1
2/*
3 * Copyright 2006 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 SkFDot6_DEFINED
11#define SkFDot6_DEFINED
12
13#include "SkScalar.h"
14#include "SkMath.h"
15
16typedef int32_t SkFDot6;
17
18/* This uses the magic number approach suggested here:
19 * http://stereopsis.com/sree/fpu2006.html and used in
20 * _cairo_fixed_from_double. It does banker's rounding
21 * (i.e. round to nearest even)
22 */
23inline SkFDot6 SkScalarRoundToFDot6(SkScalar x, int shift = 0)
24{
25    union {
26        double  fDouble;
27        int32_t fBits[2];
28    } tmp;
29    int fractionalBits = 6 + shift;
30    double magic = (1LL << (52 - (fractionalBits))) * 1.5;
31
32    tmp.fDouble = SkScalarToDouble(x) + magic;
33#ifdef SK_CPU_BENDIAN
34    return tmp.fBits[1];
35#else
36    return tmp.fBits[0];
37#endif
38}
39
40#define SK_FDot6One         (64)
41#define SK_FDot6Half        (32)
42
43#ifdef SK_DEBUG
44    inline SkFDot6 SkIntToFDot6(S16CPU x) {
45        SkASSERT(SkToS16(x) == x);
46        return x << 6;
47    }
48#else
49    #define SkIntToFDot6(x) ((x) << 6)
50#endif
51
52#define SkFDot6Floor(x)     ((x) >> 6)
53#define SkFDot6Ceil(x)      (((x) + 63) >> 6)
54#define SkFDot6Round(x)     (((x) + 32) >> 6)
55
56#define SkFixedToFDot6(x)   ((x) >> 10)
57
58inline SkFixed SkFDot6ToFixed(SkFDot6 x) {
59    SkASSERT((x << 10 >> 10) == x);
60
61    return x << 10;
62}
63
64#define SkScalarToFDot6(x)  (SkFDot6)((x) * 64)
65#define SkFDot6ToScalar(x)  ((SkScalar)(x) * 0.015625f)
66
67inline SkFixed SkFDot6Div(SkFDot6 a, SkFDot6 b) {
68    SkASSERT(b != 0);
69
70    if (a == (int16_t)a) {
71        return (a << 16) / b;
72    } else {
73        return SkFixedDiv(a, b);
74    }
75}
76
77#endif
78