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 "include/private/base/SkMath.h" 12 13 #include <cstdint> 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 */ SkSignBitTo2sCompliment(int32_t x)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 */ Sk2sComplimentToSignBit(int32_t x)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 |= 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) SkFloat2Bits(float x)45static 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) SkBits2Float(int32_t floatAsBits)52static inline float SkBits2Float(int32_t floatAsBits) { 53 SkFloatIntUnion data; 54 data.fSignBitInt = floatAsBits; 55 return data.fFloat; 56 } 57 58 constexpr int32_t gFloatBits_exponent_mask = 0x7F800000; 59 constexpr int32_t gFloatBits_matissa_mask = 0x007FFFFF; 60 SkFloatBits_IsFinite(int32_t bits)61static inline bool SkFloatBits_IsFinite(int32_t bits) { 62 return (bits & gFloatBits_exponent_mask) != gFloatBits_exponent_mask; 63 } 64 SkFloatBits_IsInf(int32_t bits)65static inline bool SkFloatBits_IsInf(int32_t bits) { 66 return ((bits & gFloatBits_exponent_mask) == gFloatBits_exponent_mask) && 67 (bits & gFloatBits_matissa_mask) == 0; 68 } 69 70 /** Return the float as a 2s compliment int. Just to be used to compare floats 71 to each other or against positive float-bit-constants (like 0). This does 72 not return the int equivalent of the float, just something cheaper for 73 compares-only. 74 */ SkFloatAs2sCompliment(float x)75static inline int32_t SkFloatAs2sCompliment(float x) { 76 return SkSignBitTo2sCompliment(SkFloat2Bits(x)); 77 } 78 79 /** Return the 2s compliment int as a float. This undos the result of 80 SkFloatAs2sCompliment 81 */ Sk2sComplimentAsFloat(int32_t x)82static inline float Sk2sComplimentAsFloat(int32_t x) { 83 return SkBits2Float(Sk2sComplimentToSignBit(x)); 84 } 85 86 // Scalar wrappers for float-bit routines 87 88 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) 89 90 #endif 91