//============================================================================
//
//   SSSS    tt          lll  lll       
//  SS  SS   tt           ll   ll        
//  SS     tttttt  eeee   ll   ll   aaaa 
//   SSSS    tt   ee  ee  ll   ll      aa
//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
//  SS  SS   tt   ee      ll   ll  aa  aa
//   SSSS     ttt  eeeee llll llll  aaaaa
//
// Copyright (c) 1995-2016 by Bradford W. Mott, Stephen Anthony
// and the Stella Team
//
// This file is derived from the RSA Data Security, Inc. MD5 Message-Digest 
// Algorithm.  See the header below for copyright information.
//
// See the file "License.txt" for information on usage and redistribution of
// this file, and for a DISCLAIMER OF ALL WARRANTIES.
//
// $Id: MD5.cxx 3239 2015-12-29 19:22:46Z stephena $
//============================================================================

#include "MD5.hxx"

/*
  Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All 
  rights reserved.

  License to copy and use this software is granted provided that it
  is identified as the "RSA Data Security, Inc. MD5 Message-Digest
  Algorithm" in all material mentioning or referencing this software
  or this function.

  License is also granted to make and use derivative works provided
  that such works are identified as "derived from the RSA Data
  Security, Inc. MD5 Message-Digest Algorithm" in all material
  mentioning or referencing the derived work.

  RSA Data Security, Inc. makes no representations concerning either
  the merchantability of this software or the suitability of this
  software for any particular purpose. It is provided "as is"
  without express or implied warranty of any kind.

  These notices must be retained in any copies of any part of this
  documentation and/or software.
*/

namespace MD5 {

// Setup the types used by the MD5 routines
using POINTER = uInt8*;

// MD5 context.
struct MD5_CTX
{
  uInt32 state[4];    /* state (ABCD) */
  uInt32 count[2];    /* number of bits, modulo 2^64 (lsb first) */
  uInt8 buffer[64];   /* input buffer */
};

// 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

static void MD5Init(MD5_CTX*);
static void MD5Update(MD5_CTX*, const uInt8*, uInt32);
static void MD5Final(uInt8[16], MD5_CTX*);
static void MD5Transform(uInt32 [4], const uInt8 [64]);
static void Encode(uInt8*, uInt32*, uInt32);
static void Decode(uInt32*, const uInt8*, uInt32);

static uInt8 PADDING[64] = {
  0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

// 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) + uInt32(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define GG(a, b, c, d, x, s, ac) { \
 (a) += G ((b), (c), (d)) + (x) + uInt32(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define HH(a, b, c, d, x, s, ac) { \
 (a) += H ((b), (c), (d)) + (x) + uInt32(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define II(a, b, c, d, x, s, ac) { \
 (a) += I ((b), (c), (d)) + (x) + uInt32(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }

// MD5 initialization. Begins an MD5 operation, writing a new context.
static void MD5Init(MD5_CTX* context)
{
  context->count[0] = context->count[1] = 0;
  /* Load magic initialization constants. */
  context->state[0] = 0x67452301;
  context->state[1] = 0xefcdab89;
  context->state[2] = 0x98badcfe;
  context->state[3] = 0x10325476;
}

// MD5 block update operation. Continues an MD5 message-digest
// operation, processing another message block, and updating the
// context.
static void MD5Update(MD5_CTX* context, const uInt8* input, 
    uInt32 inputLen)
{
  uInt32 i, index, partLen;

  /* Compute number of bytes mod 64 */
  index = uInt32((context->count[0] >> 3) & 0x3F);

  /* Update number of bits */
  if ((context->count[0] += (uInt32(inputLen) << 3))
   < (uInt32(inputLen) << 3))
    context->count[1]++;
  context->count[1] += (uInt32(inputLen) >> 29);

  partLen = 64 - index;

  /* Transform as many times as possible. */
  if (inputLen >= partLen) {
    memcpy (const_cast<POINTER>(&context->buffer[index]),
            const_cast<POINTER>(input), partLen);
    MD5Transform (context->state, context->buffer);

    for (i = partLen; i + 63 < inputLen; i += 64)
      MD5Transform (context->state, &input[i]);

    index = 0;
  }
  else
    i = 0;

  /* Buffer remaining input */
  memcpy(const_cast<POINTER>(&context->buffer[index]),
         const_cast<POINTER>(&input[i]), inputLen-i);
}

// MD5 finalization. Ends an MD5 message-digest operation, writing the
// the message digest and zeroizing the context.
static void MD5Final(uInt8 digest[16], MD5_CTX* context)
{
  uInt8 bits[8];
  uInt32 index, padLen;

  /* Save number of bits */
  Encode (bits, context->count, 8);

  /* Pad out to 56 mod 64. */
  index = uInt32((context->count[0] >> 3) & 0x3f);
  padLen = (index < 56) ? (56 - index) : (120 - index);
  MD5Update (context, PADDING, padLen);

  /* Append length (before padding) */
  MD5Update (context, bits, 8);
  /* Store state in digest */
  Encode (digest, context->state, 16);

  /* Zeroize sensitive information. */
  memset (reinterpret_cast<POINTER>(context), 0, sizeof(*context));
}

// MD5 basic transformation. Transforms state based on block.
static void MD5Transform(uInt32 state[4], const uInt8 block[64])
{
  uInt32 a = state[0], b = state[1], c = state[2], d = state[3], x[16];

  Decode (x, block, 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;

  /* Zeroize sensitive information. */
  memset (reinterpret_cast<POINTER>(x), 0, sizeof(x));
}

// Encodes input (uInt32) into output (uInt8). Assumes len is
// a multiple of 4.
static void Encode(uInt8* output, uInt32* input, uInt32 len)
{
  uInt32 i, j;

  for (i = 0, j = 0; j < len; i++, j += 4) {
    output[j]   = uInt8(input[i] & 0xff);
    output[j+1] = uInt8((input[i] >> 8) & 0xff);
    output[j+2] = uInt8((input[i] >> 16) & 0xff);
    output[j+3] = uInt8((input[i] >> 24) & 0xff);
  }
}

// Decodes input (uInt8) into output (uInt32). Assumes len is
// a multiple of 4.
static void Decode(uInt32* output, const uInt8* input, uInt32 len)
{
  uInt32 i, j;

  for (i = 0, j = 0; j < len; i++, j += 4)
    output[i] = (uInt32(input[j])) | ((uInt32(input[j+1])) << 8) |
    ((uInt32(input[j+2])) << 16) | ((uInt32(input[j+3])) << 24);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
string hash(const BytePtr& buffer, uInt32 length)
{
  return hash(buffer.get(), length);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
string hash(const uInt8* buffer, uInt32 length)
{
  char hex[] = "0123456789abcdef";
  MD5_CTX context;
  uInt8 md5[16];

  MD5Init(&context);
  MD5Update(&context, buffer, length);
  MD5Final(md5, &context);

  string result;
  for(int t = 0; t < 16; ++t)
  {
    result += hex[(md5[t] >> 4) & 0x0f];
    result += hex[md5[t] & 0x0f];
  }

  return result;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
string hash(const FilesystemNode& node)
{
  BytePtr image;
  uInt32 size = 0;
  try
  {
    size = node.read(image);
  }
  catch(...)
  {
    return EmptyString;
  }

  const string& md5 = hash(image, size);
  return md5;
}

}  // Namespace MD5
