1 2/* 3 * Copyright 2008 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 SkFloatBits_DEFINED 11#define SkFloatBits_DEFINED 12 13#include "SkTypes.h" 14 15/** Convert a sign-bit int (i.e. float interpreted as int) into a 2s compliement 16 int. This also converts -0 (0x80000000) to 0. Doing this to a float allows 17 it to be compared using normal C operators (<, <=, etc.) 18*/ 19static inline int32_t SkSignBitTo2sCompliment(int32_t x) { 20 if (x < 0) { 21 x &= 0x7FFFFFFF; 22 x = -x; 23 } 24 return x; 25} 26 27/** Convert a 2s compliment int to a sign-bit (i.e. int interpreted as float). 28 This undoes the result of SkSignBitTo2sCompliment(). 29 */ 30static inline int32_t Sk2sComplimentToSignBit(int32_t x) { 31 int sign = x >> 31; 32 // make x positive 33 x = (x ^ sign) - sign; 34 // set the sign bit as needed 35 x |= sign << 31; 36 return x; 37} 38 39/** Given the bit representation of a float, return its value cast to an int. 40 If the value is out of range, or NaN, return return +/- SK_MaxS32 41*/ 42int32_t SkFloatBits_toIntCast(int32_t floatBits); 43 44/** Given the bit representation of a float, return its floor as an int. 45 If the value is out of range, or NaN, return return +/- SK_MaxS32 46 */ 47SK_API int32_t SkFloatBits_toIntFloor(int32_t floatBits); 48 49/** Given the bit representation of a float, return it rounded to an int. 50 If the value is out of range, or NaN, return return +/- SK_MaxS32 51 */ 52SK_API int32_t SkFloatBits_toIntRound(int32_t floatBits); 53 54/** Given the bit representation of a float, return its ceiling as an int. 55 If the value is out of range, or NaN, return return +/- SK_MaxS32 56 */ 57SK_API int32_t SkFloatBits_toIntCeil(int32_t floatBits); 58 59 60union SkFloatIntUnion { 61 float fFloat; 62 int32_t fSignBitInt; 63}; 64 65// Helper to see a float as its bit pattern (w/o aliasing warnings) 66static inline int32_t SkFloat2Bits(float x) { 67 SkFloatIntUnion data; 68 data.fFloat = x; 69 return data.fSignBitInt; 70} 71 72// Helper to see a bit pattern as a float (w/o aliasing warnings) 73static inline float SkBits2Float(int32_t floatAsBits) { 74 SkFloatIntUnion data; 75 data.fSignBitInt = floatAsBits; 76 return data.fFloat; 77} 78 79/** Return the float as a 2s compliment int. Just to be used to compare floats 80 to each other or against positive float-bit-constants (like 0). This does 81 not return the int equivalent of the float, just something cheaper for 82 compares-only. 83 */ 84static inline int32_t SkFloatAs2sCompliment(float x) { 85 return SkSignBitTo2sCompliment(SkFloat2Bits(x)); 86} 87 88/** Return the 2s compliment int as a float. This undos the result of 89 SkFloatAs2sCompliment 90 */ 91static inline float Sk2sComplimentAsFloat(int32_t x) { 92 return SkBits2Float(Sk2sComplimentToSignBit(x)); 93} 94 95/** Return x cast to a float (i.e. (float)x) 96*/ 97float SkIntToFloatCast(int x); 98 99/** Return the float cast to an int. 100 If the value is out of range, or NaN, return +/- SK_MaxS32 101*/ 102static inline int32_t SkFloatToIntCast(float x) { 103 return SkFloatBits_toIntCast(SkFloat2Bits(x)); 104} 105 106/** Return the floor of the float as an int. 107 If the value is out of range, or NaN, return +/- SK_MaxS32 108*/ 109static inline int32_t SkFloatToIntFloor(float x) { 110 return SkFloatBits_toIntFloor(SkFloat2Bits(x)); 111} 112 113/** Return the float rounded to an int. 114 If the value is out of range, or NaN, return +/- SK_MaxS32 115*/ 116static inline int32_t SkFloatToIntRound(float x) { 117 return SkFloatBits_toIntRound(SkFloat2Bits(x)); 118} 119 120/** Return the ceiling of the float as an int. 121 If the value is out of range, or NaN, return +/- SK_MaxS32 122*/ 123static inline int32_t SkFloatToIntCeil(float x) { 124 return SkFloatBits_toIntCeil(SkFloat2Bits(x)); 125} 126 127// Scalar wrappers for float-bit routines 128 129#define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) 130#define Sk2sComplimentAsScalar(x) Sk2sComplimentAsFloat(x) 131 132#endif 133