1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkClampRange.h"
/*
* returns [0..count] for the number of steps (<= count) for which x0 <= edge
* given each step is followed by x0 += dx
*/
static int chop(int64_t x0, SkFixed edge, int64_t x1, int64_t dx, int count) {
SkASSERT(dx > 0);
SkASSERT(count >= 0);
if (x0 >= edge) {
return 0;
}
if (x1 <= edge) {
return count;
}
int64_t n = (edge - x0 + dx - 1) / dx;
SkASSERT(n >= 0);
SkASSERT(n <= count);
return (int)n;
}
static bool overflows_fixed(int64_t x) {
return x < -SK_FixedMax || x > SK_FixedMax;
}
void SkClampRange::initFor1(SkFixed fx) {
fCount0 = fCount1 = fCount2 = 0;
if (fx <= 0) {
fCount0 = 1;
} else if (fx < 0xFFFF) {
fCount1 = 1;
fFx1 = fx;
} else {
fCount2 = 1;
}
}
void SkClampRange::init(SkFixed fx0, SkFixed dx0, int count, int v0, int v1) {
SkASSERT(count > 0);
fV0 = v0;
fV1 = v1;
fOverflowed = false;
// special case 1 == count, as it is slightly common for skia
// and avoids us ever calling divide or 64bit multiply
if (1 == count) {
this->initFor1(fx0);
return;
}
int64_t fx = fx0;
int64_t dx = dx0;
// start with ex equal to the last computed value
int64_t ex = fx + (count - 1) * dx;
fOverflowed = overflows_fixed(ex);
if ((uint64_t)(fx | ex) <= 0xFFFF) {
fCount0 = fCount2 = 0;
fCount1 = count;
fFx1 = fx0;
return;
}
if (fx <= 0 && ex <= 0) {
fCount1 = fCount2 = 0;
fCount0 = count;
return;
}
if (fx >= 0xFFFF && ex >= 0xFFFF) {
fCount0 = fCount1 = 0;
fCount2 = count;
return;
}
int extraCount = 0;
// now make ex be 1 past the last computed value
ex += dx;
fOverflowed = overflows_fixed(ex);
// now check for over/under flow
if (fOverflowed) {
int originalCount = count;
int64_t ccount;
bool swap = dx < 0;
if (swap) {
dx = -dx;
fx = -fx;
}
ccount = (SK_FixedMax - fx + dx - 1) / dx;
if (swap) {
dx = -dx;
fx = -fx;
}
SkASSERT(ccount > 0 && ccount <= SK_FixedMax);
count = (int)ccount;
if (0 == count) {
this->initFor1(fx0);
if (dx > 0) {
fCount2 += originalCount - 1;
} else {
fCount0 += originalCount - 1;
}
return;
}
extraCount = originalCount - count;
ex = fx + dx * count;
}
bool doSwap = dx < 0;
if (doSwap) {
ex -= dx;
fx -= dx;
SkTSwap(fx, ex);
dx = -dx;
}
fCount0 = chop(fx, 0, ex, dx, count);
count -= fCount0;
fx += fCount0 * dx;
SkASSERT(fx >= 0);
SkASSERT(fCount0 == 0 || (fx - dx) < 0);
fCount1 = chop(fx, 0xFFFF, ex, dx, count);
count -= fCount1;
fCount2 = count;
#ifdef SK_DEBUG
fx += fCount1 * dx;
SkASSERT(fx <= ex);
if (fCount2 > 0) {
SkASSERT(fx >= 0xFFFF);
if (fCount1 > 0) {
SkASSERT(fx - dx < 0xFFFF);
}
}
#endif
if (doSwap) {
SkTSwap(fCount0, fCount2);
SkTSwap(fV0, fV1);
dx = -dx;
}
if (fCount1 > 0) {
fFx1 = fx0 + fCount0 * (int)dx;
}
if (dx > 0) {
fCount2 += extraCount;
} else {
fCount0 += extraCount;
}
}
|
