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 */
20static 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 */
29static 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;
37static 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 */
48static 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 */
58int32_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 */
67static 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 */
77static 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 */
93template <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 */
103static 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 */
115static 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 */
125template <typename In, typename Out>
126inline 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