Experimental CompressibleString UMA

third_party/WebKit/Source/platform/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 "platform/PlatformExport.h"
+#include "wtf/text/Unicode.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+// TODO(hajimehoshi): Now these classes are in platform/text to use UMA. Move
+// them to wtf/text.
+
+class PLATFORM_EXPORT CompressibleStringImpl final : public RefCounted<CompressibleStringImpl> {
+    WTF_MAKE_NONCOPYABLE(CompressibleStringImpl);
+public:
+    static void compressAll();
+    static void setPageBackground(bool);
+
+    CompressibleStringImpl()
+        : m_string()
+        , m_isCompressed(false)
+    {
+    }
+
+    explicit CompressibleStringImpl(PassRefPtr<StringImpl>);
+    ~CompressibleStringImpl();
+
+    bool isEmpty() const { return originalLength() == 0; }
+
+    bool isCompressed() const { return m_isCompressed; }
+    unsigned originalLength() const { return m_string.length(); }
+    bool is8Bit() const { return m_string.is8Bit(); }
+
+    unsigned originalContentSizeInBytes() const
+    {
+        if (is8Bit())
+            return originalLength() * sizeof(LChar);
+        return originalLength() * sizeof(UChar);
+    }
+
+    // TODO(hajimehoshi): Update this once we implement compression.
+    unsigned currentSizeInBytes() const
+    {
+        return originalContentSizeInBytes();
+    }
+
+    const String& toString()
+    {
+        if (UNLIKELY(isCompressed()))
+            decompressString();
+        return m_string;
+    }
+
+    const LChar* characters8()
+    {
+        return toString().characters8();
+    }
+
+    const UChar* characters16()
+    {
+        return toString().characters16();
+    }
+
+    void compressString();
+    void decompressString();
+
+private:
+    static bool s_isPageBackground;
+
+    String m_string;
+    bool m_isCompressed;
+};
+
+class PLATFORM_EXPORT CompressibleString final {
+public:
+    CompressibleString()
+        : m_impl(nullptr)
+    {
+    }
+
+    CompressibleString(const CompressibleString& rhs)
+        : m_impl(rhs.m_impl)
+    {
+    }
+
+    explicit CompressibleString(PassRefPtr<StringImpl> impl)
+        : m_impl(impl ? adoptRef(new CompressibleStringImpl(impl)) : nullptr)
+    {
+    }
+
+    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 ? m_impl->is8Bit() : false; }
+
+    const String& toString() const { return m_impl ? m_impl->toString() : emptyString(); }
+    const LChar* characters8() const { return m_impl ? m_impl->characters8() : nullptr; }
+    const UChar* characters16() const { return m_impl ? m_impl->characters16() : nullptr; }
+
+    CompressibleStringImpl* impl() const { return m_impl.get(); }
+
+private:
+    void compressString() const { m_impl->compressString(); }
+    void decompressString() const { m_impl->decompressString(); }
+
+    mutable RefPtr<CompressibleStringImpl> m_impl;
+};
+
+} // namespace blink
+
+using blink::CompressibleString;
+using blink::CompressibleStringImpl;
+
+#endif