The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \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.
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include <inttypes.h>
#include <stdio.h>

#ifdef WORDS_BIGENDIAN
#   include "../../common/bswap.h"
#endif


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] = bswap_32(crc32_table[s][b]);
#endif

    return;
}


static void
print_crc32_table(void)
{
    printf("/* This file has been automatically 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;
}


int
main(void)
{
    init_crc32_table();
    print_crc32_table();
    return 0;
}