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 "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 /** Given an integer and a positive (max) integer, return the value
25 * pinned against 0 and max, inclusive.
26 * @param value The value we want returned pinned between [0...max]
27 * @param max The positive max value
28 * @return 0 if value < 0, max if value > max, else value
29 */
SkClampMax(int value,int max)30 static inline int SkClampMax(int value, int max) {
31 // ensure that max is positive
32 SkASSERT(max >= 0);
33 if (value < 0) {
34 value = 0;
35 }
36 if (value > max) {
37 value = max;
38 }
39 return value;
40 }
41
42 /**
43 * Returns true if value is a power of 2. Does not explicitly check for
44 * value <= 0.
45 */
SkIsPow2(T value)46 template <typename T> constexpr inline bool SkIsPow2(T value) {
47 return (value & (value - 1)) == 0;
48 }
49
50 ///////////////////////////////////////////////////////////////////////////////
51
52 /**
53 * Return a*b/((1 << shift) - 1), rounding any fractional bits.
54 * Only valid if a and b are unsigned and <= 32767 and shift is > 0 and <= 8
55 */
SkMul16ShiftRound(U16CPU a,U16CPU b,int shift)56 static inline unsigned SkMul16ShiftRound(U16CPU a, U16CPU b, int shift) {
57 SkASSERT(a <= 32767);
58 SkASSERT(b <= 32767);
59 SkASSERT(shift > 0 && shift <= 8);
60 unsigned prod = a*b + (1 << (shift - 1));
61 return (prod + (prod >> shift)) >> shift;
62 }
63
64 /**
65 * Return a*b/255, rounding any fractional bits.
66 * Only valid if a and b are unsigned and <= 32767.
67 */
SkMulDiv255Round(U16CPU a,U16CPU b)68 static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
69 SkASSERT(a <= 32767);
70 SkASSERT(b <= 32767);
71 unsigned prod = a*b + 128;
72 return (prod + (prod >> 8)) >> 8;
73 }
74
75 #endif
76