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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 <netdissect-stdinc.h>
37 
38 #include "cpack.h"
39 #include "extract.h"
40 
41 const uint8_t *
cpack_next_boundary(const uint8_t * buf,const uint8_t * p,size_t alignment)42 cpack_next_boundary(const uint8_t *buf, const uint8_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 const uint8_t *
cpack_align_and_reserve(struct cpack_state * cs,size_t wordsize)57 cpack_align_and_reserve(struct cpack_state *cs, size_t wordsize)
58 {
59 	const uint8_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 /* Advance by N bytes without returning them. */
72 int
cpack_advance(struct cpack_state * cs,const size_t toskip)73 cpack_advance(struct cpack_state *cs, const size_t toskip)
74 {
75 	/* No space left? */
76 	if (cs->c_next - cs->c_buf + toskip > cs->c_len)
77 		return -1;
78 	cs->c_next += toskip;
79 	return 0;
80 }
81 
82 int
cpack_init(struct cpack_state * cs,const uint8_t * buf,size_t buflen)83 cpack_init(struct cpack_state *cs, const uint8_t *buf, size_t buflen)
84 {
85 	memset(cs, 0, sizeof(*cs));
86 
87 	cs->c_buf = buf;
88 	cs->c_len = buflen;
89 	cs->c_next = cs->c_buf;
90 
91 	return 0;
92 }
93 
94 /* Unpack a 64-bit unsigned integer. */
95 int
cpack_uint64(struct cpack_state * cs,uint64_t * u)96 cpack_uint64(struct cpack_state *cs, uint64_t *u)
97 {
98 	const uint8_t *next;
99 
100 	if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
101 		return -1;
102 
103 	*u = EXTRACT_LE_64BITS(next);
104 
105 	/* Move pointer past the uint64_t. */
106 	cs->c_next = next + sizeof(*u);
107 	return 0;
108 }
109 
110 /* Unpack a 32-bit unsigned integer. */
111 int
cpack_uint32(struct cpack_state * cs,uint32_t * u)112 cpack_uint32(struct cpack_state *cs, uint32_t *u)
113 {
114 	const uint8_t *next;
115 
116 	if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
117 		return -1;
118 
119 	*u = EXTRACT_LE_32BITS(next);
120 
121 	/* Move pointer past the uint32_t. */
122 	cs->c_next = next + sizeof(*u);
123 	return 0;
124 }
125 
126 /* Unpack a 16-bit unsigned integer. */
127 int
cpack_uint16(struct cpack_state * cs,uint16_t * u)128 cpack_uint16(struct cpack_state *cs, uint16_t *u)
129 {
130 	const uint8_t *next;
131 
132 	if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL)
133 		return -1;
134 
135 	*u = EXTRACT_LE_16BITS(next);
136 
137 	/* Move pointer past the uint16_t. */
138 	cs->c_next = next + sizeof(*u);
139 	return 0;
140 }
141 
142 /* Unpack an 8-bit unsigned integer. */
143 int
cpack_uint8(struct cpack_state * cs,uint8_t * u)144 cpack_uint8(struct cpack_state *cs, uint8_t *u)
145 {
146 	/* No space left? */
147 	if ((size_t)(cs->c_next - cs->c_buf) >= cs->c_len)
148 		return -1;
149 
150 	*u = *cs->c_next;
151 
152 	/* Move pointer past the uint8_t. */
153 	cs->c_next++;
154 	return 0;
155 }
156