C语言压缩文件和用MD5算法校验文件完整性的实例教程

#ifndef MD5_H 
#define MD5_H 
 
#ifdef __cplusplus 
extern "C" 
{ 
#endif             /* __cplusplus */ 
 
#ifdef HAVE_CONfig_H 
# include "config.h" 
#endif 
 
#ifdef HAVE_STDINT_H 
  #include <stdint.h> 
  typedef uint32_t uint32; 
#else 
  /* A.Leo.: this wont work on 16 bits platforms ;) */ 
  typedef unsigned uint32; 
#endif 
 
#define MD5_FILE_BUFFER_LEN 1024 
 
struct MD5Context { 
  uint32 buf[4]; 
  uint32 bits[2]; 
  unsigned char in[64]; 
}; 
 
void MD5Init(struct MD5Context *context); 
void MD5update(struct MD5Context *context,unsigned char const *buf,unsigned len); 
void MD5Final(unsigned char digest[16],struct MD5Context *context); 
void MD5Transform(uint32 buf[4],uint32 const in[16]); 
 
int getBytesMD5(const unsigned char* src,unsigned int length,char* md5); 
int getStringMD5(const char* src,char* md5); 
int getFileMD5(const char* path,char* md5); 
 
/* 
 * This is needed to make RSAREF happy on some MS-DOS compilers. 
 */ 
typedef struct MD5Context MD5_CTX; 
 
#ifdef __cplusplus 
} 
#endif             /* __cplusplus */ 
 
#endif /* !MD5_H */ 

#include <String.h>    /* for memcpy() */ 
#include <stdio.h> 
#include "md5.h" 
 
#ifndef HIGHFIRST 
#define byteReverse(buf,len)  /* Nothing */ 
#else 
void byteReverse(unsigned char *buf,unsigned longs); 
 
#ifndef ASM_MD5 
/* 
 * Note: this code is harmless on little-endian machines. 
 */ 
void byteReverse(unsigned char *buf,unsigned longs) 
{ 
  uint32 t; 
  do { 
    t = (uint32) ((unsigned) buf[3] << 8 | buf[2]) << 16 | 
    ((unsigned) buf[1] << 8 | buf[0]); 
    *(uint32 *) buf = t; 
    buf += 4; 
  }while (--longs); 
} 
#endif 
#endif 
 
static void putu32(uint32 data,unsigned char *addr) { 
  addr[0] = (unsigned char) data; 
  addr[1] = (unsigned char) (data >> 8); 
  addr[2] = (unsigned char) (data >> 16); 
  addr[3] = (unsigned char) (data >> 24); 
} 
 
/* 
 * Start MD5 accumulation. Set bit count to 0 and buffer to mysterIoUs 
 * initialization constants. 
 */ 
void MD5Init(struct MD5Context *ctX) { 
  ctx->buf[0] = 0x67452301; 
  ctx->buf[1] = 0xefcdab89; 
  ctx->buf[2] = 0x98badcfe; 
  ctx->buf[3] = 0x10325476; 
 
  ctx->bits[0] = 0; 
  ctx->bits[1] = 0; 
} 
 
/* 
 * update context to reflect the concatenation of another buffer full 
 * of bytes. 
 */ 
void MD5update(struct MD5Context *ctx,unsigned len) { 
  uint32 t; 
 
  /* update bitcount */ 
 
  t = ctx->bits[0]; 
  if ((ctx->bits[0] = t + ((uint32) len << 3)) < t) 
    ctx->bits[1]++; /* Carry from low to high */ 
  ctx->bits[1] += len >> 29; 
 
  t = (t >> 3) & 0x3f; /* Bytes already in shsInfo->data */ 
 
  /* Handle any leading odd-sized chunks */ 
 
  if (t) { 
    unsigned char *p = (unsigned char *) ctx->in + t; 
 
    t = 64 - t; 
    if (len < t) { 
      memcpy(p,buf,len); 
      return; 
    } 
    memcpy(p,t); 
    byteReverse(ctx->in,16); 
    MD5Transform(ctx->buf,(uint32 *) ctx->in); 
    buf += t; 
    len -= t; 
  } 
  /* Process data in 64-byte chunks */ 
 
  while (len >= 64) { 
    memcpy(ctx->in,64); 
    byteReverse(ctx->in,(uint32 *) ctx->in); 
    buf += 64; 
    len -= 64; 
  } 
 
  /* Handle any remaining bytes of data. */ 
 
  memcpy(ctx->in,len); 
} 
 
/* 
 * Final wrapup - pad to 64-byte boundary with the bit pattern 
 * 1 0* (64-bit count of bits processed,MSB-first) 
 */ 
void MD5Final(unsigned char digest[16],struct MD5Context *ctX) { 
  unsigned count; 
  unsigned char *p; 
 
  /* Compute number of bytes mod 64 */ 
  count = (ctx->bits[0] >> 3) & 0x3F; 
 
  /* Set the first char of padding to 0x80. This is safe since there is 
   always at least one byte free */ 
  p = ctx->in + count; 
  *p++ = 0x80; 
 
  /* Bytes of padding needed to make 64 bytes */ 
  count = 64 - 1 - count; 
 
  /* Pad out to 56 mod 64 */ 
  if (count < 8) { 
    /* Two lots of padding: Pad the first block to 64 bytes */ 
    memset(p,count); 
    byteReverse(ctx->in,(uint32 *) ctx->in); 
 
    /* Now fill the next block with 56 bytes */ 
    memset(ctx->in,56); 
  } else { 
    /* Pad block to 56 bytes */ 
    memset(p,count - 8); 
  } byteReverse(ctx->in,14); 
 
  /* Append length in bits and transform */ 
  //((uint32 *) ctx->in)[14] = ctx->bits[0]; 
  //((uint32 *) ctx->in)[15] = ctx->bits[1]; 
  putu32(ctx->bits[0],ctx->in + 56); 
  putu32(ctx->bits[1],ctx->in + 60); 
 
  MD5Transform(ctx->buf,(uint32 *) ctx->in); 
  byteReverse((unsigned char *) ctx->buf,4); 
  memcpy(digest,ctx->buf,16); 
  memset(ctx,sizeof(*ctX)); /* In case it's sensitive */ 
} 
 
#ifndef ASM_MD5 
 
/* The four core functions - F1 is optimized somewhat */ 
 
/* #define F1(x,y,z) (x & y | ~x & z) */ 
#define F1(x,z) (z ^ (x & (y ^ z))) 
#define F2(x,z) F1(z,x,y) 
#define F3(x,z) (x ^ y ^ z) 
#define F4(x,z) (y ^ (x | ~z)) 
 
/* This is the central step in the MD5 algorithm. */ 
#define MD5STEP(f,w,z,data,s) \ 
  ( w += f(x,z) + data,w = w<<s | w>>(32-s),w += x ) 
 
/* 
 * The core of the MD5 algorithm,this alters an exisTing MD5 hash to 
 * reflect the addition of 16 longwords of new data. MD5update blocks 
 * the data and converts bytes into longwords for this routIne. 
 */ 
void MD5Transform(uint32 buf[4],uint32 const in[16]) { 
  register uint32 a,b,c,d; 
 
  a = buf[0]; 
  b = buf[1]; 
  c = buf[2]; 
  d = buf[3]; 
 
  MD5STEP(F1,a,d,in[0] + 0xd76aa478,7); 
  MD5STEP(F1,in[1] + 0xe8c7b756,12); 
  MD5STEP(F1,in[2] + 0x242070db,17); 
  MD5STEP(F1,in[3] + 0xc1bdceee,22); 
  MD5STEP(F1,in[4] + 0xf57c0faf,in[5] + 0x4787c62a,in[6] + 0xa8304613,in[7] + 0xfd469501,in[8] + 0x698098d8,in[9] + 0x8b44f7af,in[10] + 0xffff5bb1,in[11] + 0x895cd7be,in[12] + 0x6b901122,in[13] + 0xfd987193,in[14] + 0xa679438e,in[15] + 0x49b40821,22); 
 
  MD5STEP(F2,in[1] + 0xf61e2562,5); 
  MD5STEP(F2,in[6] + 0xc040b340,9); 
  MD5STEP(F2,in[11] + 0x265e5a51,14); 
  MD5STEP(F2,in[0] + 0xe9b6c7aa,20); 
  MD5STEP(F2,in[5] + 0xd62f105d,in[10] + 0x02441453,in[15] + 0xd8a1e681,in[4] + 0xe7d3fbc8,in[9] + 0x21e1cde6,in[14] + 0xc33707d6,in[3] + 0xf4d50d87,in[8] + 0x455a14ed,in[13] + 0xa9e3e905,in[2] + 0xfcefa3f8,in[7] + 0x676f02d9,in[12] + 0x8d2a4c8a,20); 
 
  MD5STEP(F3,in[5] + 0xfffa3942,4); 
  MD5STEP(F3,in[8] + 0x8771f681,11); 
  MD5STEP(F3,in[11] + 0x6d9d6122,16); 
  MD5STEP(F3,in[14] + 0xfde5380c,23); 
  MD5STEP(F3,in[1] + 0xa4beea44,in[4] + 0x4bdecfa9,in[7] + 0xf6bb4b60,in[10] + 0xbebfbc70,in[13] + 0x289b7ec6,in[0] + 0xeaa127fa,in[3] + 0xd4ef3085,in[6] + 0x04881d05,in[9] + 0xd9d4d039,in[12] + 0xe6db99e5,in[15] + 0x1fa27cf8,in[2] + 0xc4ac5665,23); 
 
  MD5STEP(F4,in[0] + 0xf4292244,6); 
  MD5STEP(F4,in[7] + 0x432aff97,10); 
  MD5STEP(F4,in[14] + 0xab9423a7,15); 
  MD5STEP(F4,in[5] + 0xfc93a039,21); 
  MD5STEP(F4,in[12] + 0x655b59c3,in[3] + 0x8f0ccc92,in[10] + 0xffeff47d,in[1] + 0x85845dd1,in[8] + 0x6fa87e4f,in[15] + 0xfe2ce6e0,in[6] + 0xa3014314,in[13] + 0x4e0811a1,in[4] + 0xf7537e82,in[11] + 0xbd3af235,in[2] + 0x2ad7d2bb,in[9] + 0xeb86d391,21); 
 
  buf[0] += a; 
  buf[1] += b; 
  buf[2] += c; 
  buf[3] += d; 
} 
 
/* 
 * get MD5 of a byte buffer 
 */ 
int getBytesMD5(const unsigned char* src,char* md5) { 
  unsigned char i = 0; 
  unsigned char md5Bytes[16] = { 0 }; 
  MD5_CTX context; 
  if (src == NULL || md5 == NULL) 
  { 
    return -1; 
  } 
  MD5Init(&context); 
  MD5update(&context,src,length); 
  MD5Final(md5Bytes,&context); 
  for (i = 0; i < 16; i++) { 
    sprintf(md5,"%02X",md5Bytes[i]); 
    md5 += 2; 
  } 
  *md5 = '\0'; 
  return 0; 
} 
 
/* 
 * get MD5 for a String 
 */ 
int getStringMD5(const char* src,char* md5) { 
  return getBytesMD5((unsigned char*) src,strlen((char*) srC),md5); 
} 
 
/** 
 * get MD5 of a file 
 */ 
int getFileMD5(const char* path,char* md5) { 
  FILE* fp = NULL; 
  unsigned char buffer[MD5_FILE_BUFFER_LEN] = { 0 }; 
  int count = 0; 
  MD5_CTX context; 
  unsigned char md5Bytes[16] = { 0 }; 
  int i; 
  if (path == NULL || md5 == NULL) { 
    return -1; 
  } 
  fp = fopen(path,"rb"); 
  if (fp == NULL) { 
    return -1; 
  } 
  MD5Init(&context); 
  while ((count = fread(buffer,1,MD5_FILE_BUFFER_LEN,fp)) > 0) { 
    MD5update(&context,buffer,count); 
  } 
  MD5Final(md5Bytes,md5Bytes[i]); 
    md5 += 2; 
  } 
  *md5 = '\0'; 
  return 0; 
} 
 
#endif 

#include <stdio.h> 
#include <String.h> 
 
#include "md5.h" 
 
int main(int c,char** v){ 
  char buffer[128]; 
  getStringMD5("Hello world",buffer); 
  printf("%s\n",buffer); 
  getFileMD5("Hello.pdf",buffer); 
  return 0; 
}