arch/all-pc/boot/grub2-aros/grub-core/lib/adler32.c

   1 /*
   2  *  GRUB  --  GRand Unified Bootloader
   3  *  Copyright (C) 2012  Free Software Foundation, Inc.
   4  *
   5  *  GRUB is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  GRUB is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19
  20 #include <grub/dl.h>
  21 #include <grub/crypto.h>
  22
  23 GRUB_MOD_LICENSE ("GPLv3+");
  24
  25 struct adler32_context
  26 {
  27   grub_uint16_t a, b;
  28   grub_uint32_t c;
  29 };
  30
  31 static void
  32 adler32_init (void *context)
  33 {
  34   struct adler32_context *ctx = context;
  35
  36   ctx->a = 1;
  37   ctx->b = 0;
  38 }
  39
  40 #define MOD 65521
  41
  42 static grub_uint16_t
  43 mod_add (grub_uint16_t a, grub_uint16_t b)
  44 {
  45   if ((grub_uint32_t) a + (grub_uint32_t) b >= MOD)
  46     return a + b - MOD;
  47   return a + b;
  48 }
  49
  50 static void
  51 adler32_write (void *context, const void *inbuf, grub_size_t inlen)
  52 {
  53   struct adler32_context *ctx = context;
  54   const grub_uint8_t *ptr = inbuf;
  55
  56   while (inlen)
  57     {
  58       ctx->a = mod_add (ctx->a, *ptr);
  59       ctx->b = mod_add (ctx->a, ctx->b);
  60       inlen--;
  61       ptr++;
  62     }
  63 }
  64
  65 static void
  66 adler32_final (void *context __attribute__ ((unused)))
  67 {
  68 }
  69
  70 static grub_uint8_t *
  71 adler32_read (void *context)
  72 {
  73   struct adler32_context *ctx = context;
  74   if (ctx->a > MOD)
  75     ctx->a -= MOD;
  76   if (ctx->b > MOD)
  77     ctx->b -= MOD;
  78   ctx->c = grub_cpu_to_be32 (ctx->a | (ctx->b << 16));
  79   return (grub_uint8_t *) &ctx->c;
  80 }
  81
  82 static gcry_md_spec_t spec_adler32 =
  83   {
  84     "ADLER32", 0, 0, 0, 4,
  85     adler32_init, adler32_write, adler32_final, adler32_read,
  86     sizeof (struct adler32_context),
  87 #ifdef GRUB_UTIL
  88     .modname = "adler32",
  89 #endif
  90     .blocksize = 64
  91   };
  92
  93
  94 GRUB_MOD_INIT(adler32)
  95 {
  96   grub_md_register (&spec_adler32);
  97 }
  98
  99 GRUB_MOD_FINI(adler32)
 100 {
 101   grub_md_unregister (&spec_adler32);
 102 }