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
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* Implementation details of the atoms table.
*/
#ifndef vm_AtomsTable_h
#define vm_AtomsTable_h
#include "gc/Barrier.h"
#include "js/GCHashTable.h"
#include "js/TypeDecls.h"
#include "js/Vector.h"
#include "vm/StringType.h"
/*
* The atoms table is a mapping from strings to JSAtoms that supports
* incremental sweeping.
*/
namespace js {
struct AtomHasher {
struct Lookup;
static inline HashNumber hash(const Lookup& l);
static MOZ_ALWAYS_INLINE bool match(const WeakHeapPtr<JSAtom*>& entry,
const Lookup& lookup);
static void rekey(WeakHeapPtr<JSAtom*>& k,
const WeakHeapPtr<JSAtom*>& newKey) {
k = newKey;
}
};
struct js::AtomHasher::Lookup {
union {
const JS::Latin1Char* latin1Chars;
const char16_t* twoByteChars;
const char* utf8Bytes;
};
enum { TwoByteChar, Latin1, UTF8 } type;
size_t length;
size_t byteLength;
const JSAtom* atom; /* Optional. */
JS::AutoCheckCannotGC nogc;
HashNumber hash;
MOZ_ALWAYS_INLINE Lookup(const char* utf8Bytes, size_t byteLen, size_t length,
HashNumber hash)
: utf8Bytes(utf8Bytes),
type(UTF8),
length(length),
byteLength(byteLen),
atom(nullptr),
hash(hash) {}
MOZ_ALWAYS_INLINE Lookup(const char16_t* chars, size_t length)
: twoByteChars(chars),
type(TwoByteChar),
length(length),
atom(nullptr),
hash(mozilla::HashString(chars, length)) {}
MOZ_ALWAYS_INLINE Lookup(const JS::Latin1Char* chars, size_t length)
: latin1Chars(chars),
type(Latin1),
length(length),
atom(nullptr),
hash(mozilla::HashString(chars, length)) {}
MOZ_ALWAYS_INLINE Lookup(HashNumber hash, const char16_t* chars,
size_t length)
: twoByteChars(chars),
type(TwoByteChar),
length(length),
atom(nullptr),
hash(hash) {
MOZ_ASSERT(hash == mozilla::HashString(chars, length));
}
MOZ_ALWAYS_INLINE Lookup(HashNumber hash, const JS::Latin1Char* chars,
size_t length)
: latin1Chars(chars),
type(Latin1),
length(length),
atom(nullptr),
hash(hash) {
MOZ_ASSERT(hash == mozilla::HashString(chars, length));
}
inline explicit Lookup(const JSAtom* atom)
: type(atom->hasLatin1Chars() ? Latin1 : TwoByteChar),
length(atom->length()),
atom(atom),
hash(atom->hash()) {
if (type == Latin1) {
latin1Chars = atom->latin1Chars(nogc);
MOZ_ASSERT(mozilla::HashString(latin1Chars, length) == hash);
} else {
MOZ_ASSERT(type == TwoByteChar);
twoByteChars = atom->twoByteChars(nogc);
MOZ_ASSERT(mozilla::HashString(twoByteChars, length) == hash);
}
}
// Return: true iff the string in |atom| matches the string in this Lookup.
bool StringsMatch(const JSAtom& atom) const;
};
// Note: Use a 'class' here to make forward declarations easier to use.
class AtomSet : public JS::GCHashSet<WeakHeapPtr<JSAtom*>, AtomHasher,
SystemAllocPolicy> {
using Base =
JS::GCHashSet<WeakHeapPtr<JSAtom*>, AtomHasher, SystemAllocPolicy>;
public:
AtomSet() = default;
explicit AtomSet(size_t length) : Base(length){};
};
// This class is a wrapper for AtomSet that is used to ensure the AtomSet is
// not modified. It should only expose read-only methods from AtomSet.
// Note however that the atoms within the table can be marked during GC.
class FrozenAtomSet {
AtomSet* mSet;
public:
// This constructor takes ownership of the passed-in AtomSet.
explicit FrozenAtomSet(AtomSet* set) { mSet = set; }
~FrozenAtomSet() { js_delete(mSet); }
MOZ_ALWAYS_INLINE AtomSet::Ptr readonlyThreadsafeLookup(
const AtomSet::Lookup& l) const;
size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
return mSet->shallowSizeOfIncludingThis(mallocSizeOf);
}
using Range = AtomSet::Range;
AtomSet::Range all() const { return mSet->all(); }
};
class AtomsTable {
// Use a low initial capacity for atom hash tables to avoid penalizing
// runtimes which create a small number of atoms.
static const size_t InitialTableSize = 16;
// The main atoms set.
AtomSet atoms;
// Set of atoms added while the |atoms| set is being swept.
AtomSet* atomsAddedWhileSweeping;
// List of pinned atoms that are traced in every GC.
Vector<JSAtom*, 0, SystemAllocPolicy> pinnedAtoms;
public:
// An iterator used for sweeping atoms incrementally.
using SweepIterator = AtomSet::Enum;
AtomsTable();
~AtomsTable();
bool init();
template <typename CharT>
MOZ_ALWAYS_INLINE JSAtom* atomizeAndCopyCharsNonStaticValidLength(
JSContext* cx, const CharT* chars, size_t length,
const mozilla::Maybe<uint32_t>& indexValue,
const AtomHasher::Lookup& lookup);
bool maybePinExistingAtom(JSContext* cx, JSAtom* atom);
void tracePinnedAtoms(JSTracer* trc);
// Sweep all atoms non-incrementally.
void traceWeak(JSTracer* trc);
bool startIncrementalSweep(mozilla::Maybe<SweepIterator>& atomsToSweepOut);
// Sweep some atoms incrementally and return whether we finished.
bool sweepIncrementally(SweepIterator& atomsToSweep, SliceBudget& budget);
size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
private:
void mergeAtomsAddedWhileSweeping();
};
bool AtomIsPinned(JSContext* cx, JSAtom* atom);
} // namespace js
#endif /* vm_AtomsTable_h */
|