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 #include <cstring> 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 // Helper to see a float as its bit pattern (w/o aliasing warnings) SkFloat2Bits(float value)41static inline uint32_t SkFloat2Bits(float value) { 42 uint32_t bits; 43 memcpy(&bits, &value, sizeof(uint32_t)); 44 return bits; 45 } 46 47 // Helper to see a bit pattern as a float (w/o aliasing warnings) SkBits2Float(uint32_t bits)48static inline float SkBits2Float(uint32_t bits) { 49 float value; 50 memcpy(&value, &bits, sizeof(float)); 51 return value; 52 } 53 54 /** Return the float as a 2s compliment int. Just to be used to compare floats 55 to each other or against positive float-bit-constants (like 0). This does 56 not return the int equivalent of the float, just something cheaper for 57 compares-only. 58 */ SkFloatAs2sCompliment(float x)59static inline int32_t SkFloatAs2sCompliment(float x) { 60 return SkSignBitTo2sCompliment((int32_t)SkFloat2Bits(x)); 61 } 62 63 /** Return the 2s compliment int as a float. This undos the result of 64 SkFloatAs2sCompliment 65 */ Sk2sComplimentAsFloat(int32_t x)66static inline float Sk2sComplimentAsFloat(int32_t x) { 67 return SkBits2Float((uint32_t)Sk2sComplimentToSignBit(x)); 68 } 69 70 // Scalar wrappers for float-bit routines 71 72 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) 73 74 #endif 75