C++ 遞歸遍歷文件並計算MD5的實例代碼

  #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];
    enum { 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;
    }

    int main() {

         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;
    }

/*	遍歷目錄下所有文件,對比 md5
	path：文件夾路徑（末尾不要有‘\‘）
	format：要篩選的文件後綴名
	str_md5：md5 字符串
	isFound：是否匹配到與 str_md5 相等的 md5 值
*/ 
void findAllFile_MD5(const char * path,const char * format,string str_md5,BOOL &isFound)
{
	// 路徑末尾追加 ‘\*.*‘
    char newpath[200];
    strcpy(newpath, path);
    strcat(newpath, "\\*.*");
    
   // 找到目錄下的第一個文件 #include <io.h>
	_finddata_t findData;
	/*	文件信息結構體
		struct _finddata_t{
             unsigned attrib;			// 文件屬性
             time_t time_create;		// 創建時的時間戳
             time_t time_access;		// 最後一次被訪問時的時間戳
             time_t time_write;			// 最後一次被修改時的時間戳
             _fsize_t size;				// 文件字節大小
             char name[_MAX_FNAME];		// 文件名
        };
	*/
	long handle = _findfirst(newpath, &findData);
	if (handle == -1){return;}     
     
	// 遍歷文件和文件夾
    while (_findnext(handle, &findData) == 0){
        // 文件夾
		if (findData.attrib & _A_SUBDIR){
			// 文件夾名不能有敏感字符 ‘.‘、‘..‘
			if (strcmp(findData.name, ".") == 0 || strcmp(findData.name, "..") == 0){continue;}
                
			// 進入這個文件夾繼續遍歷
            strcpy(newpath, path);
            strcat(newpath, "\\");
            strcat(newpath, findData.name);
            findAllFile_MD5(newpath,format,str_md5,isFound);
		}
		// 文件
        else{
			// 判斷是不是指定後綴的文件
            if(strstr( findData.name,format)){    
                // 輸出（用來測試）
				//cout << "findData.size = " << findData.size << endl;
				//cout << "findData.name = " << findData.name << endl;
				//cout << "path = " << path << endl;
				
				// 取文件全路徑
				string str_fullPath = path;
				str_fullPath+="\\"; str_fullPath+=findData.name;

				// 取文件 md5,判斷是否匹配特征
				MD5 md5;
				md5.reset();
				md5.update(ifstream(str_fullPath));
				if(md5.toString() == str_md5){isFound = TRUE;}
            }
        }
    }

	// 關閉搜索句柄
    _findclose(handle);    
}

	// 獲取 %temp% 目錄
	TCHAR lpTempPathBuffer[MAX_PATH];
	GetTempPath(MAX_PATH,lpTempPathBuffer);

	// 刪除末尾 ‘\‘
	string str_tempPath = lpTempPathBuffer;
	str_tempPath = str_tempPath.substr(0,str_tempPath.length()-1);

	// 遍歷目錄下所有 exe 文件,匹配 MD5
	BOOL isFound = FALSE;
	findAllFile_MD5(stringToCharP(str_tempPath),".exe","52f5ce92c6f72c7e193b560bf4e76330",isFound);
	if(isFound){cout << "找到瞭！" << endl;;}

#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);
}