JUCE/modules/juce_core/text/juce_StringRef.h

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

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided 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.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

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

namespace juce
{

//==============================================================================
/**
    A simple class for holding temporary references to a string literal or String.

    Unlike a real String object, the StringRef does not allocate any memory or
    take ownership of the strings you give to it - it simply holds a reference to
    a string that has been allocated elsewhere.
    The main purpose of the class is to be used instead of a const String& as the type
    of function arguments where the caller may pass either a string literal or a String
    object. This means that when the called uses a string literal, there's no need
    for an temporary String object to be allocated, and this cuts down overheads
    substantially.

    Because the class is simply a wrapper around a pointer, you should always pass
    it by value, not by reference.

    @code
    void myStringFunction1 (const String&);
    void myStringFunction2 (StringRef);

    myStringFunction1 ("abc"); // Implicitly allocates a temporary String object.
    myStringFunction2 ("abc"); // Much faster, as no local allocations are needed.
    @endcode

    For examples of it in use, see the XmlElement or StringArray classes.

    Bear in mind that there are still many cases where it's better to use an argument
    which is a const String&. For example if the function stores the string or needs
    to internally create a String from the argument, then it's better for the original
    argument to already be a String.

    @see String

    @tags{Core}
*/
class JUCE_API  StringRef  final
{
public:
    /** Creates a StringRef from a raw string literal.
        The StringRef object does NOT take ownership or copy this data, so you must
        ensure that the data does not change during the lifetime of the StringRef.
        Note that this pointer cannot be null!
    */
    StringRef (const char* stringLiteral) noexcept;

    /** Creates a StringRef from a raw char pointer.
        The StringRef object does NOT take ownership or copy this data, so you must
        ensure that the data does not change during the lifetime of the StringRef.
    */
    StringRef (String::CharPointerType stringLiteral) noexcept;

    /** Creates a StringRef from a String.
        The StringRef object does NOT take ownership or copy the data from the String,
        so you must ensure that the String is not modified or deleted during the lifetime
        of the StringRef.
    */
    StringRef (const String& string) noexcept;

    /** Creates a StringRef from a String.
        The StringRef object does NOT take ownership or copy the data from the std::string,
        so you must ensure that the source string object is not modified or deleted during
        the lifetime of the StringRef.
    */
    StringRef (const std::string& string);

    /** Creates a StringRef pointer to an empty string. */
    StringRef() noexcept;

    //==============================================================================
    /** Returns a raw pointer to the underlying string data. */
    operator const String::CharPointerType::CharType*() const noexcept  { return text.getAddress(); }
    /** Returns a pointer to the underlying string data as a char pointer object. */
    operator String::CharPointerType() const noexcept                   { return text; }

    /** Returns true if the string is empty. */
    bool isEmpty() const noexcept                                       { return text.isEmpty(); }
    /** Returns true if the string is not empty. */
    bool isNotEmpty() const noexcept                                    { return ! text.isEmpty(); }
    /** Returns the number of characters in the string. */
    int length() const noexcept                                         { return (int) text.length(); }

    /** Retrieves a character by index. */
    juce_wchar operator[] (int index) const noexcept                    { return text[index]; }

    /** Compares this StringRef with a String. */
    bool operator== (const String& s) const noexcept                    { return text.compare (s.getCharPointer()) == 0; }
    /** Compares this StringRef with a String. */
    bool operator!= (const String& s) const noexcept                    { return text.compare (s.getCharPointer()) != 0; }

    /** Case-sensitive comparison of two StringRefs. */
    bool operator== (StringRef s) const noexcept                        { return text.compare (s.text) == 0; }
    /** Case-sensitive comparison of two StringRefs. */
    bool operator!= (StringRef s) const noexcept                        { return text.compare (s.text) != 0; }

    //==============================================================================
    /** The text that is referenced. */
    String::CharPointerType text;

    #if JUCE_STRING_UTF_TYPE != 8 && ! defined (DOXYGEN)
     // Sorry, non-UTF8 people, you're unable to take advantage of StringRef, because
     // you've chosen a character encoding that doesn't match C++ string literals.
     String stringCopy;
    #endif
};

//==============================================================================
/** Case-sensitive comparison of two strings. */
JUCE_API bool JUCE_CALLTYPE operator== (const String& string1, StringRef string2) noexcept;
/** Case-sensitive comparison of two strings. */
JUCE_API bool JUCE_CALLTYPE operator!= (const String& string1, StringRef string2) noexcept;

inline String operator+ (String s1, StringRef s2)           { return s1 += String (s2.text); }
inline String operator+ (StringRef s1, const String& s2)    { return String (s1.text) + s2; }
inline String operator+ (const char* s1, StringRef s2)      { return String (s1) + String (s2.text); }
inline String operator+ (StringRef s1, const char* s2)      { return String (s1.text) + String (s2); }

} // namespace juce