contrib/tcpdump/cpack.c

   1 /*-
   2  * Copyright (c) 2003, 2004 David Young.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  * 3. The name of David Young may not be used to endorse or promote
  13  *    products derived from this software without specific prior
  14  *    written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY DAVID YOUNG ``AS IS'' AND ANY
  17  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  18  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  19  * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DAVID
  20  * YOUNG BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  21  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
  22  * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  25  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
  27  * OF SUCH DAMAGE.
  28  */
  29
  30 #ifdef HAVE_CONFIG_H
  31 #include "config.h"
  32 #endif
  33
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include <tcpdump-stdinc.h>
  37
  38 #include "cpack.h"
  39 #include "extract.h"
  40
  41 static u_int8_t *
  42 cpack_next_boundary(u_int8_t *buf, u_int8_t *p, size_t alignment)
  43 {
  44         size_t misalignment = (size_t)(p - buf) % alignment;
  45
  46         if (misalignment == 0)
  47                 return p;
  48
  49         return p + (alignment - misalignment);
  50 }
  51
  52 /* Advance to the next wordsize boundary. Return NULL if fewer than
  53  * wordsize bytes remain in the buffer after the boundary.  Otherwise,
  54  * return a pointer to the boundary.
  55  */
  56 static u_int8_t *
  57 cpack_align_and_reserve(struct cpack_state *cs, size_t wordsize)
  58 {
  59         u_int8_t *next;
  60
  61         /* Ensure alignment. */
  62         next = cpack_next_boundary(cs->c_buf, cs->c_next, wordsize);
  63
  64         /* Too little space for wordsize bytes? */
  65         if (next - cs->c_buf + wordsize > cs->c_len)
  66                 return NULL;
  67
  68         return next;
  69 }
  70
  71 int
  72 cpack_init(struct cpack_state *cs, u_int8_t *buf, size_t buflen)
  73 {
  74         memset(cs, 0, sizeof(*cs));
  75
  76         cs->c_buf = buf;
  77         cs->c_len = buflen;
  78         cs->c_next = cs->c_buf;
  79
  80         return 0;
  81 }
  82
  83 /* Unpack a 64-bit unsigned integer. */
  84 int
  85 cpack_uint64(struct cpack_state *cs, u_int64_t *u)
  86 {
  87         u_int8_t *next;
  88
  89         if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
  90                 return -1;
  91
  92         *u = EXTRACT_LE_64BITS(next);
  93
  94         /* Move pointer past the u_int64_t. */
  95         cs->c_next = next + sizeof(*u);
  96         return 0;
  97 }
  98
  99 /* Unpack a 32-bit unsigned integer. */
 100 int
 101 cpack_uint32(struct cpack_state *cs, u_int32_t *u)
 102 {
 103         u_int8_t *next;
 104
 105         if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
 106                 return -1;
 107
 108         *u = EXTRACT_LE_32BITS(next);
 109
 110         /* Move pointer past the u_int32_t. */
 111         cs->c_next = next + sizeof(*u);
 112         return 0;
 113 }
 114
 115 /* Unpack a 16-bit unsigned integer. */
 116 int
 117 cpack_uint16(struct cpack_state *cs, u_int16_t *u)
 118 {
 119         u_int8_t *next;
 120
 121         if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
 122                 return -1;
 123
 124         *u = EXTRACT_LE_16BITS(next);
 125
 126         /* Move pointer past the u_int16_t. */
 127         cs->c_next = next + sizeof(*u);
 128         return 0;
 129 }
 130
 131 /* Unpack an 8-bit unsigned integer. */
 132 int
 133 cpack_uint8(struct cpack_state *cs, u_int8_t *u)
 134 {
 135         /* No space left? */
 136         if ((size_t)(cs->c_next - cs->c_buf) >= cs->c_len)
 137                 return -1;
 138
 139         *u = *cs->c_next;
 140
 141         /* Move pointer past the u_int8_t. */
 142         cs->c_next++;
 143         return 0;
 144 }