1
2 /*
3 * Copyright 2006 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10 #ifndef SkMath_DEFINED
11 #define SkMath_DEFINED
12
13 #include "SkTypes.h"
14
15 // 64bit -> 32bit utilities
16
17 /**
18 * Return true iff the 64bit value can exactly be represented in signed 32bits
19 */
sk_64_isS32(int64_t value)20 static inline bool sk_64_isS32(int64_t value) {
21 return (int32_t)value == value;
22 }
23
24 /**
25 * Return the 64bit argument as signed 32bits, asserting in debug that the arg
26 * exactly fits in signed 32bits. In the release build, no checks are preformed
27 * and the return value if the arg does not fit is undefined.
28 */
sk_64_asS32(int64_t value)29 static inline int32_t sk_64_asS32(int64_t value) {
30 SkASSERT(sk_64_isS32(value));
31 return (int32_t)value;
32 }
33
34 // Handy util that can be passed two ints, and will automatically promote to
35 // 64bits before the multiply, so the caller doesn't have to remember to cast
36 // e.g. (int64_t)a * b;
sk_64_mul(int64_t a,int64_t b)37 static inline int64_t sk_64_mul(int64_t a, int64_t b) {
38 return a * b;
39 }
40
41 ///////////////////////////////////////////////////////////////////////////////
42
43 /**
44 * Computes numer1 * numer2 / denom in full 64 intermediate precision.
45 * It is an error for denom to be 0. There is no special handling if
46 * the result overflows 32bits.
47 */
SkMulDiv(int32_t numer1,int32_t numer2,int32_t denom)48 static inline int32_t SkMulDiv(int32_t numer1, int32_t numer2, int32_t denom) {
49 SkASSERT(denom);
50
51 int64_t tmp = sk_64_mul(numer1, numer2) / denom;
52 return sk_64_asS32(tmp);
53 }
54
55 /**
56 * Return the integer square root of value, with a bias of bitBias
57 */
58 int32_t SkSqrtBits(int32_t value, int bitBias);
59
60 /** Return the integer square root of n, treated as a SkFixed (16.16)
61 */
62 #define SkSqrt32(n) SkSqrtBits(n, 15)
63
64 /**
65 * Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
66 */
SkClampPos(int value)67 static inline int SkClampPos(int value) {
68 return value & ~(value >> 31);
69 }
70
71 /** Given an integer and a positive (max) integer, return the value
72 * pinned against 0 and max, inclusive.
73 * @param value The value we want returned pinned between [0...max]
74 * @param max The positive max value
75 * @return 0 if value < 0, max if value > max, else value
76 */
SkClampMax(int value,int max)77 static inline int SkClampMax(int value, int max) {
78 // ensure that max is positive
79 SkASSERT(max >= 0);
80 if (value < 0) {
81 value = 0;
82 }
83 if (value > max) {
84 value = max;
85 }
86 return value;
87 }
88
89 /**
90 * Returns true if value is a power of 2. Does not explicitly check for
91 * value <= 0.
92 */
SkIsPow2(T value)93 template <typename T> constexpr inline bool SkIsPow2(T value) {
94 return (value & (value - 1)) == 0;
95 }
96
97 ///////////////////////////////////////////////////////////////////////////////
98
99 /**
100 * Return a*b/((1 << shift) - 1), rounding any fractional bits.
101 * Only valid if a and b are unsigned and <= 32767 and shift is > 0 and <= 8
102 */
SkMul16ShiftRound(U16CPU a,U16CPU b,int shift)103 static inline unsigned SkMul16ShiftRound(U16CPU a, U16CPU b, int shift) {
104 SkASSERT(a <= 32767);
105 SkASSERT(b <= 32767);
106 SkASSERT(shift > 0 && shift <= 8);
107 unsigned prod = a*b + (1 << (shift - 1));
108 return (prod + (prod >> shift)) >> shift;
109 }
110
111 /**
112 * Return a*b/255, rounding any fractional bits.
113 * Only valid if a and b are unsigned and <= 32767.
114 */
SkMulDiv255Round(U16CPU a,U16CPU b)115 static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
116 SkASSERT(a <= 32767);
117 SkASSERT(b <= 32767);
118 unsigned prod = a*b + 128;
119 return (prod + (prod >> 8)) >> 8;
120 }
121
122 /**
123 * Stores numer/denom and numer%denom into div and mod respectively.
124 */
125 template <typename In, typename Out>
SkTDivMod(In numer,In denom,Out * div,Out * mod)126 inline void SkTDivMod(In numer, In denom, Out* div, Out* mod) {
127 #ifdef SK_CPU_ARM32
128 // If we wrote this as in the else branch, GCC won't fuse the two into one
129 // divmod call, but rather a div call followed by a divmod. Silly! This
130 // version is just as fast as calling __aeabi_[u]idivmod manually, but with
131 // prettier code.
132 //
133 // This benches as around 2x faster than the code in the else branch.
134 const In d = numer/denom;
135 *div = static_cast<Out>(d);
136 *mod = static_cast<Out>(numer-d*denom);
137 #else
138 // On x86 this will just be a single idiv.
139 *div = static_cast<Out>(numer/denom);
140 *mod = static_cast<Out>(numer%denom);
141 #endif
142 }
143
144 #endif
145