text: /*
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version 2
   * of the License, or (at your option) any later version.
   *
   * This program 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 General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
   * Copyright (C) 1995 Software Foundation, Inc.
   *
   * Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>.
   */
  
  /** \file
   * \ingroup bli
   *
   *  Functions to compute MD5 message digest of files or memory blocks
   *  according to the definition of MD5 in RFC 1321 from April 1992.
   */
  
  #include <stdlib.h>
  #include <string.h>
  #include <stdio.h>
  #include <sys/types.h>
  
  #include "BLI_hash_md5.h" /* own include */
  
  #if defined HAVE_LIMITS_H || defined _LIBC
  #  include <limits.h>
  #endif
  
  /* The following contortions are an attempt to use the C preprocessor to determine an unsigned
   * integral type that is 32 bits wide.
   * An alternative approach is to use autoconf's AC_CHECK_SIZEOF macro, but doing that would require
   * that the configure script compile and *run* the resulting executable.
   * Locally running cross-compiled executables is usually not possible.
   */
  
  #if defined __STDC__ && __STDC__
  #  define UINT_MAX_32_BITS 4294967295U
  #else
  #  define UINT_MAX_32_BITS 0xFFFFFFFF
  #endif
  
  /* If UINT_MAX isn't defined, assume it's a 32-bit type.
   * This should be valid for all systems GNU cares about
   * because that doesn't include 16-bit systems, and only modern systems
   * (that certainly have <limits.h>) have 64+-bit integral types.
   */
  
  #ifndef UINT_MAX
  #  define UINT_MAX UINT_MAX_32_BITS
  #endif
  
  #if UINT_MAX == UINT_MAX_32_BITS
  typedef unsigned int md5_uint32;
  #else
  #  if USHRT_MAX == UINT_MAX_32_BITS
  typedef unsigned short md5_uint32;
  #  else
  #    if ULONG_MAX == UINT_MAX_32_BITS
  typedef unsigned long md5_uint32;
  #    else
  /* The following line is intended to evoke an error. Using #error is not portable enough. */
  "Cannot determine unsigned 32-bit data type."
  #    endif
  #  endif
  #endif
  
  /* Following code is low level, upon which are built up the functions
   * 'BLI_hash_md5_stream' and 'BLI_hash_md5_buffer'. */
  
  /* Structure to save state of computation between the single steps. */
  struct md5_ctx {
    md5_uint32 A;
    md5_uint32 B;
    md5_uint32 C;
    md5_uint32 D;
  };
  
  #ifdef __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)
   */
  static void md5_init_ctx(struct md5_ctx *ctx)
  {
    ctx->A = 0x67452301;
    ctx->B = 0xefcdab89;
    ctx->C = 0x98badcfe;
    ctx->D = 0x10325476;
  }
  
  /**
   * Starting with the result of former calls of this function (or the initialization),
   * this function updates the 'ctx' context for the next 'len' bytes starting at 'buffer'.
   * It is necessary that 'len' is a multiple of 64!!!
   */
  static void md5_process_block(const void *buffer, size_t len, struct md5_ctx *ctx)
  {
  /* 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))
  
  /* 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)))
  
    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;
  
    /* 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) \
    a += FF(b, c, d) + (*cwp++ = SWAP(*words)) + T; \
    ++words; \
    CYCLIC(a, s); \
    a += b; \
    (void)0
  
      /* 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);
  
  #undef OP
  
      /* 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.
       */
  #define OP(f, a, b, c, d, k, s, T) \
    a += f(b, c, d) + correct_words[k] + T; \
    CYCLIC(a, s); \
    a += b; \
    (void)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);
  
  #undef OP
  
      /* 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;
  
  #undef FF
  #undef FG
  #undef FH
  #undef FI
  #undef CYCLIC
  }
  
  /**
   * Put result from 'ctx' in first 16 bytes of 'resbuf'.
   * 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.
   */
  static void *md5_read_ctx(const struct md5_ctx *ctx, void *resbuf)
  {
    md5_uint32 *digest = resbuf;
    digest[0] = SWAP(ctx->A);
    digest[1] = SWAP(ctx->B);
    digest[2] = SWAP(ctx->C);
    digest[3] = SWAP(ctx->D);
  
    return resbuf;
  }
  
  /* Top level public functions. */
  
  /** Compute MD5 message digest for bytes read from 'stream'.
   *  The resulting message digest number will be written into the 16 bytes beginning at 'resblock'.
   * \return Non-zero if an error occurred.
   */
  int BLI_hash_md5_stream(FILE *stream, void *resblock)
  {
  #define BLOCKSIZE 4096 /* Important: must be a multiple of 64. */
    struct md5_ctx ctx;
    md5_uint32 len[2];
    char buffer[BLOCKSIZE + 72];
    size_t pad, sum;
  
    /* Initialize the computation context. */
    md5_init_ctx(&ctx);
  
    len[0] = 0;
    len[1] = 0;
  
    /* 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, 1, BLOCKSIZE - sum, stream);
        sum += n;
      } while (sum < BLOCKSIZE && n != 0);
  
      if (n == 0 && ferror(stream)) {
        return 1;
      }
  
      /* 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.
       */
      len[0] += sum;
      if (len[0] < sum) {
        ++len[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);
    }
  
    /* We can copy 64 bytes because the buffer is always big enough.
     * 'fillbuf' contains the needed bits. */
    memcpy(&buffer[sum], fillbuf, 64);
  
    /* Compute amount of padding bytes needed. Alignment is done to (N + PAD) % 64 == 56.
     * There is always at least one byte padded, i.e. if the alignment is correctly aligned,
     * 64 padding bytes are added.
     */
    pad = sum & 63;
    pad = pad >= 56 ? 64 + 56 - pad : 56 - pad;
  
    /* Put the 64-bit file length in *bits* at the end of the buffer. */
    *(md5_uint32 *)&buffer[sum + pad] = SWAP(len[0] << 3);
    *(md5_uint32 *)&buffer[sum + pad + 4] = SWAP((len[1] << 3) | (len[0] >> 29));
  
    /* Process last bytes.  */
    md5_process_block(buffer, sum + pad + 8, &ctx);
  
    /* Construct result in desired memory.  */
    md5_read_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 *BLI_hash_md5_buffer(const char *buffer, size_t len, void *resblock)
  {
    struct md5_ctx ctx;
    char restbuf[64 + 72];
    size_t blocks = len & ~63;
    size_t pad, rest;
  
    /* Initialize the computation context.  */
    md5_init_ctx(&ctx);
  
    /* Process whole buffer but last len % 64 bytes.  */
    md5_process_block(buffer, blocks, &ctx);
  
    /* REST bytes are not processed yet.  */
    rest = len - blocks;
    /* Copy to own buffer.  */
    memcpy(restbuf, &buffer[blocks], rest);
    /* Append needed fill bytes at end of buffer.
     * We can copy 64 bytes because the buffer is always big enough. */
    memcpy(&restbuf[rest], fillbuf, 64);
  
    /* PAD bytes are used for padding to correct alignment.
     * Note that always at least one byte is padded. */
    pad = rest >= 56 ? 64 + 56 - rest : 56 - rest;
  
    /* Put length of buffer in *bits* in last eight bytes. */
    *(md5_uint32 *)&restbuf[rest + pad] = (md5_uint32)SWAP(len << 3);
    *(md5_uint32 *)&restbuf[rest + pad + 4] = (md5_uint32)SWAP(len >> 29);
  
    /* Process last bytes. */
    md5_process_block(restbuf, rest + pad + 8, &ctx);
  
    /* Put result in desired memory area. */
    return md5_read_ctx(&ctx, resblock);
  }
  
  char *BLI_hash_md5_to_hexdigest(void *resblock, char r_hex_digest[33])
  {
    static const char hex_map[17] = "0123456789abcdef";
    const unsigned char *p;
    char *q;
    short len;
  
    for (q = r_hex_digest, p = (const unsigned char *)resblock, len = 0; len < 16; ++p, ++len) {
      const unsigned char c = *p;
      *q++ = hex_map[c >> 4];
      *q++ = hex_map[c & 15];
    }
    *q = '\0';
  
    return r_hex_digest;
  }
  