1 /*
2 * Copyright 2006 The Android Open Source Project
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #ifndef SkMath_DEFINED
9 #define SkMath_DEFINED
10
11 #include "include/core/SkTypes.h"
12
13 // 64bit -> 32bit utilities
14
15 // Handy util that can be passed two ints, and will automatically promote to
16 // 64bits before the multiply, so the caller doesn't have to remember to cast
17 // e.g. (int64_t)a * b;
sk_64_mul(int64_t a,int64_t b)18 static inline int64_t sk_64_mul(int64_t a, int64_t b) {
19 return a * b;
20 }
21
22 ///////////////////////////////////////////////////////////////////////////////
23
24 /**
25 * Returns true if value is a power of 2. Does not explicitly check for
26 * value <= 0.
27 */
SkIsPow2(T value)28 template <typename T> constexpr inline bool SkIsPow2(T value) {
29 return (value & (value - 1)) == 0;
30 }
31
32 ///////////////////////////////////////////////////////////////////////////////
33
34 /**
35 * Return a*b/((1 << shift) - 1), rounding any fractional bits.
36 * Only valid if a and b are unsigned and <= 32767 and shift is > 0 and <= 8
37 */
SkMul16ShiftRound(U16CPU a,U16CPU b,int shift)38 static inline unsigned SkMul16ShiftRound(U16CPU a, U16CPU b, int shift) {
39 SkASSERT(a <= 32767);
40 SkASSERT(b <= 32767);
41 SkASSERT(shift > 0 && shift <= 8);
42 unsigned prod = a*b + (1 << (shift - 1));
43 return (prod + (prod >> shift)) >> shift;
44 }
45
46 /**
47 * Return a*b/255, rounding any fractional bits.
48 * Only valid if a and b are unsigned and <= 32767.
49 */
SkMulDiv255Round(U16CPU a,U16CPU b)50 static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
51 return SkMul16ShiftRound(a,b,8);
52 }
53
54 #endif
55