src/liblzma/check/crc64_tablegen.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       crc64_tablegen.c
   4 /// \brief      Generate crc64_table_le.h and crc64_table_be.h
   5 ///
   6 /// Compiling: gcc -std=c99 -o crc64_tablegen crc64_tablegen.c
   7 /// Add -DWORDS_BIGENDIAN to generate big endian table.
   8 //
   9 //  This code has been put into the public domain.
  10 //
  11 //  This library is distributed in the hope that it will be useful,
  12 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  14 //
  15 ///////////////////////////////////////////////////////////////////////////////
  16
  17 #include <inttypes.h>
  18 #include <stdio.h>
  19
  20 #ifdef WORDS_BIGENDIAN
  21 #       include "../../common/bswap.h"
  22 #endif
  23
  24
  25 static uint64_t crc64_table[4][256];
  26
  27
  28 extern void
  29 init_crc64_table(void)
  30 {
  31         static const uint64_t poly64 = UINT64_C(0xC96C5795D7870F42);
  32
  33         for (size_t s = 0; s < 4; ++s) {
  34                 for (size_t b = 0; b < 256; ++b) {
  35                         uint64_t r = s == 0 ? b : crc64_table[s - 1][b];
  36
  37                         for (size_t i = 0; i < 8; ++i) {
  38                                 if (r & 1)
  39                                         r = (r >> 1) ^ poly64;
  40                                 else
  41                                         r >>= 1;
  42                         }
  43
  44                         crc64_table[s][b] = r;
  45                 }
  46         }
  47
  48 #ifdef WORDS_BIGENDIAN
  49         for (size_t s = 0; s < 4; ++s)
  50                 for (size_t b = 0; b < 256; ++b)
  51                         crc64_table[s][b] = bswap_64(crc64_table[s][b]);
  52 #endif
  53
  54         return;
  55 }
  56
  57
  58 static void
  59 print_crc64_table(void)
  60 {
  61         printf("/* This file has been automatically generated by "
  62                         "crc64_tablegen.c. */\n\n"
  63                         "const uint64_t lzma_crc64_table[4][256] = {\n\t{");
  64
  65         for (size_t s = 0; s < 4; ++s) {
  66                 for (size_t b = 0; b < 256; ++b) {
  67                         if ((b % 2) == 0)
  68                                 printf("\n\t\t");
  69
  70                         printf("UINT64_C(0x%016" PRIX64 ")",
  71                                         crc64_table[s][b]);
  72
  73                         if (b != 255)
  74                                 printf(",%s", (b+1) % 2 == 0 ? "" : " ");
  75                 }
  76
  77                 if (s == 3)
  78                         printf("\n\t}\n};\n");
  79                 else
  80                         printf("\n\t}, {");
  81         }
  82
  83         return;
  84 }
  85
  86
  87 int
  88 main(void)
  89 {
  90         init_crc64_table();
  91         print_crc64_table();
  92         return 0;
  93 }