C++中md5 算法实现代码

在网上找了份c++ MD5的代码，就简单保存一下：

首先md5.h

#ifndef MD5_H
#define MD5_H

#include <string>
#include <fstream>

/* Type define */
typedef unsigned char byte;
typedef unsigned long ulong;

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 ulong *input, byte *output, size_t length);
  void decode(const byte *input, ulong *output, size_t length);
  string bytesToHexString(const byte *input, size_t length);

  /* class uncopyable */
  MD5(const MD5&);
  MD5& operator=(const MD5&);
private:
  ulong _state[4];  /* state (ABCD) */
  ulong _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*/

然后是接口的实现文件（md5.cpp）

#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) {

  ulong i, index, partLen;

  _finished = false;

  /* Compute number of bytes mod 64 */
  index = (ulong)((_count[0] >> 3) & 0x3f);

  /* update number of bits */
  if((_count[0] += ((ulong)length << 3)) < ((ulong)length << 3))
    _count[1]++;
  _count[1] += ((ulong)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];
  ulong oldState[4];
  ulong oldCount[2];
  ulong 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 = (ulong)((_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]) {

  ulong 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 ulong *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, ulong *output, size_t length) {

  for(size_t i=0, j=0; j<length; i++, j+=4) {
    output[i] = ((ulong)input[j]) | (((ulong)input[j+1]) << 8) |
      (((ulong)input[j+2]) << 16) | (((ulong)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);
}

//test.cpp

#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 << FileDigest("D:\\staticDll.dll") << endl;

  return 0;
}

最后main函数中，一个是生成字符串的md5码，另外一个是读取文件生成md5码，然后和python生成的md5码一比较就可以判断文件有没有被修改。

因为需要校验文件，所以要使用md5算法，发现用python脚本生成文件的md5值不要太简单啊

#-*- coding:utf-8 –*-
import os,sys
from hashlib import md5
#文件的MD5校验码是根据文件的内容生成的信息摘要，方法如下，
<span style="background-color: rgb(255, 0, 0);">def md5_file(name):
  m = md5()
  fd = open(name, 'rb')  #需要使用二进制格式读取文件内容
  m.update(fd.read())
  fd.close()
  return m.hexdigest()</span>


def usage():
  print 'Usage:'
  print 'timestamp.py dllFilesFullPath md5Path'
  print '处理文件 dll文件夹路径 存储的文件路径（txt格式）'


if(len(sys.argv)<3): #如果参数不对，给出提示
  usage()
  sys.exit(0)
dllFilePath = sys.argv[1]
md5File = sys.argv[2]
f = open(md5File, 'wb')
listfile=os.listdir(dllFilePath)
for name in listfile:
<span style="white-space:pre">  </span>ext_name = name[-4:]
<span style="white-space:pre">  </span>if ext_name =='.dll' or ext_name=='.exe':
<span style="white-space:pre">    </span>dllName = '%s/%s' % (dllFilePath,name)
<span style="white-space:pre">    </span>mdKey = md5_file(dllName)
<span style="white-space:pre">    </span>f.write(name)
<span style="white-space:pre">    </span>f.write('\n')
<span style="white-space:pre">    </span>f.write(mdKey)
<span style="white-space:pre">    </span>f.write('\n')
f.close()

几行代码搞定，还要算上打开文件的操作，最后txt中存放了dll或exe文件的名称与md5，为了简单奇数行是文件名称，偶数行是md5值

PS：推荐一款MD5在线加密工具 https://tool.zzvips.com/t/md5/

但是用c++来读取文件校验md5的值的话就好麻烦啊，吐槽一句：越来越不喜欢重度的语言了，越来越喜欢python了~~