gfx/2d/NumericTools.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef MOZILLA_GFX_NUMERICTOOLS_H_
   8 #define MOZILLA_GFX_NUMERICTOOLS_H_
   9
  10 #include <cstdint>
  11
  12 namespace mozilla {
  13
  14 // XXX - Move these into mfbt/MathAlgorithms.h?
  15
  16 // Returns the largest multiple of aMultiplied that's <= x.
  17 // Same as int32_t(floor(double(x) / aMultiplier)) * aMultiplier,
  18 // but faster.
  19 inline int32_t RoundDownToMultiple(int32_t x, int32_t aMultiplier) {
  20   // We don't use float division + floor because that's hard for the compiler
  21   // to optimize.
  22   int mod = x % aMultiplier;
  23   if (x > 0) {
  24     return x - mod;
  25   }
  26   return mod ? x - aMultiplier - mod : x;
  27 }
  28
  29 // Returns the smallest multiple of aMultiplied that's >= x.
  30 // Same as int32_t(ceil(double(x) / aMultiplier)) * aMultiplier,
  31 // but faster.
  32 inline int32_t RoundUpToMultiple(int32_t x, int32_t aMultiplier) {
  33   int mod = x % aMultiplier;
  34   if (x > 0) {
  35     return mod ? x + aMultiplier - mod : x;
  36   }
  37   return x - mod;
  38 }
  39
  40 inline int32_t RoundToMultiple(int32_t x, int32_t aMultiplier) {
  41   return RoundDownToMultiple(x + aMultiplier / 2, aMultiplier);
  42 }
  43
  44 }  // namespace mozilla
  45
  46 #endif /* MOZILLA_GFX_NUMERICTOOLS_H_ */