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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 72 static inline unsigned SkDiv255Round(unsigned prod) { 73 prod += 128; 74 return (prod + (prod >> 8)) >> 8; 75 } 76 77 #endif 78
