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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 | |
99 /** Return the float cast to an int. | |
100 If the value is out of range, or NaN, return +/- SK_MaxS32 | |
101 */ | |
102 static inline int32_t SkFloatToIntCast(float x) { | |
103 return SkFloatBits_toIntCast(SkFloat2Bits(x)); | |
104 } | |
105 | |
106 /** Return the floor of the float as an int. | |
107 If the value is out of range, or NaN, return +/- SK_MaxS32 | |
108 */ | |
109 static inline int32_t SkFloatToIntFloor(float x) { | |
110 return SkFloatBits_toIntFloor(SkFloat2Bits(x)); | |
111 } | |
112 | |
113 /** Return the float rounded to an int. | |
114 If the value is out of range, or NaN, return +/- SK_MaxS32 | |
115 */ | |
116 static inline int32_t SkFloatToIntRound(float x) { | |
117 return SkFloatBits_toIntRound(SkFloat2Bits(x)); | |
118 } | |
119 | |
120 /** Return the ceiling of the float as an int. | |
121 If the value is out of range, or NaN, return +/- SK_MaxS32 | |
122 */ | |
123 static inline int32_t SkFloatToIntCeil(float x) { | |
124 return SkFloatBits_toIntCeil(SkFloat2Bits(x)); | |
125 } | |
126 | |
127 // Scalar wrappers for float-bit routines | |
128 | |
129 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x) | |
130 #define Sk2sComplimentAsScalar(x) Sk2sComplimentAsFloat(x) | |
131 | |
132 #endif | |
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