JUCE/modules/juce_core/text/juce_StringPool.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2016 - ROLI Ltd.

   Permission is granted to use this software under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license/

   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.

   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.

   -----------------------------------------------------------------------------

   To release a closed-source product which uses other parts of JUCE not
   licensed under the ISC terms, commercial licenses are available: visit
   www.juce.com for more information.

  ==============================================================================
*/

#pragma once


//==============================================================================
/**
    A StringPool holds a set of shared strings, which reduces storage overheads and improves
    comparison speed when dealing with many duplicate strings.

    When you add a string to a pool using getPooledString, it'll return a character
    array containing the same string. This array is owned by the pool, and the same array
    is returned every time a matching string is asked for. This means that it's trivial to
    compare two pooled strings for equality, as you can simply compare their pointers. It
    also cuts down on storage if you're using many copies of the same string.
*/
class JUCE_API  StringPool
{
public:
    //==============================================================================
    /** Creates an empty pool. */
    StringPool() noexcept;

    /** Destructor */
    ~StringPool();

    //==============================================================================
    /** Returns a pointer to a shared copy of the string that is passed in.
        The pool will always return the same String object when asked for a string that matches it.
    */
    String getPooledString (const String& original);

    /** Returns a pointer to a copy of the string that is passed in.
        The pool will always return the same String object when asked for a string that matches it.
    */
    String getPooledString (const char* original);

    /** Returns a pointer to a shared copy of the string that is passed in.
        The pool will always return the same String object when asked for a string that matches it.
    */
    String getPooledString (StringRef original);

    /** Returns a pointer to a copy of the string that is passed in.
        The pool will always return the same String object when asked for a string that matches it.
    */
    String getPooledString (String::CharPointerType start, String::CharPointerType end);

    //==============================================================================
    /** Scans the pool, and removes any strings that are unreferenced.
        You don't generally need to call this - it'll be called automatically when the pool grows
        large enough to warrant it.
    */
    void garbageCollect();

    /** Returns a shared global pool which is used for things like Identifiers, XML parsing. */
    static StringPool& getGlobalPool() noexcept;

private:
    Array<String> strings;
    CriticalSection lock;
    uint32 lastGarbageCollectionTime;

    void garbageCollectIfNeeded();

    JUCE_DECLARE_NON_COPYABLE (StringPool)
};