1 /*
2 * Copyright (c) 2012, Google Inc. 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 are
6 * met:
7 *
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 * * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #ifndef SaturatedArithmetic_h
32 #define SaturatedArithmetic_h
33
34 #include <limits>
35 #include <stdint.h>
36
saturatedAddition(int32_t a,int32_t b)37 ALWAYS_INLINE int32_t saturatedAddition(int32_t a, int32_t b)
38 {
39 uint32_t ua = a;
40 uint32_t ub = b;
41 uint32_t result = ua + ub;
42
43 // Can only overflow if the signed bit of the two values match. If the signed
44 // bit of the result and one of the values differ it did overflow.
45 if (!((ua ^ ub) >> 31) & (result ^ ua) >> 31)
46 result = std::numeric_limits<int>::max() + (ua >> 31);
47
48 return result;
49 }
50
saturatedSubtraction(int32_t a,int32_t b)51 ALWAYS_INLINE int32_t saturatedSubtraction(int32_t a, int32_t b)
52 {
53 uint32_t ua = a;
54 uint32_t ub = b;
55 uint32_t result = ua - ub;
56
57 // Can only overflow if the signed bit of the two values do not match. If the
58 // signed bit of the result and the first value differ it did overflow.
59 if ((ua ^ ub) >> 31 & (result ^ ua) >> 31)
60 result = std::numeric_limits<int>::max() + (ua >> 31);
61
62 return result;
63 }
64
65 #endif // SaturatedArithmetic_h
66