/////////////////////////////////////////////////////////////////////////////
// Name:        string.h
// Purpose:     interface of wxStringBuffer, wxString
// Author:      wxWidgets team
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////


/**
    @class wxString

    String class for passing textual data to or receiving it from wxWidgets.

    @note
    While the use of wxString is unavoidable in wxWidgets programs, you are
    encouraged to use the standard string classes @c std::string or @c
    std::wstring in your applications and convert them to and from wxString
    only when interacting with wxWidgets.


    wxString is a class representing a Unicode character string but with
    methods taking or returning both @c wchar_t wide characters and @c wchar_t*
    wide strings and traditional @c char characters and @c char* strings. The
    dual nature of wxString API makes it simple to use in all cases and,
    importantly, allows the code written for either ANSI or Unicode builds of
    the previous wxWidgets versions to compile and work correctly with the
    single unified build of wxWidgets 3.0 and later. It is also mostly
    transparent when using wxString with the few exceptions described below.


    @section string_api API overview

    wxString tries to be similar to both @c std::string and @c std::wstring and
    can mostly be used as either class. It provides practically all of the
    methods of these classes, which behave exactly the same as in the standard
    C++, and so are not documented here (please see documentation at
    https://en.cppreference.com/w/cpp/string/basic_string for this).

    In addition to these standard methods, wxString adds functions dealing with
    the conversions between different string encodings, described below, as
    well as many extra helpers such as functions for formatted output
    (Printf(), Format(), ...), case conversion (MakeUpper(), Capitalize(), ...)
    and various others (Trim(), StartsWith(), Matches(), ...). All of the
    non-standard methods follow wxWidgets "CamelCase" naming convention and are
    documented here.

    Notice that some wxString methods exist in several versions for
    compatibility reasons. For example all of length(), Length() and Len() are
    provided. In such cases it is recommended to use the standard string-like
    method, i.e. length() in this case.


    @section string_conv Converting to and from wxString

    wxString can be created from:
        - ASCII string guaranteed to contain only 7 bit characters using
        wxString::FromAscii().
        - Narrow @c char* string in the current locale encoding using implicit
        wxString::wxString(const char*) constructor or using more explicit
        wxString::wxString(const char*, const wxMBConv&) constructor passing it
        wxConvLibc as the second argument.
        - Narrow @c char* string in UTF-8 encoding using wxString::FromUTF8().
        - Narrow @c char* string in the given encoding using
        wxString::wxString(const char*, const wxMBConv&) constructor passing a
        wxCSConv corresponding to the encoding as the second argument.
        - Standard @c std::string using implicit
        wxString::wxString(const std::string&) constructor.
        Notice that this constructor supposes that the string contains data in
        the current locale encoding, use FromUTF8() if the string contains
        UTF-8-encoded data instead.
        - Standard @c std::string_view using implicit wxString::wxString(std::string_view)
        constructor.
        Notice that this constructor supposes that the string contains data in
        the current locale encoding, use FromUTF8() if the string contains
        UTF-8-encoded data instead.
        - Wide @c wchar_t* string using implicit
        wxString::wxString(const wchar_t*) constructor.
        - Standard @c std::wstring using implicit
        wxString::wxString(const std::wstring&) constructor.
        - Standard @c std::wstring_view using implicit
        wxString::wxString(std::wstring_view) constructor.

    Notice that many of the constructors are implicit, meaning that you don't
    even need to write them at all to pass the existing string to some
    wxWidgets function taking a wxString. This is convenient, but can also be
    dangerous when constructing wxString from `char*` or `std::string` if it
    doesn't have the expected encoding, as the resulting string will be empty
    if the conversion from the current locale encoding fails. If you want to
    disable all such conversions at compile-time, you may predefine
    `wxNO_IMPLICIT_WXSTRING_ENCODING` when compiling the application code and
    the corresponding conversions become inaccessible, i.e.
    @code
        wxString s;
        // s = "world"; does not compile with wxNO_IMPLICIT_WXSTRING_ENCODING
        s = wxString::FromAscii("world"); // Always compiles
        s = wxASCII_STR("world"); // shorthand for the above
        s = wxString::FromUTF8("world"); // Always compiles
        s = wxString("world", wxConvLibc); // Always compiles, explicit encoding
        s = wxASCII_STR("Grüße"); // Always compiles but s may be empty!
    @endcode

    The only case in which such conversions are fully safe is when the library
    is compiled with `wxUSE_UTF8_LOCALE_ONLY` option set to 1, as all the
    strings are assumed to be in UTF-8 encoding then.


    Similarly, wxString can be converted to:
        - ASCII string using wxString::ToAscii(). This is a potentially
        destructive operation as all non-ASCII string characters are replaced
        with a placeholder character.
        - String in the current locale encoding implicitly or using c_str() or
        mb_str() methods. This is a potentially destructive operation as an @e
        empty string is returned if the conversion fails.
        - String in UTF-8 encoding using wxString::utf8_str().
        - String in any given encoding using mb_str() with the appropriate
        wxMBConv object. This is also a potentially destructive operation.
        - Standard @c std::string using wxString::ToStdString(). The encoding
        of the returned string is specified with a wxMBConv object, so this
        conversion is potentially destructive as well. To ensure that there is
        no data loss, use @c wxConvUTF8 conversion or wxString::utf8_string().
        - Wide C string using implicit conversion or wxString::wc_str()
        explicitly.
        - Standard @c std::wstring using wxString::ToStdWstring() or its
        synonym wxString::wc_string().


    As above, defining `wxNO_IMPLICIT_WXSTRING_ENCODING` when compiling
    application code prevents the implicit use of the current locale encoding
    and disables implicit conversions to `char*` and `std::string` as well as
    using mb_str() and ToStdString() without explicitly specifying the
    encoding:
    @code
        const char *c;
        // c = s.c_str();  does not compile with wxNO_IMPLICIT_WXSTRING_ENCODING
        // c = s.mb_str(); does not compile with wxNO_IMPLICIT_WXSTRING_ENCODING
        c = s.ToAscii(); // Always compiles, encoding may fail
        c = s.ToUTF8(); // Always compiles, encoding never fails
        c = s.utf8_str(); // Alias for the above
        c = s.mb_str(wxConvLibc); // Always compiles, explicit encoding, but
                                  // conversion may fail!
    @endcode

    However, if completely disabling conversions to narrow strings by defining
    `wxNO_IMPLICIT_WXSTRING_ENCODING` is undesirable, it is also possible to
    disable implicit conversions by predefining `wxNO_UNSAFE_WXSTRING_CONV`
    instead, i.e. with this symbol defined implicit conversion to `const char*`
    becomes unavailable -- but explicit conversions using c_str() and mb_str()
    still work.

    Finally, please note that implicit conversion to both `const char*` (which
    is unsafe for the reasons explained above) and to `const wchar_t*` (which
    is safe from this point of view, but may still be considered dangerous, as
    any implicit conversion) may be entirely disabled by defining
    `wxNO_IMPLICIT_WXSTRING_CONV_TO_PTR` when building the application.


    To summarize, the safest way to use wxString is to always define
    `wxNO_IMPLICIT_WXSTRING_ENCODING` in the application compilation options to
    disable all implicit uses of encoding and specify it explicitly, typically
    by using utf8_str() or utf8_string() and FromUTF8() for conversions, for
    every operation. If this is impossible, for example because it would
    require too many changes to the existing code, consider defining
    `wxNO_UNSAFE_WXSTRING_CONV` to at least disable implicit unsafe conversions.


    @section string_gotchas Traps for the unwary

    As mentioned above, wxString tries to be compatible with both narrow and
    wide standard string classes and mostly does it transparently, but there
    are some exceptions.

    @subsection string_gotchas_element String element access

    Some problems are caused by wxString::operator[]() which returns an object
    of a special proxy class allowing to assign either a simple @c char or a @c
    wchar_t to the given index. Because of this, the return type of this
    operator is neither @c char nor @c wchar_t nor a reference to one of these
    types but wxUniCharRef which is not a primitive type and hence can't be
    used in the @c switch statement. So the following code does @e not compile
        @code
            wxString s(...);
            switch ( s[n] ) {
                case 'A':
                    ...
                    break;
            }
        @endcode
    and you need to use
        @code
            switch ( s[n].GetValue() ) {
                ...
            }
        @endcode
    instead. Alternatively, you can use an explicit cast:
        @code
            switch ( static_cast<char>(s[n]) ) {
                ...
            }
        @endcode
    but notice that this will result in an assert failure if the character at
    the given position is not representable as a single @c char in the current
    encoding, so you may want to cast to @c int instead if non-ASCII values can
    be used.

    Another consequence of this unusual return type arises when it is used with
    template deduction or C++11 @c auto keyword. Unlike with the normal
    references which are deduced to be of the referenced type, the deduced type
    for wxUniCharRef is wxUniCharRef itself. This results in potentially
    unexpected behaviour, for example:
        @code
            wxString s("abc");
            auto c = s[0];
            c = 'x';            // Modifies the string!
            wxASSERT( s == "xbc" );
        @endcode
    Due to this, either explicitly specify the variable type:
        @code
            int c = s[0];
            c = 'x';            // Doesn't modify the string any more.
            wxASSERT( s == "abc" );
        @endcode
    or explicitly convert the return value:
        @code
            auto c = s[0].GetValue();
            c = 'x';            // Doesn't modify the string either.
            wxASSERT( s == "abc" );
        @endcode


    @subsection string_gotchas_conv Conversion to C string

    A different class of problems happens due to the dual nature of the return
    value of wxString::c_str() method, which is also used for implicit
    conversions. The result of calls to this method is convertible to either
    narrow @c char* string or wide @c wchar_t* string and so, again, has
    neither the former nor the latter type. Usually, the correct type will be
    chosen depending on how you use the result but sometimes the compiler can't
    choose it because of an ambiguity, e.g.:
        @code
            // Some non-wxWidgets functions existing for both narrow and wide
            // strings:
            void dump_text(const char* text);       // Version (1)
            void dump_text(const wchar_t* text);    // Version (2)

            wxString s(...);
            dump_text(s);           // ERROR: ambiguity.
            dump_text(s.c_str());   // ERROR: still ambiguous.
        @endcode
    In this case you need to explicitly convert to the type that you need to
    use or use a different, non-ambiguous, conversion function (which is
    usually the best choice):
        @code
            dump_text(static_cast<const char*>(s));            // OK, calls (1)
            dump_text(static_cast<const wchar_t*>(s.c_str())); // OK, calls (2)
            dump_text(s.mb_str());                             // OK, calls (1)
            dump_text(s.wc_str());                             // OK, calls (2)
            dump_text(s.wx_str());                             // OK, calls ???
        @endcode

    @subsection string_vararg Using wxString with vararg functions

    A special subclass of the problems arising due to the polymorphic nature of
    wxString::c_str() result type happens when using functions taking an
    arbitrary number of arguments, such as the standard @c printf(). Due to the
    rules of the C++ language, the types for the "variable" arguments of such
    functions are not specified and hence the compiler cannot convert wxString
    objects, or the objects returned by wxString::c_str(), to these unknown
    types automatically. Hence neither wxString objects nor the results of most
    of the conversion functions can be passed as vararg arguments:
        @code
            // ALL EXAMPLES HERE DO NOT WORK, DO NOT USE THEM!
            printf("Don't do this: %s", s);
            printf("Don't do that: %s", s.c_str());
            printf("Nor even this: %s", s.mb_str());
            wprintf("And even not always this: %s", s.wc_str());
        @endcode
    Instead you need to either explicitly cast to the needed type:
        @code
            // These examples work but are not the best solution, see below.
            printf("You can do this: %s", static_cast<const char*>(s));
            printf("Or this: %s", static_cast<const char*>(s.c_str()));
            printf("And this: %s", static_cast<const char*>(s.mb_str()));
            wprintf("Or this: %s", static_cast<const wchar_t*>(s.wc_str()));
        @endcode
    But a better solution is to use wxWidgets-provided functions, if possible,
    as is the case for @c printf family of functions:
        @code
            // This is the recommended way.
            wxPrintf("You can do just this: %s", s);
            wxPrintf("And this (but it is redundant): %s", s.c_str());
            wxPrintf("And this (not using Unicode): %s", s.mb_str());
            wxPrintf("And this (always Unicode): %s", s.wc_str());
        @endcode
    Notice that wxPrintf() replaces both @c printf() and @c wprintf() and
    accepts wxString objects, results of c_str() calls but also @c char* and
    @c wchar_t* strings directly.

    wxWidgets provides wx-prefixed equivalents to all the standard vararg
    functions and a few more, notably wxString::Format(), wxLogMessage(),
    wxLogError() and other log functions. But if you can't use one of those
    functions and need to pass wxString objects to non-wx vararg functions, you
    need to use the explicit casts as explained above.


    @section string_performance Performance characteristics

    wxString uses @c std::basic_string internally to store its content and it
    therefore inherits many features from the standard class. In particular,
    most implementations of @c std::basic_string use small string optimization,
    meaning that they avoid allocating heap memory for short strings, and this
    is also true for wxString.

    By default, wxString uses @c std::basic_string specialized for the
    platform-dependent @c wchar_t type, meaning that it is not memory-efficient
    for ASCII strings, especially under Unix platforms where every ASCII
    character, normally fitting in a byte, is represented by a 4 byte @c
    wchar_t.

    It is possible to build wxWidgets with @c wxUSE_UNICODE_UTF8 set to 1 in
    which case an UTF-8-encoded string representation is stored in @c
    std::basic_string specialized for @c char, i.e. the usual @c std::string.
    In this case the memory efficiency problem mentioned above doesn't arise
    but run-time performance of many wxString methods changes dramatically, in
    particular accessing the N-th character of the string becomes an operation
    taking O(N) time instead of O(1), i.e. constant, time by default. Thus, if
    you do use this so called UTF-8 build, you should avoid using indices to
    access the strings whenever possible and use the iterators instead. As an
    example, traversing the string using iterators is an O(N), where N is the
    string length, operation in both the normal ("wchar_t") and UTF-8 builds
    but doing it using indices becomes O(N^2) in UTF-8 case meaning that simply
    checking every character of a reasonably long (e.g. a couple of millions
    elements) string can take an unreasonably long time.

    However, if you do use iterators, UTF-8 build can be a better choice than
    the default build, especially for the memory-constrained embedded systems.
    Notice also that GTK+ and DirectFB use UTF-8 internally, so using this
    build not only saves memory for ASCII strings but also avoids conversions
    between wxWidgets and the underlying toolkit.


    @section string_index Index of the member groups

    Links for quick access to the various categories of wxString functions:
    - @ref_member_group{ctor, Constructors and assignment operators}
    - @ref_member_group{length, Length functions}
    - @ref_member_group{ch_access, Character access functions}
    - @ref_member_group{conv, Conversions functions}
    - @ref_member_group{concat, Concatenation functions}
    - @ref_member_group{cmp, Comparison functions}
    - @ref_member_group{substring, Substring extraction functions}
    - @ref_member_group{caseconv, Case conversion functions}
    - @ref_member_group{search, Searching and replacing functions}
    - @ref_member_group{numconv, Conversion to numbers functions}
    - @ref_member_group{fmt, Formatting and printing functions}
    - @ref_member_group{mem, Memory management functions}
    - @ref_member_group{misc, Miscellaneous functions}
    - @ref_member_group{iter, Iterator interface functions}
    - @ref_member_group{stl, STL interface functions}


    @library{wxbase}
    @category{data}

    @stdobjects
    ::wxEmptyString

    @see @ref overview_string, @ref overview_unicode,
         @ref group_funcmacro_string "String-related functions", wxUString,
         wxCharBuffer, wxUniChar, wxStringTokenizer, wxStringBuffer, wxStringBufferLength
*/
class wxString
{
public:
    /**
        @name Standard types

        Types used with wxString.
    */
    ///@{
    typedef wxUniChar value_type;
    typedef wxUniChar char_type;
    typedef wxUniCharRef reference;
    typedef wxChar* pointer;
    typedef const wxChar* const_pointer;
    typedef size_t size_type;
    typedef wxUniChar const_reference;
    ///@}


    /**
        @member_group_name{ctor, Constructors and assignment operators}

        A string may be constructed either from a C string, (some number of copies of)
        a single character or a wide (Unicode) string. For all constructors (except the
        default which creates an empty string) there is also a corresponding assignment
        operator.

        See also the assign() STL-like function.
    */
    ///@{

    /**
       Default constructor
    */
    wxString();

    /**
       Creates a string from another string.
       Just increases the ref count by 1.
    */
    wxString(const wxString& stringSrc);

    /**
       Construct a string consisting of @a nRepeat copies of ch.
    */
    wxString(wxUniChar ch, size_t nRepeat = 1);

    /**
       Construct a string consisting of @a nRepeat copies of ch.
    */
    wxString(wxUniCharRef ch, size_t nRepeat = 1);

    /**
       Construct a string consisting of @a nRepeat copies of ch
       converted to Unicode using the current locale encoding.
    */
    wxString(char ch, size_t nRepeat = 1);

    /**
       Construct a string consisting of @a nRepeat copies of ch.
    */
    wxString(wchar_t ch, size_t nRepeat = 1);

    /**
       Constructs a string from the string literal @a psz using
       the current locale encoding to convert it to Unicode (wxConvLibc).
    */
    wxString(const char *psz);

    /**
       Constructs a string from the string literal @a psz using
       @a conv to convert it Unicode.
    */
    wxString(const char *psz, const wxMBConv& conv);

    /**
       Constructs a string from the first @a nLength bytes of the string literal @a psz using
       the current locale encoding to convert it to Unicode (wxConvLibc).
    */
    wxString(const char *psz, size_t nLength);

    /**
       Constructs a string from the first @a nLength bytes of the string literal @a psz using
       @a conv to convert it Unicode.
    */
    wxString(const char *psz, const wxMBConv& conv, size_t nLength);

    /**
       Constructs a string from the string literal @a pwz.
    */
    wxString(const wchar_t *pwz);

    /**
       Constructs a string from the first @a nLength characters of the string literal @a pwz.
    */
    wxString(const wchar_t *pwz, size_t nLength);

    /**
       Constructs a string from @a buf using the using the current locale
        encoding to convert it to Unicode.
    */
    wxString(const wxCharBuffer& buf);

    /**
       Constructs a string from @a buf.
    */
    wxString(const wxWCharBuffer& buf);

    /**
       Constructs a string from @a str using the using the current locale encoding
       to convert it to Unicode (wxConvLibc).

       @see ToStdString()
    */
    wxString(const std::string& str);

    /**
       Constructs a string from @a str using the using the current locale encoding
       to convert it to Unicode (wxConvLibc).

       @note Requires the application to be compiled with C++17

       @since 3.3.0
    */
    wxString(std::string_view str);

    /**
       Constructs a string from @a str.

       @see ToStdWstring(), wc_string()
    */
    wxString(const std::wstring& str);

    /**
       Constructs a string from @a str.

       @note Requires the application to be compiled with C++17

       @since 3.3.0
    */
    wxString(std::wstring_view str);

    /**
        String destructor.

        Note that this is not virtual, so wxString must not be inherited from.
    */
    ~wxString();

    /**
        Assignment: see the relative wxString constructor.
    */
    wxString operator =(const wxString& str);

    /**
        Assignment: see the relative wxString constructor.
    */
    wxString operator =(wxUniChar c);

    ///@}



    /**
        @member_group_name{length, String length}

        These functions return the string length and/or check whether the string
        is empty.

        See also the length(), size() or empty() STL-like functions.
    */
    ///@{


    /**
        Returns the length of the string.
    */
    size_t Len() const;

    /**
        Returns the length of the string (same as Len).
        This is a wxWidgets 1.xx compatibility function; you should not use it in new
        code.
    */
    size_t Length() const;

    /**
        Returns @true if the string is empty.
    */
    bool IsEmpty() const;

    /**
        Returns @true if the string is empty (same as wxString::IsEmpty).
        This is a wxWidgets 1.xx compatibility function; you should not use it in new
        code.
    */
    bool IsNull() const;

    /**
        Empty string is @false, so !string will only return @true if the
        string is empty.

        @see IsEmpty().
    */
    bool operator!() const;

    ///@}



    /**
        @member_group_name{ch_access, Character access}

        Many functions below take a character index in the string.
        As with C strings and arrays, the indices start from 0, so the first character
        of a string is string[0]. An attempt to access a character beyond the end of the
        string (which may even be 0 if the string is empty) will provoke an assert
        failure in @ref overview_debugging "debug builds", but no checks are
        done in release builds.
    */
    ///@{

    /**
        Returns the character at position @a n (read-only).
    */
    wxUniChar GetChar(size_t n) const;

    /**
        wxWidgets compatibility conversion. Same as c_str().
    */
    const wxCStrData GetData() const;

    /**
        Returns a reference to the character at position @a n.
    */
    wxUniCharRef GetWritableChar(size_t n);

    /**
        Sets the character at position @e n.
    */
    void SetChar(size_t n, wxUniChar ch);

    /**
        Returns the last character.

        This is a wxWidgets 1.xx compatibility function;
        you should not use it in new code.
    */
    wxUniChar Last() const;

    /**
        Returns a reference to the last character (writable).

        This is a wxWidgets 1.xx compatibility function;
        you should not use it in new code.
    */
    wxUniCharRef Last();

    /**
        Returns the @a i-th character of the string.
    */
    wxUniChar operator [](size_t i) const;

    /**
        Returns a writable reference to the @a i-th character of the string.
    */
    wxUniCharRef operator [](size_t i);

    ///@}


    /**
        @member_group_name{conv, Conversions}

        This section contains both implicit and explicit conversions to C style
        strings. Although implicit conversion is quite convenient, you are advised
        to use wc_str() for the sake of clarity.
    */
    ///@{

    /**
        Returns a lightweight intermediate class which is in turn implicitly
        convertible to both @c const @c char* and to @c const @c wchar_t*.
        Given this ambiguity it is mostly better to use wc_str(), mb_str() or
        utf8_str() instead.

        Please see the @ref overview_unicode for more information about it.

        Note that the returned value is not convertible to @c char* or
        @c wchar_t*, use char_str() or wchar_str() if you need to pass
        string value to a function expecting non-const pointer.

        @see wc_str(), utf8_str(), c_str(), mb_str(), fn_str()
    */
    wxCStrData c_str() const;

    /**
        Returns an object with string data that is implicitly convertible to
        @c char* pointer. Note that any change to the returned buffer is lost and so
        this function is only usable for passing strings to legacy libraries that
        don't have const-correct API. Use wxStringBuffer if you want to modify
        the string.

        @see c_str()
    */
    wxWritableCharBuffer char_str(const wxMBConv& conv = wxConvLibc) const;

    /**
        Returns buffer of the specified type containing the string data.

        This method is only useful in template code, otherwise you should
        directly call mb_str() or wc_str() if you need to retrieve a narrow or
        wide string from this wxString. The template parameter @a t should be
        either @c char or @c wchar_t.

        Notice that retrieving a char buffer in UTF-8 build will return the
        internal string representation in UTF-8 while in wchar_t build the char
        buffer will contain the conversion of the string to the encoding of the
        current locale (and so can fail).

        @param len
            If non-null, filled with the length of the returned buffer.

        @return
            buffer containing the string contents in the specified type,
            notice that it may be @NULL if the conversion failed (e.g. Unicode
            string couldn't be converted to the current encoding when @a T is
            @c char).
     */
    template <typename T>
    wxCharTypeBuffer<T> tchar_str(size_t *len = nullptr) const;

    /**
        Returns a string representation suitable for passing to OS' functions
        for file handling.

        Depending on OS and configuration, TYPE is either @c wchar_t*,
        @c char*, or wxCharBuffer.
    */
    const TYPE fn_str() const;

    /**
        Returns the multibyte (C string) representation of the string
        using @e conv's wxMBConv::cWC2MB method and returns wxCharBuffer.

        @see wc_str(), utf8_str(), c_str(), wxMBConv
    */
    const wxCharBuffer mb_str(const wxMBConv& conv = wxConvLibc) const;

    /**
        Converts the strings contents to UTF-8 and returns it either as a
        temporary wxCharBuffer object or as a pointer to the internal
        string contents in UTF-8 build.

        @see wc_str(), c_str(), mb_str()
    */
    const wxScopedCharBuffer utf8_str() const;

    /**
        Return the string as an std::string using UTF-8 encoding.

        This is a shorter and more readable equivalent of calling ToStdString()
        with @c wxConvUTF8 argument.

        @since 3.1.5
     */
    const std::string utf8_string() const;

    /**
        Returns the strings contents as a wide character string.

        wxWX2WCbuf is macro which can be either `wchar_t*` or wxWCharBuffer
        depending on whether wxUSE_UNICODE_UTF8 is 0 or 1.

        @see utf8_str(), c_str(), mb_str(), fn_str(), wchar_str()
    */
    const wxWX2WCbuf wc_str() const;

    /**
        Returns the strings contents as a wide character string.

        This is a somewhat more readable synonym for ToStdWstring().

        The return type of this function is actually `const std::wstring&` in
        wxWidgets builds using `wxUSE_UNICODE_WCHAR==1` (which is the default),
        i.e. in this build there is no copying of string contents, however a
        temporary copy of the string is returned in `wxUSE_UNICODE_UTF8==1`
        build.

        @since 3.3.0
     */
    std::wstring wc_string() const;

    /**
        Returns an object with string data that is implicitly convertible to
        @c char* pointer. Note that changes to the returned buffer may or may
        not be lost (depending on the build) and so this function is only usable for
        passing strings to legacy libraries that don't have const-correct API. Use
        wxStringBuffer if you want to modify the string.

        @see mb_str(), wc_str(), fn_str(), c_str(), char_str()
    */
    wxWritableWCharBuffer wchar_str() const;

    /**
       Explicit conversion to C string in the internal representation (either
       wchar_t* or UTF-8-encoded char*, depending on the build).
    */
    const wxStringCharType *wx_str() const;

    /**
        Converts the string to an 8-bit string in ISO-8859-1 encoding in the
        form of a wxCharBuffer.

        @note It is not recommended to use wxString for storing binary data.

        This is a convenience method useful when storing binary data in
        wxString. It should be used @em only for this purpose. It is only valid
        to call this method on strings created using From8BitData().

        @since 2.8.4

        @see wxString::From8BitData()
    */
    const wxScopedCharBuffer To8BitData() const;

    /**
        Converts the string to an ASCII, 7-bit string.

        Note that this conversion is only lossless if the string contains only
        ASCII characters as all the non-ASCII ones are replaced with the (same)
        provided replacement character.

        Use mb_str() or utf8_str() to convert to other encodings.

        @param replaceWith
            The character used to replace any non-ASCII characters, default to
            underscore (@c "_"). This parameter is new since wxWidgets 3.1.0.
    */
    const wxCharBuffer ToAscii(char replaceWith = '_') const;

    /**
        Return the string as a std::string using @e conv's wxMBConv::cWC2MB method.

        Note that if the conversion of (Unicode) string contents using @e conv
        fails, the return string will be empty. Be sure to check for
        this to avoid silent data loss. Alternatively, pass @c wxConvUTF8 as @a
        conv or use utf8_string() to always use UTF-8 encoding, rather than the
        current one.

        Instead of using this function it's also possible to write
        @code
        std::string s;
        wxString wxs;
        ...
        s = std::string(wxs);
        @endcode
        but using ToStdString() may make the code more clear.

        @param conv
            The converter to be used. This parameter is new in wxWidgets 3.1.1.

        @since 2.9.1
    */
    std::string ToStdString(const wxMBConv& conv = wxConvLibc) const;

    /**
        Return the string as a std::wstring.

        Unlike ToStdString(), there is no danger of data loss when using this
        function.

        Note that the return type of this function is actually `const
        std::wstring&` in wxWidgets builds using `wxUSE_UNICODE_WCHAR==1`
        (which is the default), i.e. in this build there is no copying of
        string contents, however a temporary copy of the string is returned in
        `wxUSE_UNICODE_UTF8==1` build.

        @since 2.9.1

        @see wc_string()
    */
    std::wstring ToStdWstring() const;

    /**
        Same as utf8_str().
    */
    const wxScopedCharBuffer ToUTF8() const;

    ///@}


    /**
        @member_group_name{concat, Concatenation}

        Almost anything may be concatenated (appended to) with a string!

        Note that the various operator<<() overloads work as C++ stream insertion
        operators. They insert the given value into the string.
        Precision and format cannot be set using them. Use Printf() instead.

        See also the insert() and append() STL-like functions.
    */
    ///@{

    /**
       Appends the string literal @a psz.
    */
    wxString& Append(const char* psz);

    /**
       Appends the wide string literal @a pwz.
    */
    wxString& Append(const wchar_t* pwz);

    /**
       Appends the string literal @a psz with max length @a nLen.
    */
    wxString& Append(const char* psz, size_t nLen);

    /**
       Appends the wide string literal @a psz with max length @a nLen.
    */
    wxString& Append(const wchar_t* pwz, size_t nLen);

    /**
       Appends the string @a s.
    */
    wxString& Append(const wxString& s);

    /**
       Appends the character @a ch @a count times.
    */
    wxString &Append(wxUniChar ch, size_t count = 1u);

    /**
        Prepends @a str to this string, returning a reference to this string.
    */
    wxString& Prepend(const wxString& str);

    /**
        Concatenation: returns a new string equal to the concatenation of the operands.
    */
    friend wxString operator +(const wxString& x, const wxString& y);

    /**
        @overload
    */
    friend wxString operator +(const wxString& x, wxUniChar y);

    wxString& operator<<(const wxString& s);
    wxString& operator<<(const char* psz);
    wxString& operator<<(const wchar_t* pwz);
    wxString& operator<<(const wxCStrData& psz);
    wxString& operator<<(char ch);
    wxString& operator<<(unsigned char ch);
    wxString& operator<<(wchar_t ch);
    wxString& operator<<(const wxCharBuffer& s);
    wxString& operator<<(const wxWCharBuffer& s);
    wxString& operator<<(wxUniChar ch);
    wxString& operator<<(wxUniCharRef ch);
    wxString& operator<<(unsigned int ui);
    wxString& operator<<(long l);
    wxString& operator<<(unsigned long ul);
    wxString& operator<<(wxLongLong_t ll);
    wxString& operator<<(wxULongLong_t ul);
    wxString& operator<<(float f);
    wxString& operator<<(double d);

    /**
        Concatenation in place: the argument is appended to the string.
    */
    void operator +=(const wxString& str);

    /**
        @overload
    */
    void operator +=(wxUniChar c);

    ///@}


    /**
        @member_group_name{cmp, Comparison}

        The default comparison function Cmp() is case-sensitive and so is the default
        version of IsSameAs(). For case insensitive comparisons you should use CmpNoCase()
        or give a second parameter to IsSameAs(). This last function is maybe more
        convenient if only equality of the strings matters because it returns a boolean
        @true value if the strings are the same and not 0 (which is usually @false
        in C) as Cmp() does.

        Matches() is a poor man's regular expression matcher: it only understands
        '*' and '?' metacharacters in the sense of DOS command line interpreter.

        StartsWith() is helpful when parsing a line of text which should start
        with some predefined prefix and is more efficient than doing direct string
        comparison as you would also have to precalculate the length of the prefix.

        See also the compare() STL-like function.
    */
    ///@{

    /**
        Case-sensitive comparison.
        Returns a positive value if the string is greater than the argument,
        zero if it is equal to it or a negative value if it is less than the
        argument (same semantics as the standard @c strcmp() function).

        @see CmpNoCase(), IsSameAs().
    */
    int Cmp(const wxString& s) const;

    /**
        Case-insensitive comparison.
        Returns a positive value if the string is greater than the argument,
        zero if it is equal to it or a negative value if it is less than the
        argument (same semantics as the standard @c strcmp() function).

        @see Cmp(), IsSameAs().
    */
    int CmpNoCase(const wxString& s) const;

    /**
        Test whether the string is equal to another string @a s.

        The test is case-sensitive if @a caseSensitive is @true (default) or not if it is
        @false.

        @return @true if the string is equal to the other one, @false otherwise.

        @see Cmp(), CmpNoCase()
    */
    bool IsSameAs(const wxString& s, bool caseSensitive = true) const;

    /**
        Test whether the string is equal to the single character @a ch.

        The test is case-sensitive if @a caseSensitive is @true (default) or not if it is
        @false.

        @return @true if the string is equal to this character, @false otherwise.

        @see Cmp(), CmpNoCase()
    */
    bool IsSameAs(wxUniChar ch, bool caseSensitive = true) const;

    ///@{
    /**
        Comparison operator for string types.
    */
    friend bool operator==(const wxString& s1, const wxString& s2);
    friend bool operator!=(const wxString& s1, const wxString& s2);
    friend bool operator< (const wxString& s1, const wxString& s2);
    friend bool operator> (const wxString& s1, const wxString& s2);
    friend bool operator<=(const wxString& s1, const wxString& s2);
    friend bool operator>=(const wxString& s1, const wxString& s2);
    friend bool operator==(const wxString& s1, const wxCStrData& s2);
    friend bool operator==(const wxCStrData& s1, const wxString& s2);
    friend bool operator!=(const wxString& s1, const wxCStrData& s2);
    friend bool operator!=(const wxCStrData& s1, const wxString& s2);
    friend bool operator==(const wxString& s1, const wxWCharBuffer& s2);
    friend bool operator==(const wxWCharBuffer& s1, const wxString& s2);
    friend bool operator!=(const wxString& s1, const wxWCharBuffer& s2);
    friend bool operator!=(const wxWCharBuffer& s1, const wxString& s2);
    friend bool operator==(const wxString& s1, const wxCharBuffer& s2);
    friend bool operator==(const wxCharBuffer& s1, const wxString& s2);
    friend bool operator!=(const wxString& s1, const wxCharBuffer& s2);
    friend bool operator!=(const wxCharBuffer& s1, const wxString& s2);
    ///@}

    ///@{
    /**
        Comparison operators char types.
    */
    friend bool operator==(const wxUniChar& c, const wxString& s);
    friend bool operator==(const wxUniCharRef& c, const wxString& s);
    friend bool operator==(char c, const wxString& s);
    friend bool operator==(wchar_t c, const wxString& s);
    friend bool operator==(int c, const wxString& s);
    friend bool operator==(const wxString& s, const wxUniChar& c);
    friend bool operator==(const wxString& s, const wxUniCharRef& c);
    friend bool operator==(const wxString& s, char c);
    friend bool operator==(const wxString& s, wchar_t c);
    friend bool operator!=(const wxUniChar& c, const wxString& s);
    friend bool operator!=(const wxUniCharRef& c, const wxString& s);
    friend bool operator!=(char c, const wxString& s);
    friend bool operator!=(wchar_t c, const wxString& s);
    friend bool operator!=(int c, const wxString& s);
    friend bool operator!=(const wxString& s, const wxUniChar& c);
    friend bool operator!=(const wxString& s, const wxUniCharRef& c);
    friend bool operator!=(const wxString& s, char c);
    friend bool operator!=(const wxString& s, wchar_t c);
    ///@}

    /**
        Returns @true if the string contents matches a mask containing '*' and '?'.
    */
    bool Matches(const wxString& mask) const;

    /**
        This function can be used to test if the string starts with the specified
        @a prefix.

        If it does, the function will return @true and put the rest of the string
        (i.e. after the prefix) into @a rest string if it is not @NULL.
        Otherwise, the function returns @false and doesn't modify the @a rest.
    */
    bool StartsWith(const wxString& prefix, wxString *rest = nullptr) const;

    /**
        This function can be used to test if the string ends with the specified
        @e suffix. If it does, the function will return @true and put the
        beginning of the string before the suffix into @e rest string if it is not
        @NULL. Otherwise, the function returns @false and doesn't
        modify the @e rest.
    */
    bool EndsWith(const wxString& suffix, wxString *rest = nullptr) const;

    ///@}


    /**
        @member_group_name{substring, Substring extraction}

        These functions allow you to extract a substring from the string. The
        original string is not modified and the function returns the extracted
        substring.

        See also the at() and the substr() STL-like functions.
    */
    ///@{

    /**
        Returns a substring starting at @e first, with length @e count, or the rest of
        the string if @a count is the default value.
    */
    wxString Mid(size_t first, size_t nCount = wxString::npos) const;

    /**
        Returns the part of the string between the indices @a from and @a to
        inclusive.

        This is a wxWidgets 1.xx compatibility function, use Mid()
        instead (but note that parameters have different meaning).
    */
    wxString SubString(size_t from, size_t to) const;

    /**
        Same as Mid() (substring extraction).
    */
    wxString operator()(size_t start, size_t len) const;

    /**
        Returns the first @a count characters of the string.
    */
    wxString Left(size_t count) const;

    /**
        Returns the last @a count characters.
    */
    wxString Right(size_t count) const;

    /**
        Gets all the characters after the first occurrence of @e ch.
        Returns the empty string if @e ch is not found.
    */
    wxString AfterFirst(wxUniChar ch) const;

    /**
        Gets all the characters after the last occurrence of @e ch.
        Returns the whole string if @e ch is not found.
    */
    wxString AfterLast(wxUniChar ch) const;

    /**
        Gets all characters before the first occurrence of @e ch.
        Returns the whole string if @a ch is not found.

        @param ch The character to look for.
        @param rest Filled with the part of the string following the first
            occurrence of @a ch or cleared if it was not found. The same string
            is returned by AfterFirst() but it is more efficient to use this
            output parameter if both the "before" and "after" parts are needed
            than calling both functions one after the other. This parameter is
            available in wxWidgets version 2.9.2 and later only.
        @return Part of the string before the first occurrence of @a ch.
    */
    wxString BeforeFirst(wxUniChar ch, wxString *rest = nullptr) const;

    /**
        Gets all characters before the last occurrence of @e ch.
        Returns the empty string if @a ch is not found.

        @param ch The character to look for.
        @param rest Filled with the part of the string following the last
            occurrence of @a ch or the copy of this string if it was not found.
            The same string is returned by AfterLast() but it is more efficient
            to use this output parameter if both the "before" and "after" parts
            are needed than calling both functions one after the other. This
            parameter is available in wxWidgets version 2.9.2 and later only.
        @return Part of the string before the last occurrence of @a ch.
    */
    wxString BeforeLast(wxUniChar ch, wxString *rest = nullptr) const;

    ///@}


    /**
        @member_group_name{caseconv, Case conversion}

        The MakeXXX() variants modify the string in place, while the other functions
        return a new string which contains the original text converted to the upper or
        lower case and leave the original string unchanged.
    */
    ///@{

    /**
        Return the copy of the string with the first string character in the
        upper case and the subsequent ones in the lower case.

        @since 2.9.0

        @see MakeCapitalized()
     */
    wxString Capitalize() const;

    /**
        Returns this string converted to the lower case.

        @see MakeLower()
    */
    wxString Lower() const;

    /**
        Same as MakeLower.
        This is a wxWidgets 1.xx compatibility function; you should not use it in new
        code.
    */
    void LowerCase();

    /**
        Converts the first characters of the string to the upper case and all
        the subsequent ones to the lower case and returns the result.

        @since 2.9.0

        @see Capitalize()
    */
    wxString& MakeCapitalized();

    /**
        Converts all characters to lower case and returns the reference to the
        modified string.

        @see Lower()
    */
    wxString& MakeLower();

    /**
        Converts all characters to upper case and returns the reference to the
        modified string.

        @see Upper()
    */
    wxString& MakeUpper();

    /**
        Returns this string converted to upper case.

        @see MakeUpper()
    */
    wxString Upper() const;

    /**
        The same as MakeUpper().

        This is a wxWidgets 1.xx compatibility function; you should not use it in new
        code.
    */
    void UpperCase();

    ///@}


    /**
        @member_group_name{search, Searching and replacing}

        These functions replace the standard @c strchr() and @c strstr()
        functions.

        See also the find(), rfind(), replace() STL-like functions.
    */
    ///@{

    /**
        Searches for the given character @a ch.
        Returns the position or @c wxNOT_FOUND if not found.
    */
    int Find(wxUniChar ch, bool fromEnd = false) const;

    /**
        Searches for the given string @a sub.
        Returns the starting position or @c wxNOT_FOUND if not found.
    */
    int Find(const wxString& sub) const;

    /**
        Same as Find().

        This is a wxWidgets 1.xx compatibility function;
        you should not use it in new code.
    */
    int First(wxUniChar ch) const;

    /**
        Same as Find().

        This is a wxWidgets 1.xx compatibility function;
        you should not use it in new code.
    */
    int First(const wxString& str) const;

    /**
        Replace first (or all) occurrences of substring with another one.

        @param strOld
            The string to search for replacing.
        @param strNew
            The substitution string.
        @param replaceAll
            If @true a global replace will be done (default), otherwise only the
            first occurrence will be replaced.

        Returns the number of replacements made.
    */
    size_t Replace(const wxString& strOld, const wxString& strNew,
                   bool replaceAll = true);

    ///@}



    /**
        @member_group_name{numconv, Conversion to numbers}

        The string provides functions for conversion to signed and unsigned integer and
        floating point numbers.

        All functions take a pointer to the variable to put the numeric value
        in and return @true if the @b entire string could be converted to a
        number. Notice if there is a valid number in the beginning of the
        string, it is returned in the output parameter even if the function
        returns @false because there is more text following it.
     */
    ///@{

    /**
        Attempts to convert the string to a floating point number.

        Returns @true on success (the number is stored in the location pointed to by
        @a val) or @false if the string does not represent such number (the value of
        @a val may still be modified in this case).

        Note that unlike ToCDouble() this function uses a localized version of
        @c wxStrtod() and thus needs as decimal point (and thousands separator) the
        locale-specific decimal point. Thus you should use this function only when
        you are sure that this string contains a floating point number formatted with
        the rules of the locale currently in use (see wxLocale).

        Also notice that even this function is locale-specific it does not
        support strings with thousands separators in them, even if the current
        locale uses digits grouping. You may use wxNumberFormatter::FromString()
        to parse such strings.

        Please refer to the documentation of the standard function @c strtod()
        for more details about the supported syntax.

        @see ToCDouble(), ToLong(), ToULong()
    */
    bool ToDouble(double* val) const;

    /**
        Variant of ToDouble(), always working in "C" locale.

        Works like ToDouble(), but this function expects the floating point
        number to be formatted always with the rules dictated by the "C" locale
        (in particular, the decimal point must be a dot), independently from the
        current application-wide locale (see wxLocale).

        @code
        double val(0);

        // Will extract 2.2 from the string, but returns
        // false because the "lbs" section of the string
        // was not part of the conversion.
        wxString str("2.2lbs");
        bool fullStringConverted = str.ToCDouble(&val);

        // Will also extract 2.2, but returns true because
        // the entirety of the string was converted to a double.
        str.assign("2.2");
        fullStringConverted = str.ToCDouble(&val);
        @endcode

        @see ToDouble(), ToLong(), ToULong()
    */
    bool ToCDouble(double* val) const;

    /**
        Works like ToLong() but for signed integers.

        @see ToLong(), ToUInt(), ToDouble()

        @since 3.1.6
    */
    bool ToInt(int *val, int base = 10) const;

    /**
        Works like ToULong() but for unsigned integers.

        @see ToInt(), ToULong(), ToDouble()

        @since 3.1.6
    */
    bool ToUInt(unsigned int *val, int base = 10) const;

    /**
        Attempts to convert the string to a signed integer in base @a base.

        Returns @true on success in which case the number is stored in the location
        pointed to by @a val or @false if the string does not represent a
        valid number in the given base (the value of @a val may still be
        modified in this case).

        The value of @a base must be comprised between 2 and 36, inclusive, or
        be a special value 0 which means that the usual rules of @c C numbers are
        applied: if the number starts with @c 0x it is considered to be in base
        16, if it starts with @c 0 - in base 8 and in base 10 otherwise. Note
        that you may not want to specify the base 0 if you are parsing the numbers
        which may have leading zeroes as they can yield unexpected (to the user not
        familiar with C) results.

        Note that unlike ToCLong() this function uses a localized version of
        @c wxStrtol(). Thus you should use this function only when you are sure
        that this string contains an integer number formatted with
        the rules of the locale currently in use (see wxLocale).

        As with ToDouble(), this function does not support strings containing
        thousands separators even if the current locale uses digits grouping.
        You may use wxNumberFormatter::FromString() to parse such strings.

        Please refer to the documentation of the standard function @c strtol()
        for more details about the supported syntax.

        @see ToCDouble(), ToDouble(), ToULong(), ToInt()
    */
    bool ToLong(long* val, int base = 10) const;

    /**
        Variant of ToLong() always working in "C" locale.

        Works like ToLong() but unlike it this function expects the integer
        number to be formatted always with the rules dictated by the "C" locale,
        independently from the current application-wide locale (see wxLocale).

        @see ToDouble(), ToLong(), ToULong()
    */
    bool ToCLong(long* val, int base = 10) const;

    /**
        This is exactly the same as ToLong() but works with 64 bit integer numbers.

        Notice that currently it doesn't work (always returns @false) if parsing of 64
        bit numbers is not supported by the underlying C run-time library. Compilers
        with C99 support and Microsoft Visual C++ version 7 and higher do support this.

        @see ToLong(), ToULongLong()
    */
    bool ToLongLong(wxLongLong_t* val, int base = 10) const;

    /**
        Attempts to convert the string to an unsigned integer in base @a base.

        Returns @true on success in which case the number is stored in the
        location pointed to by @a val or @false if the string does not
        represent a valid number in the given base (the value of @a val may
        still be modified in this case).

        Please notice that this function  behaves in the same way as the standard
        @c strtoul() and so it simply converts negative numbers to unsigned
        representation instead of rejecting them (e.g. -1 is returned as @c ULONG_MAX).

        See ToLong() for the more detailed description of the @a base parameter
        (and of the locale-specific behaviour of this function).

        @see ToCULong(), ToDouble(), ToLong()
    */
    bool ToULong(unsigned long* val, int base = 10) const;

    /**
        Variant of ToULong() always working in "C" locale.

        Works like ToULong() but unlike it this function expects the integer
        number to be formatted always with the rules dictated by the "C" locale,
        independently from the current application-wide locale (see wxLocale).

        @see ToDouble(), ToLong(), ToULong()
    */
    bool ToCULong(unsigned long* val, int base = 10) const;

    /**
        This is exactly the same as ToULong() but works with 64 bit integer
        numbers.

        Please see ToLongLong() for additional remarks.
    */
    bool ToULongLong(wxULongLong_t* val, int base = 10) const;

    ///@}


    /**
        @member_group_name{fmt, Formatting and printing}

        Both formatted versions (Printf/() and stream-like insertion operators
        exist (for basic types only).

        See also the static Format() and FormatV() functions.
    */
    ///@{

    /**
        Similar to the standard function @e sprintf(). Returns the number of
        characters written, or an integer less than zero on error.
        Note that if @c wxUSE_PRINTF_POS_PARAMS is set to 1, then this function supports
        Unix98-style positional parameters:

        @code
        wxString str;

        str.Printf("%d %d %d", 1, 2, 3);
        // str now contains "1 2 3"

        str.Printf("%2$d %3$d %1$d", 1, 2, 3);
        // str now contains "2 3 1"
        @endcode

        @note This function will use a safe version of @e vsprintf() (usually called
        @e vsnprintf()) whenever available to always allocate the buffer of correct
        size. Unfortunately, this function is not available on all platforms and the
        dangerous @e vsprintf() will be used then which may lead to buffer overflows.
    */
    int Printf(const wxString& pszFormat, ...);

    /**
        Similar to vprintf. Returns the number of characters written, or an integer
        less than zero
        on error.
    */
    int PrintfV(const wxString& pszFormat, va_list argPtr);

    ///@}


    /**
        @member_group_name{mem, Memory management}

        The following are "advanced" functions and they will be needed rarely.
        Alloc() and Shrink() are only interesting for optimization purposes.
        wxStringBuffer and wxStringBufferLength classes may be very useful when working
        with some external API which requires the caller to provide a writable buffer.

        See also the `reserve()`, `resize()` and `shrink_to_fit()` STL-like functions.
    */
    ///@{

    /**
        Preallocate enough space for wxString to store @a nLen characters.

        Please note that this method does the same thing as the standard
        reserve() one and shouldn't be used in new code.

        This function may be used to increase speed when the string is
        constructed by repeated concatenation as in

        @code
            // delete all vowels from the string
            wxString DeleteAllVowels(const wxString& original)
            {
                wxString result;

                size_t len = original.length();

                result.Alloc(len);

                for ( size_t n = 0; n < len; n++ )
                {
                    if ( strchr("aeuio", tolower(original[n])) == nullptr )
                        result += original[n];
                }

                return result;
            }
        @endcode

        because it will avoid the need to reallocate string memory many times
        (in case of long strings). Note that it does not set the maximal length
        of a string -- it will still expand if more than @a nLen characters are
        stored in it. Also, it does not truncate the existing string (use
        Truncate() for this) even if its current length is greater than @a nLen.

        @return @true if memory was successfully allocated, @false otherwise.
    */
    bool Alloc(size_t nLen);

    /**
        Minimizes the string's memory.

        Please note that this method does the same thing as the standard
        shrink_to_fit() one and shouldn't be used in new code.

        This can be useful after a call to Alloc() if too much memory were
        preallocated.

        @return Always returns @true
    */
    bool Shrink();

    /**
        Returns a copy of the string.

        This method is obsolete as wxString doesn't use reference-counted
        implementation any longer and so all string copies are deep and
        assignment operator or copy constructor can be used instead of this
        function.

        @since 2.9.0
     */
    wxString Clone() const;

    /**
        Clears the string's content, setting its length to zero.

        This is the same as `clear()` and does @e not free the memory used by
        the string. To do this, call standard-like `shrink_to_fit()` or
        Shrink() after calling this function.

        @see Empty()
    */
    void Clear();

    ///@}



    /**
        @member_group_name{misc, Miscellaneous}

        Miscellaneous other string functions.
    */
    ///@{

    /**
        Returns @true if target appears anywhere in wxString; else @false.

        This is a wxWidgets 1.xx compatibility function; you should not use it in new code.
    */
    bool Contains(const wxString& str) const;

    /**
        This is a synonym for Clear().

        Prefer using `clear()` instead of this function in new code, especially
        considering that this function is very different from the standard
        `empty()` function.
    */
    void Empty();

    /**
        Returns the number of occurrences of @e ch in the string.

        This is a wxWidgets 1.xx compatibility function; you should not use it in new code.
    */
    int Freq(wxUniChar ch) const;

    /**
        Returns @true if the string contains only ASCII characters.
        See wxUniChar::IsAscii for more details.

        This is a wxWidgets 1.xx compatibility function; you should not use it in new
        code.
    */
    bool IsAscii() const;

    /**
        Returns @true if the string is an integer (with possible sign).

        This is a wxWidgets 1.xx compatibility function; you should not use it in new code.
    */
    bool IsNumber() const;

    /**
        Returns @true if the string is a word.

        This is a wxWidgets 1.xx compatibility function; you should not use it in new code.
    */
    bool IsWord() const;

    /**
        Adds @a count copies of @a chPad to the beginning, or to the end of the
        string (the default).

        By default, appends the given number of spaces to the string. The
        character being added and whether it is appended or prepended can be
        changed by providing non-default parameter values.
    */
    wxString& Pad(size_t count, wxUniChar chPad = ' ', bool fromRight = true);

    /**
        Removes all characters from the string starting at @a pos.
        Use Truncate() as a more readable alternative.

        This is a wxWidgets 1.xx compatibility function; you should not use it in new code.
    */
    wxString& Remove(size_t pos);

    /**
        Removes @a len characters from the string, starting at @a pos.

        This is a wxWidgets 1.xx compatibility function; you should not use it in new code.
    */
    wxString& Remove(size_t pos, size_t len);

    /**
        Removes the last character.
    */
    wxString& RemoveLast(size_t n = 1);

    /**
        Strip characters at the front and/or end.

        This is the same as Trim() except that it doesn't change this string.

        This is a wxWidgets 1.xx compatibility function; you should not use it in new code.
    */
    wxString Strip(stripType s = trailing) const;

    /**
        Removes white-space (space, tabs, form feed, newline and carriage return) from
        the left or from the right end of the string (right is default).
    */
    wxString& Trim(bool fromRight = true);

    /**
        Truncate the string to the given length.
    */
    wxString& Truncate(size_t len);

    ///@}




    /**
        @member_group_name{iter, Iterator interface}

        These methods return iterators to the beginning or end of the string.

        Please see any STL reference (e.g. http://www.cppreference.com/wiki/string/start)
        for their documentation.
    */
    ///@{

    const_iterator begin() const;
    iterator begin();
    const_iterator cbegin() const;
    const_iterator end() const;
    iterator end();
    const_iterator cend() const;

    const_reverse_iterator rbegin() const;
    reverse_iterator rbegin();
    const_reverse_iterator crbegin() const;
    const_reverse_iterator rend() const;
    reverse_iterator rend();
    const_reverse_iterator crend() const;

    ///@}



    /**
        @member_group_name{stl, STL interface}

        The supported STL functions are listed here.

        Please see any STL reference (e.g. http://www.cppreference.com/wiki/string/start)
        for their documentation.
    */
    ///@{

    wxString& append(const wxString& str, size_t pos, size_t n);
    wxString& append(const wxString& str);
    wxString& append(const char *sz, size_t n);
    wxString& append(const wchar_t *sz, size_t n);
    wxString& append(size_t n, wxUniChar ch);
    wxString& append(const_iterator first, const_iterator last);

    wxString& assign(const wxString& str, size_t pos, size_t n);
    wxString& assign(const wxString& str);
    wxString& assign(const char *sz, size_t n);
    wxString& assign(const wchar_t *sz, size_t n);
    wxString& assign(size_t n, wxUniChar ch);
    wxString& assign(const_iterator first, const_iterator last);

    wxUniChar at(size_t n) const;
    wxUniCharRef at(size_t n);

    void clear();

    size_type capacity() const;

    int compare(const wxString& str) const;
    int compare(size_t nStart, size_t nLen, const wxString& str) const;
    int compare(size_t nStart, size_t nLen,
            const wxString& str, size_t nStart2, size_t nLen2) const;
    int compare(size_t nStart, size_t nLen,
            const char* sz, size_t nCount = npos) const;
    int compare(size_t nStart, size_t nLen,
            const wchar_t* sz, size_t nCount = npos) const;

    wxCStrData data() const;

    bool empty() const;

    wxString& erase(size_type pos = 0, size_type n = npos);
    iterator erase(iterator first, iterator last);
    iterator erase(iterator first);

    size_t find(const wxString& str, size_t nStart = 0) const;
    size_t find(const char* sz, size_t nStart = 0, size_t n = npos) const;
    size_t find(const wchar_t* sz, size_t nStart = 0, size_t n = npos) const;
    size_t find(wxUniChar ch, size_t nStart = 0) const;
    size_t find_first_of(const char* sz, size_t nStart = 0) const;
    size_t find_first_of(const wchar_t* sz, size_t nStart = 0) const;
    size_t find_first_of(const char* sz, size_t nStart, size_t n) const;
    size_t find_first_of(const wchar_t* sz, size_t nStart, size_t n) const;
    size_t find_first_of(wxUniChar c, size_t nStart = 0) const;
    size_t find_last_of (const wxString& str, size_t nStart = npos) const;
    size_t find_last_of (const char* sz, size_t nStart = npos) const;
    size_t find_last_of (const wchar_t* sz, size_t nStart = npos) const;
    size_t find_last_of(const char* sz, size_t nStart, size_t n) const;
    size_t find_last_of(const wchar_t* sz, size_t nStart, size_t n) const;
    size_t find_last_of(wxUniChar c, size_t nStart = npos) const;
    size_t find_first_not_of(const wxString& str, size_t nStart = 0) const;
    size_t find_first_not_of(const char* sz, size_t nStart = 0) const;
    size_t find_first_not_of(const wchar_t* sz, size_t nStart = 0) const;
    size_t find_first_not_of(const char* sz, size_t nStart, size_t n) const;
    size_t find_first_not_of(const wchar_t* sz, size_t nStart, size_t n) const;
    size_t find_first_not_of(wxUniChar ch, size_t nStart = 0) const;
    size_t find_last_not_of(const wxString& str, size_t nStart = npos) const;
    size_t find_last_not_of(const char* sz, size_t nStart = npos) const;
    size_t find_last_not_of(const wchar_t* sz, size_t nStart = npos) const;
    size_t find_last_not_of(const char* sz, size_t nStart, size_t n) const;
    size_t find_last_not_of(const wchar_t* sz, size_t nStart, size_t n) const;

    wxString& insert(size_t nPos, const wxString& str);
    wxString& insert(size_t nPos, const wxString& str, size_t nStart, size_t n);
    wxString& insert(size_t nPos, const char *sz, size_t n);
    wxString& insert(size_t nPos, const wchar_t *sz, size_t n);
    wxString& insert(size_t nPos, size_t n, wxUniChar ch);
    iterator insert(iterator it, wxUniChar ch);
    void insert(iterator it, const_iterator first, const_iterator last);
    void insert(iterator it, size_type n, wxUniChar ch);

    size_t length() const;

    size_type max_size() const;

    void reserve(size_t sz);
    void resize(size_t nSize, wxUniChar ch = '\0');

    wxString& replace(size_t nStart, size_t nLen, const wxString& str);
    wxString& replace(size_t nStart, size_t nLen, size_t nCount, wxUniChar ch);
    wxString& replace(size_t nStart, size_t nLen,
                        const wxString& str, size_t nStart2, size_t nLen2);
    wxString& replace(size_t nStart, size_t nLen,
                        const char* sz, size_t nCount);
    wxString& replace(size_t nStart, size_t nLen,
                        const wchar_t* sz, size_t nCount);
    wxString& replace(size_t nStart, size_t nLen,
                        const wxString& s, size_t nCount);
    wxString& replace(iterator first, iterator last, const wxString& s);
    wxString& replace(iterator first, iterator last, const char* s, size_type n);
    wxString& replace(iterator first, iterator last, const wchar_t* s, size_type n);
    wxString& replace(iterator first, iterator last, size_type n, wxUniChar ch);
    wxString& replace(iterator first, iterator last,
                        const_iterator first1, const_iterator last1);
    wxString& replace(iterator first, iterator last,
                        const char *first1, const char *last1);
    wxString& replace(iterator first, iterator last,
                        const wchar_t *first1, const wchar_t *last1);

    size_t rfind(const wxString& str, size_t nStart = npos) const;
    size_t rfind(const char* sz, size_t nStart = npos, size_t n = npos) const;
    size_t rfind(const wchar_t* sz, size_t nStart = npos, size_t n = npos) const;
    size_t rfind(wxUniChar ch, size_t nStart = npos) const;

    size_type size() const;
    wxString substr(size_t nStart = 0, size_t nLen = npos) const;
    void swap(wxString& str);

    bool starts_with(const wxString &str) const;
    bool starts_with(const char *sz) const;
    bool starts_with(const wchar_t *sz) const;

    bool ends_with(const wxString &str) const;
    bool ends_with(const char *sz) const;
    bool ends_with(const wchar_t *sz) const;

    ///@}



    // STATIC FUNCTIONS
    // Keep these functions separated from the other groups or Doxygen gets confused
    // -----------------------------------------------------------------------------

    /**
        An 'invalid' value for string index
    */
    static const size_t npos;

    /**
        This static function returns the string containing the result of calling
        Printf() with the passed parameters on it.

        @see FormatV(), Printf()
    */
    static wxString Format(const wxString& format, ...);

    /**
        This static function returns the string containing the result of calling
        PrintfV() with the passed parameters on it.

        @see Format(), PrintfV()
    */
    static wxString FormatV(const wxString& format, va_list argptr);

    ///@{
    /**
        Converts given buffer of binary data from 8-bit string to wxString.

        @note Using `std::vector<wxUint8>` is both simpler and more efficient
        than using wxString for storing binary data. See also more specialized
        classes provided by wxWidgets for working with binary data, such as
        wxMemoryBuffer and wxMemoryOutputStream and wxMemoryInputStream.

        In Unicode build, the string is interpreted as being in ISO-8859-1
        encoding. The version without @e len parameter takes NUL-terminated
        data.

        This is a convenience method useful when storing binary data in
        wxString. It should be used @em only for that purpose and only in
        conjunction with To8BitData(). Use mb_str() for conversion of character
        data to known encoding.

        @since 2.8.4

        @see wxString::To8BitData()
    */
    static wxString From8BitData(const char* buf, size_t len);
    static wxString From8BitData(const char* buf);
    ///@}

    ///@{
    /**
        Converts the string or character from an ASCII, 7-bit form
        to the native wxString representation.

        Input must consist only of 7-bit (i.e. less than 128) ASCII characters,
        the behaviour in presence of non-ASCII characters is undefined but will
        result in assert failures.

        @see wxASCII_STR()
    */
    static wxString FromAscii(const char* s);
    static wxString FromAscii(const unsigned char* s);
    static wxString FromAscii(const char* s, size_t len);
    static wxString FromAscii(const unsigned char* s, size_t len);
    static wxString FromAscii(char c);
    ///@}

    /**
        Returns a string with the textual representation of the number in C
        locale.

        Unlike FromDouble() the string returned by this function always uses
        the period character as decimal separator, independently of the current
        locale. Otherwise its behaviour is identical to the other function.

        @since 2.9.1

        @see ToCDouble()
     */
    static wxString FromCDouble(double val, int precision = -1);

    /**
        Returns a string with the textual representation of the number.

        For the default value of @a precision, this function behaves as a
        simple wrapper for @code wxString::Format("%g", val) @endcode. If @a
        precision is positive (or zero), the @c %.Nf format is used with the
        given precision value.

        Notice that the string returned by this function uses the decimal
        separator appropriate for the current locale, e.g. @c "," and not a
        period in French locale. Use FromCDouble() if this is unwanted.

        @param val
            The value to format.
        @param precision
            The number of fractional digits to use in or -1 to use the most
            appropriate format. This parameter is new in wxWidgets 2.9.2.

        @since 2.9.1

        @see ToDouble()
     */
    static wxString FromDouble(double val, int precision = -1);

    ///@{
    /**
        Converts C string encoded in UTF-8 to wxString.

        If @a s is not a valid UTF-8 string, an empty string is returned.

        Notice that when using UTF-8 wxWidgets build there is a more efficient
        alternative to this function called FromUTF8Unchecked() which, unlike
        this one, doesn't check that the input string is valid.

        The overload taking @c std::string is only available starting with
        wxWidgets 3.1.1.

        The overload taking @c std::string_view is only available starting with
        wxWidgets 3.3.0 and requires the consumer application to use C++17.

        @since 2.8.4
    */
    static wxString FromUTF8(const char* s);
    static wxString FromUTF8(const char* s, size_t len);
    static wxString FromUTF8(const std::string& s);
    static wxString FromUTF8(std::string_view s);
    ///@}

    ///@{
    /**
        Converts C string encoded in UTF-8 to wxString without checking its
        validity.

        This method assumes that @a s is a valid UTF-8 sequence and doesn't do
        any validation (although an assert failure is triggered in debug builds
        if the string is invalid). Only use it if you are absolutely sure that
        @a s is a correct UTF-8 string (e.g. because it comes from another
        library using UTF-8) and if the performance matters, otherwise use
        slower (in UTF-8 build) but safer FromUTF8(). Passing a bad UTF-8
        string to this function will result in creating a corrupted wxString
        and all the subsequent operations on it will be undefined.

        The overload taking @c std::string is only available starting with
        wxWidgets 3.1.1.

        The overload taking @c std::string_view is only available starting with
        wxWidgets 3.3.0 and requires the consumer application to use C++17.

        @since 2.8.9
    */
    static wxString FromUTF8Unchecked(const char* s);
    static wxString FromUTF8Unchecked(const char* s, size_t len);
    static wxString FromUTF8Unchecked(const std::string& s);
    static wxString FromUTF8Unchecked(std::string_view s);
    ///@}
};



/**
    The global wxString instance of an empty string.
    Used extensively in the entire wxWidgets API.
*/
wxString wxEmptyString;



/**
    @class wxStringBufferLength

    This helper class allows you to conveniently access the wxString internal buffer
    as a writable pointer and requires explicitly specifying the actual length.

    For example, assuming you have a low-level OS function called
    @c "int GetMeaningOfLifeAsString(char *)" copying the value in the provided
    buffer (which must be writable, of course), and returning the actual length
    of the string, you might call it like this:

    @code
        wxString theAnswer;
        {
            wxStringBufferLength theAnswerBuffer(theAnswer, 1024);
            int nLength = GetMeaningOfLifeAsString(theAnswerBuffer);
            theAnswerBuffer.SetLength(nLength);
        } // The buffer is destroyed here, allowing the string to be used.
        if ( theAnswer != "42" )
            wxLogError("Something is very wrong!");
    @endcode

    Note that the string can't be used in any way while a buffer associated
    with it exists, the buffer must be destroyed to allow using the string
    again.

    If possible, this class uses the internal wxString storage directly,
    however this may not be the case depending on wxWidgets build options.

    Note that wxStringBuffer::SetLength @b must be called before
    wxStringBufferLength destructs.

    @library{wxbase}
    @category{data}
*/
class wxStringBufferLength
{
public:
    /**
        Constructs a writable string buffer object associated with the given string
        and containing enough space for at least @a len characters.
    */
    wxStringBufferLength(wxString& str, size_t len);

    /**
        Restores the string passed to the constructor to the usable state.
    */
    ~wxStringBufferLength();

    /**
        Sets the internal length of the string referred to by wxStringBufferLength to
        @a nLength characters.

        Must be called before wxStringBufferLength destructs.
    */
    void SetLength(size_t nLength);

    /**
        Returns the writable pointer to a buffer of the size at least equal to the
        length specified in the constructor.
    */
    wxChar* operator wxChar *();
};


/**
    @class wxStringBuffer

    This helper class allows you to conveniently access the wxString internal buffer
    as a writable pointer and automatically determines its length.

    This class is similar to wxStringBufferLength, but sets the length of the
    buffer automatically, by assuming that the string is NUL-terminated.

    @library{wxbase}
    @category{data}
*/
class wxStringBuffer
{
public:
    /**
        Constructs a writable string buffer object associated with the given string
        and containing enough space for at least @a len characters.
    */
    wxStringBuffer(wxString& str, size_t len);

    /**
        Restores the string passed to the constructor to the usable state.
    */
    ~wxStringBuffer();

    /**
        Returns the writable pointer to a buffer of the size at least equal to the
        length specified in the constructor.
    */
    wxStringCharType* operator wxStringCharType *();
};


/** @addtogroup group_funcmacro_string */
///@{

/**
    Allows extending a function with the signature:
    @code bool SomeFunc(const wxUniChar& c) @endcode
    which operates on a single character, to an entire wxString.

    E.g. if you want to check if an entire string contains only digits,
    you can do:
    @code
        if (wxStringCheck<wxIsdigit>(myString))
            ... // the entire string contains only digits!
        else
            ... // at least one character of myString is not a digit
    @endcode

    @return @true if the given function returns a non-zero value for all
            characters of the @a val string.
*/
template<bool (T)(const wxUniChar& c)>
    inline bool wxStringCheck(const wxString& val);

/**
    Convenience macro for explicitly constructing wxString from ASCII strings.

    This macro simply expands to a call to wxString::FromAscii() but is
    slightly shorter.

    @since 3.1.4
 */
wxString wxASCII_STR(const char* s);

///@}
