external/bsd/tcpdump/dist/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  *
  13  * THIS SOFTWARE IS PROVIDED BY DAVID YOUNG ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  16  * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DAVID
  17  * YOUNG BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
  19  * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  21  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  22  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
  24  * OF SUCH DAMAGE.
  25  */
  26
  27 #define NETDISSECT_REWORKED
  28 #ifdef HAVE_CONFIG_H
  29 #include "config.h"
  30 #endif
  31
  32 #include <stdlib.h>
  33 #include <string.h>
  34 #include <tcpdump-stdinc.h>
  35
  36 #include "cpack.h"
  37 #include "extract.h"
  38
  39 uint8_t *
  40 cpack_next_boundary(uint8_t *buf, uint8_t *p, size_t alignment)
  41 {
  42         size_t misalignment = (size_t)(p - buf) % alignment;
  43
  44         if (misalignment == 0)
  45                 return p;
  46
  47         return p + (alignment - misalignment);
  48 }
  49
  50 /* Advance to the next wordsize boundary. Return NULL if fewer than
  51  * wordsize bytes remain in the buffer after the boundary.  Otherwise,
  52  * return a pointer to the boundary.
  53  */
  54 uint8_t *
  55 cpack_align_and_reserve(struct cpack_state *cs, size_t wordsize)
  56 {
  57         uint8_t *next;
  58
  59         /* Ensure alignment. */
  60         next = cpack_next_boundary(cs->c_buf, cs->c_next, wordsize);
  61
  62         /* Too little space for wordsize bytes? */
  63         if (next - cs->c_buf + wordsize > cs->c_len)
  64                 return NULL;
  65
  66         return next;
  67 }
  68
  69 /* Advance by N bytes without returning them. */
  70 int
  71 cpack_advance(struct cpack_state *cs, const size_t toskip)
  72 {
  73         /* No space left? */
  74         if (cs->c_next - cs->c_buf + toskip > cs->c_len)
  75                 return -1;
  76         cs->c_next += toskip;
  77         return 0;
  78 }
  79
  80 int
  81 cpack_init(struct cpack_state *cs, uint8_t *buf, size_t buflen)
  82 {
  83         memset(cs, 0, sizeof(*cs));
  84
  85         cs->c_buf = buf;
  86         cs->c_len = buflen;
  87         cs->c_next = cs->c_buf;
  88
  89         return 0;
  90 }
  91
  92 /* Unpack a 64-bit unsigned integer. */
  93 int
  94 cpack_uint64(struct cpack_state *cs, uint64_t *u)
  95 {
  96         uint8_t *next;
  97
  98         if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
  99                 return -1;
 100
 101         *u = EXTRACT_LE_64BITS(next);
 102
 103         /* Move pointer past the uint64_t. */
 104         cs->c_next = next + sizeof(*u);
 105         return 0;
 106 }
 107
 108 /* Unpack a 32-bit unsigned integer. */
 109 int
 110 cpack_uint32(struct cpack_state *cs, uint32_t *u)
 111 {
 112         uint8_t *next;
 113
 114         if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
 115                 return -1;
 116
 117         *u = EXTRACT_LE_32BITS(next);
 118
 119         /* Move pointer past the uint32_t. */
 120         cs->c_next = next + sizeof(*u);
 121         return 0;
 122 }
 123
 124 /* Unpack a 16-bit unsigned integer. */
 125 int
 126 cpack_uint16(struct cpack_state *cs, uint16_t *u)
 127 {
 128         uint8_t *next;
 129
 130         if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
 131                 return -1;
 132
 133         *u = EXTRACT_LE_16BITS(next);
 134
 135         /* Move pointer past the uint16_t. */
 136         cs->c_next = next + sizeof(*u);
 137         return 0;
 138 }
 139
 140 /* Unpack an 8-bit unsigned integer. */
 141 int
 142 cpack_uint8(struct cpack_state *cs, uint8_t *u)
 143 {
 144         /* No space left? */
 145         if ((size_t)(cs->c_next - cs->c_buf) >= cs->c_len)
 146                 return -1;
 147
 148         *u = *cs->c_next;
 149
 150         /* Move pointer past the uint8_t. */
 151         cs->c_next++;
 152         return 0;
 153 }