contrib/bind-9.5.2/lib/isc/bitstring.c

   1 /*
   2  * Copyright (C) 2004, 2005, 2007  Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (C) 1999-2001  Internet Software Consortium.
   4  *
   5  * Permission to use, copy, modify, and/or 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 1.17 2007/06/19 23:47:17 tbox Exp $ */
  19
  20 /*! \file */
  21
  22 #include <config.h>
  23
  24 #include <stddef.h>
  25
  26 #include <isc/magic.h>
  27 #include <isc/bitstring.h>
  28 #include <isc/util.h>
  29
  30 #define DIV8(x)                 ((x) >> 3)
  31 #define MOD8(x)                 ((x) & 0x00000007U)
  32 #define OCTETS(n)               (((n) + 7) >> 3)
  33 #define PADDED(n)               ((((n) + 7) >> 3) << 3)
  34 #define BITSET(bs, n)           (((bs)->data[DIV8(n)] & \
  35                                  (1 << (7 - MOD8(n)))) != 0)
  36 #define SETBIT(bs, n)           (bs)->data[DIV8(n)] |= (1 << (7 - MOD8(n)))
  37 #define CLEARBIT(bs, n)         (bs)->data[DIV8(n)] &= ~(1 << (7 - MOD8(n)))
  38
  39 #define BITSTRING_MAGIC         ISC_MAGIC('B', 'S', 't', 'r')
  40 #define VALID_BITSTRING(b)      ISC_MAGIC_VALID(b, BITSTRING_MAGIC)
  41
  42 void
  43 isc_bitstring_init(isc_bitstring_t *bitstring, unsigned char *data,
  44                    unsigned int length, unsigned int size, isc_boolean_t lsb0)
  45 {
  46         /*
  47          * Make 'bitstring' refer to the bitstring of 'size' bits starting
  48          * at 'data'.  'length' bits of the bitstring are valid.  If 'lsb0'
  49          * is set then, bit 0 refers to the least significant bit of the
  50          * bitstring.  Otherwise bit 0 is the most significant bit.
  51          */
  52
  53         REQUIRE(bitstring != NULL);
  54         REQUIRE(data != NULL);
  55         REQUIRE(length <= size);
  56
  57         bitstring->magic = BITSTRING_MAGIC;
  58         bitstring->data = data;
  59         bitstring->length = length;
  60         bitstring->size = size;
  61         bitstring->lsb0 = lsb0;
  62 }
  63
  64 void
  65 isc_bitstring_invalidate(isc_bitstring_t *bitstring) {
  66
  67         /*
  68          * Invalidate 'bitstring'.
  69          */
  70
  71         REQUIRE(VALID_BITSTRING(bitstring));
  72
  73         bitstring->magic = 0;
  74         bitstring->data = NULL;
  75         bitstring->length = 0;
  76         bitstring->size = 0;
  77         bitstring->lsb0 = ISC_FALSE;
  78 }
  79
  80 void
  81 isc_bitstring_copy(isc_bitstring_t *source, unsigned int sbitpos,
  82                    isc_bitstring_t *target, unsigned int tbitpos,
  83                    unsigned int n)
  84 {
  85         unsigned int tlast;
  86
  87         /*
  88          * Starting at bit 'sbitpos', copy 'n' bits from 'source' to
  89          * the 'n' bits of 'target' starting at 'tbitpos'.
  90          */
  91
  92         REQUIRE(VALID_BITSTRING(source));
  93         REQUIRE(VALID_BITSTRING(target));
  94         REQUIRE(source->lsb0 == target->lsb0);
  95         if (source->lsb0) {
  96                 REQUIRE(sbitpos <= source->length);
  97                 sbitpos = PADDED(source->size) - sbitpos;
  98                 REQUIRE(sbitpos >= n);
  99                 sbitpos -= n;
 100         } else
 101                 REQUIRE(sbitpos + n <= source->length);
 102         tlast = tbitpos + n;
 103         if (target->lsb0) {
 104                 REQUIRE(tbitpos <= target->length);
 105                 tbitpos = PADDED(target->size) - tbitpos;
 106                 REQUIRE(tbitpos >= n);
 107                 tbitpos -= n;
 108         } else
 109                 REQUIRE(tlast <= target->size);
 110
 111         if (tlast > target->length)
 112                 target->length = tlast;
 113
 114         /*
 115          * This is far from optimal...
 116          */
 117
 118         while (n > 0) {
 119                 if (BITSET(source, sbitpos))
 120                         SETBIT(target, tbitpos);
 121                 else
 122                         CLEARBIT(target, tbitpos);
 123                 sbitpos++;
 124                 tbitpos++;
 125                 n--;
 126         }
 127 }