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 #ifdef SK_BUILD_FOR_IOS
14 // The iOS ARM processor discards small denormalized numbers to go faster.
15 // Algorithms that rely on denormalized numbers need alternative implementations.
16 #define SK_DISCARD_DENORMALIZED_FOR_SPEED
17 #endif
18
19 /** Returns -1 if n < 0, else returns 0
20 */
21 #define SkExtractSign(n) ((int32_t)(n) >> 31)
22
23 /** If sign == -1, returns -n, else sign must be 0, and returns n.
24 Typically used in conjunction with SkExtractSign().
25 */
SkApplySign(int32_t n,int32_t sign)26 static inline int32_t SkApplySign(int32_t n, int32_t sign) {
27 SkASSERT(sign == 0 || sign == -1);
28 return (n ^ sign) - sign;
29 }
30
31 /** Return x with the sign of y */
SkCopySign32(int32_t x,int32_t y)32 static inline int32_t SkCopySign32(int32_t x, int32_t y) {
33 return SkApplySign(x, SkExtractSign(x ^ y));
34 }
35
36 /** Given a positive value and a positive max, return the value
37 pinned against max.
38 Note: only works as long as max - value doesn't wrap around
39 @return max if value >= max, else value
40 */
SkClampUMax(unsigned value,unsigned max)41 static inline unsigned SkClampUMax(unsigned value, unsigned max) {
42 if (value > max) {
43 value = max;
44 }
45 return value;
46 }
47
48 ///////////////////////////////////////////////////////////////////////////////
49
50 /** Return a*b/255, truncating away any fractional bits. Only valid if both
51 a and b are 0..255
52 */
SkMulDiv255Trunc(U8CPU a,U8CPU b)53 static inline U8CPU SkMulDiv255Trunc(U8CPU a, U8CPU b) {
54 SkASSERT((uint8_t)a == a);
55 SkASSERT((uint8_t)b == b);
56 unsigned prod = SkMulS16(a, b) + 1;
57 return (prod + (prod >> 8)) >> 8;
58 }
59
60 /** Return (a*b)/255, taking the ceiling of any fractional bits. Only valid if
61 both a and b are 0..255. The expected result equals (a * b + 254) / 255.
62 */
SkMulDiv255Ceiling(U8CPU a,U8CPU b)63 static inline U8CPU SkMulDiv255Ceiling(U8CPU a, U8CPU b) {
64 SkASSERT((uint8_t)a == a);
65 SkASSERT((uint8_t)b == b);
66 unsigned prod = SkMulS16(a, b) + 255;
67 return (prod + (prod >> 8)) >> 8;
68 }
69
70 /** Just the rounding step in SkDiv255Round: round(value / 255)
71 */
SkDiv255Round(unsigned prod)72 static inline unsigned SkDiv255Round(unsigned prod) {
73 prod += 128;
74 return (prod + (prod >> 8)) >> 8;
75 }
76
77 #endif
78