1/*
2 * Copyright 2008 The Android Open Source Project
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkFloatBits_DEFINED
9#define SkFloatBits_DEFINED
10
11#include "include/core/SkTypes.h"
12#include "include/private/SkSafe_math.h"
13
14#include <float.h>
15
16/** Convert a sign-bit int (i.e. float interpreted as int) into a 2s compliement
17 int. This also converts -0 (0x80000000) to 0. Doing this to a float allows
18 it to be compared using normal C operators (<, <=, etc.)
19*/
20static inline int32_t SkSignBitTo2sCompliment(int32_t x) {
21 if (x < 0) {
22 x &= 0x7FFFFFFF;
23 x = -x;
24 }
25 return x;
26}
27
28/** Convert a 2s compliment int to a sign-bit (i.e. int interpreted as float).
29 This undoes the result of SkSignBitTo2sCompliment().
30 */
31static inline int32_t Sk2sComplimentToSignBit(int32_t x) {
32 int sign = x >> 31;
33 // make x positive
34 x = (x ^ sign) - sign;
35 // set the sign bit as needed
36 x |= SkLeftShift(sign, 31);
37 return x;
38}
39
40union SkFloatIntUnion {
41 float fFloat;
42 int32_t fSignBitInt;
43};
44
45// Helper to see a float as its bit pattern (w/o aliasing warnings)
46static inline int32_t SkFloat2Bits(float x) {
47 SkFloatIntUnion data;
48 data.fFloat = x;
49 return data.fSignBitInt;
50}
51
52// Helper to see a bit pattern as a float (w/o aliasing warnings)
53static inline float SkBits2Float(int32_t floatAsBits) {
54 SkFloatIntUnion data;
55 data.fSignBitInt = floatAsBits;
56 return data.fFloat;
57}
58
59constexpr int32_t gFloatBits_exponent_mask = 0x7F800000;
60constexpr int32_t gFloatBits_matissa_mask = 0x007FFFFF;
61
62static inline bool SkFloatBits_IsFinite(int32_t bits) {
63 return (bits & gFloatBits_exponent_mask) != gFloatBits_exponent_mask;
64}
65
66static inline bool SkFloatBits_IsInf(int32_t bits) {
67 return ((bits & gFloatBits_exponent_mask) == gFloatBits_exponent_mask) &&
68 (bits & gFloatBits_matissa_mask) == 0;
69}
70
71/** Return the float as a 2s compliment int. Just to be used to compare floats
72 to each other or against positive float-bit-constants (like 0). This does
73 not return the int equivalent of the float, just something cheaper for
74 compares-only.
75 */
76static inline int32_t SkFloatAs2sCompliment(float x) {
77 return SkSignBitTo2sCompliment(SkFloat2Bits(x));
78}
79
80/** Return the 2s compliment int as a float. This undos the result of
81 SkFloatAs2sCompliment
82 */
83static inline float Sk2sComplimentAsFloat(int32_t x) {
84 return SkBits2Float(Sk2sComplimentToSignBit(x));
85}
86
87// Scalar wrappers for float-bit routines
88
89#define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x)
90
91#endif
92