C++ MD5的源码实例详解

#ifndef MD5_H 
#define MD5_H 
 
#include <string> 
#include <fstream> 
 
/* Type define */ 
typedef unsigned char byte; 
typedef unsigned int uint32; 
 
using std::string; 
using std::ifstream; 
 
/* MD5 declaration. */ 
class MD5 { 
public: 
 MD5(); 
 MD5(const void *input, size_t length); 
 MD5(const string &str); 
 MD5(ifstream &in); 
 void update(const void *input, size_t length); 
 void update(const string &str); 
 void update(ifstream &in); 
 const byte* digest(); 
 string toString(); 
 void reset(); 
private: 
 void update(const byte *input, size_t length); 
 void final(); 
 void transform(const byte block[64]); 
 void encode(const uint32 *input, byte *output, size_t length); 
 void decode(const byte *input, uint32 *output, size_t length); 
 string bytesToHexString(const byte *input, size_t length); 
 
 /* class uncopyable */ 
 MD5(const MD5&); 
 MD5& operator=(const MD5&); 
private: 
 uint32 _state[4]; /* state (ABCD) */ 
 uint32 _count[2]; /* number of bits, modulo 2^64 (low-order word first) */ 
 byte _buffer[64]; /* input buffer */ 
 byte _digest[16]; /* message digest */ 
 bool _finished; /* calculate finished ? */ 
 
 static const byte PADDING[64]; /* padding for calculate */ 
 static const char HEX[16]; 
 static const size_t BUFFER_SIZE = 1024; 
}; 
 
#endif/*MD5_H*/ 

#include "md5.h" 
 
using namespace std; 
 
/* Constants for MD5Transform routine. */ 
#define S11 7 
#define S12 12 
#define S13 17 
#define S14 22 
#define S21 5 
#define S22 9 
#define S23 14 
#define S24 20 
#define S31 4 
#define S32 11 
#define S33 16 
#define S34 23 
#define S41 6 
#define S42 10 
#define S43 15 
#define S44 21 
 
 
/* F, G, H and I are basic MD5 functions. 
*/ 
#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))) 
 
/* ROTATE_LEFT rotates x left n bits. 
*/ 
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n)))) 
 
/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4. 
Rotation is separate from addition to prevent recomputation. 
*/ 
#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); \ 
} 
 
 
const byte MD5::PADDING[64] = { 0x80 }; 
const char MD5::HEX[16] = { 
 '0', '1', '2', '3', 
 '4', '5', '6', '7', 
 '8', '9', 'a', 'b', 
 'c', 'd', 'e', 'f' 
}; 
 
/* Default construct. */ 
MD5::MD5() { 
 reset(); 
} 
 
/* Construct a MD5 object with a input buffer. */ 
MD5::MD5(const void *input, size_t length) { 
 reset(); 
 update(input, length); 
} 
 
/* Construct a MD5 object with a string. */ 
MD5::MD5(const string &str) { 
 reset(); 
 update(str); 
} 
 
/* Construct a MD5 object with a file. */ 
MD5::MD5(ifstream &in) { 
 reset(); 
 update(in); 
} 
 
/* Return the message-digest */ 
const byte* MD5::digest() { 
 if (!_finished) { 
 _finished = true; 
 final(); 
 } 
 return _digest; 
} 
 
/* Reset the calculate state */ 
void MD5::reset() { 
 
 _finished = false; 
 /* reset number of bits. */ 
 _count[0] = _count[1] = 0; 
 /* Load magic initialization constants. */ 
 _state[0] = 0x67452301; 
 _state[1] = 0xefcdab89; 
 _state[2] = 0x98badcfe; 
 _state[3] = 0x10325476; 
} 
 
/* Updating the context with a input buffer. */ 
void MD5::update(const void *input, size_t length) { 
 update((const byte*)input, length); 
} 
 
/* Updating the context with a string. */ 
void MD5::update(const string &str) { 
 update((const byte*)str.c_str(), str.length()); 
} 
 
/* Updating the context with a file. */ 
void MD5::update(ifstream &in) { 
 
 if (!in) 
 return; 
 
 std::streamsize length; 
 char buffer[BUFFER_SIZE]; 
 while (!in.eof()) { 
 in.read(buffer, BUFFER_SIZE); 
 length = in.gcount(); 
 if (length > 0) 
  update(buffer, length); 
 } 
 in.close(); 
} 
 
/* MD5 block update operation. Continues an MD5 message-digest 
operation, processing another message block, and updating the 
context. 
*/ 
void MD5::update(const byte *input, size_t length) { 
 
 uint32 i, index, partLen; 
 
 _finished = false; 
 
 /* Compute number of bytes mod 64 */ 
 index = (uint32)((_count[0] >> 3) & 0x3f); 
 
 /* update number of bits */ 
 if((_count[0] += ((uint32)length << 3)) < ((uint32)length << 3)) 
 _count[1]++; 
 _count[1] += ((uint32)length >> 29); 
 
 partLen = 64 - index; 
 
 /* transform as many times as possible. */ 
 if(length >= partLen) { 
 
 memcpy(&_buffer[index], input, partLen); 
 transform(_buffer); 
 
 for (i = partLen; i + 63 < length; i += 64) 
  transform(&input[i]); 
 index = 0; 
 
 } else { 
 i = 0; 
 } 
 
 /* Buffer remaining input */ 
 memcpy(&_buffer[index], &input[i], length-i); 
} 
 
/* MD5 finalization. Ends an MD5 message-_digest operation, writing the 
the message _digest and zeroizing the context. 
*/ 
void MD5::final() { 
 
 byte bits[8]; 
 uint32 oldState[4]; 
 uint32 oldCount[2]; 
 uint32 index, padLen; 
 
 /* Save current state and count. */ 
 memcpy(oldState, _state, 16); 
 memcpy(oldCount, _count, 8); 
 
 /* Save number of bits */ 
 encode(_count, bits, 8); 
 
 /* Pad out to 56 mod 64. */ 
 index = (uint32)((_count[0] >> 3) & 0x3f); 
 padLen = (index < 56) ? (56 - index) : (120 - index); 
 update(PADDING, padLen); 
 
 /* Append length (before padding) */ 
 update(bits, 8); 
 
 /* Store state in digest */ 
 encode(_state, _digest, 16); 
 
 /* Restore current state and count. */ 
 memcpy(_state, oldState, 16); 
 memcpy(_count, oldCount, 8); 
} 
 
/* MD5 basic transformation. Transforms _state based on block. */ 
void MD5::transform(const byte block[64]) { 
 
 uint32 a = _state[0], b = _state[1], c = _state[2], d = _state[3], x[16]; 
 
 decode(block, x, 64); 
 
 /* Round 1 */ 
 FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */ 
 FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */ 
 FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */ 
 FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */ 
 FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */ 
 FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */ 
 FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */ 
 FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */ 
 FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */ 
 FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */ 
 FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */ 
 FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */ 
 FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */ 
 FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */ 
 FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */ 
 FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */ 
 
 /* Round 2 */ 
 GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */ 
 GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */ 
 GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */ 
 GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */ 
 GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */ 
 GG (d, a, b, c, x[10], S22, 0x2441453); /* 22 */ 
 GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */ 
 GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */ 
 GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */ 
 GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */ 
 GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */ 
 GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */ 
 GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */ 
 GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */ 
 GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */ 
 GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */ 
 
 /* Round 3 */ 
 HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */ 
 HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */ 
 HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */ 
 HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */ 
 HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */ 
 HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */ 
 HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */ 
 HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */ 
 HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */ 
 HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */ 
 HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */ 
 HH (b, c, d, a, x[ 6], S34, 0x4881d05); /* 44 */ 
 HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */ 
 HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */ 
 HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */ 
 HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */ 
 
 /* Round 4 */ 
 II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */ 
 II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */ 
 II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */ 
 II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */ 
 II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */ 
 II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */ 
 II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */ 
 II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */ 
 II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */ 
 II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */ 
 II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */ 
 II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */ 
 II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */ 
 II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */ 
 II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */ 
 II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */ 
 
 _state[0] += a; 
 _state[1] += b; 
 _state[2] += c; 
 _state[3] += d; 
} 
 
/* Encodes input (ulong) into output (byte). Assumes length is 
a multiple of 4. 
*/ 
void MD5::encode(const uint32 *input, byte *output, size_t length) { 
 
 for(size_t i=0, j=0; j<length; i++, j+=4) { 
 output[j]= (byte)(input[i] & 0xff); 
 output[j+1] = (byte)((input[i] >> 8) & 0xff); 
 output[j+2] = (byte)((input[i] >> 16) & 0xff); 
 output[j+3] = (byte)((input[i] >> 24) & 0xff); 
 } 
} 
 
/* Decodes input (byte) into output (ulong). Assumes length is 
a multiple of 4. 
*/ 
void MD5::decode(const byte *input, uint32 *output, size_t length) { 
 
 for(size_t i=0, j=0; j<length; i++, j+=4) { 
 output[i] = ((uint32)input[j]) | (((uint32)input[j+1]) << 8) | 
  (((uint32)input[j+2]) << 16) | (((uint32)input[j+3]) << 24); 
 } 
} 
 
/* Convert byte array to hex string. */ 
string MD5::bytesToHexString(const byte *input, size_t length) { 
 string str; 
 str.reserve(length << 1); 
 for(size_t i = 0; i < length; i++) { 
 int t = input[i]; 
 int a = t / 16; 
 int b = t % 16; 
 str.append(1, HEX[a]); 
 str.append(1, HEX[b]); 
 } 
 return str; 
} 
 
/* Convert digest to string value */ 
string MD5::toString() { 
 return bytesToHexString(digest(), 16); 
} 

#include "md5.h" 
#include <iostream> 
 
using namespace std; 
 
void PrintMD5(const string &str, MD5 &md5) { 
 cout << "MD5(\"" << str << "\") = " << md5.toString() << endl; 
} 
 
string FileDigest(const string &file) { 
 
 ifstream in(file.c_str(), ios::binary); 
 if (!in) 
 return ""; 
 
 MD5 md5; 
 std::streamsize length; 
 char buffer[1024]; 
 while (!in.eof()) { 
 in.read(buffer, 1024); 
 length = in.gcount(); 
 if (length > 0) 
  md5.update(buffer, length); 
 } 
 in.close(); 
 return md5.toString(); 
} 
 
int main() { 
 
 cout << MD5("abc").toString() << endl; 
 cout << MD5(ifstream("D:\\test.txt")).toString() << endl; 
 cout << MD5(ifstream("D:\\test.exe", ios::binary)).toString() << endl; 
 cout << FileDigest("D:\\test.exe") << endl; 
 
 MD5 md5; 
 md5.update(""); 
 PrintMD5("", md5); 
 
 md5.update("a"); 
 PrintMD5("a", md5); 
 
 md5.update("bc"); 
 PrintMD5("abc", md5); 
 
 md5.update("defghijklmnopqrstuvwxyz"); 
 PrintMD5("abcdefghijklmnopqrstuvwxyz", md5); 
 
 md5.reset(); 
 md5.update("message digest"); 
 PrintMD5("message digest", md5); 
 
 md5.reset(); 
 md5.update(ifstream("D:\\test.txt")); 
 PrintMD5("D:\\test.txt", md5); 
 return 0; 
} 

MD5();          //默认构造函数
MD5(const void *input, size_t length);   //输入内存地址与长度信息的构造函数
MD5(const string &str);      //输入字符串的构造函数
MD5(ifstream &in);       //输入流的构造函数
3个Update函数:
void update(const void *input, size_t length); //往MD5对象内添加内存块
void update(const string &str);    //添加字符串
void update(ifstream &in);     //添加流

const byte* digest();       //计算MD5码,并返回指向它的指针
string toString();       //计算MD5,并返回其对应的字符串
void reset();        //重置,