and it may be completely 15 * The 256 element lookup table takes 1024 bytes, and it may be completely
16 * cached after processing about 30-60 bytes. So for short messages 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 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 18 * to CPU cache line size. Of course, the small table adds code inside
19 * CRC32 cycle, but cache misses overhead is bigger than overhead of 19 * CRC32 loop, but the cache misses overhead is bigger than overhead of
20 * the additional code. For example, ngx_crc32_short() of 16 byte message 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(). 21 * takes half as much CPU clocks than ngx_crc32_long().
22 */ 22 */
23 23
24 24
25 static uint32_t ngx_crc32_table16[] = { 25 static uint32_t ngx_crc32_table16[] = {