// Stream buffer classes -*- C++ -*-
-// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002
+// 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
#include <bits/c++config.h>
#include <iosfwd>
-#include <cstdio> // For SEEK_SET, SEEK_CUR, SEEK_END
#include <bits/localefwd.h>
#include <bits/ios_base.h>
namespace std
{
+ /**
+ * @if maint
+ * Does stuff.
+ * @endif
+ */
template<typename _CharT, typename _Traits>
streamsize
__copy_streambufs(basic_ios<_CharT, _Traits>& _ios,
basic_streambuf<_CharT, _Traits>* __sbin,
basic_streambuf<_CharT, _Traits>* __sbout);
- // 27.5.2 Template class basic_streambuf<_CharT, _Traits>
+ /**
+ * @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 <em>beginning pointer</em>, or lowest element address in the
+ * array (called @e xbeg here);
+ * - the <em>next pointer</em>, or next element address that is a
+ * current candidate for reading or writing (called @e xnext here);
+ * - the <em>end pointer</em>, 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 <em>write position</em> 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 <em>putback position</em> 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 <em>read position</em> 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<typename _CharT, typename _Traits>
class basic_streambuf
{
public:
- // Types:
+ //@{
+ /**
+ * 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;
-
- // Non-standard Types:
+ //@}
+
+ //@{
+ /**
+ * @if maint
+ * These are non-standard types.
+ * @endif
+ */
typedef ctype<char_type> __ctype_type;
typedef basic_streambuf<char_type, traits_type> __streambuf_type;
+ typedef typename traits_type::state_type __state_type;
+ //@}
friend class basic_ios<char_type, traits_type>;
friend class basic_istream<char_type, traits_type>;
__streambuf_type* __sbin,__streambuf_type* __sbout);
protected:
- // 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.
- char_type* _M_buf;
-
- // Actual size of allocated internal buffer, in bytes.
- int_type _M_buf_size;
-
- // Optimal or preferred size of internal buffer, in bytes.
- int_type _M_buf_size_opt;
-
- // True iff _M_in_* and _M_out_* buffers should always point to
- // the same place. True for fstreams, false for sstreams.
+ /**
+ * @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;
- // 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
- 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.
-
- // Place to stash in || out || in | out settings for current streambuf.
+ //@{
+ /**
+ * @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
+ * setp (and _M_set_buffer(0) in basic_filebuf) set it equal to
+ * _M_out_beg, then at each put operation it may be moved
+ * forward (toward _M_out_end) by _M_out_cur_move.
+ * @endif
+ */
+ char_type* _M_out_lim; // End limit of used put area.
+
+ //@}
+
+ /**
+ * @if maint
+ * Place to stash in || out || in | out settings for current streambuf.
+ * @endif
+ */
ios_base::openmode _M_mode;
- // Current locale setting.
+ /**
+ * @if maint
+ * Current locale setting.
+ * @endif
+ */
locale _M_buf_locale;
- // True iff locale is initialized.
- bool _M_buf_locale_init;
-
- // 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...
- // NB: pbacks of over one character are not currently supported.
- static const int_type _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;
-
- // 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)
- {
- int_type __dist = _M_in_end - _M_in_cur;
- int_type __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()
- {
- if (_M_pback_init)
- {
- // Length _M_in_cur moved in the pback buffer.
- int_type __off_cur = _M_in_cur - _M_pback;
-
- // For in | out buffers, the end can be pushed back...
- int_type __off_end = 0;
- int_type __pback_len = _M_in_end - _M_pback;
- int_type __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;
- }
- }
+ /**
+ * @if maint
+ * Yet unused.
+ * @endif
+ */
+ fpos<__state_type> _M_pos;
// 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 +-
+ _M_move_in_cur(off_type __n) // argument needs to be +-
{
- bool __testout = _M_out_cur;
+ const 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.
+ // appropriate _M_out_lim and _M_in_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
+ // __n + _M_out_[cur, lim] <= _M_out_end
+ // Assuming all _M_out_[beg, cur, lim] pointers are operating on
// the same range:
- // _M_buf <= _M_*_ <= _M_buf + _M_buf_size
+ // _M_out_beg <= _M_*_ <= _M_out_end
void
- _M_out_cur_move(off_type __n) // argument needs to be +-
+ _M_move_out_cur(off_type __n) // argument needs to be +-
{
- bool __testin = _M_in_cur;
+ const 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)
+ if (_M_out_cur > _M_out_lim)
{
- _M_out_end = _M_out_cur;
+ _M_out_lim = _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);
- _M_buf_locale_init = false;
}
- // Locales:
+ // [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)
{
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
- {
- if (_M_buf_locale_init)
- return _M_buf_locale;
- else
- return locale();
- }
-
- // Buffer and positioning:
+ { 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); }
int
pubsync() { return this->sync(); }
-
- // Get and put areas:
- // Get area:
+ //@}
+
+ // [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)
- {
- int_type __save_len = _M_pback_end_save - _M_pback_cur_save;
- int_type __pback_len = _M_in_cur - _M_pback;
- __ret = __save_len - __pback_len;
- }
- else
- __ret = this->egptr() - this->gptr();
- }
- else
- __ret = this->showmanyc();
- return __ret;
+ streamsize __ret = _M_in_end - _M_in_cur;
+ return __ret ? __ret : this->showmanyc();
}
+ /**
+ * @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 (this->sbumpc() == __eof ? __eof : this->sgetc());
+ int_type __ret = traits_type::eof();
+ if (!traits_type::eq_int_type(this->sbumpc(), __ret))
+ __ret = this->sgetc();
+ return __ret;
}
+ /**
+ * @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()));
+ if (_M_in_cur < _M_in_end)
+ __ret = traits_type::to_int_type(*this->_M_in_cur);
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); }
- // Putback:
+ // [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();
- // Put area:
+ // [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(static_cast<int_type>(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_buf_locale_init(false), _M_pback_cur_save(0), _M_pback_end_save(0),
- _M_pback_init(false)
+ : _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_out_lim(0), _M_mode(ios_base::openmode(0)),
+ _M_buf_locale(locale())
{ }
- // Get area:
+ // [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*
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;
}
- // Put area:
+ // [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*
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;
+ _M_out_beg = _M_out_cur = _M_out_lim = __pbeg;
+ _M_out_end = __pend;
}
- // Virtual functions:
- // Locales:
+ // [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)
{
- _M_buf_locale_init = true;
if (_M_buf_locale != __loc)
_M_buf_locale = __loc;
}
- // Buffer management and positioning:
+ // [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<char_type,_Traits>*
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; }
- // Get area:
+ // [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 <em>pending sequence</em>.
+ *
+ * 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 <em>pending sequence</em>.
+ *
+ * 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 = this->underflow() == __ret;
- bool __testpending = _M_in_cur && _M_in_cur < _M_in_end;
- if (!__testeof && __testpending)
+ const bool __testeof = traits_type::eq_int_type(this->underflow(),
+ __ret);
+ if (!__testeof && _M_in_cur < _M_in_end)
{
__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;
}
- // Putback:
+ // [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
- // http://gcc.gnu.org/ml/libstdc++/2002-05/msg00168.html
// 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()
{
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