C语言求文件MD5的函数用法

#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

源文件md5.c

#include <memory.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 = partleni+64 <= inputleni+=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)/* 1 */

FF(d, a, b, c, x[ 1], 12, 0xe8c7b756)/* 2 */

FF(c, d, a, b, x[ 2], 17, 0x242070db)/* 3 */

FF(b, c, d, a, x[ 3], 22, 0xc1bdceee)/* 4 */

FF(a, b, c, d, x[ 4], 7, 0xf57c0faf)/* 5 */

FF(d, a, b, c, x[ 5], 12, 0x4787c62a)/* 6 */

FF(c, d, a, b, x[ 6], 17, 0xa8304613)/* 7 */

FF(b, c, d, a, x[ 7], 22, 0xfd469501)/* 8 */

FF(a, b, c, d, x[ 8], 7, 0x698098d8)/* 9 */

FF(d, a, b, c, x[ 9], 12, 0x8b44f7af)/* 10 */

FF(c, d, a, b, x[10], 17, 0xffff5bb1)/* 11 */

FF(b, c, d, a, x[11], 22, 0x895cd7be)/* 12 */

FF(a, b, c, d, x[12], 7, 0x6b901122)/* 13 */

FF(d, a, b, c, x[13], 12, 0xfd987193)/* 14 */

FF(c, d, a, b, x[14], 17, 0xa679438e)/* 15 */

FF(b, c, d, a, x[15], 22, 0x49b40821)/* 16 */

查阅fread函数，可以实现按照字节批次读取，你的文件最好用二进制方式打开。

查阅剩余数据，恐怕得实际读取才知道，但是每次读取文件都会改变文件指针的位置，你需要用fseek来移动文件指针回到原本的位置。

函数 size_t fread(void * ptr,size_t size,size_t nmemb,FILE * stream)函数说明 fread()用来从文件流中读取数据。参数stream为已打开的文件指针,参数ptr 指向欲存放

读取进来的数据空间，读取的字符数以参数size*nmemb来决定。Fread()会返回实际读取到的nmemb数目，

如果此值比参数nmemb 来得小，则代表可能读到了文件尾或有错误发生，这时必须用feof()或ferror()

来决定发生什么情况。

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