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 */
SkSignBitTo2sCompliment(int32_t x)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 */
Sk2sComplimentToSignBit(int32_t x)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 #ifdef SK_CAN_USE_FLOAT
61
62 union SkFloatIntUnion {
63 float fFloat;
64 int32_t fSignBitInt;
65 };
66
67 // Helper to see a float as its bit pattern (w/o aliasing warnings)
SkFloat2Bits(float x)68 static inline int32_t SkFloat2Bits(float x) {
69 SkFloatIntUnion data;
70 data.fFloat = x;
71 return data.fSignBitInt;
72 }
73
74 // Helper to see a bit pattern as a float (w/o aliasing warnings)
SkBits2Float(int32_t floatAsBits)75 static inline float SkBits2Float(int32_t floatAsBits) {
76 SkFloatIntUnion data;
77 data.fSignBitInt = floatAsBits;
78 return data.fFloat;
79 }
80
81 /** Return the float as a 2s compliment int. Just to be used to compare floats
82 to each other or against positive float-bit-constants (like 0). This does
83 not return the int equivalent of the float, just something cheaper for
84 compares-only.
85 */
SkFloatAs2sCompliment(float x)86 static inline int32_t SkFloatAs2sCompliment(float x) {
87 return SkSignBitTo2sCompliment(SkFloat2Bits(x));
88 }
89
90 /** Return the 2s compliment int as a float. This undos the result of
91 SkFloatAs2sCompliment
92 */
Sk2sComplimentAsFloat(int32_t x)93 static inline float Sk2sComplimentAsFloat(int32_t x) {
94 return SkBits2Float(Sk2sComplimentToSignBit(x));
95 }
96
97 /** Return x cast to a float (i.e. (float)x)
98 */
99 float SkIntToFloatCast(int x);
100 float SkIntToFloatCast_NoOverflowCheck(int x);
101
102 /** Return the float cast to an int.
103 If the value is out of range, or NaN, return +/- SK_MaxS32
104 */
SkFloatToIntCast(float x)105 static inline int32_t SkFloatToIntCast(float x) {
106 return SkFloatBits_toIntCast(SkFloat2Bits(x));
107 }
108
109 /** Return the floor of the float as an int.
110 If the value is out of range, or NaN, return +/- SK_MaxS32
111 */
SkFloatToIntFloor(float x)112 static inline int32_t SkFloatToIntFloor(float x) {
113 return SkFloatBits_toIntFloor(SkFloat2Bits(x));
114 }
115
116 /** Return the float rounded to an int.
117 If the value is out of range, or NaN, return +/- SK_MaxS32
118 */
SkFloatToIntRound(float x)119 static inline int32_t SkFloatToIntRound(float x) {
120 return SkFloatBits_toIntRound(SkFloat2Bits(x));
121 }
122
123 /** Return the ceiling of the float as an int.
124 If the value is out of range, or NaN, return +/- SK_MaxS32
125 */
SkFloatToIntCeil(float x)126 static inline int32_t SkFloatToIntCeil(float x) {
127 return SkFloatBits_toIntCeil(SkFloat2Bits(x));
128 }
129
130 #endif
131
132 // Scalar wrappers for float-bit routines
133
134 #ifdef SK_SCALAR_IS_FLOAT
135 #define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x)
136 #define Sk2sComplimentAsScalar(x) Sk2sComplimentAsFloat(x)
137 #else
138 #define SkScalarAs2sCompliment(x) (x)
139 #define Sk2sComplimentAsScalar(x) (x)
140 #endif
141
142 #endif
143
144