[代码实例][C语言]计算文件的MD5值

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>

#define BITS_PER_BYTE   8

#define GROUP_BITS      512
#define GROUP_SIZE      (GROUP_BITS / BITS_PER_BYTE)    // 64

#define SUBGROUPS_PER_GROUP 16
#define SUBGROUP_BITS       (GROUP_BITS / SUBGROUPS_PER_GROUP)  // 32
#define SUBGROUP_SIZE       (GROUP_SIZE / SUBGROUPS_PER_GROUP)  // 4

#define VAR_INPUT_LEN_SIZE  8

#define ROL(val,n)  (((val) << (n)) | ((val) >> (32 - (n))))
#define ABS(x)      ((x) >= 0 ? (x) : -(x))

#define F(x,y,z)    (((x) & (y)) | ((~(x)) & (z)))
#define G(x,y,z)    (((x) & (z)) | ((y) & (~(z))))
#define H(x,y,z)    ((x) ^ (y) ^ (z))
#define I(x,y,z)    (y ^ ((x) | (~(z))))

#define BUF_SIZE    1024
static unsigned char read_buf[BUF_SIZE + GROUP_SIZE] = {0};

static bool has_init_ti = false;

static unsigned int state_init[] = {
    0x67452301,
    0xEFCDAB89,
    0x98BADCFE,
    0x10325476
};

static unsigned int ti[64];
static unsigned int round_index[64];
static const unsigned int s[][4] = {
    {7, 12, 17, 22}, {7, 12, 17, 22}, {7, 12, 17, 22}, {7, 12, 17, 22}, 
    {5, 9, 14, 20}, {5, 9, 14, 20}, {5, 9, 14, 20}, {5, 9, 14, 20}, 
    {4, 11, 16, 23}, {4, 11, 16, 23}, {4, 11, 16, 23}, {4, 11, 16, 23}, 
    {6, 10, 15, 21}, {6, 10, 15, 21}, {6, 10, 15, 21}, {6, 10, 15, 21}
};

static int add_bits(unsigned char * buf, size_t src_len);
static void transform(unsigned char sub_group[SUBGROUPS_PER_GROUP][SUBGROUP_SIZE], unsigned int * state);
char * md54file(const char * filename, char * md5str, bool isupper);
static void md5init(void);

int main(int argc, char * argv[])
{
    char md5str[33] = {0};

    if(argc == 1)
    {
        printf("Usage: %s <filename>\n", argv[0]);
        return EXIT_SUCCESS;
    }

    for(int i = 1; i < argc; i++)
    {
        if(md54file(argv[i], md5str, false))
            printf("%s  %s\n", md5str, argv[i]);
    }

    return EXIT_SUCCESS;
}

static void md5init(void)
{
    if(!has_init_ti)
    {
        for(int i = 0; i < 64; i++)
            ti[i] = (1UL << 32) * ABS(sin(i + 1));
        has_init_ti = true;
    }

}

char * md54file(const char * filename, char * md5str, bool isupper)
{
    unsigned char * group_start = NULL;
    size_t dest_len = 0;
    unsigned char sub_group[SUBGROUPS_PER_GROUP][SUBGROUP_SIZE] = {0};
    unsigned int state[4] = {0};
    unsigned char * pstate = (unsigned char *)state;
    char * poutput = md5str;

    md5init();

    FILE * fp;
    size_t count;

    if((fp = fopen(filename, "r")) == NULL)
    {
        perror("fopen");
        return NULL;
    }

    memcpy(state, state_init, sizeof(int) * 4);

    memset(read_buf, 0, BUF_SIZE + GROUP_SIZE);
    while((count = fread(read_buf, 1, BUF_SIZE, fp)) > 0)
    {
        dest_len += count;
        group_start = read_buf;
        for(int i = 0;
            i < count / GROUP_SIZE;
            i++, group_start += GROUP_SIZE)
        {
            memcpy((unsigned char *)sub_group, group_start, GROUP_SIZE);
            transform(sub_group, state);
        }

        if(count % GROUP_SIZE != 0)
        {
            count %= GROUP_SIZE;
            break;
        }

        memset(read_buf, 0, BUF_SIZE);
    }
    if(ferror(fp))
    {
        perror("fread");
        return NULL;
    }
    else if(feof(fp))
    {
        int times = 0;
        if(count == 0)
        {
            memset(read_buf, 0, BUF_SIZE);
            group_start = read_buf;
        }
        else
            memset(group_start + count, 0, GROUP_SIZE - count);
        times = add_bits(group_start, dest_len);

        for(int i = 0; i < times; i++)
        {
            memcpy((unsigned char *)sub_group, group_start, GROUP_SIZE);
            transform(sub_group, state);
            group_start += GROUP_SIZE;
        }
    }

    if(fclose(fp) != 0)
    {
        perror("fclose");
        return NULL;
    }

    for(int i = 0; i < 16; i++)
    {
        if(isupper)
            snprintf(poutput, 3, "%02X", *pstate);
        else
            snprintf(poutput, 3, "%02x", *pstate);
        poutput += 2;
        pstate++;
    }

    return md5str;
}

static int add_bits(unsigned char * buf, size_t src_len)
{
    size_t current_len;
    size_t rest_len;
    size_t dest_len;
    unsigned char * dest;
    int times = 1;

    current_len = src_len % GROUP_SIZE;
    if(current_len == 0)
        dest_len = GROUP_SIZE;
    else
        dest_len = (current_len + GROUP_SIZE - 1) / GROUP_SIZE * GROUP_SIZE;
    rest_len = GROUP_SIZE - current_len % GROUP_SIZE;

    if(rest_len <= VAR_INPUT_LEN_SIZE)
    {
        dest_len += GROUP_SIZE;
        memset(read_buf + BUF_SIZE, 0, GROUP_SIZE);
        times++;
    }

    buf[current_len] = 0x80;
    *(unsigned long long *)(buf + dest_len - VAR_INPUT_LEN_SIZE) = (unsigned long long)src_len * BITS_PER_BYTE;

    return times;
}

/*
 * transform: 转换分组
 */
static void transform(unsigned char sub_group[SUBGROUPS_PER_GROUP][SUBGROUP_SIZE], unsigned int * state)
{
    unsigned int a;
    unsigned int b;
    unsigned int c;
    unsigned int d;
    unsigned int tmp;

    unsigned int result, index;

    a = state[0];
    b = state[1];
    c = state[2];
    d = state[3];

    for(int i = 0; i < 64; i++)
    {
        if(i < 16)
        {
            result = F(b, c, d);
            index = i;
        }
        else if(i < 32)
        {
            result = G(b, c, d);
            index = (5 * i + 1) % 16;
        }
        else if(i < 48)
        {
            result = H(b, c, d);
            index = (3 * i + 5) % 16;
        }
        else
        {
            result = I(b, c, d);
            index = (7 * i) % 16;
        }

        tmp = d;
        d = c;
        c = b;
        b = b + ROL(
                    a + result + *(unsigned int *)&sub_group[index] + ti[i],
                    *((const unsigned int *)s + i));
        a = tmp;
    }

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
}