MapViewOfFile と CRC32 の計算

mixi のC言語コミュの某トピックがなぜか Kusakabe さん作 CRC32 vs FastCRC な流れになっている。
団子厨氏の絡んだ現在の流れ自体に言いたいことがないではないが、とりあえず MapViewOfFile による Memory Mapped File な CRC32 の実装とかしてみた。Pentium M 2.0GHz で 100MBytes 程度のファイルは 0.5 秒ぐらいで計算できる*1。
しかし、MapViewOfFile なんて初めて使ったがえらく面倒だな。ていうか GetFileSize のファイルサイズの下位バイトを返して、上位バイトは引数のポインタに格納するって、どんな仕様だよ。

#include <stdio.h>
#include <windows.h>
#include "table.h"

static void print_error(void);
static void process_file(const char* filename);
static void crc32(unsigned char* content, size_t size, const char* filename);

int main(int argc, char *argv[])
{
    int i;
    for (i = 1; i < argc; i++) {
        process_file(argv[i]);
    }

    return 0;
}

static void process_file(const char *filename)
{
    HANDLE hFile, hFileMap;
    DWORD fileSizeLow, fileSizeHigh;
    unsigned char *content;

    hFile = CreateFile(filename, GENERIC_READ, FILE_SHARE_READ, 
        NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile == INVALID_HANDLE_VALUE) {
        print_error();
        return;
    }

    fileSizeLow = GetFileSize(hFile, &fileSizeHigh);
    if (fileSizeLow == -1) {
        print_error();
        CloseHandle(hFile);
        return;
    }
    if (fileSizeHigh != 0) {
        fprintf(stderr, "%s is too large\n", filename);
        CloseHandle(hFile);
        return;
    }

    hFileMap = CreateFileMapping(hFile, NULL, 
        PAGE_READONLY, fileSizeHigh, fileSizeLow, NULL);
    if (hFileMap == INVALID_HANDLE_VALUE) {
        print_error();
        CloseHandle(hFile);
        return;
    }

    content = (char *) MapViewOfFile(hFileMap, FILE_MAP_READ, 0, 0, 0);
    if (content == NULL) {
        print_error();
        CloseHandle(hFileMap);
        CloseHandle(hFile);
        return;
    }

    crc32(content, fileSizeLow, filename);

    UnmapViewOfFile(content);
    CloseHandle(hFileMap);
    CloseHandle(hFile);
}

static void crc32(unsigned char* content, size_t size, const char *filename)
{
    unsigned long crc;
    size_t i;

    crc = 0xffffffff;
    for (i = 0; i < size; i++) {
        crc = table[(crc ^ content[i]) & 0xff] ^ (crc >> 8);
    }
    crc = ~crc;
    printf("%08lx %7ld %s\n", crc, size, filename);
}

static void print_error(void)
{
    LPVOID buffer;
    FormatMessage(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
        FORMAT_MESSAGE_IGNORE_INSERTS, 
        NULL, GetLastError(), MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPSTR) &buffer, 0, NULL);
    fprintf(stderr, "%s\n", (const char *) buffer);
}

table.h はこんなの。

/* CRC polynomial 0xedb88320 */
static unsigned long    table[] ={
        0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
        0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
        0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
        0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
        0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
        0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
        0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
        0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
        0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
        0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
        0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
        0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
        0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
        0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
        0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
        0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
        0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
        0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
        0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
        0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
        0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
        0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
        0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
        0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
        0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
        0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
        0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
        0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
        0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
        0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
        0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
        0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
        0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
        0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
        0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
        0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
        0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
        0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
        0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
        0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
        0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
        0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
        0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
        0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
        0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
        0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
        0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
        0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
        0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
        0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
        0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
        0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
        0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
        0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
        0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
        0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
        0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
        0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
        0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
        0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
        0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
        0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
        0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
        0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};

*1:ちなみにfgetcで1byte読み込むと10秒以上かかる