// Stream buffer classes -*- C++ -*- // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003 // 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, // 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. // // ISO C++ 14882: 27.5 Stream buffers // /** @file streambuf * This is a Standard C++ Library header. You should @c #include this header * in your programs, rather than any of the "st[dl]_*.h" implementation files. */ #ifndef _CPP_STREAMBUF #define _CPP_STREAMBUF 1 #pragma GCC system_header #include #include #include // For SEEK_SET, SEEK_CUR, SEEK_END #include #include namespace std { /** * @if maint * Does stuff. * @endif */ template streamsize __copy_streambufs(basic_ios<_CharT, _Traits>& _ios, basic_streambuf<_CharT, _Traits>* __sbin, basic_streambuf<_CharT, _Traits>* __sbout); /** * @brief The actual work of input and output (interface). * * This is a base class. Derived stream buffers each control a * pair of character sequences: one for input, and one for output. * * Section [27.5.1] of the standard describes the requirements and * behavior of stream buffer classes. That section (three paragraphs) * is reproduced here, for simplicity and accuracy. * * -# Stream buffers can impose various constraints on the sequences * they control. Some constraints are: * - The controlled input sequence can be not readable. * - The controlled output sequence can be not writable. * - The controlled sequences can be associated with the contents of * other representations for character sequences, such as external * files. * - The controlled sequences can support operations @e directly to or * from associated sequences. * - The controlled sequences can impose limitations on how the * program can read characters from a sequence, write characters to * a sequence, put characters back into an input sequence, or alter * the stream position. * . * -# Each sequence is characterized by three pointers which, if non-null, * all point into the same @c charT array object. The array object * represents, at any moment, a (sub)sequence of characters from the * sequence. Operations performed on a sequence alter the values * stored in these pointers, perform reads and writes directly to or * from associated sequences, and alter "the stream position" and * conversion state as needed to maintain this subsequence relationship. * The three pointers are: * - the beginning pointer, or lowest element address in the * array (called @e xbeg here); * - the next pointer, or next element address that is a * current candidate for reading or writing (called @e xnext here); * - the end pointer, or first element address beyond the * end of the array (called @e xend here). * . * -# The following semantic constraints shall always apply for any set * of three pointers for a sequence, using the pointer names given * immediately above: * - If @e xnext is not a null pointer, then @e xbeg and @e xend shall * also be non-null pointers into the same @c charT array, as * described above; otherwise, @e xbeg and @e xend shall also be null. * - If @e xnext is not a null pointer and @e xnext < @e xend for an * output sequence, then a write position is available. * In this case, @e *xnext shall be assignable as the next element * to write (to put, or to store a character value, into the sequence). * - If @e xnext is not a null pointer and @e xbeg < @e xnext for an * input sequence, then a putback position is available. * In this case, @e xnext[-1] shall have a defined value and is the * next (preceding) element to store a character that is put back * into the input sequence. * - If @e xnext is not a null pointer and @e xnext< @e xend for an * input sequence, then a read position is available. * In this case, @e *xnext shall have a defined value and is the * next element to read (to get, or to obtain a character value, * from the sequence). */ template class basic_streambuf { public: //@{ /** * These are standard types. They permit a standardized way of * referring to names of (or names dependant on) the template * parameters, which are specific to the implementation. */ typedef _CharT char_type; typedef _Traits traits_type; typedef typename traits_type::int_type int_type; typedef typename traits_type::pos_type pos_type; typedef typename traits_type::off_type off_type; //@} //@{ /** * @if maint * These are non-standard types. * @endif */ typedef ctype __ctype_type; typedef basic_streambuf __streambuf_type; typedef typename traits_type::state_type __state_type; //@} friend class basic_ios; friend class basic_istream; friend class basic_ostream; friend class istreambuf_iterator; friend class ostreambuf_iterator; friend streamsize __copy_streambufs<>(basic_ios& __ios, __streambuf_type* __sbin,__streambuf_type* __sbout); protected: /** * @if maint * Pointer to the beginning of internally-allocated space. Filebuf * manually allocates/deallocates this, whereas stringstreams attempt * to use the built-in intelligence of the string class. If you are * managing memory, set this. If not, leave it NULL. * @endif */ char_type* _M_buf; /** * @if maint * Actual size of allocated internal buffer, in bytes. * @endif */ size_t _M_buf_size; /** * @if maint * Optimal or preferred size of internal buffer, in bytes. * @endif */ size_t _M_buf_size_opt; /** * @if maint * True iff _M_in_* and _M_out_* buffers should always point to * the same place. True for fstreams, false for sstreams. * @endif */ bool _M_buf_unified; //@{ /** * @if maint * This is based on _IO_FILE, just reordered to be more consistent, * and is intended to be the most minimal abstraction for an * internal buffer. * - get == input == read * - put == output == write * @endif */ char_type* _M_in_beg; // Start of get area. char_type* _M_in_cur; // Current read area. char_type* _M_in_end; // End of get area. char_type* _M_out_beg; // Start of put area. char_type* _M_out_cur; // Current put area. char_type* _M_out_end; // End of put area. //@} /** * @if maint * Place to stash in || out || in | out settings for current streambuf. * @endif */ ios_base::openmode _M_mode; /** * @if maint * Current locale setting. * @endif */ locale _M_buf_locale; /** * @if maint * True iff locale is initialized. * @endif */ bool _M_buf_locale_init; //@{ /** * @if maint * Necessary bits for putback buffer management. Only used in * the basic_filebuf class, as necessary for the standard * requirements. The only basic_streambuf member function that * needs access to these data members is in_avail... * * @note pbacks of over one character are not currently supported. * @endif */ static const size_t _S_pback_size = 1; char_type _M_pback[_S_pback_size]; char_type* _M_pback_cur_save; char_type* _M_pback_end_save; bool _M_pback_init; //@} /** * @if maint * Yet unused. * @endif */ fpos<__state_type> _M_pos; // Initializes pback buffers, and moves normal buffers to safety. // Assumptions: // _M_in_cur has already been moved back void _M_pback_create() { if (!_M_pback_init) { size_t __dist = _M_in_end - _M_in_cur; size_t __len = min(_S_pback_size, __dist); traits_type::copy(_M_pback, _M_in_cur, __len); _M_pback_cur_save = _M_in_cur; _M_pback_end_save = _M_in_end; this->setg(_M_pback, _M_pback, _M_pback + __len); _M_pback_init = true; } } // Deactivates pback buffer contents, and restores normal buffer. // Assumptions: // The pback buffer has only moved forward. void _M_pback_destroy() throw() { if (_M_pback_init) { // Length _M_in_cur moved in the pback buffer. size_t __off_cur = _M_in_cur - _M_pback; // For in | out buffers, the end can be pushed back... size_t __off_end = 0; size_t __pback_len = _M_in_end - _M_pback; size_t __save_len = _M_pback_end_save - _M_buf; if (__pback_len > __save_len) __off_end = __pback_len - __save_len; this->setg(_M_buf, _M_pback_cur_save + __off_cur, _M_pback_end_save + __off_end); _M_pback_cur_save = NULL; _M_pback_end_save = NULL; _M_pback_init = false; } } // Correctly sets the _M_in_cur pointer, and bumps the // _M_out_cur pointer as well if necessary. void _M_in_cur_move(off_type __n) // argument needs to be +- { bool __testout = _M_out_cur; _M_in_cur += __n; if (__testout && _M_buf_unified) _M_out_cur += __n; } // Correctly sets the _M_out_cur pointer, and bumps the // appropriate _M_*_end pointers as well. Necessary for the // un-tied stringbufs, in in|out mode. // Invariant: // __n + _M_out_[cur, end] <= _M_buf + _M_buf_size // Assuming all _M_*_[beg, cur, end] pointers are operating on // the same range: // _M_buf <= _M_*_ <= _M_buf + _M_buf_size void _M_out_cur_move(off_type __n) // argument needs to be +- { bool __testin = _M_in_cur; _M_out_cur += __n; if (__testin && _M_buf_unified) _M_in_cur += __n; if (_M_out_cur > _M_out_end) { _M_out_end = _M_out_cur; // NB: in | out buffers drag the _M_in_end pointer along... if (__testin) _M_in_end += __n; } } // Return the size of the output buffer. This depends on the // buffer in use: allocated buffers have a stored size in // _M_buf_size and setbuf() buffers don't. off_type _M_out_buf_size() { off_type __ret = 0; if (_M_out_cur) { // Using allocated buffer. if (_M_out_beg == _M_buf) __ret = _M_out_beg + _M_buf_size - _M_out_cur; // Using non-allocated buffer. else __ret = _M_out_end - _M_out_cur; } return __ret; } public: /// Destructor deallocates no buffer space. virtual ~basic_streambuf() { _M_buf_unified = false; _M_buf_size = 0; _M_buf_size_opt = 0; _M_mode = ios_base::openmode(0); } // [27.5.2.2.1] locales /** * @brief Entry point for imbue(). * @param loc The new locale. * @return The previous locale. * * Calls the derived imbue(loc). */ locale pubimbue(const locale &__loc) { locale __tmp(this->getloc()); this->imbue(__loc); return __tmp; } /** * @brief Locale access. * @return The current locale in effect. * * If pubimbue(loc) has been called, then the most recent @c loc * is returned. Otherwise the global locale in effect at the time * of construction is returned. */ locale getloc() const { return _M_buf_locale; } // [27.5.2.2.2] buffer management and positioning //@{ /** * @brief Entry points for derived buffer functions. * * The public versions of @c pubfoo dispatch to the protected * derived @c foo member functions, passing the arguments (if any) * and returning the result unchanged. */ __streambuf_type* pubsetbuf(char_type* __s, streamsize __n) { return this->setbuf(__s, __n); } pos_type pubseekoff(off_type __off, ios_base::seekdir __way, ios_base::openmode __mode = ios_base::in | ios_base::out) { return this->seekoff(__off, __way, __mode); } pos_type pubseekpos(pos_type __sp, ios_base::openmode __mode = ios_base::in | ios_base::out) { return this->seekpos(__sp, __mode); } int pubsync() { return this->sync(); } //@} // [27.5.2.2.3] get area /** * @brief Looking ahead into the stream. * @return The number of characters available. * * If a read position is available, returns the number of characters * available for reading before the buffer must be refilled. * Otherwise returns the derived @c showmanyc(). */ streamsize in_avail() { streamsize __ret; if (_M_in_cur && _M_in_cur < _M_in_end) { if (_M_pback_init) { size_t __save_len = _M_pback_end_save - _M_pback_cur_save; size_t __pback_len = _M_in_cur - _M_pback; __ret = __save_len - __pback_len; } else __ret = this->egptr() - this->gptr(); } else __ret = this->showmanyc(); return __ret; } /** * @brief Getting the next character. * @return The next character, or eof. * * Calls @c sbumpc(), and if that function returns * @c traits::eof(), so does this function. Otherwise, @c sgetc(). */ int_type snextc() { int_type __eof = traits_type::eof(); return (traits_type::eq_int_type(this->sbumpc(), __eof) ? __eof : this->sgetc()); } /** * @brief Getting the next character. * @return The next character, or eof. * * If the input read position is available, returns that character * and increments the read pointer, otherwise calls and returns * @c uflow(). */ int_type sbumpc(); /** * @brief Getting the next character. * @return The next character, or eof. * * If the input read position is available, returns that character, * otherwise calls and returns @c underflow(). Does not move the * read position after fetching the character. */ int_type sgetc() { int_type __ret; if (_M_in_cur && _M_in_cur < _M_in_end) __ret = traits_type::to_int_type(*(this->gptr())); else __ret = this->underflow(); return __ret; } /** * @brief Entry point for xsgetn. * @param s A buffer area. * @param n A count. * * Returns xsgetn(s,n). The effect is to fill @a s[0] through * @a s[n-1] with characters from the input sequence, if possible. */ streamsize sgetn(char_type* __s, streamsize __n) { return this->xsgetn(__s, __n); } // [27.5.2.2.4] putback /** * @brief Pushing characters back into the input stream. * @param c The character to push back. * @return The previous character, if possible. * * Similar to sungetc(), but @a c is pushed onto the stream instead * of "the previous character". If successful, the next character * fetched from the input stream will be @a c. */ int_type sputbackc(char_type __c); /** * @brief Moving backwards in the input stream. * @return The previous character, if possible. * * If a putback position is available, this function decrements the * input pointer and returns that character. Otherwise, calls and * returns pbackfail(). The effect is to "unget" the last character * "gotten". */ int_type sungetc(); // [27.5.2.2.5] put area /** * @brief Entry point for all single-character output functions. * @param c A character to output. * @return @a c, if possible. * * One of two public output functions. * * If a write position is available for the output sequence (i.e., * the buffer is not full), stores @a c in that position, increments * the position, and returns @c traits::to_int_type(c). If a write * position is not available, returns @c overflow(c). */ int_type sputc(char_type __c); /** * @brief Entry point for all single-character output functions. * @param s A buffer read area. * @param n A count. * * One of two public output functions. * * * Returns xsputn(s,n). The effect is to write @a s[0] through * @a s[n-1] to the output sequence, if possible. */ streamsize sputn(const char_type* __s, streamsize __n) { return this->xsputn(__s, __n); } protected: /** * @brief Base constructor. * * Only called from derived constructors, and sets up all the * buffer data to zero, including the pointers described in the * basic_streambuf class description. Note that, as a result, * - the class starts with no read nor write positions available, * - this is not an error */ basic_streambuf() : _M_buf(NULL), _M_buf_size(0), _M_buf_size_opt(BUFSIZ), _M_buf_unified(false), _M_in_beg(0), _M_in_cur(0), _M_in_end(0), _M_out_beg(0), _M_out_cur(0), _M_out_end(0), _M_mode(ios_base::openmode(0)), _M_buf_locale(locale()), _M_pback_cur_save(0), _M_pback_end_save(0), _M_pback_init(false) { } // [27.5.2.3.1] get area access //@{ /** * @brief Access to the get area. * * These functions are only available to other protected functions, * including derived classes. * * - eback() returns the beginning pointer for the input sequence * - gptr() returns the next pointer for the input sequence * - egptr() returns the end pointer for the input sequence */ char_type* eback() const { return _M_in_beg; } char_type* gptr() const { return _M_in_cur; } char_type* egptr() const { return _M_in_end; } //@} /** * @brief Moving the read position. * @param n The delta by which to move. * * This just advances the read position without returning any data. */ void gbump(int __n) { _M_in_cur += __n; } /** * @brief Setting the three read area pointers. * @param gbeg A pointer. * @param gnext A pointer. * @param gend A pointer. * @post @a gbeg == @c eback(), @a gnext == @c gptr(), and * @a gend == @c egptr() */ void setg(char_type* __gbeg, char_type* __gnext, char_type* __gend) { _M_in_beg = __gbeg; _M_in_cur = __gnext; _M_in_end = __gend; if (!(_M_mode & ios_base::in) && __gbeg && __gnext && __gend) _M_mode = _M_mode | ios_base::in; } // [27.5.2.3.2] put area access //@{ /** * @brief Access to the put area. * * These functions are only available to other protected functions, * including derived classes. * * - pbase() returns the beginning pointer for the output sequence * - pptr() returns the next pointer for the output sequence * - epptr() returns the end pointer for the output sequence */ char_type* pbase() const { return _M_out_beg; } char_type* pptr() const { return _M_out_cur; } char_type* epptr() const { return _M_out_end; } //@} /** * @brief Moving the write position. * @param n The delta by which to move. * * This just advances the write position without returning any data. */ void pbump(int __n) { _M_out_cur += __n; } /** * @brief Setting the three write area pointers. * @param pbeg A pointer. * @param pend A pointer. * @post @a pbeg == @c pbase(), @a pbeg == @c pptr(), and * @a pend == @c epptr() */ void setp(char_type* __pbeg, char_type* __pend) { _M_out_beg = _M_out_cur = __pbeg; _M_out_end = __pend; if (!(_M_mode & ios_base::out) && __pbeg && __pend) _M_mode = _M_mode | ios_base::out; } // [27.5.2.4] virtual functions // [27.5.2.4.1] locales /** * @brief Changes translations. * @param loc A new locale. * * Translations done during I/O which depend on the current locale * are changed by this call. The standard adds, "Between invocations * of this function a class derived from streambuf can safely cache * results of calls to locale functions and to members of facets * so obtained." This function simply stores the new locale for use * by derived classes. */ virtual void imbue(const locale& __loc) { if (_M_buf_locale != __loc) _M_buf_locale = __loc; } // [27.5.2.4.2] buffer management and positioning /** * @brief Maniuplates the buffer. * * Each derived class provides its own appropriate behavior. See * the next-to-last paragraph of * http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#2 for * more on this function. * * @note Base class version does nothing, returns @c this. */ virtual basic_streambuf* setbuf(char_type*, streamsize) { return this; } /** * @brief Alters the stream positions. * * Each derived class provides its own appropriate behavior. * @note Base class version does nothing, returns a @c pos_type * that represents an invalid stream position. */ virtual pos_type seekoff(off_type, ios_base::seekdir, ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out) { return pos_type(off_type(-1)); } /** * @brief Alters the stream positions. * * Each derived class provides its own appropriate behavior. * @note Base class version does nothing, returns a @c pos_type * that represents an invalid stream position. */ virtual pos_type seekpos(pos_type, ios_base::openmode /*__mode*/ = ios_base::in | ios_base::out) { return pos_type(off_type(-1)); } /** * @brief Synchronizes the buffer arrays with the controlled sequences. * @return -1 on failure. * * Each derived class provides its own appropriate behavior, * including the definition of "failure". * @note Base class version does nothing, returns zero. */ virtual int sync() { return 0; } // [27.5.2.4.3] get area /** * @brief Investigating the data available. * @return An estimate of the number of characters available in the * input sequence, or -1. * * "If it returns a positive value, then successive calls to * @c underflow() will not return @c traits::eof() until at least that * number of characters have been supplied. If @c showmanyc() * returns -1, then calls to @c underflow() or @c uflow() will fail." * [27.5.2.4.3]/1 * * @note Base class version does nothing, returns zero. * @note The standard adds that "the intention is not only that the * calls [to underflow or uflow] will not return @c eof() but * that they will return "immediately". * @note The standard adds that "the morphemes of @c showmanyc are * "es-how-many-see", not "show-manic". */ virtual streamsize showmanyc() { return 0; } /** * @brief Multiple character extraction. * @param s A buffer area. * @param n Maximum number of characters to assign. * @return The number of characters assigned. * * Fills @a s[0] through @a s[n-1] with characters from the input * sequence, as if by @c sbumpc(). Stops when either @a n characters * have been copied, or when @c traits::eof() would be copied. * * It is expected that derived classes provide a more efficient * implementation by overriding this definition. */ virtual streamsize xsgetn(char_type* __s, streamsize __n); /** * @brief Fetches more data from the controlled sequence. * @return The first character from the pending sequence. * * Informally, this function is called when the input buffer is * exhausted (or does not exist, as buffering need not actually be * done). If a buffer exists, it is "refilled". In either case, the * next available character is returned, or @c traits::eof() to * indicate a null pending sequence. * * For a formal definiton of the pending sequence, see a good text * such as Langer & Kreft, or [27.5.2.4.3]/7-14. * * A functioning input streambuf can be created by overriding only * this function (no buffer area will be used). For an example, see * http://gcc.gnu.org/onlinedocs/libstdc++/27_io/howto.html#6 * * @note Base class version does nothing, returns eof(). */ virtual int_type underflow() { return traits_type::eof(); } /** * @brief Fetches more data from the controlled sequence. * @return The first character from the pending sequence. * * Informally, this function does the same thing as @c underflow(), * and in fact is required to call that function. It also returns * the new character, like @c underflow() does. However, this * function also moves the read position forward by one. */ virtual int_type uflow() { int_type __ret = traits_type::eof(); bool __testeof = traits_type::eq_int_type(this->underflow(), __ret); bool __testpending = _M_in_cur && _M_in_cur < _M_in_end; if (!__testeof && __testpending) { __ret = traits_type::to_int_type(*_M_in_cur); ++_M_in_cur; if (_M_buf_unified && _M_mode & ios_base::out) ++_M_out_cur; } return __ret; } // [27.5.2.4.4] putback /** * @brief Tries to back up the input sequence. * @param c The character to be inserted back into the sequence. * @return eof() on failure, "some other value" on success * @post The constraints of @c gptr(), @c eback(), and @c pptr() * are the same as for @c underflow(). * * @note Base class version does nothing, returns eof(). */ virtual int_type pbackfail(int_type /* __c */ = traits_type::eof()) { return traits_type::eof(); } // Put area: /** * @brief Multiple character insertion. * @param s A buffer area. * @param n Maximum number of characters to write. * @return The number of characters written. * * Writes @a s[0] through @a s[n-1] to the output sequence, as if * by @c sputc(). Stops when either @a n characters have been * copied, or when @c sputc() would return @c traits::eof(). * * It is expected that derived classes provide a more efficient * implementation by overriding this definition. */ virtual streamsize xsputn(const char_type* __s, streamsize __n); /** * @brief Consumes data from the buffer; writes to the * controlled sequence. * @param c An additional character to consume. * @return eof() to indicate failure, something else (usually * @a c, or not_eof()) * * Informally, this function is called when the output buffer is full * (or does not exist, as buffering need not actually be done). If a * buffer exists, it is "consumed", with "some effect" on the * controlled sequence. (Typically, the buffer is written out to the * sequence verbatim.) In either case, the character @a c is also * written out, if @a c is not @c eof(). * * For a formal definiton of this function, see a good text * such as Langer & Kreft, or [27.5.2.4.5]/3-7. * * A functioning output streambuf can be created by overriding only * this function (no buffer area will be used). * * @note Base class version does nothing, returns eof(). */ virtual int_type overflow(int_type /* __c */ = traits_type::eof()) { return traits_type::eof(); } #ifdef _GLIBCPP_DEPRECATED // Annex D.6 public: /** * @brief Tosses a character. * * Advances the read pointer, ignoring the character that would have * been read. * * See http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html * * @note This function has been deprecated by the standard. You * must define @c _GLIBCPP_DEPRECATED to make this visible; see * c++config.h. */ void stossc() { if (_M_in_cur < _M_in_end) ++_M_in_cur; else this->uflow(); } #endif #ifdef _GLIBCPP_RESOLVE_LIB_DEFECTS // Side effect of DR 50. private: basic_streambuf(const __streambuf_type&) { }; __streambuf_type& operator=(const __streambuf_type&) { return *this; }; #endif }; } // namespace std #ifdef _GLIBCPP_NO_TEMPLATE_EXPORT # define export #endif #ifdef _GLIBCPP_FULLY_COMPLIANT_HEADERS #include #endif #endif