source: vbox/trunk/src/libs/liblzma-5.8.1/check/crc32_tablegen.c

// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////
//
/// \file       crc32_tablegen.c
/// \brief      Generate crc32_table_le.h and crc32_table_be.h
///
/// Compiling: gcc -std=c99 -o crc32_tablegen crc32_tablegen.c
/// Add -DWORDS_BIGENDIAN to generate big endian table.
/// Add -DLZ_HASH_TABLE to generate lz_encoder_hash_table.h (little endian).
//
//  Author:     Lasse Collin
//
///////////////////////////////////////////////////////////////////////////////

#include <stdio.h>
#include "../../common/tuklib_integer.h"


static uint32_t crc32_table[8][256];


static void
init_crc32_table(void)
{
        static const uint32_t poly32 = UINT32_C(0xEDB88320);

        for (size_t s = 0; s < 8; ++s) {
                for (size_t b = 0; b < 256; ++b) {
                        uint32_t r = s == 0 ? b : crc32_table[s - 1][b];

                        for (size_t i = 0; i < 8; ++i) {
                                if (r & 1)
                                        r = (r >> 1) ^ poly32;
                                else
                                        r >>= 1;
                        }

                        crc32_table[s][b] = r;
                }
        }

#ifdef WORDS_BIGENDIAN
        for (size_t s = 0; s < 8; ++s)
                for (size_t b = 0; b < 256; ++b)
                        crc32_table[s][b] = byteswap32(crc32_table[s][b]);
#endif

        return;
}


static void
print_crc32_table(void)
{
        // Split the SPDX string so that it won't accidentally match
        // when tools search for the string.
        printf("// SPDX" "-License-Identifier" ": 0BSD\n\n"
                "// This file has been generated by crc32_tablegen.c.\n\n"
                "const uint32_t lzma_crc32_table[8][256] = {\n\t{");

        for (size_t s = 0; s < 8; ++s) {
                for (size_t b = 0; b < 256; ++b) {
                        if ((b % 4) == 0)
                                printf("\n\t\t");

                        printf("0x%08" PRIX32, crc32_table[s][b]);

                        if (b != 255)
                                printf(",%s", (b+1) % 4 == 0 ? "" : " ");
                }

                if (s == 7)
                        printf("\n\t}\n};\n");
                else
                        printf("\n\t}, {");
        }

        return;
}


static void
print_lz_table(void)
{
        // Split the SPDX string so that it won't accidentally match
        // when tools search for the string.
        printf("// SPDX" "-License-Identifier" ": 0BSD\n\n"
                "// This file has been generated by crc32_tablegen.c.\n\n"
                "const uint32_t lzma_lz_hash_table[256] = {");

        for (size_t b = 0; b < 256; ++b) {
                if ((b % 4) == 0)
                        printf("\n\t");

                printf("0x%08" PRIX32, crc32_table[0][b]);

                if (b != 255)
                        printf(",%s", (b+1) % 4 == 0 ? "" : " ");
        }

        printf("\n};\n");

        return;
}


int
main(void)
{
        init_crc32_table();

#ifdef LZ_HASH_TABLE
        print_lz_table();
#else
        print_crc32_table();
#endif

        return 0;
}