141 lines
5.1 KiB
C++
141 lines
5.1 KiB
C++
///////////////////////////////////////////////////////////////////////////////
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// Name: wx/anystr.h
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// Purpose: wxAnyStrPtr class declaration
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// Author: Vadim Zeitlin
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// Created: 2009-03-23
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// RCS-ID: $Id: anystr.h 59829 2009-03-25 09:54:10Z VZ $
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// Copyright: (c) 2008 Vadim Zeitlin <vadim@wxwidgets.org>
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// Licence: wxWindows licence
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///////////////////////////////////////////////////////////////////////////////
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#ifndef _WX_ANYSTR_H_
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#define _WX_ANYSTR_H_
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#include "wx/string.h"
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// ----------------------------------------------------------------------------
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// wxAnyStrPtr
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//
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// Notice that this is an internal and intentionally not documented class. It
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// is only used by wxWidgets itself to ensure compatibility with previous
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// versions and shouldn't be used by user code. When you see a function
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// returning it you should just know that you can treat it as a string pointer.
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// ----------------------------------------------------------------------------
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// This is a helper class convertible to either narrow or wide string pointer.
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// It is similar to wxCStrData but, unlike it, can be NULL which is required to
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// represent the return value of wxDateTime::ParseXXX() methods for example.
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//
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// NB: this class is fully inline and so doesn't need to be DLL-exported
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class wxAnyStrPtr
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{
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public:
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// ctors: this class must be created from the associated string or using
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// its default ctor for an invalid NULL-like object; notice that it is
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// immutable after creation.
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// ctor for invalid pointer
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wxAnyStrPtr()
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: m_str(NULL)
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{
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}
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// ctor for valid pointer into the given string (whose lifetime must be
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// greater than ours and which should remain constant while we're used)
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wxAnyStrPtr(const wxString& str, const wxString::const_iterator& iter)
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: m_str(&str),
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m_iter(iter)
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{
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}
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// default copy ctor is ok and so is default dtor, in particular we do not
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// free the string
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// various operators meant to make this class look like a superposition of
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// char* and wchar_t*
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// this one is needed to allow boolean expressions involving these objects,
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// e.g. "if ( FuncReturningAnyStrPtr() && ... )" (unfortunately using
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// unspecified_bool_type here wouldn't help with ambiguity between all the
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// different conversions to pointers)
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operator bool() const { return m_str != NULL; }
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// at least VC6 and VC7 also need this one or they complain about ambiguity
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// for !anystr expressions
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bool operator!() const { return !((bool)*this); }
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// and these are the conversions operator which allow to assign the result
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// of FuncReturningAnyStrPtr() to either char* or wxChar* (i.e. wchar_t*)
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operator const char *() const
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{
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if ( !m_str )
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return NULL;
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// check if the string is convertible to char at all
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//
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// notice that this pointer points into wxString internal buffer
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// containing its char* representation and so it can be kept for as
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// long as wxString is not modified -- which is long enough for our
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// needs
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const char *p = m_str->c_str().AsChar();
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if ( *p )
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{
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// find the offset of the character corresponding to this iterator
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// position in bytes: we don't have any direct way to do it so we
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// need to redo the conversion again for the part of the string
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// before the iterator to find its length in bytes in current
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// locale
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//
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// NB: conversion won't fail as it succeeded for the entire string
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p += strlen(wxString(m_str->begin(), m_iter).mb_str());
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}
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//else: conversion failed, return "" as we can't do anything else
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return p;
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}
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operator const wchar_t *() const
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{
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if ( !m_str )
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return NULL;
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// no complications with wide strings (as long as we discount
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// surrogates as we do for now)
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//
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// just remember that this works as long as wxString keeps an internal
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// buffer with its wide wide char representation, just as with AsChar()
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// above
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return m_str->c_str().AsWChar() + (m_iter - m_str->begin());
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}
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// Because the objects of this class are only used as return type for
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// functions which can return NULL we can skip providing dereferencing
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// operators: the code using this class must test it for NULL first and if
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// it does anything else with it it has to assign it to either char* or
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// wchar_t* itself, before dereferencing.
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//
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// IOW this
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//
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// if ( *FuncReturningAnyStrPtr() )
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//
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// is invalid because it could crash. And this
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//
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// const char *p = FuncReturningAnyStrPtr();
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// if ( p && *p )
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//
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// already works fine.
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private:
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// the original string and the position in it we correspond to, if the
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// string is NULL this object is NULL pointer-like
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const wxString * const m_str;
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const wxString::const_iterator m_iter;
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wxDECLARE_NO_ASSIGN_CLASS(wxAnyStrPtr);
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};
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#endif // _WX_ANYSTR_H_
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