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#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*/ 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 */ 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 40union SkFloatIntUnion { 41 float fFloat; 42 int32_t fSignBitInt; 43}; 44 45// Helper to see a float as its bit pattern (w/o aliasing warnings) 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) 53static inline float SkBits2Float(int32_t floatAsBits) { 54 SkFloatIntUnion data; 55 data.fSignBitInt = floatAsBits; 56 return data.fFloat; 57} 58 59/** Return the float as a 2s compliment int. Just to be used to compare floats 60 to each other or against positive float-bit-constants (like 0). This does 61 not return the int equivalent of the float, just something cheaper for 62 compares-only. 63 */ 64static inline int32_t SkFloatAs2sCompliment(float x) { 65 return SkSignBitTo2sCompliment(SkFloat2Bits(x)); 66} 67 68/** Return the 2s compliment int as a float. This undos the result of 69 SkFloatAs2sCompliment 70 */ 71static inline float Sk2sComplimentAsFloat(int32_t x) { 72 return SkBits2Float(Sk2sComplimentToSignBit(x)); 73} 74 75// Scalar wrappers for float-bit routines 76 77#define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) 78 79#endif 80