WIP: Introduce CompressibleString

third_party/WebKit/Source/wtf/text/CompressibleString.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CompressibleString_h
+#define CompressibleString_h
+
+#include "wtf/HashTableDeletedValueType.h"
+#include "wtf/text/Unicode.h"
+#include "wtf/text/WTFString.h"
+
+namespace WTF {
+
+class WTF_EXPORT CompressibleStringImpl : public RefCounted<CompressibleStringImpl> {
+    WTF_MAKE_NONCOPYABLE(CompressibleStringImpl);
+public:
+    static void purgeMemory();
+
+    CompressibleStringImpl(PassRefPtr<StringImpl>);
+    ~CompressibleStringImpl();
+
+    bool isEmpty() const { return m_originalLength == 0; }
+
+    PassRefPtr<StringImpl> impl() { return m_impl; }
+    bool isCompressed() const { return !!m_compressedData; }
+    unsigned originalLength() const { return m_originalLength; }
+    bool is8Bit() const { return m_is8Bit; }
+
+    unsigned originalContentSizeInBytes() const;
+    unsigned currentSizeInBytes() const;
+
+    String toString();
+    const LChar* characters8();
+    const UChar* characters16();
+
+    void compressString();
+    void uncompressString();
+
+private:
+    RefPtr<StringImpl> m_impl;
+    const unsigned m_originalLength;
+    void* m_compressedData;
+    unsigned m_compressedDataSize;
+    const bool m_is8Bit;
+};
+
+class WTF_EXPORT CompressibleString {
+public:
+    CompressibleString();
+    CompressibleString(const CompressibleString&);
+    explicit CompressibleString(PassRefPtr<StringImpl>);
+
+    bool isNull() const { return !m_impl; }
+    bool isEmpty() const { return isNull() || m_impl->isEmpty(); }
+    unsigned length() const { return m_impl ? m_impl->originalLength() : 0; }
+
+    unsigned currentSizeInBytes() const { return m_impl ? m_impl->currentSizeInBytes() : 0; }
+
+    bool isCompressed() const { return m_impl ? m_impl->isCompressed() : false; }
+    bool is8Bit() const { return m_impl->is8Bit(); }
+
+    String toString() const { return m_impl ? m_impl->toString() : String(); }
+    const LChar* characters8() const { return m_impl ? m_impl->characters8() : nullptr; }
+    const UChar* characters16() const { return m_impl ? m_impl->characters16() : nullptr; }
+
+    PassRefPtr<CompressibleStringImpl> impl() const { return m_impl; }
+
+private:
+    void compressString() const;
+    void uncompressString() const;
+
+    mutable RefPtr<CompressibleStringImpl> m_impl;
+};
+
+} // namespace WTF
+
+using WTF::CompressibleString;
+using WTF::CompressibleStringImpl;
+
+#endif