char_traits.h

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// Character Traits for use by standard string and iostream -*- C++ -*-

// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
// 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 2, 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.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/** @file char_traits.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

//
// ISO C++ 14882: 21  Strings library
//

#ifndef _CHAR_TRAITS_H
#define _CHAR_TRAITS_H 1

#pragma GCC system_header

#include <cstring>            // For memmove, memset, memchr
#include <bits/stl_algobase.h>// For copy, lexicographical_compare, fill_n
#include <bits/postypes.h>    // For streampos

_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)

  /**
   *  @brief  Mapping from character type to associated types.
   *
   *  @note This is an implementation class for the generic version
   *  of char_traits.  It defines int_type, off_type, pos_type, and
   *  state_type.  By default these are unsigned long, streamoff,
   *  streampos, and mbstate_t.  Users who need a different set of
   *  types, but who don't need to change the definitions of any function
   *  defined in char_traits, can specialize __gnu_cxx::_Char_types
   *  while leaving __gnu_cxx::char_traits alone. */
  template <class _CharT>
    struct _Char_types
    {
      typedef unsigned long   int_type;
      typedef std::streampos  pos_type;
      typedef std::streamoff  off_type;
      typedef std::mbstate_t  state_type;
    };


  /**
   *  @brief  Base class used to implement std::char_traits.
   *
   *  @note For any given actual character type, this definition is
   *  probably wrong.  (Most of the member functions are likely to be
   *  right, but the int_type and state_type typedefs, and the eof()
   *  member function, are likely to be wrong.)  The reason this class
   *  exists is so users can specialize it.  Classes in namespace std
   *  may not be specialized for fundamentl types, but classes in
   *  namespace __gnu_cxx may be.
   *
   *  See http://gcc.gnu.org/onlinedocs/libstdc++/21_strings/howto.html#5
   *  for advice on how to make use of this class for "unusual" character
   *  types. Also, check out include/ext/pod_char_traits.h.  
   */
  template<typename _CharT>
    struct char_traits
    {
      typedef _CharT                                    char_type;
      typedef typename _Char_types<_CharT>::int_type    int_type;
      typedef typename _Char_types<_CharT>::pos_type    pos_type;
      typedef typename _Char_types<_CharT>::off_type    off_type;
      typedef typename _Char_types<_CharT>::state_type  state_type;

      static void
      assign(char_type& __c1, const char_type& __c2)
      { __c1 = __c2; }

      static bool
      eq(const char_type& __c1, const char_type& __c2)
      { return __c1 == __c2; }

      static bool
      lt(const char_type& __c1, const char_type& __c2)
      { return __c1 < __c2; }

      static int
      compare(const char_type* __s1, const char_type* __s2, std::size_t __n);

      static std::size_t
      length(const char_type* __s);

      static const char_type*
      find(const char_type* __s, std::size_t __n, const char_type& __a);

      static char_type*
      move(char_type* __s1, const char_type* __s2, std::size_t __n);

      static char_type*
      copy(char_type* __s1, const char_type* __s2, std::size_t __n);

      static char_type*
      assign(char_type* __s, std::size_t __n, char_type __a);

      static char_type
      to_char_type(const int_type& __c)
      { return static_cast<char_type>(__c); }

      static int_type
      to_int_type(const char_type& __c)
      { return static_cast<int_type>(__c); }

      static bool
      eq_int_type(const int_type& __c1, const int_type& __c2)
      { return __c1 == __c2; }

      static int_type
      eof()
      { return static_cast<int_type>(EOF); }

      static int_type
      not_eof(const int_type& __c)
      { return !eq_int_type(__c, eof()) ? __c : to_int_type(char_type()); }
    };

  template<typename _CharT>
    int
    char_traits<_CharT>::
    compare(const char_type* __s1, const char_type* __s2, std::size_t __n)
    {
      for (std::size_t __i = 0; __i < __n; ++__i)
    if (lt(__s1[__i], __s2[__i]))
      return -1;
    else if (lt(__s2[__i], __s1[__i]))
      return 1;
      return 0;
    }

  template<typename _CharT>
    std::size_t
    char_traits<_CharT>::
    length(const char_type* __p)
    {
      std::size_t __i = 0;
      while (!eq(__p[__i], char_type()))
        ++__i;
      return __i;
    }

  template<typename _CharT>
    const typename char_traits<_CharT>::char_type*
    char_traits<_CharT>::
    find(const char_type* __s, std::size_t __n, const char_type& __a)
    {
      for (std::size_t __i = 0; __i < __n; ++__i)
        if (eq(__s[__i], __a))
          return __s + __i;
      return 0;
    }

  template<typename _CharT>
    typename char_traits<_CharT>::char_type*
    char_traits<_CharT>::
    move(char_type* __s1, const char_type* __s2, std::size_t __n)
    {
      return static_cast<_CharT*>(std::memmove(__s1, __s2,
                           __n * sizeof(char_type)));
    }

  template<typename _CharT>
    typename char_traits<_CharT>::char_type*
    char_traits<_CharT>::
    copy(char_type* __s1, const char_type* __s2, std::size_t __n)
    {
      std::copy(__s2, __s2 + __n, __s1);
      return __s1;
    }

  template<typename _CharT>
    typename char_traits<_CharT>::char_type*
    char_traits<_CharT>::
    assign(char_type* __s, std::size_t __n, char_type __a)
    {
      std::fill_n(__s, __n, __a);
      return __s;
    }

_GLIBCXX_END_NAMESPACE

_GLIBCXX_BEGIN_NAMESPACE(std)

  // 21.1
  /**
   *  @brief  Basis for explicit traits specializations.
   *
   *  @note  For any given actual character type, this definition is
   *  probably wrong.  Since this is just a thin wrapper around
   *  __gnu_cxx::char_traits, it is possible to achieve a more
   *  appropriate definition by specializing __gnu_cxx::char_traits.
   *
   *  See http://gcc.gnu.org/onlinedocs/libstdc++/21_strings/howto.html#5
   *  for advice on how to make use of this class for "unusual" character
   *  types. Also, check out include/ext/pod_char_traits.h.
  */
  template<class _CharT>
    struct char_traits : public __gnu_cxx::char_traits<_CharT>
    { };


  /// @brief  21.1.3.1  char_traits specializations
  template<>
    struct char_traits<char>
    {
      typedef char              char_type;
      typedef int               int_type;
      typedef streampos         pos_type;
      typedef streamoff         off_type;
      typedef mbstate_t         state_type;

      static void
      assign(char_type& __c1, const char_type& __c2)
      { __c1 = __c2; }

      static bool
      eq(const char_type& __c1, const char_type& __c2)
      { return __c1 == __c2; }

      static bool
      lt(const char_type& __c1, const char_type& __c2)
      { return __c1 < __c2; }

      static int
      compare(const char_type* __s1, const char_type* __s2, size_t __n)
      { return memcmp(__s1, __s2, __n); }

      static size_t
      length(const char_type* __s)
      { return strlen(__s); }

      static const char_type*
      find(const char_type* __s, size_t __n, const char_type& __a)
      { return static_cast<const char_type*>(memchr(__s, __a, __n)); }

      static char_type*
      move(char_type* __s1, const char_type* __s2, size_t __n)
      { return static_cast<char_type*>(memmove(__s1, __s2, __n)); }

      static char_type*
      copy(char_type* __s1, const char_type* __s2, size_t __n)
      { return static_cast<char_type*>(memcpy(__s1, __s2, __n)); }

      static char_type*
      assign(char_type* __s, size_t __n, char_type __a)
      { return static_cast<char_type*>(memset(__s, __a, __n)); }

      static char_type
      to_char_type(const int_type& __c)
      { return static_cast<char_type>(__c); }

      // To keep both the byte 0xff and the eof symbol 0xffffffff
      // from ending up as 0xffffffff.
      static int_type
      to_int_type(const char_type& __c)
      { return static_cast<int_type>(static_cast<unsigned char>(__c)); }

      static bool
      eq_int_type(const int_type& __c1, const int_type& __c2)
      { return __c1 == __c2; }

      static int_type
      eof() { return static_cast<int_type>(EOF); }

      static int_type
      not_eof(const int_type& __c)
      { return (__c == eof()) ? 0 : __c; }
  };


#ifdef _GLIBCXX_USE_WCHAR_T
  /// @brief  21.1.3.2  char_traits specializations
  template<>
    struct char_traits<wchar_t>
    {
      typedef wchar_t           char_type;
      typedef wint_t            int_type;
      typedef streamoff         off_type;
      typedef wstreampos        pos_type;
      typedef mbstate_t         state_type;

      static void
      assign(char_type& __c1, const char_type& __c2)
      { __c1 = __c2; }

      static bool
      eq(const char_type& __c1, const char_type& __c2)
      { return __c1 == __c2; }

      static bool
      lt(const char_type& __c1, const char_type& __c2)
      { return __c1 < __c2; }

      static int
      compare(const char_type* __s1, const char_type* __s2, size_t __n)
      { return wmemcmp(__s1, __s2, __n); }

      static size_t
      length(const char_type* __s)
      { return wcslen(__s); }

      static const char_type*
      find(const char_type* __s, size_t __n, const char_type& __a)
      { return wmemchr(__s, __a, __n); }

      static char_type*
      move(char_type* __s1, const char_type* __s2, size_t __n)
      { return wmemmove(__s1, __s2, __n); }

      static char_type*
      copy(char_type* __s1, const char_type* __s2, size_t __n)
      { return wmemcpy(__s1, __s2, __n); }

      static char_type*
      assign(char_type* __s, size_t __n, char_type __a)
      { return wmemset(__s, __a, __n); }

      static char_type
      to_char_type(const int_type& __c) { return char_type(__c); }

      static int_type
      to_int_type(const char_type& __c) { return int_type(__c); }

      static bool
      eq_int_type(const int_type& __c1, const int_type& __c2)
      { return __c1 == __c2; }

      static int_type
      eof() { return static_cast<int_type>(WEOF); }

      static int_type
      not_eof(const int_type& __c)
      { return eq_int_type(__c, eof()) ? 0 : __c; }
  };
#endif //_GLIBCXX_USE_WCHAR_T

_GLIBCXX_END_NAMESPACE

#endif

---