Line data Source code
1 : /*
2 : * Copyright 2012 Google Inc.
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 SkMathPriv_DEFINED
9 : #define SkMathPriv_DEFINED
10 :
11 : #include "SkMath.h"
12 :
13 : #if defined(SK_BUILD_FOR_IOS) && (defined(SK_BUILD_FOR_ARM32) || defined(SK_BUILD_FOR_ARM64))
14 : // iOS on ARM starts processes with the Flush-To-Zero (FTZ) and
15 : // Denormals-Are-Zero (DAZ) bits in the fpscr register set.
16 : // Algorithms that rely on denormalized numbers need alternative implementations.
17 : // This can also be controlled in SSE with the MXCSR register,
18 : // x87 with FSTCW/FLDCW, and mips with FCSR. This should be detected at runtime,
19 : // or the library built one way or the other more generally (by the build).
20 : #define SK_CPU_FLUSH_TO_ZERO
21 : #endif
22 :
23 : /** Returns -1 if n < 0, else returns 0
24 : */
25 : #define SkExtractSign(n) ((int32_t)(n) >> 31)
26 :
27 : /** If sign == -1, returns -n, else sign must be 0, and returns n.
28 : Typically used in conjunction with SkExtractSign().
29 : */
30 : static inline int32_t SkApplySign(int32_t n, int32_t sign) {
31 : SkASSERT(sign == 0 || sign == -1);
32 : return (n ^ sign) - sign;
33 : }
34 :
35 : /** Return x with the sign of y */
36 : static inline int32_t SkCopySign32(int32_t x, int32_t y) {
37 : return SkApplySign(x, SkExtractSign(x ^ y));
38 : }
39 :
40 : /** Given a positive value and a positive max, return the value
41 : pinned against max.
42 : Note: only works as long as max - value doesn't wrap around
43 : @return max if value >= max, else value
44 : */
45 : static inline unsigned SkClampUMax(unsigned value, unsigned max) {
46 : if (value > max) {
47 : value = max;
48 : }
49 : return value;
50 : }
51 :
52 : ///////////////////////////////////////////////////////////////////////////////
53 :
54 : /** Return a*b/255, truncating away any fractional bits. Only valid if both
55 : a and b are 0..255
56 : */
57 : static inline U8CPU SkMulDiv255Trunc(U8CPU a, U8CPU b) {
58 : SkASSERT((uint8_t)a == a);
59 : SkASSERT((uint8_t)b == b);
60 : unsigned prod = a*b + 1;
61 : return (prod + (prod >> 8)) >> 8;
62 : }
63 :
64 : /** Return (a*b)/255, taking the ceiling of any fractional bits. Only valid if
65 : both a and b are 0..255. The expected result equals (a * b + 254) / 255.
66 : */
67 : static inline U8CPU SkMulDiv255Ceiling(U8CPU a, U8CPU b) {
68 : SkASSERT((uint8_t)a == a);
69 : SkASSERT((uint8_t)b == b);
70 : unsigned prod = a*b + 255;
71 : return (prod + (prod >> 8)) >> 8;
72 : }
73 :
74 : /** Just the rounding step in SkDiv255Round: round(value / 255)
75 : */
76 0 : static inline unsigned SkDiv255Round(unsigned prod) {
77 0 : prod += 128;
78 0 : return (prod + (prod >> 8)) >> 8;
79 : }
80 :
81 : static inline float SkPinToUnitFloat(float x) {
82 : return SkTMin(SkTMax(x, 0.0f), 1.0f);
83 : }
84 :
85 : /**
86 : * Swap byte order of a 4-byte value, e.g. 0xaarrggbb -> 0xbbggrraa.
87 : */
88 : #if defined(_MSC_VER)
89 : #include <intrin.h>
90 : static inline uint32_t SkBSwap32(uint32_t v) { return _byteswap_ulong(v); }
91 : #else
92 : static inline uint32_t SkBSwap32(uint32_t v) { return __builtin_bswap32(v); }
93 : #endif
94 :
95 : //! Returns the number of leading zero bits (0...32)
96 : int SkCLZ_portable(uint32_t);
97 :
98 : #ifndef SkCLZ
99 : #if defined(SK_BUILD_FOR_WIN32)
100 : #include <intrin.h>
101 :
102 : static inline int SkCLZ(uint32_t mask) {
103 : if (mask) {
104 : unsigned long index;
105 : _BitScanReverse(&index, mask);
106 : // Suppress this bogus /analyze warning. The check for non-zero
107 : // guarantees that _BitScanReverse will succeed.
108 : #pragma warning(suppress : 6102) // Using 'index' from failed function call
109 : return index ^ 0x1F;
110 : } else {
111 : return 32;
112 : }
113 : }
114 : #elif defined(SK_CPU_ARM32) || defined(__GNUC__) || defined(__clang__)
115 627 : static inline int SkCLZ(uint32_t mask) {
116 : // __builtin_clz(0) is undefined, so we have to detect that case.
117 627 : return mask ? __builtin_clz(mask) : 32;
118 : }
119 : #else
120 : #define SkCLZ(x) SkCLZ_portable(x)
121 : #endif
122 : #endif
123 :
124 : /**
125 : * Returns the smallest power-of-2 that is >= the specified value. If value
126 : * is already a power of 2, then it is returned unchanged. It is undefined
127 : * if value is <= 0.
128 : */
129 0 : static inline int SkNextPow2(int value) {
130 0 : SkASSERT(value > 0);
131 0 : return 1 << (32 - SkCLZ(value - 1));
132 : }
133 :
134 : /**
135 : * Returns the largest power-of-2 that is <= the specified value. If value
136 : * is already a power of 2, then it is returned unchanged. It is undefined
137 : * if value is <= 0.
138 : */
139 : static inline int SkPrevPow2(int value) {
140 : SkASSERT(value > 0);
141 : return 1 << (32 - SkCLZ(value >> 1));
142 : }
143 :
144 : /**
145 : * Returns the log2 of the specified value, were that value to be rounded up
146 : * to the next power of 2. It is undefined to pass 0. Examples:
147 : * SkNextLog2(1) -> 0
148 : * SkNextLog2(2) -> 1
149 : * SkNextLog2(3) -> 2
150 : * SkNextLog2(4) -> 2
151 : * SkNextLog2(5) -> 3
152 : */
153 214 : static inline int SkNextLog2(uint32_t value) {
154 214 : SkASSERT(value != 0);
155 214 : return 32 - SkCLZ(value - 1);
156 : }
157 :
158 : /**
159 : * Returns the log2 of the specified value, were that value to be rounded down
160 : * to the previous power of 2. It is undefined to pass 0. Examples:
161 : * SkPrevLog2(1) -> 0
162 : * SkPrevLog2(2) -> 1
163 : * SkPrevLog2(3) -> 1
164 : * SkPrevLog2(4) -> 2
165 : * SkPrevLog2(5) -> 2
166 : */
167 : static inline int SkPrevLog2(uint32_t value) {
168 : SkASSERT(value != 0);
169 : return 32 - SkCLZ(value >> 1);
170 : }
171 :
172 : ///////////////////////////////////////////////////////////////////////////////
173 :
174 : /**
175 : * Return the next power of 2 >= n.
176 : */
177 : static inline uint32_t GrNextPow2(uint32_t n) {
178 : return n ? (1 << (32 - SkCLZ(n - 1))) : 1;
179 : }
180 :
181 : /**
182 : * Returns the next power of 2 >= n or n if the next power of 2 can't be represented by size_t.
183 : */
184 0 : static inline size_t GrNextSizePow2(size_t n) {
185 0 : constexpr int kNumSizeTBits = 8 * sizeof(size_t);
186 0 : constexpr size_t kHighBitSet = size_t(1) << (kNumSizeTBits - 1);
187 :
188 0 : if (!n) {
189 0 : return 1;
190 0 : } else if (n >= kHighBitSet) {
191 0 : return n;
192 : }
193 :
194 0 : n--;
195 0 : uint32_t shift = 1;
196 0 : while (shift < kNumSizeTBits) {
197 0 : n |= n >> shift;
198 0 : shift <<= 1;
199 : }
200 0 : return n + 1;
201 : }
202 :
203 0 : static inline int GrNextPow2(int n) {
204 0 : SkASSERT(n >= 0); // this impl only works for non-neg.
205 0 : return n ? (1 << (32 - SkCLZ(n - 1))) : 1;
206 : }
207 : #endif
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