[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;
}