/*
 * This code implements the MD5 message-digest algorithm.
 * The algorithm is due to Ron Rivest.	This code was
 * written by Colin Plumb in 1993, no copyright is claimed.
 * This code is in the public domain; do with it what you wish.
 *
 * Equivalent code is available from RSA Data Security, Inc.
 * This code has been tested against that, and is equivalent,
 * except that you don't need to include two pages of legalese
 * with every copy.
 *
 * To compute the message digest of a chunk of bytes, declare an
 * MD5Context structure, pass it to MHD_MD5Init, call MHD_MD5Update as
 * needed on buffers full of bytes, and then call MHD_MD5Final, which
 * will fill a supplied 16-byte array with the digest.
 */

/* Based on OpenBSD modifications.
 * Optimized by Karlson2k (Evgeny Grin). */

#include "md5.h"
#include <string.h>
#ifdef HAVE_MEMORY_H
#include <memory.h>
#endif /* HAVE_MEMORY_H */
#include "mhd_bithelpers.h"
#include "mhd_assert.h"


/**
 * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
 * initialization constants.
 *
 * @param ctx must be a `struct MD5Context *`
 */
void
MHD_MD5Init (void *ctx_)
{
  struct MD5Context *ctx = ctx_;

  mhd_assert (ctx != NULL);
  ctx->count = 0;
  ctx->state[0] = 0x67452301;
  ctx->state[1] = 0xefcdab89;
  ctx->state[2] = 0x98badcfe;
  ctx->state[3] = 0x10325476;
}

static void
MD5Transform (uint32_t state[4],
              const uint8_t block[MD5_BLOCK_SIZE]);


/**
 * Final wrapup, fill in digest and zero out ctx.
 *
 * @param ctx must be a `struct MD5Context *`
 */
void
MHD_MD5Final (void *ctx_,
          uint8_t digest[MD5_DIGEST_SIZE])
{
  struct MD5Context *ctx = ctx_;
  uint64_t count_bits;
  size_t have_bytes;

  mhd_assert (ctx != NULL);
  mhd_assert (digest != NULL);

  /* Convert count to 8 bytes in little endian order. */
  have_bytes = (ctx->count) & (MD5_BLOCK_SIZE - 1);

  /* Pad data */
  /* Buffer always have space for one byte or more. */
  ctx->buffer[have_bytes++] = 0x80; /* First padding byte is 0x80 */

  if (MD5_BLOCK_SIZE - have_bytes < 8)
    { /* Not enough space to put number of bits */
      while (have_bytes < MD5_BLOCK_SIZE) ctx->buffer[have_bytes++] = 0;
      MD5Transform(ctx->state, ctx->buffer);
      have_bytes = 0; /* Additional block */
    }
  /* Pad out to 56 */
  memset(ctx->buffer + have_bytes, 0, MD5_BLOCK_SIZE - have_bytes - 8);

  /* Put number of bits */
  count_bits = ctx->count << 3;
  _MHD_PUT_64BIT_LE(ctx->buffer + 56, count_bits);
  MD5Transform(ctx->state, ctx->buffer);

  /* Put digest in LE mode */
  _MHD_PUT_32BIT_LE(digest, ctx->state[0]);
  _MHD_PUT_32BIT_LE(digest + 4, ctx->state[1]);
  _MHD_PUT_32BIT_LE(digest + 8, ctx->state[2]);
  _MHD_PUT_32BIT_LE(digest + 12, ctx->state[3]);

  /* Erase buffer */
  memset(ctx, 0, sizeof(*ctx));
}


/**
 * Number of bytes in single SHA-256 word
 * used to process data
 */
#define MD5_BYTES_IN_WORD (32 / 8)

/* 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.  MHD_MD5Update blocks
 * the data and converts bytes into longwords for this routine.
 */
static void
MD5Transform (uint32_t state[4],
              const uint8_t block[MD5_BLOCK_SIZE])
{
  uint32_t a, b, c, d;

#if _MHD_BYTE_ORDER == _MHD_LITTLE_ENDIAN
  const uint32_t *in = (const uint32_t *)block;
#else
  uint32_t in[MD5_BLOCK_SIZE / MD5_BYTES_IN_WORD];
  int i;

  for (i = 0; i < MD5_BLOCK_SIZE / MD5_BYTES_IN_WORD; i++)
  {
    in[i] = _MHD_GET_32BIT_LE(block + i * MD5_BYTES_IN_WORD);
  }
#endif

  a = state[0];
  b = state[1];
  c = state[2];
  d = state[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);

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


/**
 * Update context to reflect the concatenation of another buffer full
 * of bytes.
 */
void
MHD_MD5Update (void *ctx_,
           const uint8_t *input,
           size_t len)
{
  struct MD5Context *ctx = ctx_;
  size_t have, need;

  mhd_assert (ctx != NULL);
  mhd_assert ((ctx != NULL) || (len == 0));

  /* Check how many bytes we already have and how many more we need. */
  have = (size_t)((ctx->count) & (MD5_BLOCK_SIZE - 1));
  need = MD5_BLOCK_SIZE - have;

  /* Update bytecount */
  ctx->count += (uint64_t)len;

  if (len >= need)
  {
    if (have != 0)
    {
      memcpy (ctx->buffer + have,
              input,
              need);
      MD5Transform(ctx->state, ctx->buffer);
      input += need;
      len -= need;
      have = 0;
    }

    /* Process data in MD5_BLOCK_SIZE-byte chunks. */
    while (len >= MD5_BLOCK_SIZE)
    {
      MD5Transform (ctx->state,
                    (const unsigned char *) input);
      input += MD5_BLOCK_SIZE;
      len -= MD5_BLOCK_SIZE;
    }
  }

  /* Handle any remaining bytes of data. */
  if (0 != len)
    memcpy (ctx->buffer + have,
            input,
            len);
}


/* end of md5.c */