-
Notifications
You must be signed in to change notification settings - Fork 0
/
memoize.dart
67 lines (60 loc) · 1.93 KB
/
memoize.dart
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
part of '../../memoization.dart';
/// Parses [parser] and returns the result of parsing.
///
/// This is a lightweight implementation of (on demand) memoization with saving
/// only one state of parsing (just for a specific case)
///
/// This parser works as follows:
///
/// After parsing, the parsed state is stored for a current position.
///
/// If a parsed state is requested for a saved position, then the parsed state
/// is restored.
@experimental
class Memoize<I, O> extends ParserBuilder<I, O> {
static const _template = '''
final {{memo}} = state.memoized<{{type}}>({{id}}, false, state.pos);
if ({{memo}} != null) {
{{res0}} = {{memo}}.restore(state);
} else {
final {{pos}} = state.pos;
{{p1}}
state.memoize<{{type}}>({{id}}, false, {{pos}}, {{res0}});
}''';
static const _templateFast = '''
final {{memo}} = state.memoized<void>({{id}}, true, state.pos);
if ({{memo}} != null) {
{{memo}}.restore(state);
} else {
final {{pos}} = state.pos;
{{p1}}
state.memoize<void>({{id}}, true, {{pos}});
}''';
final ParserBuilder<I, O> parser;
const Memoize(this.parser);
@override
String build(Context context, ParserResult? result) {
final fast = result == null;
ParseRuntime.addCapability(
context, ParseRuntimeCapability.memoization, true);
final values = context.allocateLocals(['memo', 'pos']);
final id = _allocateId(context);
values.addAll({
'id': '$id',
'p1': parser.build(context, result),
'type': parser.getResultType(),
});
return render2(fast, _templateFast, _template, values, [result]);
}
int _allocateId(Context context) {
int getId() {
final id = context.readRegistryValue(
context.globalRegistry, Memoize, 'id', () => 0);
context.writeRegistryValue(context.globalRegistry, Memoize, 'id', id + 1);
return id;
}
final result =
context.readRegistryValue(context.globalRegistry, this, 'id', getId);
return result;
}
}