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 */ 19 static 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 */ 30 static 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 */ 42 int32_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 */ 47 SK_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 */ 52 SK_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 */ 57 SK_API int32_t SkFloatBits_toIntCeil(int32_t floatBits); 58 59 60 union SkFloatIntUnion { 61 float fFloat; 62 int32_t fSignBitInt; 63 }; 64 65 // Helper to see a float as its bit pattern (w/o aliasing warnings) 66 static 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) 73 static 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 */ 84 static 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 */ 91 static 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 */ 97 float SkIntToFloatCast(int x); 98 float SkIntToFloatCast_NoOverflowCheck(int x); 99 100 /** Return the float cast to an int. 101 If the value is out of range, or NaN, return +/- SK_MaxS32 102 */ 103 static inline int32_t SkFloatToIntCast(float x) { 104 return SkFloatBits_toIntCast(SkFloat2Bits(x)); 105 } 106 107 /** Return the floor of the float as an int. 108 If the value is out of range, or NaN, return +/- SK_MaxS32 109 */ 110 static inline int32_t SkFloatToIntFloor(float x) { 111 return SkFloatBits_toIntFloor(SkFloat2Bits(x)); 112 } 113 114 /** Return the float rounded to an int. 115 If the value is out of range, or NaN, return +/- SK_MaxS32 116 */ 117 static inline int32_t SkFloatToIntRound(float x) { 118 return SkFloatBits_toIntRound(SkFloat2Bits(x)); 119 } 120 121 /** Return the ceiling of the float as an int. 122 If the value is out of range, or NaN, return +/- SK_MaxS32 123 */ 124 static inline int32_t SkFloatToIntCeil(float x) { 125 return SkFloatBits_toIntCeil(SkFloat2Bits(x)); 126 } 127 128 // Scalar wrappers for float-bit routines 129 130 #ifdef SK_SCALAR_IS_FLOAT 131 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) 132 #define Sk2sComplimentAsScalar(x) Sk2sComplimentAsFloat(x) 133 #else 134 #define SkScalarAs2sCompliment(x) (x) 135 #define Sk2sComplimentAsScalar(x) (x) 136 #endif 137 138 #endif 139
