836e2af925
Precompute more crc32 values(0xcc00, 0xcc0000 and 0xcc000000) into tables. This increases the table size from 1KB to 4KB but the performance benfit makes it worth it: 28% faster on MPC8321, 266 MHz 2x faster on Core 2 Duo, 3.1GHz [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
99 lines
2.2 KiB
C
99 lines
2.2 KiB
C
#include <stdio.h>
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#include "crc32defs.h"
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#include <inttypes.h>
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#define ENTRIES_PER_LINE 4
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#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
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#define BE_TABLE_SIZE (1 << CRC_BE_BITS)
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static uint32_t crc32table_le[4][LE_TABLE_SIZE];
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static uint32_t crc32table_be[4][BE_TABLE_SIZE];
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/**
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* crc32init_le() - allocate and initialize LE table data
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*
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* crc is the crc of the byte i; other entries are filled in based on the
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* fact that crctable[i^j] = crctable[i] ^ crctable[j].
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*
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*/
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static void crc32init_le(void)
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{
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unsigned i, j;
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uint32_t crc = 1;
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crc32table_le[0][0] = 0;
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for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
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crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
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for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
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crc32table_le[0][i + j] = crc ^ crc32table_le[0][j];
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}
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for (i = 0; i < LE_TABLE_SIZE; i++) {
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crc = crc32table_le[0][i];
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for (j = 1; j < 4; j++) {
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crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8);
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crc32table_le[j][i] = crc;
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}
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}
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}
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/**
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* crc32init_be() - allocate and initialize BE table data
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*/
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static void crc32init_be(void)
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{
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unsigned i, j;
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uint32_t crc = 0x80000000;
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crc32table_be[0][0] = 0;
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for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
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crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
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for (j = 0; j < i; j++)
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crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
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}
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for (i = 0; i < BE_TABLE_SIZE; i++) {
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crc = crc32table_be[0][i];
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for (j = 1; j < 4; j++) {
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crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
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crc32table_be[j][i] = crc;
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}
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}
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}
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static void output_table(uint32_t table[4][256], int len, char *trans)
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{
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int i, j;
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for (j = 0 ; j < 4; j++) {
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printf("{");
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for (i = 0; i < len - 1; i++) {
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if (i % ENTRIES_PER_LINE == 0)
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printf("\n");
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printf("%s(0x%8.8xL), ", trans, table[j][i]);
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}
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printf("%s(0x%8.8xL)},\n", trans, table[j][len - 1]);
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}
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}
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int main(int argc, char** argv)
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{
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printf("/* this file is generated - do not edit */\n\n");
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if (CRC_LE_BITS > 1) {
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crc32init_le();
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printf("static const u32 crc32table_le[4][256] = {");
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output_table(crc32table_le, LE_TABLE_SIZE, "tole");
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printf("};\n");
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}
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if (CRC_BE_BITS > 1) {
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crc32init_be();
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printf("static const u32 crc32table_be[4][256] = {");
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output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
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printf("};\n");
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}
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return 0;
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}
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