// //////////////////////////////////////////////////////////

// md5.cpp

// Copyright (c) 2014,2015 Stephan Brumme. All rights reserved.

// see http://create.stephan-brumme.com/disclaimer.html

//

#include "md5.h"

#include "EndianPortable.h"

/// same as reset()

MD5::MD5()

{

  reset();

}

/// restart

void MD5::reset()

{

  m_numBytes   = 0;

  m_bufferSize = 0;

  // according to RFC 1321

  m_hash[0] = 0x67452301;

  m_hash[1] = 0xefcdab89;

  m_hash[2] = 0x98badcfe;

  m_hash[3] = 0x10325476;

}

namespace

{

  // mix functions for processBlock()

  inline uint32_t f1(uint32_t b, uint32_t c, uint32_t d)

  {

    return d ^ (b & (c ^ d)); // original: f = (b & c) | ((~b) & d);

  }

  inline uint32_t f2(uint32_t b, uint32_t c, uint32_t d)

  {

    return c ^ (d & (b ^ c)); // original: f = (b & d) | (c & (~d));

  }

  inline uint32_t f3(uint32_t b, uint32_t c, uint32_t d)

  {

    return b ^ c ^ d;

  }

  inline uint32_t f4(uint32_t b, uint32_t c, uint32_t d)

  {

    return c ^ (b | ~d);

  }

  inline uint32_t rotate(uint32_t a, uint32_t c)

  {

    return (a << c) | (a >> (32 - c));

  }

#if defined(__BYTE_ORDER) && (__BYTE_ORDER != 0) && (__BYTE_ORDER == __BIG_ENDIAN)

  inline uint32_t swap(uint32_t x)

  {

#if defined(__GNUC__) || defined(__clang__)

    return __builtin_bswap32(x);

#endif

#ifdef MSC_VER

    return _byteswap_ulong(x);

#endif

    return (x >> 24) |

          ((x >>  8) & 0x0000FF00) |

          ((x <<  8) & 0x00FF0000) |

           (x << 24);

  }

#endif

}

/// process 64 bytes

void MD5::processBlock(const void* data)

{

  // get last hash

  uint32_t a = m_hash[0];

  uint32_t b = m_hash[1];

  uint32_t c = m_hash[2];

  uint32_t d = m_hash[3];

  // data represented as 16x 32-bit words

  const uint32_t* words = (uint32_t*) data;

  // computations are little endian, swap data if necessary

#if defined(__BYTE_ORDER) && (__BYTE_ORDER != 0) && (__BYTE_ORDER == __BIG_ENDIAN)

#define HASH_LIB_LITTLEENDIAN(x) swap(x)

#else

#define HASH_LIB_LITTLEENDIAN(x) (x)

#endif

  // first round

  uint32_t word0  = HASH_LIB_LITTLEENDIAN(words[ 0]);

  a = rotate(a + f1(b,c,d) + word0  + 0xd76aa478,  7) + b;

  uint32_t word1  = HASH_LIB_LITTLEENDIAN(words[ 1]);

  d = rotate(d + f1(a,b,c) + word1  + 0xe8c7b756, 12) + a;

  uint32_t word2  = HASH_LIB_LITTLEENDIAN(words[ 2]);

  c = rotate(c + f1(d,a,b) + word2  + 0x242070db, 17) + d;

  uint32_t word3  = HASH_LIB_LITTLEENDIAN(words[ 3]);

  b = rotate(b + f1(c,d,a) + word3  + 0xc1bdceee, 22) + c;

  uint32_t word4  = HASH_LIB_LITTLEENDIAN(words[ 4]);

  a = rotate(a + f1(b,c,d) + word4  + 0xf57c0faf,  7) + b;

  uint32_t word5  = HASH_LIB_LITTLEENDIAN(words[ 5]);

  d = rotate(d + f1(a,b,c) + word5  + 0x4787c62a, 12) + a;

  uint32_t word6  = HASH_LIB_LITTLEENDIAN(words[ 6]);

  c = rotate(c + f1(d,a,b) + word6  + 0xa8304613, 17) + d;

  uint32_t word7  = HASH_LIB_LITTLEENDIAN(words[ 7]);

  b = rotate(b + f1(c,d,a) + word7  + 0xfd469501, 22) + c;

  uint32_t word8  = HASH_LIB_LITTLEENDIAN(words[ 8]);

  a = rotate(a + f1(b,c,d) + word8  + 0x698098d8,  7) + b;

  uint32_t word9  = HASH_LIB_LITTLEENDIAN(words[ 9]);

  d = rotate(d + f1(a,b,c) + word9  + 0x8b44f7af, 12) + a;

  uint32_t word10 = HASH_LIB_LITTLEENDIAN(words[10]);

  c = rotate(c + f1(d,a,b) + word10 + 0xffff5bb1, 17) + d;

  uint32_t word11 = HASH_LIB_LITTLEENDIAN(words[11]);

  b = rotate(b + f1(c,d,a) + word11 + 0x895cd7be, 22) + c;

  uint32_t word12 = HASH_LIB_LITTLEENDIAN(words[12]);

  a = rotate(a + f1(b,c,d) + word12 + 0x6b901122,  7) + b;

  uint32_t word13 = HASH_LIB_LITTLEENDIAN(words[13]);

  d = rotate(d + f1(a,b,c) + word13 + 0xfd987193, 12) + a;

  uint32_t word14 = HASH_LIB_LITTLEENDIAN(words[14]);

  c = rotate(c + f1(d,a,b) + word14 + 0xa679438e, 17) + d;

  uint32_t word15 = HASH_LIB_LITTLEENDIAN(words[15]);

  b = rotate(b + f1(c,d,a) + word15 + 0x49b40821, 22) + c;

  // second round

  a = rotate(a + f2(b,c,d) + word1  + 0xf61e2562,  5) + b;

  d = rotate(d + f2(a,b,c) + word6  + 0xc040b340,  9) + a;

  c = rotate(c + f2(d,a,b) + word11 + 0x265e5a51, 14) + d;

  b = rotate(b + f2(c,d,a) + word0  + 0xe9b6c7aa, 20) + c;

  a = rotate(a + f2(b,c,d) + word5  + 0xd62f105d,  5) + b;

  d = rotate(d + f2(a,b,c) + word10 + 0x02441453,  9) + a;

  c = rotate(c + f2(d,a,b) + word15 + 0xd8a1e681, 14) + d;

  b = rotate(b + f2(c,d,a) + word4  + 0xe7d3fbc8, 20) + c;

  a = rotate(a + f2(b,c,d) + word9  + 0x21e1cde6,  5) + b;

  d = rotate(d + f2(a,b,c) + word14 + 0xc33707d6,  9) + a;

  c = rotate(c + f2(d,a,b) + word3  + 0xf4d50d87, 14) + d;

  b = rotate(b + f2(c,d,a) + word8  + 0x455a14ed, 20) + c;

  a = rotate(a + f2(b,c,d) + word13 + 0xa9e3e905,  5) + b;

  d = rotate(d + f2(a,b,c) + word2  + 0xfcefa3f8,  9) + a;

  c = rotate(c + f2(d,a,b) + word7  + 0x676f02d9, 14) + d;

  b = rotate(b + f2(c,d,a) + word12 + 0x8d2a4c8a, 20) + c;

  // third round

  a = rotate(a + f3(b,c,d) + word5  + 0xfffa3942,  4) + b;

  d = rotate(d + f3(a,b,c) + word8  + 0x8771f681, 11) + a;

  c = rotate(c + f3(d,a,b) + word11 + 0x6d9d6122, 16) + d;

  b = rotate(b + f3(c,d,a) + word14 + 0xfde5380c, 23) + c;

  a = rotate(a + f3(b,c,d) + word1  + 0xa4beea44,  4) + b;

  d = rotate(d + f3(a,b,c) + word4  + 0x4bdecfa9, 11) + a;

  c = rotate(c + f3(d,a,b) + word7  + 0xf6bb4b60, 16) + d;

  b = rotate(b + f3(c,d,a) + word10 + 0xbebfbc70, 23) + c;

  a = rotate(a + f3(b,c,d) + word13 + 0x289b7ec6,  4) + b;

  d = rotate(d + f3(a,b,c) + word0  + 0xeaa127fa, 11) + a;

  c = rotate(c + f3(d,a,b) + word3  + 0xd4ef3085, 16) + d;

  b = rotate(b + f3(c,d,a) + word6  + 0x04881d05, 23) + c;

  a = rotate(a + f3(b,c,d) + word9  + 0xd9d4d039,  4) + b;

  d = rotate(d + f3(a,b,c) + word12 + 0xe6db99e5, 11) + a;

  c = rotate(c + f3(d,a,b) + word15 + 0x1fa27cf8, 16) + d;

  b = rotate(b + f3(c,d,a) + word2  + 0xc4ac5665, 23) + c;

  // fourth round

  a = rotate(a + f4(b,c,d) + word0  + 0xf4292244,  6) + b;

  d = rotate(d + f4(a,b,c) + word7  + 0x432aff97, 10) + a;

  c = rotate(c + f4(d,a,b) + word14 + 0xab9423a7, 15) + d;

  b = rotate(b + f4(c,d,a) + word5  + 0xfc93a039, 21) + c;

  a = rotate(a + f4(b,c,d) + word12 + 0x655b59c3,  6) + b;

  d = rotate(d + f4(a,b,c) + word3  + 0x8f0ccc92, 10) + a;

  c = rotate(c + f4(d,a,b) + word10 + 0xffeff47d, 15) + d;

  b = rotate(b + f4(c,d,a) + word1  + 0x85845dd1, 21) + c;

  a = rotate(a + f4(b,c,d) + word8  + 0x6fa87e4f,  6) + b;

  d = rotate(d + f4(a,b,c) + word15 + 0xfe2ce6e0, 10) + a;

  c = rotate(c + f4(d,a,b) + word6  + 0xa3014314, 15) + d;

  b = rotate(b + f4(c,d,a) + word13 + 0x4e0811a1, 21) + c;

  a = rotate(a + f4(b,c,d) + word4  + 0xf7537e82,  6) + b;

  d = rotate(d + f4(a,b,c) + word11 + 0xbd3af235, 10) + a;

  c = rotate(c + f4(d,a,b) + word2  + 0x2ad7d2bb, 15) + d;

  b = rotate(b + f4(c,d,a) + word9  + 0xeb86d391, 21) + c;

  // update hash

  m_hash[0] += a;

  m_hash[1] += b;

  m_hash[2] += c;

  m_hash[3] += d;

}

/// add arbitrary number of bytes

void MD5::add(const void* data, size_t numBytes)

{

  const uint8_t* current = (const uint8_t*) data;

  if (m_bufferSize > 0)

  {

    while (numBytes > 0 && m_bufferSize < BlockSize)

    {

      m_buffer[m_bufferSize++] = *current++;

      numBytes--;

    }

  }

  // full buffer

  if (m_bufferSize == BlockSize)

  {

    processBlock(m_buffer);

    m_numBytes  += BlockSize;

    m_bufferSize = 0;

  }

  // no more data ?

  if (numBytes == 0)

    return;

  // process full blocks

  while (numBytes >= BlockSize)

  {

    processBlock(current);

    current    += BlockSize;

    m_numBytes += BlockSize;

    numBytes   -= BlockSize;

  }

  // keep remaining bytes in buffer

  while (numBytes > 0)

  {

    m_buffer[m_bufferSize++] = *current++;

    numBytes--;

  }

}

/// process final block, less than 64 bytes

void MD5::processBuffer()

{

  // the input bytes are considered as bits strings, where the first bit is the most significant bit of the byte

  // - append "1" bit to message

  // - append "0" bits until message length in bit mod 512 is 448

  // - append length as 64 bit integer

  // number of bits

  size_t paddedLength = m_bufferSize * 8;

  // plus one bit set to 1 (always appended)

  paddedLength++;

  // number of bits must be (numBits % 512) = 448

  size_t lower11Bits = paddedLength & 511;

  if (lower11Bits <= 448)

    paddedLength +=       448 - lower11Bits;

  else

    paddedLength += 512 + 448 - lower11Bits;

  // convert from bits to bytes

  paddedLength /= 8;

  // only needed if additional data flows over into a second block

  unsigned char extra[BlockSize];

  // append a "1" bit, 128 => binary 10000000

  if (m_bufferSize < BlockSize)

    m_buffer[m_bufferSize] = 128;

  else

    extra[0] = 128;

  size_t i;

  for (i = m_bufferSize + 1; i < BlockSize; i++)

    m_buffer[i] = 0;

  for (; i < paddedLength; i++)

    extra[i - BlockSize] = 0;

  // add message length in bits as 64 bit number

  uint64_t msgBits = 8 * (m_numBytes + m_bufferSize);

  // find right position

  unsigned char* addLength;

  if (paddedLength < BlockSize)

    addLength = m_buffer + paddedLength;

  else

    addLength = extra + paddedLength - BlockSize;

  // must be little endian

  *addLength++ = msgBits & 0xFF; msgBits >>= 8;

  *addLength++ = msgBits & 0xFF; msgBits >>= 8;

  *addLength++ = msgBits & 0xFF; msgBits >>= 8;

  *addLength++ = msgBits & 0xFF; msgBits >>= 8;

  *addLength++ = msgBits & 0xFF; msgBits >>= 8;

  *addLength++ = msgBits & 0xFF; msgBits >>= 8;

  *addLength++ = msgBits & 0xFF; msgBits >>= 8;

  *addLength++ = msgBits & 0xFF;

  // process blocks

  processBlock(m_buffer);

  // flowed over into a second block ?

  if (paddedLength > BlockSize)

    processBlock(extra);

}

/// return latest hash as 32 hex characters

std::string MD5::getHash()

{

  // compute hash (as raw bytes)

  unsigned char rawHash[HashBytes];

  getHash(rawHash);

  // convert to hex string

  std::string result;

  result.reserve(2 * HashBytes);

  for (int i = 0; i < HashBytes; i++)

  {

    static const char dec2hex[16+1] = "0123456789abcdef";

    result += dec2hex[(rawHash[i] >> 4) & 15];

    result += dec2hex[ rawHash[i]       & 15];

  }

  return result;

}

/// return latest hash as bytes

void MD5::getHash(unsigned char buffer[MD5::HashBytes])

{

  // save old hash if buffer is partially filled

  uint32_t oldHash[HashValues];

  for (int i = 0; i < HashValues; i++)

    oldHash[i] = m_hash[i];

  // process remaining bytes

  processBuffer();

  unsigned char* current = buffer;

  for (int i = 0; i < HashValues; i++)

  {

    *current++ =  m_hash[i]        & 0xFF;

    *current++ = (m_hash[i] >>  8) & 0xFF;

    *current++ = (m_hash[i] >> 16) & 0xFF;

    *current++ = (m_hash[i] >> 24) & 0xFF;

    // restore old hash

    m_hash[i] = oldHash[i];

  }

}

/// compute MD5 of a memory block

std::string MD5::operator()(const void* data, size_t numBytes)

{

  reset();

  add(data, numBytes);

  return getHash();

}

/// compute MD5 of a string, excluding final zero

std::string MD5::operator()(const std::string& text)

{

  reset();

  add(text.c_str(), text.size());

  return getHash();

}