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comparison: gfx/skia/trunk/include/core/SkFloatBits.h
gfx/skia/trunk/include/core/SkFloatBits.h
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- TOR_BUG_3246
- changeset 7
- 129ffea94266
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| -1:000000000000 | 0:231aff49abf1 |
|---|---|
| 1 | |
| 2 /* | |
| 3 * Copyright 2008 The Android Open Source Project | |
| 4 * | |
| 5 * Use of this source code is governed by a BSD-style license that can be | |
| 6 * found in the LICENSE file. | |
| 7 */ | |
| 8 | |
| 9 | |
| 10 #ifndef SkFloatBits_DEFINED | |
| 11 #define SkFloatBits_DEFINED | |
| 12 | |
| 13 #include "SkTypes.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 |= sign << 31; | |
| 36 return x; | |
| 37 } | |
| 38 | |
| 39 /** Given the bit representation of a float, return its value cast to an int. | |
| 40 If the value is out of range, or NaN, return return +/- SK_MaxS32 | |
| 41 */ | |
| 42 int32_t SkFloatBits_toIntCast(int32_t floatBits); | |
| 43 | |
| 44 /** Given the bit representation of a float, return its floor as an int. | |
| 45 If the value is out of range, or NaN, return return +/- SK_MaxS32 | |
| 46 */ | |
| 47 SK_API int32_t SkFloatBits_toIntFloor(int32_t floatBits); | |
| 48 | |
| 49 /** Given the bit representation of a float, return it rounded to an int. | |
| 50 If the value is out of range, or NaN, return return +/- SK_MaxS32 | |
| 51 */ | |
| 52 SK_API int32_t SkFloatBits_toIntRound(int32_t floatBits); | |
| 53 | |
| 54 /** Given the bit representation of a float, return its ceiling as an int. | |
| 55 If the value is out of range, or NaN, return return +/- SK_MaxS32 | |
| 56 */ | |
| 57 SK_API int32_t SkFloatBits_toIntCeil(int32_t floatBits); | |
| 58 | |
| 59 | |
| 60 union SkFloatIntUnion { | |
| 61 float fFloat; | |
| 62 int32_t fSignBitInt; | |
| 63 }; | |
| 64 | |
| 65 // Helper to see a float as its bit pattern (w/o aliasing warnings) | |
| 66 static inline int32_t SkFloat2Bits(float x) { | |
| 67 SkFloatIntUnion data; | |
| 68 data.fFloat = x; | |
| 69 return data.fSignBitInt; | |
| 70 } | |
| 71 | |
| 72 // Helper to see a bit pattern as a float (w/o aliasing warnings) | |
| 73 static inline float SkBits2Float(int32_t floatAsBits) { | |
| 74 SkFloatIntUnion data; | |
| 75 data.fSignBitInt = floatAsBits; | |
| 76 return data.fFloat; | |
| 77 } | |
| 78 | |
| 79 /** Return the float as a 2s compliment int. Just to be used to compare floats | |
| 80 to each other or against positive float-bit-constants (like 0). This does | |
| 81 not return the int equivalent of the float, just something cheaper for | |
| 82 compares-only. | |
| 83 */ | |
| 84 static inline int32_t SkFloatAs2sCompliment(float x) { | |
| 85 return SkSignBitTo2sCompliment(SkFloat2Bits(x)); | |
| 86 } | |
| 87 | |
| 88 /** Return the 2s compliment int as a float. This undos the result of | |
| 89 SkFloatAs2sCompliment | |
| 90 */ | |
| 91 static inline float Sk2sComplimentAsFloat(int32_t x) { | |
| 92 return SkBits2Float(Sk2sComplimentToSignBit(x)); | |
| 93 } | |
| 94 | |
| 95 /** Return x cast to a float (i.e. (float)x) | |
| 96 */ | |
| 97 float SkIntToFloatCast(int x); | |
| 98 float SkIntToFloatCast_NoOverflowCheck(int x); | |
| 99 | |
| 100 /** Return the float cast to an int. | |
| 101 If the value is out of range, or NaN, return +/- SK_MaxS32 | |
| 102 */ | |
| 103 static inline int32_t SkFloatToIntCast(float x) { | |
| 104 return SkFloatBits_toIntCast(SkFloat2Bits(x)); | |
| 105 } | |
| 106 | |
| 107 /** Return the floor of the float as an int. | |
| 108 If the value is out of range, or NaN, return +/- SK_MaxS32 | |
| 109 */ | |
| 110 static inline int32_t SkFloatToIntFloor(float x) { | |
| 111 return SkFloatBits_toIntFloor(SkFloat2Bits(x)); | |
| 112 } | |
| 113 | |
| 114 /** Return the float rounded to an int. | |
| 115 If the value is out of range, or NaN, return +/- SK_MaxS32 | |
| 116 */ | |
| 117 static inline int32_t SkFloatToIntRound(float x) { | |
| 118 return SkFloatBits_toIntRound(SkFloat2Bits(x)); | |
| 119 } | |
| 120 | |
| 121 /** Return the ceiling of the float as an int. | |
| 122 If the value is out of range, or NaN, return +/- SK_MaxS32 | |
| 123 */ | |
| 124 static inline int32_t SkFloatToIntCeil(float x) { | |
| 125 return SkFloatBits_toIntCeil(SkFloat2Bits(x)); | |
| 126 } | |
| 127 | |
| 128 // Scalar wrappers for float-bit routines | |
| 129 | |
| 130 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) | |
| 131 #define Sk2sComplimentAsScalar(x) Sk2sComplimentAsFloat(x) | |
| 132 | |
| 133 #endif |
