测试结果和百度百科测试例子一致。

实现过程中需要注意事项：最后把四个变量A B C D 链接成结果时 ，注意变量高低位的先后顺序，具体参考 LinkResult（）方法。

md5.h

#ifndef _MD5_H_#define _MD5_H_#include <iostream>#include <string>using namespace std;class MD5{ public: typedef unsigned char uchar8; //make sure it is 8bit typedef char char8; //make sure it is 8bit MD5(); void init(); void UpdateMd5(const uchar8 input[], const int length); void UpdateMd5(const char8 input[], const int length); void Finalize(); void ComputMd5(const uchar8 input[], const int length); void ComputMd5(const char8 input[], const int length); string GetMd5(); void printMd5(); private: typedef unsigned int uint32; //make sure it is 32 bit; typedef unsigned long long uint64; //make sure it is 64 bit; uint32 A, B, C, D; const static int blockLen_ = 64; // 512/8 //the remain after last updata (because md5 may be computed segment by segment) uchar8 remain_[blockLen_]; int remainNum_ ; // the number of remain_, < 64 uint64 totalInputBits_; uchar8 md5Result_[16]; //bit style md5 result,totally 128 bit char md5Result_hex_[33]; //hexadecimal style result; md5Result_hex_[32]='\0' bool isDone_; // indicate the comput is finished; inline uint32 RotateLeft(const uint32 x, int n); inline uint32 F(const uint32 x, const uint32 y, const uint32 z); inline uint32 G(const uint32 x, const uint32 y, const uint32 z); inline uint32 H(const uint32 x, const uint32 y, const uint32 z); inline uint32 I(const uint32 x, const uint32 y, const uint32 z); inline void FF(uint32 &a, const uint32 b, const uint32 c, const uint32 d, const uint32 Mj, const int s, const uint32 ti); inline void GG(uint32 &a, const uint32 b, const uint32 c, const uint32 d, const uint32 Mj, const int s, const uint32 ti); inline void HH(uint32 &a, const uint32 b, const uint32 c, const uint32 d, const uint32 Mj, const int s, const uint32 ti); inline void II(uint32 &a, const uint32 b, const uint32 c, const uint32 d, const uint32 Mj, const int s, const uint32 ti); void UcharToUint(uint32 output[], const uchar8 input[], const unsigned int transLength); void FourRound(const uchar8 block[]); void LinkResult(); };#endif

md5.cpp

#include"md5.h"#include<iostream>using namespace std;const int S[4][4] = {7, 12, 17, 22, 5, 9, 14, 20, 4, 11, 16, 23, 6, 10, 15, 21};void MD5::init(){ A = 0x67452301; B = 0xefcdab89; C = 0x98badcfe; D = 0x10325476; remainNum_ = 0; remain_[0] = '\0'; md5Result_hex_[0] = '\0'; md5Result_[0] = '\0'; totalInputBits_ = 0; isDone_ = false;}MD5::MD5(){ init();}inline MD5::uint32 MD5::RotateLeft(const uint32 x, int n){ return (x << n) | (x >> (32-n)); // if x is signed, use: (x << n) | ((x & 0xFFFFFFFF) >> (32-n))}inline MD5::uint32 MD5::F(const uint32 x, const uint32 y, const uint32 z){ return (x & y) | ((~x) & z);}inline MD5::uint32 MD5::G(const uint32 x, const uint32 y, const uint32 z){ return (x & z) | (y & (~z));}inline MD5::uint32 MD5::H(const uint32 x, const uint32 y, const uint32 z){ return x ^ y ^ z;}inline MD5::uint32 MD5::I(const uint32 x, const uint32 y, const uint32 z){ return y ^ (x | (~z));}inline void MD5::FF(uint32 &a, const uint32 b, const uint32 c, const uint32 d, const uint32 Mj, const int s, const uint32 ti){ a = b + RotateLeft(a + F(b, c, d) + Mj + ti, s);} inline void MD5::GG(uint32 &a, const uint32 b, const uint32 c, const uint32 d, const uint32 Mj, const int s, const uint32 ti){ a = b + RotateLeft(a + G(b, c, d) + Mj + ti, s);} inline void MD5::HH(uint32 &a, const uint32 b, const uint32 c, const uint32 d, const uint32 Mj, const int s, const uint32 ti){ a = b + RotateLeft(a + H(b, c, d) + Mj + ti, s);} inline void MD5::II(uint32 &a, const uint32 b, const uint32 c, const uint32 d, const uint32 Mj, const int s, const uint32 ti){ a = b + RotateLeft(a + I(b, c, d) + Mj + ti, s);} // link A B C D to result(bit style result and hexadecimal style result)void MD5::LinkResult(){ //bit style result for(int i = 0; i < 4; i++) //link A: low to high { md5Result_[i] = (A >> 8*i) & 0xff; } for(int i = 4; i<8; i++) //link B: low to high { md5Result_[i] = (B >> 8*(i - 4)) & 0xff; } for(int i = 8; i<12; i++) //link C: low to high { md5Result_[i] = (C >> 8*(i - 8)) & 0xff; } for(int i = 12; i<16; i++) //link D: low to high { md5Result_[i] = (D >> 8*(i - 12)) & 0xff; } //change to hexadecimal style result // note: it is not the same as simply link hex(A) hex(B) hex(C) hex(D) for(int i = 0; i < 16; i++) sprintf(& md5Result_hex_[i*2], "%02x", md5Result_[i]); md5Result_hex_[32] = '\0';}//print the md5 by hexvoid MD5::printMd5(){ if(!isDone_) { cout<< "Error: computation is not finished" <<endl; } else cout<< "MD5 Value: " << md5Result_hex_ <<endl;}//get the md5 value of hex style string MD5::GetMd5(){ if(!isDone_) { cout<< "Error: computation is not finished" <<endl; exit(0); } string a((const char *)md5Result_hex_); return a;}void MD5::UcharToUint(uint32 output[], const uchar8 input[], const unsigned int transLength) { for(int i = 0, j = 0; j < transLength; i++, j += 4) { output[i] = ((uint32)input[j]) | (((uint32)input[j+1]) << 8) | (((uint32)input[j+2]) << 16) | (((uint32)input[j+3]) << 24); }}// four round on a block of 512 bits;void MD5::FourRound(const uchar8 block[]){ uint32 a = A, b = B, c = C, d = D; uint32 M[16]; UcharToUint(M, block, blockLen_); //blockLen_ is a const int =64; //round 1 FF (a, b, c, d, M[ 0], S[0][0], 0xd76aa478); FF (d, a, b, c, M[ 1], S[0][1], 0xe8c7b756); FF (c, d, a, b, M[ 2], S[0][2], 0x242070db); FF (b, c, d, a, M[ 3], S[0][3], 0xc1bdceee); FF (a, b, c, d, M[ 4], S[0][0], 0xf57c0faf); FF (d, a, b, c, M[ 5], S[0][1], 0x4787c62a); FF (c, d, a, b, M[ 6], S[0][2], 0xa8304613); FF (b, c, d, a, M[ 7], S[0][3], 0xfd469501); FF (a, b, c, d, M[ 8], S[0][0], 0x698098d8); FF (d, a, b, c, M[ 9], S[0][1], 0x8b44f7af); FF (c, d, a, b, M[10], S[0][2], 0xffff5bb1); FF (b, c, d, a, M[11], S[0][3], 0x895cd7be); FF (a, b, c, d, M[12], S[0][0], 0x6b901122); FF (d, a, b, c, M[13], S[0][1], 0xfd987193); FF (c, d, a, b, M[14], S[0][2], 0xa679438e); FF (b, c, d, a, M[15], S[0][3], 0x49b40821); // round 2 GG (a, b, c, d, M[ 1], S[1][0], 0xf61e2562); GG (d, a, b, c, M[ 6], S[1][1], 0xc040b340); GG (c, d, a, b, M[11], S[1][2], 0x265e5a51); GG (b, c, d, a, M[ 0], S[1][3], 0xe9b6c7aa); GG (a, b, c, d, M[ 5], S[1][0], 0xd62f105d); GG (d, a, b, c, M[10], S[1][1], 0x2441453); GG (c, d, a, b, M[15], S[1][2], 0xd8a1e681); GG (b, c, d, a, M[ 4], S[1][3], 0xe7d3fbc8); GG (a, b, c, d, M[ 9], S[1][0], 0x21e1cde6); GG (d, a, b, c, M[14], S[1][1], 0xc33707d6); GG (c, d, a, b, M[ 3], S[1][2], 0xf4d50d87); GG (b, c, d, a, M[ 8], S[1][3], 0x455a14ed); GG (a, b, c, d, M[13], S[1][0], 0xa9e3e905); GG (d, a, b, c, M[ 2], S[1][1], 0xfcefa3f8); GG (c, d, a, b, M[ 7], S[1][2], 0x676f02d9); GG (b, c, d, a, M[12], S[1][3], 0x8d2a4c8a); //round 3 HH (a, b, c, d, M[ 5], S[2][0], 0xfffa3942); HH (d, a, b, c, M[ 8], S[2][1], 0x8771f681); HH (c, d, a, b, M[11], S[2][2], 0x6d9d6122); HH (b, c, d, a, M[14], S[2][3], 0xfde5380c); HH (a, b, c, d, M[ 1], S[2][0], 0xa4beea44); HH (d, a, b, c, M[ 4], S[2][1], 0x4bdecfa9); HH (c, d, a, b, M[ 7], S[2][2], 0xf6bb4b60); HH (b, c, d, a, M[10], S[2][3], 0xbebfbc70); HH (a, b, c, d, M[13], S[2][0], 0x289b7ec6); HH (d, a, b, c, M[ 0], S[2][1], 0xeaa127fa); HH (c, d, a, b, M[ 3], S[2][2], 0xd4ef3085); HH (b, c, d, a, M[ 6], S[2][3], 0x4881d05); HH (a, b, c, d, M[ 9], S[2][0], 0xd9d4d039); HH (d, a, b, c, M[12], S[2][1], 0xe6db99e5); HH (c, d, a, b, M[15], S[2][2], 0x1fa27cf8); HH (b, c, d, a, M[ 2], S[2][3], 0xc4ac5665); //round 4 II (a, b, c, d, M[ 0], S[3][0], 0xf4292244); II (d, a, b, c, M[ 7], S[3][1], 0x432aff97); II (c, d, a, b, M[14], S[3][2], 0xab9423a7); II (b, c, d, a, M[ 5], S[3][3], 0xfc93a039); II (a, b, c, d, M[12], S[3][0], 0x655b59c3); II (d, a, b, c, M[ 3], S[3][1], 0x8f0ccc92); II (c, d, a, b, M[10], S[3][2], 0xffeff47d); II (b, c, d, a, M[ 1], S[3][3], 0x85845dd1); II (a, b, c, d, M[ 8], S[3][0], 0x6fa87e4f); II (d, a, b, c, M[15], S[3][1], 0xfe2ce6e0); II (c, d, a, b, M[ 6], S[3][2], 0xa3014314); II (b, c, d, a, M[13], S[3][3], 0x4e0811a1); II (a, b, c, d, M[ 4], S[3][0], 0xf7537e82); II (d, a, b, c, M[11], S[3][1], 0xbd3af235); II (c, d, a, b, M[ 2], S[3][2], 0x2ad7d2bb); II (b, c, d, a, M[ 9], S[3][3], 0xeb86d391); A += a; B += b; C += c; D += d;}// update md5,must consider the remain_.void MD5::UpdateMd5(const uchar8 input[], const int length){ isDone_ = false; totalInputBits_ += (length << 3); int start = blockLen_ - remainNum_; //blockLen_ = 64 //copy a part of input to remain_ so it can form a block(size=64) if(start <= length) { // can form a block,then do FourRound to this block memcpy(&remain_[remainNum_], input, start) ; FourRound(remain_); int i; for(i = start; i <= length - blockLen_; i += blockLen_) { FourRound(&input[i]); } remainNum_ = length - i; memcpy(remain_, &input[i], remainNum_); } else { // can not form a block, function return; memcpy(&remain_[remainNum_], input, length); remainNum_ += length; } }void MD5::UpdateMd5(const char8 input[], const int length){ UpdateMd5((const uchar8 *)input, length);}// padding with 100000... to remain_ and add the 64bit original size of input void MD5::Finalize(){ if(isDone_ == true) return; uchar8 padding[64] = { 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 }; int temp = 56 - remainNum_; //56 = 448/8 if(temp > 0) { UpdateMd5(padding, temp); totalInputBits_ -= (temp << 3); } else if(temp < 0) { UpdateMd5(padding, 64 + temp); totalInputBits_ -= ((64 + temp) << 3); } // trans totalInputBits_ to uchar8 (64bits) uchar8 Bits[8]; for(int i = 0; i < 8; i++) { Bits[i] = (totalInputBits_ >> 8*i) & 0xff; } UpdateMd5(Bits, 8); // add the number of original input (the last 64bits) LinkResult(); isDone_ = true;}// comput the md5 based on input, (just this one input)void MD5::ComputMd5(const uchar8 input[], const int length){ init(); UpdateMd5(input, length); Finalize();}void MD5::ComputMd5(const char8 input[], const int length){ ComputMd5((const uchar8 *)input, length);}