lib/sat-math.h

   1 /*
   2  * Copyright (c) 2008 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef SAT_MATH_H
  18 #define SAT_MATH_H 1
  19
  20 #include <assert.h>
  21 #include <limits.h>
  22
  23 /* Saturating addition: overflow yields UINT_MAX. */
  24 static inline unsigned int
  25 sat_add(unsigned int x, unsigned int y)
  26 {
  27     return x + y >= x ? x + y : UINT_MAX;
  28 }
  29
  30 /* Saturating subtraction: underflow yields 0. */
  31 static inline unsigned int
  32 sat_sub(unsigned int x, unsigned int y)
  33 {
  34     return x >= y ? x - y : 0;
  35 }
  36
  37 /* Saturating multiplication: overflow yields UINT_MAX. */
  38 static inline unsigned int
  39 sat_mul(unsigned int x, unsigned int y)
  40 {
  41     return (!y ? 0
  42             : x <= UINT_MAX / y ? x * y
  43             : UINT_MAX);
  44 }
  45
  46 #endif /* sat-math.h */