Import all this stuff into a single repo called Serenity.

AK/StringImpl.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include "Retainable.h"
+#include "RetainPtr.h"
+
+namespace AK {
+
+class StringImpl : public Retainable<StringImpl> {
+public:
+    static RetainPtr<StringImpl> createUninitialized(unsigned length, char*& buffer);
+    static RetainPtr<StringImpl> create(const char* cstring);
+    static RetainPtr<StringImpl> create(const char* cstring, size_t length);
+    RetainPtr<StringImpl> toLowercase() const;
+    RetainPtr<StringImpl> toUppercase() const;
+
+    static StringImpl& theEmptyStringImpl();
+
+    ~StringImpl();
+
+    unsigned length() const { return m_length; }
+    const char* characters() const { return m_characters; }
+    char operator[](unsigned i) const { ASSERT(i < m_length); return m_characters[i]; }
+
+    unsigned hash() const
+    {
+        if (!m_hasHash)
+            computeHash();
+        return m_hash;
+    }
+
+private:
+    enum ConstructTheEmptyStringImplTag { ConstructTheEmptyStringImpl };
+    explicit StringImpl(ConstructTheEmptyStringImplTag) : m_characters("") { }
+
+    enum ConstructWithInlineBufferTag { ConstructWithInlineBuffer };
+    explicit StringImpl(ConstructWithInlineBufferTag, unsigned length) : m_length(length), m_characters(m_inlineBuffer) { }
+
+    void computeHash() const;
+
+    unsigned m_length { 0 };
+    bool m_ownsBuffer { true };
+    mutable bool m_hasHash { false };
+    const char* m_characters { nullptr };
+    mutable unsigned m_hash { 0 };
+    char m_inlineBuffer[0];
+};
+
+}
+
+using AK::StringImpl;