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