The Tor Browser / file comparison

comparison: gfx/skia/trunk/include/core/SkMath.h

gfx/skia/trunk/include/core/SkMath.h

branch
TOR_BUG_3246
changeset 7
129ffea94266
equal deleted inserted replaced
-1:000000000000 0:5bddd1419b98
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 /**
16 * Computes numer1 * numer2 / denom in full 64 intermediate precision.
17 * It is an error for denom to be 0. There is no special handling if
18 * the result overflows 32bits.
19 */
20 int32_t SkMulDiv(int32_t numer1, int32_t numer2, int32_t denom);
21
22 /**
23 * Computes (numer1 << shift) / denom in full 64 intermediate precision.
24 * It is an error for denom to be 0. There is no special handling if
25 * the result overflows 32bits.
26 */
27 int32_t SkDivBits(int32_t numer, int32_t denom, int shift);
28
29 /**
30 * Return the integer square root of value, with a bias of bitBias
31 */
32 int32_t SkSqrtBits(int32_t value, int bitBias);
33
34 /** Return the integer square root of n, treated as a SkFixed (16.16)
35 */
36 #define SkSqrt32(n) SkSqrtBits(n, 15)
37
38 // 64bit -> 32bit utilities
39
40 /**
41 * Return true iff the 64bit value can exactly be represented in signed 32bits
42 */
43 static inline bool sk_64_isS32(int64_t value) {
44 return (int32_t)value == value;
45 }
46
47 /**
48 * Return the 64bit argument as signed 32bits, asserting in debug that the arg
49 * exactly fits in signed 32bits. In the release build, no checks are preformed
50 * and the return value if the arg does not fit is undefined.
51 */
52 static inline int32_t sk_64_asS32(int64_t value) {
53 SkASSERT(sk_64_isS32(value));
54 return (int32_t)value;
55 }
56
57 // Handy util that can be passed two ints, and will automatically promote to
58 // 64bits before the multiply, so the caller doesn't have to remember to cast
59 // e.g. (int64_t)a * b;
60 static inline int64_t sk_64_mul(int64_t a, int64_t b) {
61 return a * b;
62 }
63
64 ///////////////////////////////////////////////////////////////////////////////
65
66 //! Returns the number of leading zero bits (0...32)
67 int SkCLZ_portable(uint32_t);
68
69 #ifndef SkCLZ
70 #if defined(_MSC_VER) && _MSC_VER >= 1400
71 #include <intrin.h>
72
73 static inline int SkCLZ(uint32_t mask) {
74 if (mask) {
75 DWORD index;
76 _BitScanReverse(&index, mask);
77 return index ^ 0x1F;
78 } else {
79 return 32;
80 }
81 }
82 #elif defined(SK_CPU_ARM) || defined(__GNUC__) || defined(__clang__)
83 static inline int SkCLZ(uint32_t mask) {
84 // __builtin_clz(0) is undefined, so we have to detect that case.
85 return mask ? __builtin_clz(mask) : 32;
86 }
87 #else
88 #define SkCLZ(x) SkCLZ_portable(x)
89 #endif
90 #endif
91
92 /**
93 * Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
94 */
95 static inline int SkClampPos(int value) {
96 return value & ~(value >> 31);
97 }
98
99 /** Given an integer and a positive (max) integer, return the value
100 * pinned against 0 and max, inclusive.
101 * @param value The value we want returned pinned between [0...max]
102 * @param max The positive max value
103 * @return 0 if value < 0, max if value > max, else value
104 */
105 static inline int SkClampMax(int value, int max) {
106 // ensure that max is positive
107 SkASSERT(max >= 0);
108 if (value < 0) {
109 value = 0;
110 }
111 if (value > max) {
112 value = max;
113 }
114 return value;
115 }
116
117 /**
118 * Returns the smallest power-of-2 that is >= the specified value. If value
119 * is already a power of 2, then it is returned unchanged. It is undefined
120 * if value is <= 0.
121 */
122 static inline int SkNextPow2(int value) {
123 SkASSERT(value > 0);
124 return 1 << (32 - SkCLZ(value - 1));
125 }
126
127 /**
128 * Returns the log2 of the specified value, were that value to be rounded up
129 * to the next power of 2. It is undefined to pass 0. Examples:
130 * SkNextLog2(1) -> 0
131 * SkNextLog2(2) -> 1
132 * SkNextLog2(3) -> 2
133 * SkNextLog2(4) -> 2
134 * SkNextLog2(5) -> 3
135 */
136 static inline int SkNextLog2(uint32_t value) {
137 SkASSERT(value != 0);
138 return 32 - SkCLZ(value - 1);
139 }
140
141 /**
142 * Returns true if value is a power of 2. Does not explicitly check for
143 * value <= 0.
144 */
145 static inline bool SkIsPow2(int value) {
146 return (value & (value - 1)) == 0;
147 }
148
149 ///////////////////////////////////////////////////////////////////////////////
150
151 /**
152 * SkMulS16(a, b) multiplies a * b, but requires that a and b are both int16_t.
153 * With this requirement, we can generate faster instructions on some
154 * architectures.
155 */
156 #ifdef SK_ARM_HAS_EDSP
157 static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
158 SkASSERT((int16_t)x == x);
159 SkASSERT((int16_t)y == y);
160 int32_t product;
161 asm("smulbb %0, %1, %2 \n"
162 : "=r"(product)
163 : "r"(x), "r"(y)
164 );
165 return product;
166 }
167 #else
168 #ifdef SK_DEBUG
169 static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
170 SkASSERT((int16_t)x == x);
171 SkASSERT((int16_t)y == y);
172 return x * y;
173 }
174 #else
175 #define SkMulS16(x, y) ((x) * (y))
176 #endif
177 #endif
178
179 /**
180 * Return a*b/((1 << shift) - 1), rounding any fractional bits.
181 * Only valid if a and b are unsigned and <= 32767 and shift is > 0 and <= 8
182 */
183 static inline unsigned SkMul16ShiftRound(U16CPU a, U16CPU b, int shift) {
184 SkASSERT(a <= 32767);
185 SkASSERT(b <= 32767);
186 SkASSERT(shift > 0 && shift <= 8);
187 unsigned prod = SkMulS16(a, b) + (1 << (shift - 1));
188 return (prod + (prod >> shift)) >> shift;
189 }
190
191 /**
192 * Return a*b/255, rounding any fractional bits.
193 * Only valid if a and b are unsigned and <= 32767.
194 */
195 static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
196 SkASSERT(a <= 32767);
197 SkASSERT(b <= 32767);
198 unsigned prod = SkMulS16(a, b) + 128;
199 return (prod + (prod >> 8)) >> 8;
200 }
201
202 /**
203 * Stores numer/denom and numer%denom into div and mod respectively.
204 */
205 template <typename In, typename Out>
206 inline void SkTDivMod(In numer, In denom, Out* div, Out* mod) {
207 #ifdef SK_CPU_ARM
208 // If we wrote this as in the else branch, GCC won't fuse the two into one
209 // divmod call, but rather a div call followed by a divmod. Silly! This
210 // version is just as fast as calling __aeabi_[u]idivmod manually, but with
211 // prettier code.
212 //
213 // This benches as around 2x faster than the code in the else branch.
214 const In d = numer/denom;
215 *div = static_cast<Out>(d);
216 *mod = static_cast<Out>(numer-d*denom);
217 #else
218 // On x86 this will just be a single idiv.
219 *div = static_cast<Out>(numer/denom);
220 *mod = static_cast<Out>(numer%denom);
221 #endif // SK_CPU_ARM
222 }
223
224 #endif

Mercurial Repository: The Tor Browser

Europalab SCM Repository Server

mercurial