C语言计算文件MD5

　　计算MD5这种很标准的东西，一般直接使用别人写好的了就行，本文主要针对写好的接口测试一下如何使用的问题。

下面是MD5的实现
md5.h

#ifndef MD5_H
#define MD5_H  typedef struct
{  unsigned int count[2];  unsigned int state[4];  unsigned char buffer[64];
}MD5_CTX;  #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 ROTATE_LEFT(x,n) ((x << n) | (x >> (32-n)))
#define FF(a,b,c,d,x,s,ac) \
{ \a += F(b,c,d) + x + ac; \a = ROTATE_LEFT(a,s); \a += b; \
}
#define GG(a,b,c,d,x,s,ac) \
{ \a += G(b,c,d) + x + ac; \a = ROTATE_LEFT(a,s); \a += b; \
}
#define HH(a,b,c,d,x,s,ac) \
{ \a += H(b,c,d) + x + ac; \a = ROTATE_LEFT(a,s); \a += b; \
}
#define II(a,b,c,d,x,s,ac) \
{ \a += I(b,c,d) + x + ac; \a = ROTATE_LEFT(a,s); \a += b; \
}
void MD5Init(MD5_CTX *context);
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen);
void MD5Final(MD5_CTX *context,unsigned char digest[16]);
void MD5Transform(unsigned int state[4],unsigned char block[64]);
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len);
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len);
#endif

md5.c

#include <string.h>
#include "md5.h" unsigned char PADDING[]={0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};  void MD5Init(MD5_CTX *context)
{  context->count[0] = 0;  context->count[1] = 0;  context->state[0] = 0x67452301;  context->state[1] = 0xEFCDAB89;  context->state[2] = 0x98BADCFE;  context->state[3] = 0x10325476;
}
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen)
{  unsigned int i = 0,index = 0,partlen = 0;  index = (context->count[0] >> 3) & 0x3F;  partlen = 64 - index;  context->count[0] += inputlen << 3;  if(context->count[0] < (inputlen << 3))  context->count[1]++;  context->count[1] += inputlen >> 29;  if(inputlen >= partlen)  {  memcpy(&context->buffer[index],input,partlen);  MD5Transform(context->state,context->buffer);  for(i = partlen;i+64 <= inputlen;i+=64)  MD5Transform(context->state,&input[i]);  index = 0;          }    else  {  i = 0;  }  memcpy(&context->buffer[index],&input[i],inputlen-i);
}
void MD5Final(MD5_CTX *context,unsigned char digest[16])
{  unsigned int index = 0,padlen = 0;  unsigned char bits[8];  index = (context->count[0] >> 3) & 0x3F;  padlen = (index < 56)?(56-index):(120-index);  MD5Encode(bits,context->count,8);  MD5Update(context,PADDING,padlen);  MD5Update(context,bits,8);  MD5Encode(digest,context->state,16);
}
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len)
{  unsigned int i = 0,j = 0;  while(j < len)  {  output[j] = input[i] & 0xFF;    output[j+1] = (input[i] >> 8) & 0xFF;  output[j+2] = (input[i] >> 16) & 0xFF;  output[j+3] = (input[i] >> 24) & 0xFF;  i++;  j+=4;  }
}
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len)
{  unsigned int i = 0,j = 0;  while(j < len)  {  output[i] = (input[j]) |  (input[j+1] << 8) |  (input[j+2] << 16) |  (input[j+3] << 24);  i++;  j+=4;   }
}
void MD5Transform(unsigned int state[4],unsigned char block[64])
{  unsigned int a = state[0];  unsigned int b = state[1];  unsigned int c = state[2];  unsigned int d = state[3];  unsigned int x[64];  MD5Decode(x,block,64);  FF(a, b, c, d, x[ 0], 7, 0xd76aa478);   FF(d, a, b, c, x[ 1], 12, 0xe8c7b756);   FF(c, d, a, b, x[ 2], 17, 0x242070db);   FF(b, c, d, a, x[ 3], 22, 0xc1bdceee);   FF(a, b, c, d, x[ 4], 7, 0xf57c0faf);   FF(d, a, b, c, x[ 5], 12, 0x4787c62a);   FF(c, d, a, b, x[ 6], 17, 0xa8304613);   FF(b, c, d, a, x[ 7], 22, 0xfd469501);   FF(a, b, c, d, x[ 8], 7, 0x698098d8);   FF(d, a, b, c, x[ 9], 12, 0x8b44f7af);   FF(c, d, a, b, x[10], 17, 0xffff5bb1);   FF(b, c, d, a, x[11], 22, 0x895cd7be);   FF(a, b, c, d, x[12], 7, 0x6b901122);   FF(d, a, b, c, x[13], 12, 0xfd987193);   FF(c, d, a, b, x[14], 17, 0xa679438e);   FF(b, c, d, a, x[15], 22, 0x49b40821);   GG(a, b, c, d, x[ 1], 5, 0xf61e2562);   GG(d, a, b, c, x[ 6], 9, 0xc040b340);   GG(c, d, a, b, x[11], 14, 0x265e5a51);   GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);   GG(a, b, c, d, x[ 5], 5, 0xd62f105d);   GG(d, a, b, c, x[10], 9,  0x2441453);   GG(c, d, a, b, x[15], 14, 0xd8a1e681);   GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);   GG(a, b, c, d, x[ 9], 5, 0x21e1cde6);   GG(d, a, b, c, x[14], 9, 0xc33707d6);   GG(c, d, a, b, x[ 3], 14, 0xf4d50d87);   GG(b, c, d, a, x[ 8], 20, 0x455a14ed);   GG(a, b, c, d, x[13], 5, 0xa9e3e905);   GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8);   GG(c, d, a, b, x[ 7], 14, 0x676f02d9);   GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);   HH(a, b, c, d, x[ 5], 4, 0xfffa3942);   HH(d, a, b, c, x[ 8], 11, 0x8771f681);   HH(c, d, a, b, x[11], 16, 0x6d9d6122);   HH(b, c, d, a, x[14], 23, 0xfde5380c);   HH(a, b, c, d, x[ 1], 4, 0xa4beea44);   HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);   HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60);   HH(b, c, d, a, x[10], 23, 0xbebfbc70);   HH(a, b, c, d, x[13], 4, 0x289b7ec6);   HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);   HH(c, d, a, b, x[ 3], 16, 0xd4ef3085);   HH(b, c, d, a, x[ 6], 23,  0x4881d05);   HH(a, b, c, d, x[ 9], 4, 0xd9d4d039);   HH(d, a, b, c, x[12], 11, 0xe6db99e5);   HH(c, d, a, b, x[15], 16, 0x1fa27cf8);   HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);   II(a, b, c, d, x[ 0], 6, 0xf4292244);   II(d, a, b, c, x[ 7], 10, 0x432aff97);   II(c, d, a, b, x[14], 15, 0xab9423a7);   II(b, c, d, a, x[ 5], 21, 0xfc93a039);   II(a, b, c, d, x[12], 6, 0x655b59c3);   II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);   II(c, d, a, b, x[10], 15, 0xffeff47d);   II(b, c, d, a, x[ 1], 21, 0x85845dd1);   II(a, b, c, d, x[ 8], 6, 0x6fa87e4f);   II(d, a, b, c, x[15], 10, 0xfe2ce6e0);   II(c, d, a, b, x[ 6], 15, 0xa3014314);   II(b, c, d, a, x[13], 21, 0x4e0811a1);   II(a, b, c, d, x[ 4], 6, 0xf7537e82);   II(d, a, b, c, x[11], 10, 0xbd3af235);   II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb);   II(b, c, d, a, x[ 9], 21, 0xeb86d391);   state[0] += a;  state[1] += b;  state[2] += c;  state[3] += d;
}

下面是测试程序, 主要依次调用MD5Init， MD5Update，MD5Final三个函数就行了

/************************************************************
Copyright (C), 2017, Leon, All Rights Reserved.
FileName: test_md5.c
Description: MD5函数测试
Author: Leon
Version: 1.0
Date:
Function:History:
<author>    <time>  <version>   <description>Leon
************************************************************/#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include "md5.h"/* md5函数测试 */
int main(int argc, char *argv[])
{struct stat st;unsigned char digest[16] = {0};MD5_CTX context;int i = 0;if(argc < 2)return;MD5Init(&context);if(-1 == stat(argv[1], &st)){/* 文件不存在则计算参数字符串的MD5 */MD5Update(&context, argv[1], strlen(argv[1]));}else{/* 计算文件MD5 */FILE *fp = fopen(argv[1], "r");char *data = NULL;int ret = 0;if(!fp){perror("fopen");exit(-1);}data = malloc(st.st_size);if(!data){perror("malloc");exit(-1);}ret = fread(data, 1, st.st_size, fp);if(ret != st.st_size){perror("fread");exit(-1);} MD5Update(&context, data, st.st_size);fclose(fp);free(data);}MD5Final(&context, digest);/* 打印MD5值 */printf("md5: ");for(i = 0; i < 16; i++){printf("%02x", digest[i]);}printf("\n");return 0;
}

执行结果与openssl结果对比是一致的：

测试结果：
root@ubuntu:online_upgrade# ./a.out 123.txt
md5: 86109d400f0ed29e840b47ed72777c84
root@ubuntu:online_upgrade# openssl md5 123.txt
MD5(123.txt)= 86109d400f0ed29e840b47ed72777c84

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