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 "Operations.h"
  33 #include <wtf/Noncopyable.h>
  34 #include <wtf/PassOwnPtr.h>
  35 #include <wtf/text/StringImpl.h>
  36
  37 namespace JSC {
  38
  39 static inline void finalize(JSString*& string)
  40 {
  41     if (!string || Heap::isMarked(string))
  42         return;
  43     string = 0;
  44 }
  45
  46 class SmallStringsStorage {
  47     WTF_MAKE_NONCOPYABLE(SmallStringsStorage); WTF_MAKE_FAST_ALLOCATED;
  48 public:
  49     SmallStringsStorage();
  50
  51     StringImpl* rep(unsigned char character)
  52     {
  53         return m_reps[character].get();
  54     }
  55
  56 private:
  57     static const unsigned singleCharacterStringCount = maxSingleCharacterString + 1;
  58
  59     RefPtr<StringImpl> m_reps[singleCharacterStringCount];
  60 };
  61
  62 SmallStringsStorage::SmallStringsStorage()
  63 {
  64     LChar* characterBuffer = 0;
  65     RefPtr<StringImpl> baseString = StringImpl::createUninitialized(singleCharacterStringCount, characterBuffer);
  66     for (unsigned i = 0; i < singleCharacterStringCount; ++i) {
  67         characterBuffer[i] = i;
  68         m_reps[i] = StringImpl::create(baseString, i, 1);
  69     }
  70 }
  71
  72 SmallStrings::SmallStrings()
  73     : m_emptyString(0)
  74 #define JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE(name) , m_##name(0)
  75     JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE)
  76 #undef JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE
  77 {
  78     COMPILE_ASSERT(singleCharacterStringCount == sizeof(m_singleCharacterStrings) / sizeof(m_singleCharacterStrings[0]), IsNumCharactersConstInSyncWithClassUsage);
  79
  80     for (unsigned i = 0; i < singleCharacterStringCount; ++i)
  81         m_singleCharacterStrings[i] = 0;
  82 }
  83
  84 void SmallStrings::initializeCommonStrings(VM& vm)
  85 {
  86     createEmptyString(&vm);
  87 #define JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE(name) initialize(&vm, m_##name, #name);
  88     JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE)
  89 #undef JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE
  90 }
  91
  92 void SmallStrings::visitStrongReferences(SlotVisitor& visitor)
  93 {
  94     visitor.appendUnbarrieredPointer(&m_emptyString);
  95 #define JSC_COMMON_STRINGS_ATTRIBUTE_VISIT(name) visitor.appendUnbarrieredPointer(&m_##name);
  96     JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_VISIT)
  97 #undef JSC_COMMON_STRINGS_ATTRIBUTE_VISIT
  98 }
  99
 100 SmallStrings::~SmallStrings()
 101 {
 102 }
 103
 104 void SmallStrings::finalizeSmallStrings()
 105 {
 106     finalize(m_emptyString);
 107     for (unsigned i = 0; i < singleCharacterStringCount; ++i)
 108         finalize(m_singleCharacterStrings[i]);
 109 }
 110
 111 void SmallStrings::createEmptyString(VM* vm)
 112 {
 113     ASSERT(!m_emptyString);
 114     m_emptyString = JSString::createHasOtherOwner(*vm, StringImpl::empty());
 115 }
 116
 117 void SmallStrings::createSingleCharacterString(VM* vm, unsigned char character)
 118 {
 119     if (!m_storage)
 120         m_storage = adoptPtr(new SmallStringsStorage);
 121     ASSERT(!m_singleCharacterStrings[character]);
 122     m_singleCharacterStrings[character] = JSString::createHasOtherOwner(*vm, PassRefPtr<StringImpl>(m_storage->rep(character)));
 123 }
 124
 125 StringImpl* SmallStrings::singleCharacterStringRep(unsigned char character)
 126 {
 127     if (!m_storage)
 128         m_storage = adoptPtr(new SmallStringsStorage);
 129     return m_storage->rep(character);
 130 }
 131
 132 void SmallStrings::initialize(VM* vm, JSString*& string, const char* value) const
 133 {
 134     string = JSString::create(*vm, StringImpl::create(value));
 135 }
 136
 137 } // namespace JSC