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 #ifndef SkFloatBits_DEFINED 9 #define SkFloatBits_DEFINED 10 11 #include "SkTypes.h" 12 #include "SkSafe_math.h" 13 14 #include <float.h> 15 16 /** Convert a sign-bit int (i.e. float interpreted as int) into a 2s compliement 17 int. This also converts -0 (0x80000000) to 0. Doing this to a float allows 18 it to be compared using normal C operators (<, <=, etc.) 19 */ SkSignBitTo2sCompliment(int32_t x)20static inline int32_t SkSignBitTo2sCompliment(int32_t x) { 21 if (x < 0) { 22 x &= 0x7FFFFFFF; 23 x = -x; 24 } 25 return x; 26 } 27 28 /** Convert a 2s compliment int to a sign-bit (i.e. int interpreted as float). 29 This undoes the result of SkSignBitTo2sCompliment(). 30 */ Sk2sComplimentToSignBit(int32_t x)31static inline int32_t Sk2sComplimentToSignBit(int32_t x) { 32 int sign = x >> 31; 33 // make x positive 34 x = (x ^ sign) - sign; 35 // set the sign bit as needed 36 x |= SkLeftShift(sign, 31); 37 return x; 38 } 39 40 union SkFloatIntUnion { 41 float fFloat; 42 int32_t fSignBitInt; 43 }; 44 45 // Helper to see a float as its bit pattern (w/o aliasing warnings) SkFloat2Bits(float x)46static inline int32_t SkFloat2Bits(float x) { 47 SkFloatIntUnion data; 48 data.fFloat = x; 49 return data.fSignBitInt; 50 } 51 52 // Helper to see a bit pattern as a float (w/o aliasing warnings) SkBits2Float(int32_t floatAsBits)53static inline float SkBits2Float(int32_t floatAsBits) { 54 SkFloatIntUnion data; 55 data.fSignBitInt = floatAsBits; 56 return data.fFloat; 57 } 58 59 constexpr int32_t gFloatBits_exponent_mask = 0x7F800000; 60 constexpr int32_t gFloatBits_matissa_mask = 0x007FFFFF; 61 SkFloatBits_IsFinite(int32_t bits)62static inline bool SkFloatBits_IsFinite(int32_t bits) { 63 return (bits & gFloatBits_exponent_mask) != gFloatBits_exponent_mask; 64 } 65 SkFloatBits_IsInf(int32_t bits)66static inline bool SkFloatBits_IsInf(int32_t bits) { 67 return ((bits & gFloatBits_exponent_mask) == gFloatBits_exponent_mask) && 68 (bits & gFloatBits_matissa_mask) == 0; 69 } 70 71 /** Return the float as a 2s compliment int. Just to be used to compare floats 72 to each other or against positive float-bit-constants (like 0). This does 73 not return the int equivalent of the float, just something cheaper for 74 compares-only. 75 */ SkFloatAs2sCompliment(float x)76static inline int32_t SkFloatAs2sCompliment(float x) { 77 return SkSignBitTo2sCompliment(SkFloat2Bits(x)); 78 } 79 80 /** Return the 2s compliment int as a float. This undos the result of 81 SkFloatAs2sCompliment 82 */ Sk2sComplimentAsFloat(int32_t x)83static inline float Sk2sComplimentAsFloat(int32_t x) { 84 return SkBits2Float(Sk2sComplimentToSignBit(x)); 85 } 86 87 // Scalar wrappers for float-bit routines 88 89 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) 90 91 #endif 92