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 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 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 #include <stdlib.h> 37 38 inline int32_t saturatedAddition(int32_t a, int32_t b) 39 { 40 uint32_t ua = a; 41 uint32_t ub = b; 42 uint32_t result = ua + ub; 43 44 // Can only overflow if the signed bit of the two values match. If the signed 45 // bit of the result and one of the values differ it did overflow. 46 if (!((ua ^ ub) >> 31) & (result ^ ua) >> 31) 47 result = std::numeric_limits<int>::max() + (ua >> 31); 48 49 return result; 50 } 51 52 inline int32_t saturatedSubtraction(int32_t a, int32_t b) 53 { 54 uint32_t ua = a; 55 uint32_t ub = b; 56 uint32_t result = ua - ub; 57 58 // Can only overflow if the signed bit of the two values do not match. If the 59 // signed bit of the result and the first value differ it did overflow. 60 if ((ua ^ ub) >> 31 & (result ^ ua) >> 31) 61 result = std::numeric_limits<int>::max() + (ua >> 31); 62 63 return result; 64 } 65 66 #endif // SaturatedArithmetic_h 67
