/* -----------------------------------------------------------------------------
The copyright in this software is being made available under the Clear BSD
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other Intellectual Property Rights other than the copyrights concerning 
the Software are granted under this license.

The Clear BSD License

Copyright (c) 2018-2026, Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. & The VVdeC Authors.
All rights reserved.

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are permitted (subject to the limitations in the disclaimer below) provided that
the following conditions are met:

     * Redistributions of source code must retain the above copyright notice,
     this list of conditions and the following disclaimer.

     * Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the distribution.

     * Neither the name of the copyright holder nor the names of its
     contributors may be used to endorse or promote products derived from this
     software without specific prior written permission.

NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED BY
THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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------------------------------------------------------------------------------------------- */

#pragma once

#include <stdio.h>
#include <string>
#include <stdint.h>
#include <cstring>

namespace vvdec
{

static const uint32_t MD5_DIGEST_STRING_LENGTH=16;

#ifndef __BIG_ENDIAN__
# define byteReverse(buf, len)    /* Nothing */
#else
static void byteReverse(uint32_t *buf, unsigned len);
/*
 * Note: this code is harmless on little-endian machines.
 */
static void byteReverse(uint32_t *buf, unsigned len)
{
  uint32_t t;
  do {
    char* bytes = (char *) buf;
    t = ((unsigned) bytes[3] << 8 | bytes[2]) << 16 |
        ((unsigned) bytes[1] << 8 | bytes[0]);
    *buf = t;
    buf++;
  } while (--len);
}
#endif

namespace libmd5 {


class MD5
{

public:
  typedef struct _context_md5_t {
    uint32_t buf[4];
    uint32_t bits[2];
    union {
      unsigned char b8[64];
      uint32_t b32[16];
    } in;
  } context_md5_t;


public:
  /**
   * initialize digest state
   */
  MD5()
  {
    ctx.buf[0] = 0x67452301;
    ctx.buf[1] = 0xefcdab89;
    ctx.buf[2] = 0x98badcfe;
    ctx.buf[3] = 0x10325476;

    ctx.bits[0] = 0;
    ctx.bits[1] = 0;
  }

  /**
   * compute digest over buf of length len.
   * multiple calls may extend the digest over more data.
   */
  void update(unsigned char *buf, unsigned len)
  {
    uint32_t t;

    /* Update bitcount */

    t = ctx.bits[0];
    if ((ctx.bits[0] = t + ((uint32_t) len << 3)) < t)
      ctx.bits[1]++;        /* Carry from low to high */
    ctx.bits[1] += len >> 29;

    t = (t >> 3) & 0x3f;    /* Bytes already in shsInfo->data */

    /* Handle any leading odd-sized chunks */

    if (t) {
      unsigned char *p = ctx.in.b8 + t;

      t = 64 - t;
      if (len < t) {
        ::memcpy(p, buf, len);
        return;
      }
      memcpy(p, buf, t);
      byteReverse(ctx.in.b32, 16);
      MD5Transform(ctx.buf, ctx.in.b32);
      buf += t;
      len -= t;
    }
    /* Process data in 64-byte chunks */

    while (len >= 64) {
      memcpy(ctx.in.b8, buf, 64);
      byteReverse(ctx.in.b32, 16);
      MD5Transform(ctx.buf, ctx.in.b32);
      buf += 64;
      len -= 64;
    }

      /* Handle any remaining bytes of data. */

    memcpy(ctx.in.b8, buf, len);
  }

  /**
   * flush any outstanding MD5 data, write the digest into digest.
   */
  void finalize(unsigned char digest[MD5_DIGEST_STRING_LENGTH])
  {
    unsigned count;
    unsigned char *p;

    /* Compute number of bytes mod 64 */
    count = (ctx.bits[0] >> 3) & 0x3F;

    /* Set the first char of padding to 0x80.  This is safe since there is
       always at least one byte free */
    p = ctx.in.b8 + count;
    *p++ = 0x80;

    /* Bytes of padding needed to make 64 bytes */
    count = 64 - 1 - count;

    /* Pad out to 56 mod 64 */
    if (count < 8) {
      /* Two lots of padding:  Pad the first block to 64 bytes */
      memset(p, 0, count);
      byteReverse(ctx.in.b32, 16);
      MD5Transform(ctx.buf, ctx.in.b32);

      /* Now fill the next block with 56 bytes */
      memset(ctx.in.b8, 0, 56);
    } else {
      /* Pad block to 56 bytes */
      memset(p, 0, count - 8);
    }
    byteReverse(ctx.in.b32, 14);

    /* Append length in bits and transform */
    ctx.in.b32[14] = ctx.bits[0];
    ctx.in.b32[15] = ctx.bits[1];

    MD5Transform(ctx.buf, ctx.in.b32);
    byteReverse((uint32_t *) ctx.buf, 4);
    memcpy(digest, ctx.buf, 16);

    memset(&ctx, 0, sizeof( ctx));    /* In case it's sensitive */
    /* The original version of this code omitted the asterisk. In
       effect, only the first part of ctx was wiped with zeros, not
       the whole thing. Bug found by Derek Jones. Original line: */
    // memset(ctx, 0, sizeof(ctx));    /* In case it's sensitive */
  }


private:


  /* The four core functions - F1 is optimized somewhat */

  /* #define F1(x, y, z) (x & y | ~x & z) */
  #define F1(x, y, z) (z ^ (x & (y ^ z)))
  #define F2(x, y, z) F1(z, x, y)
  #define F3(x, y, z) (x ^ y ^ z)
  #define F4(x, y, z) (y ^ (x | ~z))

  /* This is the central step in the MD5 algorithm. */
  #define MD5STEP(f, w, x, y, z, data, s) \
      ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )


  /*
   * The core of the MD5 algorithm, this alters an existing MD5 hash to
   * reflect the addition of 16 longwords of new data.  MD5Update blocks
   * the data and converts bytes into longwords for this routine.
   */
  static void MD5Transform(uint32_t buf[4], uint32_t const in[16])
  {
    uint32_t a, b, c, d;

    a = buf[0];
    b = buf[1];
    c = buf[2];
    d = buf[3];

    MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
    MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
    MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
    MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
    MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
    MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
    MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
    MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
    MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
    MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
    MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
    MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
    MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
    MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
    MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
    MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);

    MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
    MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
    MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
    MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
    MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
    MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
    MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
    MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
    MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
    MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
    MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
    MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
    MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
    MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
    MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
    MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);

    MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
    MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
    MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
    MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
    MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
    MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
    MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
    MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
    MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
    MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
    MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
    MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
    MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
    MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
    MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
    MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);

    MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
    MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
    MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
    MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
    MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
    MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
    MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
    MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
    MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
    MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
    MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
    MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
    MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
    MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
    MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
    MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);

    buf[0] += a;
    buf[1] += b;
    buf[2] += c;
    buf[3] += d;
  }

private:
  context_md5_t ctx;
};

}

} // namespace
