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„.…¯Ò¿Ö ?÷ S// Reference-counted versatile string base -*- C++ -*-
// Copyright (C) 2005-2013 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// .
/** @file ext/rc_string_base.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{ext/vstring.h}
*/
#ifndef _RC_STRING_BASE_H
#define _RC_STRING_BASE_H 1
#include
#include
namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* Documentation? What's that?
* Nathan Myers .
*
* A string looks like this:
*
* @code
* [_Rep]
* _M_length
* [__rc_string_base] _M_capacity
* _M_dataplus _M_refcount
* _M_p ----------------> unnamed array of char_type
* @endcode
*
* Where the _M_p points to the first character in the string, and
* you cast it to a pointer-to-_Rep and subtract 1 to get a
* pointer to the header.
*
* This approach has the enormous advantage that a string object
* requires only one allocation. All the ugliness is confined
* within a single pair of inline functions, which each compile to
* a single @a add instruction: _Rep::_M_refdata(), and
* __rc_string_base::_M_rep(); and the allocation function which gets a
* block of raw bytes and with room enough and constructs a _Rep
* object at the front.
*
* The reason you want _M_data pointing to the character array and
* not the _Rep is so that the debugger can see the string
* contents. (Probably we should add a non-inline member to get
* the _Rep for the debugger to use, so users can check the actual
* string length.)
*
* Note that the _Rep object is a POD so that you can have a
* static empty string _Rep object already @a constructed before
* static constructors have run. The reference-count encoding is
* chosen so that a 0 indicates one reference, so you never try to
* destroy the empty-string _Rep object.
*
* All but the last paragraph is considered pretty conventional
* for a C++ string implementation.
*/
template
class __rc_string_base
: protected __vstring_utility<_CharT, _Traits, _Alloc>
{
public:
typedef _Traits traits_type;
typedef typename _Traits::char_type value_type;
typedef _Alloc allocator_type;
typedef __vstring_utility<_CharT, _Traits, _Alloc> _Util_Base;
typedef typename _Util_Base::_CharT_alloc_type _CharT_alloc_type;
typedef typename _CharT_alloc_type::size_type size_type;
private:
// _Rep: string representation
// Invariants:
// 1. String really contains _M_length + 1 characters: due to 21.3.4
// must be kept null-terminated.
// 2. _M_capacity >= _M_length
// Allocated memory is a