contrib/bind-9.2.4rc7/lib/isc/bitstring.c

   1 /*
   2  * Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (C) 1999-2001  Internet Software Consortium.
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
  10  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  11  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
  12  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
  13  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
  14  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  15  * PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 /* $Id: bitstring.c,v 1.12.2.1 2004/03/09 06:11:45 marka Exp $ */
  19
  20 #include <config.h>
  21
  22 #include <stddef.h>
  23
  24 #include <isc/magic.h>
  25 #include <isc/bitstring.h>
  26 #include <isc/util.h>
  27
  28 #define DIV8(x)                 ((x) >> 3)
  29 #define MOD8(x)                 ((x) & 0x00000007U)
  30 #define OCTETS(n)               (((n) + 7) >> 3)
  31 #define PADDED(n)               ((((n) + 7) >> 3) << 3)
  32 #define BITSET(bs, n)           (((bs)->data[DIV8(n)] & \
  33                                  (1 << (7 - MOD8(n)))) != 0)
  34 #define SETBIT(bs, n)           (bs)->data[DIV8(n)] |= (1 << (7 - MOD8(n)))
  35 #define CLEARBIT(bs, n)         (bs)->data[DIV8(n)] &= ~(1 << (7 - MOD8(n)))
  36
  37 #define BITSTRING_MAGIC         ISC_MAGIC('B', 'S', 't', 'r')
  38 #define VALID_BITSTRING(b)      ISC_MAGIC_VALID(b, BITSTRING_MAGIC)
  39
  40 void
  41 isc_bitstring_init(isc_bitstring_t *bitstring, unsigned char *data,
  42                    unsigned int length, unsigned int size, isc_boolean_t lsb0)
  43 {
  44         /*
  45          * Make 'bitstring' refer to the bitstring of 'size' bits starting
  46          * at 'data'.  'length' bits of the bitstring are valid.  If 'lsb0'
  47          * is set then, bit 0 refers to the least significant bit of the
  48          * bitstring.  Otherwise bit 0 is the most significant bit.
  49          */
  50
  51         REQUIRE(bitstring != NULL);
  52         REQUIRE(data != NULL);
  53         REQUIRE(length <= size);
  54
  55         bitstring->magic = BITSTRING_MAGIC;
  56         bitstring->data = data;
  57         bitstring->length = length;
  58         bitstring->size = size;
  59         bitstring->lsb0 = lsb0;
  60 }
  61
  62 void
  63 isc_bitstring_invalidate(isc_bitstring_t *bitstring) {
  64
  65         /*
  66          * Invalidate 'bitstring'.
  67          */
  68
  69         REQUIRE(VALID_BITSTRING(bitstring));
  70
  71         bitstring->magic = 0;
  72         bitstring->data = NULL;
  73         bitstring->length = 0;
  74         bitstring->size = 0;
  75         bitstring->lsb0 = ISC_FALSE;
  76 }
  77
  78 void
  79 isc_bitstring_copy(isc_bitstring_t *source, unsigned int sbitpos,
  80                    isc_bitstring_t *target, unsigned int tbitpos,
  81                    unsigned int n)
  82 {
  83         unsigned int tlast;
  84
  85         /*
  86          * Starting at bit 'sbitpos', copy 'n' bits from 'source' to
  87          * the 'n' bits of 'target' starting at 'tbitpos'.
  88          */
  89
  90         REQUIRE(VALID_BITSTRING(source));
  91         REQUIRE(VALID_BITSTRING(target));
  92         REQUIRE(source->lsb0 == target->lsb0);
  93         if (source->lsb0) {
  94                 REQUIRE(sbitpos <= source->length);
  95                 sbitpos = PADDED(source->size) - sbitpos;
  96                 REQUIRE(sbitpos >= n);
  97                 sbitpos -= n;
  98         } else
  99                 REQUIRE(sbitpos + n <= source->length);
 100         tlast = tbitpos + n;
 101         if (target->lsb0) {
 102                 REQUIRE(tbitpos <= target->length);
 103                 tbitpos = PADDED(target->size) - tbitpos;
 104                 REQUIRE(tbitpos >= n);
 105                 tbitpos -= n;
 106         } else
 107                 REQUIRE(tlast <= target->size);
 108
 109         if (tlast > target->length)
 110                 target->length = tlast;
 111
 112         /*
 113          * This is far from optimal...
 114          */
 115
 116         while (n > 0) {
 117                 if (BITSET(source, sbitpos))
 118                         SETBIT(target, tbitpos);
 119                 else
 120                         CLEARBIT(target, tbitpos);
 121                 sbitpos++;
 122                 tbitpos++;
 123                 n--;
 124         }
 125 }