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
9#ifndef SkFloatBits_DEFINED
10#define SkFloatBits_DEFINED
11
12#include "SkTypes.h"
13#include "SkSafe_math.h"
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
59/** Return the float as a 2s compliment int. Just to be used to compare floats
60    to each other or against positive float-bit-constants (like 0). This does
61    not return the int equivalent of the float, just something cheaper for
62    compares-only.
63 */
64static inline int32_t SkFloatAs2sCompliment(float x) {
65    return SkSignBitTo2sCompliment(SkFloat2Bits(x));
66}
67
68/** Return the 2s compliment int as a float. This undos the result of
69    SkFloatAs2sCompliment
70 */
71static inline float Sk2sComplimentAsFloat(int32_t x) {
72    return SkBits2Float(Sk2sComplimentToSignBit(x));
73}
74
75//  Scalar wrappers for float-bit routines
76
77#define SkScalarAs2sCompliment(x)    SkFloatAs2sCompliment(x)
78
79#endif
80