runtime/SmallStrings.cpp

   1 /*
   2  * Copyright (C) 2008, 2010 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 "HeapRootVisitor.h"
  30 #include "JSGlobalObject.h"
  31 #include "JSString.h"
  32 #include <wtf/Noncopyable.h>
  33 #include <wtf/PassOwnPtr.h>
  34
  35 namespace JSC {
  36
  37 static inline void finalize(JSString*& string)
  38 {
  39     if (!string || Heap::isMarked(string))
  40         return;
  41     string = 0;
  42 }
  43
  44 class SmallStringsStorage {
  45     WTF_MAKE_NONCOPYABLE(SmallStringsStorage); WTF_MAKE_FAST_ALLOCATED;
  46 public:
  47     SmallStringsStorage();
  48
  49     StringImpl* rep(unsigned char character)
  50     {
  51         return m_reps[character].get();
  52     }
  53
  54 private:
  55     static const unsigned singleCharacterStringCount = maxSingleCharacterString + 1;
  56
  57     RefPtr<StringImpl> m_reps[singleCharacterStringCount];
  58 };
  59
  60 SmallStringsStorage::SmallStringsStorage()
  61 {
  62     LChar* characterBuffer = 0;
  63     RefPtr<StringImpl> baseString = StringImpl::createUninitialized(singleCharacterStringCount, characterBuffer);
  64     for (unsigned i = 0; i < singleCharacterStringCount; ++i) {
  65         characterBuffer[i] = i;
  66         m_reps[i] = StringImpl::create(baseString, i, 1);
  67     }
  68 }
  69
  70 SmallStrings::SmallStrings()
  71     : m_emptyString(0)
  72 #define JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE(name) , m_##name(0)
  73     JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE)
  74 #undef JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE
  75 {
  76     COMPILE_ASSERT(singleCharacterStringCount == sizeof(m_singleCharacterStrings) / sizeof(m_singleCharacterStrings[0]), IsNumCharactersConstInSyncWithClassUsage);
  77
  78     for (unsigned i = 0; i < singleCharacterStringCount; ++i)
  79         m_singleCharacterStrings[i] = 0;
  80 }
  81
  82 SmallStrings::~SmallStrings()
  83 {
  84 }
  85
  86 void SmallStrings::finalizeSmallStrings()
  87 {
  88     finalize(m_emptyString);
  89     for (unsigned i = 0; i < singleCharacterStringCount; ++i)
  90         finalize(m_singleCharacterStrings[i]);
  91 #define JSC_COMMON_STRINGS_ATTRIBUTE_FINALIZE(name) finalize(m_##name);
  92     JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_FINALIZE)
  93 #undef JSC_COMMON_STRINGS_ATTRIBUTE_FINALIZE
  94 }
  95
  96 void SmallStrings::createEmptyString(JSGlobalData* globalData)
  97 {
  98     ASSERT(!m_emptyString);
  99     m_emptyString = JSString::createHasOtherOwner(*globalData, StringImpl::empty());
 100 }
 101
 102 void SmallStrings::createSingleCharacterString(JSGlobalData* globalData, unsigned char character)
 103 {
 104     if (!m_storage)
 105         m_storage = adoptPtr(new SmallStringsStorage);
 106     ASSERT(!m_singleCharacterStrings[character]);
 107     m_singleCharacterStrings[character] = JSString::createHasOtherOwner(*globalData, PassRefPtr<StringImpl>(m_storage->rep(character)));
 108 }
 109
 110 StringImpl* SmallStrings::singleCharacterStringRep(unsigned char character)
 111 {
 112     if (!m_storage)
 113         m_storage = adoptPtr(new SmallStringsStorage);
 114     return m_storage->rep(character);
 115 }
 116
 117 void SmallStrings::initialize(JSGlobalData* globalData, JSString*& string, const char* value) const
 118 {
 119     string = JSString::create(*globalData, StringImpl::create(value));
 120 }
 121
 122 } // namespace JSC