最近接觸了HTML5中的websocket，下載了一個C實現的websocket庫，但是其MD5算法實現中，涉及到AVR相關內容，編譯時缺少頭文件，而且需要交叉編譯，我不是很清楚，于是乎，參照相關資料，實現了MD5算法。

由于我要處理的是字符串，長度較小，而且是以byte為單位，因此實現中并未以bit作為基本單位，同時內部對輸入數據進行了拷貝，不適合處理大型文件。

md5.h /*
* summary: MD5
* author: caosiyang
* email: csy3228@gmail.com
*/
#ifndef __MD5_H__
#define __MD5_H__


#include <assert.h>
#include <math.h>
#include <iostream>
#include <string>
using namespace std;


class MD5 {
public:
MD5();
~MD5();
string calc(const char *str);
string calc(const char *buf, int32_t len);

protected:
MD5(const MD5 &);
MD5& operator=(const MD5 &);

private:
uint32_t T[64];
static const uint32_t CV[4];
static const uint32_t R[64];

void prepare(const char *buf, int32_t len, char *&outbuf, int32_t &outlen);
inline uint32_t rotate_left(uint32_t num, uint32_t n) const;
string _gen_md5_str(uint32_t a, uint32_t b, uint32_t c, uint32_t d) const;
inline uint32_t _reverse(const uint32_t n) const;

inline uint32_t F(uint32_t x, uint32_t y, uint32_t z) const;
inline uint32_t G(uint32_t x, uint32_t y, uint32_t z) const;
inline uint32_t H(uint32_t x, uint32_t y, uint32_t z) const;
inline uint32_t I(uint32_t x, uint32_t y, uint32_t z) const;

#if 0
inline int32_t FF(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t);
inline int32_t GG(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t);
inline int32_t HH(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t);
inline int32_t II(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t);
#endif
};


#endif md5.cpp #include "md5.h"


const uint32_t MD5::CV[4] = {
0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476
};


const uint32_t MD5::R[64] = {
7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21
};


MD5::MD5() {
//initialize T[]
for (int i = 1; i <= 64; ++i) {
long long ti = pow(2, 32) * sin(i);
if (ti < 0) {
ti = 0 - ti;
}
T[i - 1] = ti;
}
}


MD5::~MD5() {
}


string MD5::calc(const char *str) {
return calc(str, strlen(str));
}


string MD5::calc(const char *buf, const int32_t len) {
char *outbuf = NULL;
int32_t outlen = 0;
prepare(buf, len, outbuf, outlen);
assert(outlen > 0 && outlen % 64 == 0);

uint32_t A = CV[0];
uint32_t B = CV[1];
uint32_t C = CV[2];
uint32_t D = CV[3];

for (int32_t i = 0; i < outlen / 64; ++i) {
uint32_t X[16] = {0};
for (int32_t j = 0; j < 16; ++j) {
X[j] = *(uint32_t*)(outbuf + (64 * i + 4 * j));
}

uint32_t a = A;
uint32_t b = B;
uint32_t c = C;
uint32_t d = D;

for (int i = 0; i < 64; ++i) {
int32_t g = 0;
if (i >= 0 && i <= 15) {
g = i;
a = (uint32_t)(b + rotate_left(a + F(b, c, d) + X[g] + T[i], R[i]));
} else if (i >= 16 && i <= 31) {
g = (i * 5 + 1) % 16;
a = (uint32_t)(b + rotate_left(a + G(b, c, d) + X[g] + T[i], R[i]));
} else if (i >= 32 && i <= 47) {
g = (i * 3 + 5) % 16;
a = (uint32_t)(b + rotate_left(a + H(b, c, d) + X[g] + T[i], R[i]));
} else if (i >= 48 && i <= 63) {
g = (i * 7) % 16;
a = (uint32_t)(b + rotate_left(a + I(b, c, d) + X[g] + T[i], R[i]));
}

//loop swap
uint32_t temp = d;
d = c;
c = b;
b = a;
a = temp;
}

A = A + a;
B = B + b;
C = C + c;
D = D + d;
}

return _gen_md5_str(A, B, C, D);
}


inline uint32_t MD5::rotate_left(uint32_t num, uint32_t n) const {
return (num << n) | (num >> (32 - n % 32));
}


string MD5::_gen_md5_str(uint32_t a, uint32_t b, uint32_t c, uint32_t d) const {
char res[33] = {0};
sprintf(res, "%08x%08x%08x%08x", _reverse(a), _reverse(b), _reverse(c), _reverse(d));
return res;
}


inline uint32_t MD5::_reverse(const uint32_t n) const {
return ((n & 0x000000ff) << 24) | ((n & 0x0000ff00) << 8) | ((n & 0x00ff0000) >> 8) | ((n & 0xff000000) >> 24);
}


void MD5::prepare(const char *buf, int32_t len, char *&outbuf, int32_t &outlen) {
int32_t x = len * 8 % 512;
int32_t bit_to_fill = (x < 448) ? (448 - x) : (512 - x + 448);
char c1 = 1, c2 = 0;
c1 = c1 << 7;

if (bit_to_fill % 8 == 0) {
int32_t byte_to_fill = bit_to_fill / 8;
int32_t new_len = len + byte_to_fill + 8;

char *p = new (nothrow) char[new_len];
assert(p);
char *q = p;
memcpy(q, buf, len);
q += len;
for (int i = 0; i < byte_to_fill; ++i) {
if (i == 0) {
memcpy(q, &c1, 1);
} else {
memcpy(q, &c2, 1);
}
++q;
}

int64_t length = len * 8;
memcpy(q, &length, 8);

outbuf = p;
outlen = new_len;
}
assert(bit_to_fill % 8 == 0);
}


inline uint32_t MD5::F(uint32_t x, uint32_t y, uint32_t z) const {
return (x & y) | ((~x) & z);
}


inline uint32_t MD5::G(uint32_t x, uint32_t y, uint32_t z) const {
return (x & z) | (y & (~z));
}


inline uint32_t MD5::H(uint32_t x, uint32_t y, uint32_t z) const {
return x ^ y ^ z;
}


inline uint32_t MD5::I(uint32_t x, uint32_t y, uint32_t z) const {
return y ^ (x | (~z));
}


#if 0
inline int32_t MD5::FF(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t) {
}


inline int32_t MD5::GG(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t) {
}


inline int32_t MD5::HH(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t) {
}


inline int32_t MD5::II(int32_t a, int32_t b, int32_t c, int32_t d, int32_t m, int32_t s, int32_t t) {
}
#endif demo.cpp #include "md5.h"


int main() {
MD5 md5;
string code;
code = md5.calc("");
cout << "md5 = " << code << endl;
code = md5.calc("a");
cout << "md5 = " << code << endl;
code = md5.calc("abc");
cout << "md5 = " << code << endl;
code = md5.calc("message digest");
cout << "md5 = " << code << endl;
code = md5.calc("abcdefghijklmnopqrstuvwxyz");
cout << "md5 = " << code << endl;
code = md5.calc("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
cout << "md5 = " << code << endl;
return 0;
}

轉載于:https://www.cnblogs.com/caosiyang/archive/2012/02/24/2366381.html

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