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 */ 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 */ 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; 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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> 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