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1 office 1 /**
2 * @file overflow.h
3 * @author Ambroz Bizjak <ambrop7@gmail.com>
4 *
5 * @section LICENSE
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the author nor the
15 * names of its contributors may be used to endorse or promote products
16 * derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
25 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
27 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 * @section DESCRIPTION
30 *
31 * Functions for checking for overflow of integer addition.
32 */
33  
34 #ifndef BADVPN_MISC_OVERFLOW_H
35 #define BADVPN_MISC_OVERFLOW_H
36  
37 #include <limits.h>
38 #include <stdint.h>
39  
40 #define DEFINE_UNSIGNED_OVERFLOW(_name, _type, _max) \
41 static int add_ ## _name ## _overflows (_type a, _type b) \
42 {\
43 return (b > _max - a); \
44 }
45  
46 #define DEFINE_SIGNED_OVERFLOW(_name, _type, _min, _max) \
47 static int add_ ## _name ## _overflows (_type a, _type b) \
48 {\
49 if ((a < 0) ^ (b < 0)) return 0; \
50 if (a < 0) return -(a < _min - b); \
51 return (a > _max - b); \
52 }
53  
54 DEFINE_UNSIGNED_OVERFLOW(uint, unsigned int, UINT_MAX)
55 DEFINE_UNSIGNED_OVERFLOW(uint8, uint8_t, UINT8_MAX)
56 DEFINE_UNSIGNED_OVERFLOW(uint16, uint16_t, UINT16_MAX)
57 DEFINE_UNSIGNED_OVERFLOW(uint32, uint32_t, UINT32_MAX)
58 DEFINE_UNSIGNED_OVERFLOW(uint64, uint64_t, UINT64_MAX)
59  
60 DEFINE_SIGNED_OVERFLOW(int, int, INT_MIN, INT_MAX)
61 DEFINE_SIGNED_OVERFLOW(int8, int8_t, INT8_MIN, INT8_MAX)
62 DEFINE_SIGNED_OVERFLOW(int16, int16_t, INT16_MIN, INT16_MAX)
63 DEFINE_SIGNED_OVERFLOW(int32, int32_t, INT32_MIN, INT32_MAX)
64 DEFINE_SIGNED_OVERFLOW(int64, int64_t, INT64_MIN, INT64_MAX)
65  
66 #endif