JavaScriptCore-521.tar.gz

[apple/javascriptcore.git] / runtime / SmallStrings.cpp

diff --git a/runtime/SmallStrings.cpp b/runtime/SmallStrings.cpp
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+/*
+ * Copyright (C) 2008 Apple Inc. All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "SmallStrings.h"
+
+#include "JSGlobalObject.h"
+#include "JSString.h"
+
+#include <wtf/Noncopyable.h>
+
+namespace JSC {
+static const unsigned numCharactersToStore = 0x100;
+
+class SmallStringsStorage : Noncopyable {
+public:
+    SmallStringsStorage();
+
+    UString::Rep* rep(unsigned char character) { return &m_reps[character]; }
+
+private:
+    UChar m_characters[numCharactersToStore];
+    UString::BaseString m_base;
+    UString::Rep m_reps[numCharactersToStore];
+};
+
+SmallStringsStorage::SmallStringsStorage()
+{
+    for (unsigned i = 0; i < numCharactersToStore; ++i)
+        m_characters[i] = i;
+
+    m_base.rc = numCharactersToStore + 1;
+    m_base.buf = m_characters;
+    m_base.len = numCharactersToStore;
+    m_base.offset = 0;
+    m_base._hash = 0;
+    m_base.m_baseString = 0;
+    m_base.preCapacity = 0;
+    m_base.usedPreCapacity = 0;
+    m_base.reportedCost = 0;
+
+    // make sure UString doesn't try to reuse the buffer by pretending we have one more character in it
+    m_base.usedCapacity = numCharactersToStore + 1;
+    m_base.capacity = numCharactersToStore + 1;
+    m_base.checkConsistency();
+
+    memset(&m_reps, 0, sizeof(m_reps));
+    for (unsigned i = 0; i < numCharactersToStore; ++i) {
+        m_reps[i].offset = i;
+        m_reps[i].len = 1;
+        m_reps[i].rc = 1;
+        m_reps[i].setBaseString(&m_base);
+        m_reps[i].checkConsistency();
+    }
+}
+
+SmallStrings::SmallStrings()
+    : m_emptyString(0)
+    , m_storage(0)
+{
+    COMPILE_ASSERT(numCharactersToStore == sizeof(m_singleCharacterStrings) / sizeof(m_singleCharacterStrings[0]), IsNumCharactersConstInSyncWithClassUsage);
+
+    for (unsigned i = 0; i < numCharactersToStore; ++i)
+        m_singleCharacterStrings[i] = 0;
+}
+
+SmallStrings::~SmallStrings()
+{
+}
+
+void SmallStrings::mark()
+{
+    if (m_emptyString && !m_emptyString->marked())
+        m_emptyString->mark();
+    for (unsigned i = 0; i < numCharactersToStore; ++i) {
+        if (m_singleCharacterStrings[i] && !m_singleCharacterStrings[i]->marked())
+            m_singleCharacterStrings[i]->mark();
+    }
+}
+
+unsigned SmallStrings::count() const
+{
+    unsigned count = 0;
+    if (m_emptyString)
+        ++count;
+    for (unsigned i = 0; i < numCharactersToStore; ++i) {
+        if (m_singleCharacterStrings[i])
+            ++count;
+    }
+    return count;
+}
+
+void SmallStrings::createEmptyString(JSGlobalData* globalData)
+{
+    ASSERT(!m_emptyString);
+    m_emptyString = new (globalData) JSString(globalData, "", JSString::HasOtherOwner);
+}
+
+void SmallStrings::createSingleCharacterString(JSGlobalData* globalData, unsigned char character)
+{
+    if (!m_storage)
+        m_storage.set(new SmallStringsStorage);
+    ASSERT(!m_singleCharacterStrings[character]);
+    m_singleCharacterStrings[character] = new (globalData) JSString(globalData, m_storage->rep(character), JSString::HasOtherOwner);
+}
+
+UString::Rep* SmallStrings::singleCharacterStringRep(unsigned char character)
+{
+    if (!m_storage)
+        m_storage.set(new SmallStringsStorage);
+    return m_storage->rep(character);
+}
+
+} // namespace JSC