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*/
19static 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 */
30static 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*/
42int32_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 */
47SK_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 */
52SK_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 */
57SK_API int32_t SkFloatBits_toIntCeil(int32_t floatBits);
58
59
60union SkFloatIntUnion {
61    float   fFloat;
62    int32_t fSignBitInt;
63};
64
65// Helper to see a float as its bit pattern (w/o aliasing warnings)
66static 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)
73static 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 */
84static 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 */
91static 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*/
97float SkIntToFloatCast(int x);
98float 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*/
103static 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*/
110static 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*/
117static 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*/
124static 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
134