1/*
2 * Copyright 2006 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 SkFDot6_DEFINED
9#define SkFDot6_DEFINED
10
11#include "include/core/SkMath.h"
12#include "include/core/SkScalar.h"
13#include "include/private/SkFixed.h"
14#include "include/private/SkTo.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(int 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((SkLeftShift(x, 10) >> 10) == x);
60
61 return SkLeftShift(x, 10);
62}
63
64#define SkScalarToFDot6(x) (SkFDot6)((x) * 64)
65#define SkFDot6ToScalar(x) ((SkScalar)(x) * 0.015625f)
66#define SkFDot6ToFloat SkFDot6ToScalar
67
68inline SkFixed SkFDot6Div(SkFDot6 a, SkFDot6 b) {
69 SkASSERT(b != 0);
70
71 if (SkTFitsIn<int16_t>(a)) {
72 return SkLeftShift(a, 16) / b;
73 } else {
74 return SkFixedDiv(a, b);
75 }
76}
77
78#endif
79