1 /* 2 * Copyright 2008 The Android Open Source Project 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 9 #ifndef SkFloatBits_DEFINED 10 #define SkFloatBits_DEFINED 11 12 #include "SkTypes.h" 13 #include "SkSafe_math.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 |= SkLeftShift(sign, 31); 36 return x; 37 } 38 39 union SkFloatIntUnion { 40 float fFloat; 41 int32_t fSignBitInt; 42 }; 43 44 // Helper to see a float as its bit pattern (w/o aliasing warnings) 45 static inline int32_t SkFloat2Bits(float x) { 46 SkFloatIntUnion data; 47 data.fFloat = x; 48 return data.fSignBitInt; 49 } 50 51 // Helper to see a bit pattern as a float (w/o aliasing warnings) 52 static inline float SkBits2Float(int32_t floatAsBits) { 53 SkFloatIntUnion data; 54 data.fSignBitInt = floatAsBits; 55 return data.fFloat; 56 } 57 58 /** Return the float as a 2s compliment int. Just to be used to compare floats 59 to each other or against positive float-bit-constants (like 0). This does 60 not return the int equivalent of the float, just something cheaper for 61 compares-only. 62 */ 63 static inline int32_t SkFloatAs2sCompliment(float x) { 64 return SkSignBitTo2sCompliment(SkFloat2Bits(x)); 65 } 66 67 /** Return the 2s compliment int as a float. This undos the result of 68 SkFloatAs2sCompliment 69 */ 70 static inline float Sk2sComplimentAsFloat(int32_t x) { 71 return SkBits2Float(Sk2sComplimentToSignBit(x)); 72 } 73 74 static inline int32_t pin_double_to_int(double x) { 75 return (int32_t)SkTPin<double>(x, SK_MinS32, SK_MaxS32); 76 } 77 78 /** Return the floor of the float as an int. 79 If the value is out of range, or NaN, return +/- SK_MaxS32 80 */ 81 static inline int32_t SkFloatToIntFloor(float x) { 82 return pin_double_to_int(floor(x)); 83 } 84 85 /** Return the float rounded to an int. 86 If the value is out of range, or NaN, return +/- SK_MaxS32 87 */ 88 static inline int32_t SkFloatToIntRound(float x) { 89 return pin_double_to_int(floor((double)x + 0.5)); 90 } 91 92 /** Return the ceiling of the float as an int. 93 If the value is out of range, or NaN, return +/- SK_MaxS32 94 */ 95 static inline int32_t SkFloatToIntCeil(float x) { 96 return pin_double_to_int(ceil(x)); 97 } 98 99 // Scalar wrappers for float-bit routines 100 101 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) 102 #define Sk2sComplimentAsScalar(x) Sk2sComplimentAsFloat(x) 103 104 #endif 105