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/* Functions to compute MD5 message digest of files or memory blocks.
according to the definition of MD5 in RFC 1321 from April 1992.
Copyright (C) 1995, 1996, 1997, 1999, 2000 Free Software Foundation, Inc.
This file is part of the GNU Emacs.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */

/* Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995. */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <sys/types.h>

#if STDC_HEADERS || defined _LIBC
# include <stdlib.h>
# include <string.h>
#else
# ifndef HAVE_MEMCPY
# define memcpy(d, s, n) bcopy ((s), (d), (n))
# endif
#endif

#ifdef _LIBC
# include <endian.h>
# if __BYTE_ORDER == __BIG_ENDIAN
# define WORDS_BIG_ENDIAN 1
# endif
/* We need to keep the namespace clean so define the MD5 function
protected using leading __ . */
# define md5_init_ctx __md5_init_ctx
# define md5_process_block __md5_process_block
# define md5_process_bytes __md5_process_bytes
# define md5_finish_ctx __md5_finish_ctx
# define md5_read_ctx __md5_read_ctx
# define md5_stream __md5_stream
# define md5_buffer __md5_buffer
#endif

#include "md5.h"

#ifdef WORDS_BIG_ENDIAN
# define SWAP(n) \
(((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
#else
# define SWAP(n) (n)
#endif


/* This array contains the bytes used to pad the buffer to the next
64-byte boundary. (RFC 1321, 3.1: Step 1) */
static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ... */ };


/* Initialize structure containing state of computation.
(RFC 1321, 3.3: Step 3) */
void
md5_init_ctx (ctx)
     struct md5_ctx *ctx;
{
  ctx->A = 0x67452301;
  ctx->B = 0xefcdab89;
  ctx->C = 0x98badcfe;
  ctx->D = 0x10325476;

  ctx->total[0] = ctx->total[1] = 0;
  ctx->buflen = 0;
}

/* Put result from CTX in first 16 bytes following RESBUF. The result
must be in little endian byte order.

IMPORTANT: On some systems it is required that RESBUF is correctly
aligned for a 32 bits value. */
void *
md5_read_ctx (ctx, resbuf)
     const struct md5_ctx *ctx;
     void *resbuf;
{
  ((md5_uint32 *) resbuf)[0] = SWAP (ctx->A);
  ((md5_uint32 *) resbuf)[1] = SWAP (ctx->B);
  ((md5_uint32 *) resbuf)[2] = SWAP (ctx->C);
  ((md5_uint32 *) resbuf)[3] = SWAP (ctx->D);

  return resbuf;
}

/* Process the remaining bytes in the internal buffer and the usual
prolog according to the standard and write the result to RESBUF.

IMPORTANT: On some systems it is required that RESBUF is correctly
aligned for a 32 bits value. */
void *
md5_finish_ctx (ctx, resbuf)
     struct md5_ctx *ctx;
     void *resbuf;
{
  /* Take yet unprocessed bytes into account. */
  md5_uint32 bytes = ctx->buflen;
  size_t pad;

  /* Now count remaining bytes. */
  ctx->total[0] += bytes;
  if (ctx->total[0] < bytes)
    ++ctx->total[1];

  pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
  memcpy (&ctx->buffer[bytes], fillbuf, pad);

  /* Put the 64-bit file length in *bits* at the end of the buffer. */
  *(md5_uint32 *) &ctx->buffer[bytes + pad] = SWAP (ctx->total[0] << 3);
  *(md5_uint32 *) &ctx->buffer[bytes + pad + 4] = SWAP ((ctx->total[1] << 3) |
(ctx->total[0] >> 29));

  /* Process last bytes. */
  md5_process_block (ctx->buffer, bytes + pad + 8, ctx);

  return md5_read_ctx (ctx, resbuf);
}

/* Compute MD5 message digest for bytes read from STREAM. The
resulting message digest number will be written into the 16 bytes
beginning at RESBLOCK. */
int
md5_stream (stream, resblock)
     FILE *stream;
     void *resblock;
{
  /* Important: BLOCKSIZE must be a multiple of 64. */
#define BLOCKSIZE 4096
  struct md5_ctx ctx;
  char buffer[BLOCKSIZE + 72];
  size_t sum;

  /* Initialize the computation context. */
  md5_init_ctx (&ctx);

  /* Iterate over full file contents. */
  while (1)
    {
      /* We read the file in blocks of BLOCKSIZE bytes. One call of the
computation function processes the whole buffer so that with the
next round of the loop another block can be read. */
      size_t n;
      sum = 0;

      /* Read block. Take care for partial reads. */
      do
{
n = fread (buffer + sum, 1, BLOCKSIZE - sum, stream);

sum += n;
}
      while (sum < BLOCKSIZE && n != 0);
      if (n == 0 && ferror (stream))
        return 1;

      /* If end of file is reached, end the loop. */
      if (n == 0)
break;

      /* Process buffer with BLOCKSIZE bytes. Note that
BLOCKSIZE % 64 == 0
*/
      md5_process_block (buffer, BLOCKSIZE, &ctx);
    }

  /* Add the last bytes if necessary. */
  if (sum > 0)
    md5_process_bytes (buffer, sum, &ctx);

  /* Construct result in desired memory. */
  md5_finish_ctx (&ctx, resblock);
  return 0;
}

/* Compute MD5 message digest for LEN bytes beginning at BUFFER. The
result is always in little endian byte order, so that a byte-wise
output yields to the wanted ASCII representation of the message
digest. */
void *
md5_buffer (buffer, len, resblock)
     const char *buffer;
     size_t len;
     void *resblock;
{
  struct md5_ctx ctx;

  /* Initialize the computation context. */
  md5_init_ctx (&ctx);

  /* Process whole buffer but last len % 64 bytes. */
  md5_process_bytes (buffer, len, &ctx);

  /* Put result in desired memory area. */
  return md5_finish_ctx (&ctx, resblock);
}


void
md5_process_bytes (buffer, len, ctx)
     const void *buffer;
     size_t len;
     struct md5_ctx *ctx;
{
  /* const void aligned_buffer = buffer; */

  /* When we already have some bits in our internal buffer concatenate
both inputs first. */
  if (ctx->buflen != 0)
    {
      size_t left_over = ctx->buflen;
      size_t add = 128 - left_over > len ? len : 128 - left_over;

      /* Only put full words in the buffer. */
      add -= add % __alignof__ (md5_uint32);

      memcpy (&ctx->buffer[left_over], buffer, add);
      ctx->buflen += add;

      if (ctx->buflen > 64)
{
md5_process_block (ctx->buffer, ctx->buflen & ~63, ctx);

ctx->buflen &= 63;
/* The regions in the following copy operation cannot overlap. */
memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
ctx->buflen);
}

      buffer = (const char *) buffer + add;
      len -= add;
    }

  /* Process available complete blocks. */
  if (len > 64)
    {
      md5_process_block (buffer, len & ~63, ctx);
      buffer = (const char *) buffer + (len & ~63);
      len &= 63;
    }

  /* Move remaining bytes in internal buffer. */
  if (len > 0)
    {
      size_t left_over = ctx->buflen;

      memcpy (&ctx->buffer[left_over], buffer, len);
      left_over += len;
      if (left_over >= 64)
{
md5_process_block (ctx->buffer, 64, ctx);
left_over -= 64;
memcpy (ctx->buffer, &ctx->buffer[64], left_over);
}
      ctx->buflen = left_over;
    }
}


/* These are the four functions used in the four steps of the MD5 algorithm
and defined in the RFC 1321. The first function is a little bit optimized
(as found in Colin Plumbs public domain implementation). */
/* #define FF(b, c, d) ((b & c) | (~b & d)) */
#define FF(b, c, d) (d ^ (b & (c ^ d)))
#define FG(b, c, d) FF (d, b, c)
#define FH(b, c, d) (b ^ c ^ d)
#define FI(b, c, d) (c ^ (b | ~d))

/* Process LEN bytes of BUFFER, accumulating context into CTX.
It is assumed that LEN % 64 == 0. */

void
md5_process_block (buffer, len, ctx)
     const void *buffer;
     size_t len;
     struct md5_ctx *ctx;
{
  md5_uint32 correct_words[16];
  const md5_uint32 *words = buffer;
  size_t nwords = len / sizeof (md5_uint32);
  const md5_uint32 *endp = words + nwords;
  md5_uint32 A = ctx->A;
  md5_uint32 B = ctx->B;
  md5_uint32 C = ctx->C;
  md5_uint32 D = ctx->D;

  /* First increment the byte count. RFC 1321 specifies the possible
length of the file up to 2^64 bits. Here we only compute the
number of bytes. Do a double word increment. */
  ctx->total[0] += len;
  if (ctx->total[0] < len)
    ++ctx->total[1];

  /* Process all bytes in the buffer with 64 bytes in each round of
the loop. */
  while (words < endp)
    {
      md5_uint32 *cwp = correct_words;
      md5_uint32 A_save = A;
      md5_uint32 B_save = B;
      md5_uint32 C_save = C;
      md5_uint32 D_save = D;

      /* First round: using the given function, the context and a constant
the next context is computed. Because the algorithms processing
unit is a 32-bit word and it is determined to work on words in
little endian byte order we perhaps have to change the byte order
before the computation. To reduce the work for the next steps
we store the swapped words in the array CORRECT_WORDS. */

#define OP(a, b, c, d, s, T) \
do \
{ \
a += FF (b, c, d) + (*cwp++ = SWAP (*words)) + T; \
++words; \
CYCLIC (a, s); \
a += b; \
} \
while (0)

      /* It is unfortunate that C does not provide an operator for
cyclic rotation. Hope the C compiler is smart enough. */
#define CYCLIC(w, s) (w = (w << s) | (w >> (32 - s)))

      /* Before we start, one word to the strange constants.
They are defined in RFC 1321 as

T[i] = (int) (4294967296.0 * fabs (sin (i))), i=1..64
*/

      /* Round 1. */
      OP (A, B, C, D, 7, 0xd76aa478);
      OP (D, A, B, C, 12, 0xe8c7b756);
      OP (C, D, A, B, 17, 0x242070db);
      OP (B, C, D, A, 22, 0xc1bdceee);
      OP (A, B, C, D, 7, 0xf57c0faf);
      OP (D, A, B, C, 12, 0x4787c62a);
      OP (C, D, A, B, 17, 0xa8304613);
      OP (B, C, D, A, 22, 0xfd469501);
      OP (A, B, C, D, 7, 0x698098d8);
      OP (D, A, B, C, 12, 0x8b44f7af);
      OP (C, D, A, B, 17, 0xffff5bb1);
      OP (B, C, D, A, 22, 0x895cd7be);
      OP (A, B, C, D, 7, 0x6b901122);
      OP (D, A, B, C, 12, 0xfd987193);
      OP (C, D, A, B, 17, 0xa679438e);
      OP (B, C, D, A, 22, 0x49b40821);

      /* For the second to fourth round we have the possibly swapped words
in CORRECT_WORDS. Redefine the macro to take an additional first
argument specifying the function to use. */
#undef OP
#define OP(f, a, b, c, d, k, s, T) \
do \
{ \
a += f (b, c, d) + correct_words[k] + T; \
CYCLIC (a, s); \
a += b; \
} \
while (0)

      /* Round 2. */
      OP (FG, A, B, C, D, 1, 5, 0xf61e2562);
      OP (FG, D, A, B, C, 6, 9, 0xc040b340);
      OP (FG, C, D, A, B, 11, 14, 0x265e5a51);
      OP (FG, B, C, D, A, 0, 20, 0xe9b6c7aa);
      OP (FG, A, B, C, D, 5, 5, 0xd62f105d);
      OP (FG, D, A, B, C, 10, 9, 0x02441453);
      OP (FG, C, D, A, B, 15, 14, 0xd8a1e681);
      OP (FG, B, C, D, A, 4, 20, 0xe7d3fbc8);
      OP (FG, A, B, C, D, 9, 5, 0x21e1cde6);
      OP (FG, D, A, B, C, 14, 9, 0xc33707d6);
      OP (FG, C, D, A, B, 3, 14, 0xf4d50d87);
      OP (FG, B, C, D, A, 8, 20, 0x455a14ed);
      OP (FG, A, B, C, D, 13, 5, 0xa9e3e905);
      OP (FG, D, A, B, C, 2, 9, 0xfcefa3f8);
      OP (FG, C, D, A, B, 7, 14, 0x676f02d9);
      OP (FG, B, C, D, A, 12, 20, 0x8d2a4c8a);

      /* Round 3. */
      OP (FH, A, B, C, D, 5, 4, 0xfffa3942);
      OP (FH, D, A, B, C, 8, 11, 0x8771f681);
      OP (FH, C, D, A, B, 11, 16, 0x6d9d6122);
      OP (FH, B, C, D, A, 14, 23, 0xfde5380c);
      OP (FH, A, B, C, D, 1, 4, 0xa4beea44);
      OP (FH, D, A, B, C, 4, 11, 0x4bdecfa9);
      OP (FH, C, D, A, B, 7, 16, 0xf6bb4b60);
      OP (FH, B, C, D, A, 10, 23, 0xbebfbc70);
      OP (FH, A, B, C, D, 13, 4, 0x289b7ec6);
      OP (FH, D, A, B, C, 0, 11, 0xeaa127fa);
      OP (FH, C, D, A, B, 3, 16, 0xd4ef3085);
      OP (FH, B, C, D, A, 6, 23, 0x04881d05);
      OP (FH, A, B, C, D, 9, 4, 0xd9d4d039);
      OP (FH, D, A, B, C, 12, 11, 0xe6db99e5);
      OP (FH, C, D, A, B, 15, 16, 0x1fa27cf8);
      OP (FH, B, C, D, A, 2, 23, 0xc4ac5665);

      /* Round 4. */
      OP (FI, A, B, C, D, 0, 6, 0xf4292244);
      OP (FI, D, A, B, C, 7, 10, 0x432aff97);
      OP (FI, C, D, A, B, 14, 15, 0xab9423a7);
      OP (FI, B, C, D, A, 5, 21, 0xfc93a039);
      OP (FI, A, B, C, D, 12, 6, 0x655b59c3);
      OP (FI, D, A, B, C, 3, 10, 0x8f0ccc92);
      OP (FI, C, D, A, B, 10, 15, 0xffeff47d);
      OP (FI, B, C, D, A, 1, 21, 0x85845dd1);
      OP (FI, A, B, C, D, 8, 6, 0x6fa87e4f);
      OP (FI, D, A, B, C, 15, 10, 0xfe2ce6e0);
      OP (FI, C, D, A, B, 6, 15, 0xa3014314);
      OP (FI, B, C, D, A, 13, 21, 0x4e0811a1);
      OP (FI, A, B, C, D, 4, 6, 0xf7537e82);
      OP (FI, D, A, B, C, 11, 10, 0xbd3af235);
      OP (FI, C, D, A, B, 2, 15, 0x2ad7d2bb);
      OP (FI, B, C, D, A, 9, 21, 0xeb86d391);

      /* Add the starting values of the context. */
      A += A_save;
      B += B_save;
      C += C_save;
      D += D_save;
    }

  /* Put checksum in context given as argument. */
  ctx->A = A;
  ctx->B = B;
  ctx->C = C;
  ctx->D = D;
}
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