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 #ifdef SK_CAN_USE_FLOAT 61 62 union SkFloatIntUnion { 63 float fFloat; 64 int32_t fSignBitInt; 65 }; 66 67 // Helper to see a float as its bit pattern (w/o aliasing warnings) 68 static inline int32_t SkFloat2Bits(float x) { 69 SkFloatIntUnion data; 70 data.fFloat = x; 71 return data.fSignBitInt; 72 } 73 74 // Helper to see a bit pattern as a float (w/o aliasing warnings) 75 static inline float SkBits2Float(int32_t floatAsBits) { 76 SkFloatIntUnion data; 77 data.fSignBitInt = floatAsBits; 78 return data.fFloat; 79 } 80 81 /** Return the float as a 2s compliment int. Just to be used to compare floats 82 to each other or against positive float-bit-constants (like 0). This does 83 not return the int equivalent of the float, just something cheaper for 84 compares-only. 85 */ 86 static inline int32_t SkFloatAs2sCompliment(float x) { 87 return SkSignBitTo2sCompliment(SkFloat2Bits(x)); 88 } 89 90 /** Return the 2s compliment int as a float. This undos the result of 91 SkFloatAs2sCompliment 92 */ 93 static inline float Sk2sComplimentAsFloat(int32_t x) { 94 return SkBits2Float(Sk2sComplimentToSignBit(x)); 95 } 96 97 /** Return x cast to a float (i.e. (float)x) 98 */ 99 float SkIntToFloatCast(int x); 100 float SkIntToFloatCast_NoOverflowCheck(int x); 101 102 /** Return the float cast to an int. 103 If the value is out of range, or NaN, return +/- SK_MaxS32 104 */ 105 static inline int32_t SkFloatToIntCast(float x) { 106 return SkFloatBits_toIntCast(SkFloat2Bits(x)); 107 } 108 109 /** Return the floor of the float as an int. 110 If the value is out of range, or NaN, return +/- SK_MaxS32 111 */ 112 static inline int32_t SkFloatToIntFloor(float x) { 113 return SkFloatBits_toIntFloor(SkFloat2Bits(x)); 114 } 115 116 /** Return the float rounded to an int. 117 If the value is out of range, or NaN, return +/- SK_MaxS32 118 */ 119 static inline int32_t SkFloatToIntRound(float x) { 120 return SkFloatBits_toIntRound(SkFloat2Bits(x)); 121 } 122 123 /** Return the ceiling of the float as an int. 124 If the value is out of range, or NaN, return +/- SK_MaxS32 125 */ 126 static inline int32_t SkFloatToIntCeil(float x) { 127 return SkFloatBits_toIntCeil(SkFloat2Bits(x)); 128 } 129 130 #endif 131 132 // Scalar wrappers for float-bit routines 133 134 #ifdef SK_SCALAR_IS_FLOAT 135 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) 136 #define Sk2sComplimentAsScalar(x) Sk2sComplimentAsFloat(x) 137 #else 138 #define SkScalarAs2sCompliment(x) (x) 139 #define Sk2sComplimentAsScalar(x) (x) 140 #endif 141 142 #endif 143 144
