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
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
|
/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkPEG_DEFINED
#define SkPEG_DEFINED
#include "SkTArray.h"
#include "SkTLazy.h"
namespace skpeg {
/**
* The result of an expression match attempt.
*
* If the match was successful, |fNext| points to the next unconsumed character in the
* input string, and |fValue| holds an (arbitrarily nested) match result value.
*
* Otherwise, |fNext| is nullptr and |fValue| is uninitialized.
*/
template <typename V>
struct MatchResult {
MatchResult(std::nullptr_t) : fNext(nullptr) {}
MatchResult(const char* next, const V& v) : fNext(next), fValue(&v) {}
operator bool() const {
SkASSERT(fValue.isValid() == SkToBool(fNext));
return SkToBool(fNext);
}
const V& operator* () const { return *fValue.get(); }
const V* operator->() const { return fValue.get(); }
const char* fNext;
SkTLazy<V> fValue;
};
/**
* Optional operator (e?). Always succeeds.
*
* If e also matches, then the result of e::Match() is stored in |fValue|.
* Otherwise, |fValue| is uninitialized.
*
*/
template <typename E>
struct Opt {
struct V {
V(const typename E::V* v) : fValue(v) {}
SkTLazy<typename E::V> fValue;
};
using MatchT = MatchResult<V>;
static MatchT Match(const char* in) {
const auto m = E::Match(in);
return m ? MatchT(m.fNext, V(m.fValue.get()))
: MatchT(in, nullptr);
}
};
/**
* Helper for selecting the value type of the n-th expression type in the list.
*/
template <size_t, typename... Es> struct SelectV;
template <typename E, typename... Es>
struct SelectV<0, E, Es...> {
using V = typename E::V;
};
template <size_t idx, typename E, typename... Es>
struct SelectV<idx, E, Es...> {
using V = typename SelectV<idx - 1, Es...>::V;
};
/**
* Sequence operator (e0 e1...).
*
* Succeeds when all expressions match, in sequence. The subexpression match
* results can be accessed via get<INDEX>() -- where get<0> returns the value
* of the first expression, and so on.
*
*/
template <typename... E> struct Seq;
template <>
struct Seq<> {
struct V {};
using MatchT = MatchResult<V>;
static MatchT Match(const char* in) {
return MatchT(in, V());
}
};
template <typename E, typename... Es>
struct Seq<E, Es...> {
class V {
public:
V(const typename E::V& head, const typename Seq<Es...>::V& tail)
: fHeadV(head), fTailV(tail) {}
template <size_t idx, typename std::enable_if<idx == 0, bool>::type = 0>
const typename E::V& get() const {
return fHeadV;
}
template <size_t idx, typename std::enable_if<idx != 0, bool>::type = 0>
const typename SelectV<idx, E, Es...>::V& get() const {
return fTailV.template get<idx - 1>();
}
private:
typename E::V fHeadV;
typename Seq<Es...>::V fTailV;
};
using MatchT = MatchResult<V>;
static MatchT Match(const char* in) {
const auto headMatch = E::Match(in);
if (!headMatch) {
return nullptr;
}
const auto tailMatch = Seq<Es...>::Match(headMatch.fNext);
return tailMatch ? MatchT(tailMatch.fNext, V(*headMatch, *tailMatch))
: nullptr;
}
};
/**
* Ordered choice operator (e1|e2).
*
* Succeeds when either e1 or e2 match (e1 is tried first, then e2).
*
* The (optional) match results are stored in |v1|, |v2|.
*
*/
template <typename E1, typename E2>
struct Choice {
struct V {
V (const typename E1::V* v1, const typename E2::V* v2) : v1(v1), v2(v2)
{
SkASSERT(!v1 || !v2);
}
SkTLazy<typename E1::V> v1;
SkTLazy<typename E2::V> v2;
};
using MatchT = MatchResult<V>;
static MatchT Match(const char* in) {
if (const auto m1 = E1::Match(in)) {
return MatchT(m1.fNext, V(m1.fValue.get(), nullptr));
}
if (const auto m2 = E2::Match(in)) {
return MatchT(m2.fNext, V(nullptr, m2.fValue.get()));
}
return nullptr;
}
};
/**
* Zero-or-more operator (e*). Always succeeds.
*
* Matches e greedily, and stores the match results in |fValues|.
*
*/
template <typename E>
struct Any {
struct V {
V(SkTArray<typename E::V>&& vs) : fValues(vs) {}
SkTArray<typename E::V> fValues;
};
using MatchT = MatchResult<V>;
static MatchT Match(const char* in) {
SkTArray<typename E::V> values;
while (const auto m = E::Match(in)) {
in = m.fNext;
values.push_back(*m);
}
return MatchT(in, std::move(values));
}
};
/**
* One-or-more operator (e+).
*
* Same as zero-or-more, except it fails if e doesn't match at least once.
*
*/
template <typename E>
using Some = Seq<E, Any<E>>;
/**
* End-of-string atom. Matches \0.
*/
struct EOS {
struct V {};
using MatchT = MatchResult<V>;
static MatchT Match(const char* in) {
return (*in != '\0') ? nullptr : MatchT(in, V());
}
};
/**
* Literal atom. Matches a list of char literals.
*/
template <char... Cs> struct LIT;
template <>
struct LIT<> {
struct V {};
using MatchT = MatchResult<V>;
static MatchT Match(const char* in) {
return MatchT(in, V());
}
};
template <char C, char... Cs>
struct LIT<C, Cs...> {
struct V {};
using MatchT = MatchResult<V>;
static MatchT Match(const char* in) {
if (*in != C) {
return nullptr;
}
const auto m = LIT<Cs...>::Match(in + 1);
return m ? MatchT(m.fNext, V()) : nullptr;
}
};
} // skpeg ns
#endif // SkPEG_DEFINED
|
