/**
 * @file md5.h
 * @The header file of md5.
 * @author Jiewei Wei
 * @mail weijieweijerry@163.com
 * @github https://github.com/JieweiWei
 * @data Oct 19 2014
 *
 */

#ifndef MD5_H
#define MD5_H

/* Parameters of MD5. */
#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

/**
 * @Basic MD5 functions.
 *
 * @param there bit32.
 *
 * @return one bit32.
 */
#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.
 *
 * @param {num} the raw number.
 *
 * @param {n} rotate left n.
 *
 * @return the number after rotated left.
 */
#define ROTATELEFT(num, n) (((num) << (n)) | ((num) >> (32-(n))))

/**
 * @Transformations for rounds 1, 2, 3, and 4.
 */
#define FF(a, b, c, d, x, s, ac) { \
  (a) += F ((b), (c), (d)) + (x) + ac; \
  (a) = ROTATELEFT ((a), (s)); \
  (a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
  (a) += G ((b), (c), (d)) + (x) + ac; \
  (a) = ROTATELEFT ((a), (s)); \
  (a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
  (a) += H ((b), (c), (d)) + (x) + ac; \
  (a) = ROTATELEFT ((a), (s)); \
  (a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
  (a) += I ((b), (c), (d)) + (x) + ac; \
  (a) = ROTATELEFT ((a), (s)); \
  (a) += (b); \
}

#include <string>
#include <cstring>

using std::string;

/* Define of btye.*/
typedef unsigned char byte;
/* Define of byte. */
typedef unsigned int bit32;

class MD5 {
public:
    /* Construct a MD5 object with a string. */
    MD5(const string& message);

    /* Generate md5 digest. */
    const byte* getDigest();

    /* Convert digest to string value */
    string toStr();

private:
    /* Initialization the md5 object, processing another message block,
     * and updating the context.*/
    void init(const byte* input, size_t len);

    /* MD5 basic transformation. Transforms state based on block. */
    void transform(const byte block[64]);

    /* Encodes input (usigned long) into output (byte). */
    void encode(const bit32* input, byte* output, size_t length);

    /* Decodes input (byte) into output (usigned long). */
    void decode(const byte* input, bit32* output, size_t length);

private:
    /* Flag for mark whether calculate finished. */
    bool finished;

    /* state (ABCD). */
    bit32 state[4];

    /* number of bits, low-order word first. */
    bit32 count[2];

    /* input buffer. */
    byte buffer[64];

    /* message digest. */
    byte digest[16];

    /* padding for calculate. */
    static const byte PADDING[64];

    /* Hex numbers. */
    static const char HEX_NUMBERS[16];
};

#endif // MD5_H