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 /** Computes the 64bit product of a * b, and then shifts the answer down by 43 shift bits, returning the low 32bits. shift must be [0..63] 44 e.g. to perform a fixedmul, call SkMulShift(a, b, 16) 45 */ 46 int32_t SkMulShift(int32_t a, int32_t b, unsigned shift); 47 48 /** Return the integer cube root of value, with a bias of bitBias 49 */ 50 int32_t SkCubeRootBits(int32_t value, int bitBias); 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 = SkMulS16(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 = SkMulS16(a, b) + 255; 71 return (prod + (prod >> 8)) >> 8; 72 } 73 74 /** Just the rounding step in SkDiv255Round: round(value / 255) 75 */ 76 static inline unsigned SkDiv255Round(unsigned prod) { 77 prod += 128; 78 return (prod + (prod >> 8)) >> 8; 79 } 80 81 #endif 82
