1 /*
2 * Copyright (C) 2008 Apple Inc. All Rights Reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26 #include "config.h"
27 #include "SmallStrings.h"
28
29 #include "JSGlobalObject.h"
30 #include "JSString.h"
31
32 #include <wtf/Noncopyable.h>
33
34 namespace JSC {
35 static const unsigned numCharactersToStore = 0x100;
36
37 class SmallStringsStorage : Noncopyable {
38 public:
39 SmallStringsStorage();
40
rep(unsigned char character)41 UString::Rep* rep(unsigned char character) { return &m_reps[character]; }
42
43 private:
44 UChar m_characters[numCharactersToStore];
45 UString::BaseString m_base;
46 UString::Rep m_reps[numCharactersToStore];
47 };
48
SmallStringsStorage()49 SmallStringsStorage::SmallStringsStorage()
50 {
51 for (unsigned i = 0; i < numCharactersToStore; ++i)
52 m_characters[i] = i;
53
54 m_base.rc = numCharactersToStore + 1;
55 m_base.buf = m_characters;
56 m_base.len = numCharactersToStore;
57 m_base.offset = 0;
58 m_base._hash = 0;
59 m_base.m_baseString = 0;
60 m_base.preCapacity = 0;
61 m_base.usedPreCapacity = 0;
62 m_base.reportedCost = 0;
63
64 // make sure UString doesn't try to reuse the buffer by pretending we have one more character in it
65 m_base.usedCapacity = numCharactersToStore + 1;
66 m_base.capacity = numCharactersToStore + 1;
67 m_base.checkConsistency();
68
69 memset(&m_reps, 0, sizeof(m_reps));
70 for (unsigned i = 0; i < numCharactersToStore; ++i) {
71 m_reps[i].offset = i;
72 m_reps[i].len = 1;
73 m_reps[i].rc = 1;
74 m_reps[i].setBaseString(&m_base);
75 m_reps[i].checkConsistency();
76 }
77 }
78
SmallStrings()79 SmallStrings::SmallStrings()
80 : m_emptyString(0)
81 , m_storage(0)
82 {
83 COMPILE_ASSERT(numCharactersToStore == sizeof(m_singleCharacterStrings) / sizeof(m_singleCharacterStrings[0]), IsNumCharactersConstInSyncWithClassUsage);
84
85 for (unsigned i = 0; i < numCharactersToStore; ++i)
86 m_singleCharacterStrings[i] = 0;
87 }
88
~SmallStrings()89 SmallStrings::~SmallStrings()
90 {
91 }
92
mark()93 void SmallStrings::mark()
94 {
95 if (m_emptyString && !m_emptyString->marked())
96 m_emptyString->mark();
97 for (unsigned i = 0; i < numCharactersToStore; ++i) {
98 if (m_singleCharacterStrings[i] && !m_singleCharacterStrings[i]->marked())
99 m_singleCharacterStrings[i]->mark();
100 }
101 }
102
count() const103 unsigned SmallStrings::count() const
104 {
105 unsigned count = 0;
106 if (m_emptyString)
107 ++count;
108 for (unsigned i = 0; i < numCharactersToStore; ++i) {
109 if (m_singleCharacterStrings[i])
110 ++count;
111 }
112 return count;
113 }
114
createEmptyString(JSGlobalData * globalData)115 void SmallStrings::createEmptyString(JSGlobalData* globalData)
116 {
117 ASSERT(!m_emptyString);
118 m_emptyString = new (globalData) JSString(globalData, "", JSString::HasOtherOwner);
119 }
120
createSingleCharacterString(JSGlobalData * globalData,unsigned char character)121 void SmallStrings::createSingleCharacterString(JSGlobalData* globalData, unsigned char character)
122 {
123 if (!m_storage)
124 m_storage.set(new SmallStringsStorage);
125 ASSERT(!m_singleCharacterStrings[character]);
126 m_singleCharacterStrings[character] = new (globalData) JSString(globalData, m_storage->rep(character), JSString::HasOtherOwner);
127 }
128
singleCharacterStringRep(unsigned char character)129 UString::Rep* SmallStrings::singleCharacterStringRep(unsigned char character)
130 {
131 if (!m_storage)
132 m_storage.set(new SmallStringsStorage);
133 return m_storage->rep(character);
134 }
135
136 } // namespace JSC
137