src/liblzma/lzma/fastpos_tablegen.c

   1 // SPDX-License-Identifier: 0BSD
   2
   3 ///////////////////////////////////////////////////////////////////////////////
   4 //
   5 /// \file       fastpos_tablegen.c
   6 /// \brief      Generates the lzma_fastpos[] lookup table
   7 ///
   8 //  Authors:    Igor Pavlov
   9 //              Lasse Collin
  10 //
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 #include <inttypes.h>
  14 #include <stdio.h>
  15
  16 #define lzma_attr_visibility_hidden
  17 #include "fastpos.h"
  18
  19
  20 int
  21 main(void)
  22 {
  23         uint8_t fastpos[1 << FASTPOS_BITS];
  24
  25         const uint8_t fast_slots = 2 * FASTPOS_BITS;
  26         uint32_t c = 2;
  27
  28         fastpos[0] = 0;
  29         fastpos[1] = 1;
  30
  31         for (uint8_t slot_fast = 2; slot_fast < fast_slots; ++slot_fast) {
  32                 const uint32_t k = 1 << ((slot_fast >> 1) - 1);
  33                 for (uint32_t j = 0; j < k; ++j, ++c)
  34                         fastpos[c] = slot_fast;
  35         }
  36
  37         // Split the SPDX string so that it won't accidentally match
  38         // when tools search for the string.
  39         printf("// SPDX" "-License-Identifier" ": 0BSD\n\n"
  40                 "// This file has been generated by fastpos_tablegen.c.\n\n"
  41                 "#include \"common.h\"\n"
  42                 "#include \"fastpos.h\"\n\n"
  43                 "const uint8_t lzma_fastpos[1 << FASTPOS_BITS] = {");
  44
  45         for (size_t i = 0; i < (1 << FASTPOS_BITS); ++i) {
  46                 if (i % 16 == 0)
  47                         printf("\n\t");
  48
  49                 printf("%3u", (unsigned int)(fastpos[i]));
  50
  51                 if (i != (1 << FASTPOS_BITS) - 1)
  52                         printf(",");
  53         }
  54
  55         printf("\n};\n");
  56
  57         return 0;
  58 }