xpcom/ds/nsCheapSets.h@129ffea94266
xpcom/ds/nsCheapSets.h
Sat, 03 Jan 2015 20:18:00 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Sat, 03 Jan 2015 20:18:00 +0100
- branch
- TOR_BUG_3246
- changeset 7
- 129ffea94266
- permissions
- -rw-r--r--
Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.
1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 #ifndef __nsCheapSets_h__
7 #define __nsCheapSets_h__
9 #include "nsTHashtable.h"
10 #include <stdint.h>
12 /**
13 * A set that takes up minimal size when there are 0 or 1 entries in the set.
14 * Use for cases where sizes of 0 and 1 are even slightly common.
15 */
16 template<typename EntryType>
17 class nsCheapSet
18 {
19 public:
20 typedef typename EntryType::KeyType KeyType;
21 typedef PLDHashOperator (* Enumerator)(EntryType* aEntry, void* userArg);
23 nsCheapSet() : mState(ZERO)
24 {
25 }
26 ~nsCheapSet()
27 {
28 switch (mState) {
29 case ZERO:
30 break;
31 case ONE:
32 GetSingleEntry()->~EntryType();
33 break;
34 case MANY:
35 delete mUnion.table;
36 break;
37 default:
38 NS_NOTREACHED("bogus state");
39 break;
40 }
41 }
43 nsresult Put(const KeyType aVal);
45 void Remove(const KeyType aVal);
47 bool Contains(const KeyType aVal)
48 {
49 switch (mState) {
50 case ZERO:
51 return false;
52 case ONE:
53 return GetSingleEntry()->KeyEquals(EntryType::KeyToPointer(aVal));
54 case MANY:
55 return !!mUnion.table->GetEntry(aVal);
56 default:
57 NS_NOTREACHED("bogus state");
58 return false;
59 }
60 }
62 uint32_t EnumerateEntries(Enumerator enumFunc, void* userArg)
63 {
64 switch (mState) {
65 case ZERO:
66 return 0;
67 case ONE:
68 if (enumFunc(GetSingleEntry(), userArg) == PL_DHASH_REMOVE) {
69 GetSingleEntry()->~EntryType();
70 mState = ZERO;
71 }
72 return 1;
73 case MANY:
74 return mUnion.table->EnumerateEntries(enumFunc, userArg);
75 default:
76 NS_NOTREACHED("bogus state");
77 return 0;
78 }
79 }
81 private:
82 EntryType* GetSingleEntry()
83 {
84 return reinterpret_cast<EntryType*>(&mUnion.singleEntry[0]);
85 }
87 enum SetState {
88 ZERO,
89 ONE,
90 MANY
91 };
93 union {
94 nsTHashtable<EntryType> *table;
95 char singleEntry[sizeof(EntryType)];
96 } mUnion;
97 enum SetState mState;
98 };
100 template<typename EntryType>
101 nsresult
102 nsCheapSet<EntryType>::Put(const KeyType aVal)
103 {
104 switch (mState) {
105 case ZERO:
106 new (GetSingleEntry()) EntryType(EntryType::KeyToPointer(aVal));
107 mState = ONE;
108 return NS_OK;
109 case ONE:
110 {
111 nsTHashtable<EntryType> *table = new nsTHashtable<EntryType>();
112 EntryType *entry = GetSingleEntry();
113 table->PutEntry(entry->GetKey());
114 entry->~EntryType();
115 mUnion.table = table;
116 mState = MANY;
117 }
118 // Fall through.
119 case MANY:
120 mUnion.table->PutEntry(aVal);
121 return NS_OK;
122 default:
123 NS_NOTREACHED("bogus state");
124 return NS_OK;
125 }
126 }
128 template<typename EntryType>
129 void
130 nsCheapSet<EntryType>::Remove(const KeyType aVal)
131 {
132 switch (mState) {
133 case ZERO:
134 break;
135 case ONE:
136 if (Contains(aVal)) {
137 GetSingleEntry()->~EntryType();
138 mState = ZERO;
139 }
140 break;
141 case MANY:
142 mUnion.table->RemoveEntry(aVal);
143 break;
144 default:
145 NS_NOTREACHED("bogus state");
146 break;
147 }
148 }
150 #endif
