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 0 : static inline int32_t SkSignBitTo2sCompliment(int32_t x) {
20 0 : if (x < 0) {
21 0 : x &= 0x7FFFFFFF;
22 0 : x = -x;
23 : }
24 0 : 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 : #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)
68 0 : static inline int32_t SkFloat2Bits(float x) {
69 : SkFloatIntUnion data;
70 0 : data.fFloat = x;
71 0 : return data.fSignBitInt;
72 : }
73 :
74 : // Helper to see a bit pattern as a float (w/o aliasing warnings)
75 0 : static inline float SkBits2Float(int32_t floatAsBits) {
76 : SkFloatIntUnion data;
77 0 : data.fSignBitInt = floatAsBits;
78 0 : 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 : */
86 0 : static inline int32_t SkFloatAs2sCompliment(float x) {
87 0 : return SkSignBitTo2sCompliment(SkFloat2Bits(x));
88 : }
89 :
90 : /** Return the 2s compliment int as a float. This undos the result of
91 : SkFloatAs2sCompliment
92 : */
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 : */
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 : */
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 : */
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 : */
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 :
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