streamsize showmanyc() override;
Effects: Behaves the same as basic_streambuf::showmanyc() ([streambuf.virtuals]).
Remarks: An implementation might well provide an overriding definition for this function signature if it can determine that more characters can be read from the input sequence.
int_type underflow() override;
Effects: Behaves according to the description of basic_streambuf<charT, traits>::underflow(), with the specialization that a sequence of characters is read from the input sequence as if by reading from the associated file into an internal buffer (extern_buf) and then as if by doing:
char extern_buf[XSIZE];
char* extern_end;
charT intern_buf[ISIZE];
charT* intern_end;
codecvt_base::result r =
a_codecvt.in(state, extern_buf, extern_buf+XSIZE, extern_end,
intern_buf, intern_buf+ISIZE, intern_end);This shall be done in such a way that the class can recover the position (fpos_t) corresponding to each character between intern_buf and intern_end. If the value of r indicates that a_codecvt.in() ran out of space in intern_buf, retry with a larger intern_buf.
int_type uflow() override;
Effects: Behaves according to the description of basic_streambuf<charT, traits>::uflow(), with the specialization that a sequence of characters is read from the input with the same method as used by underflow.
int_type pbackfail(int_type c = traits::eof()) override;
Effects: Puts back the character designated by c to the input sequence, if possible, in one of three ways:
If traits::eq_int_type(c, traits::eof()) returns false and if the function makes a putback position available and if traits::eq(to_char_type(c), gptr()[-1]) returns true, decrements the next pointer for the input sequence, gptr().
Returns: c.
If traits::eq_int_type(c, traits::eof()) returns false and if the function makes a putback position available and if the function is permitted to assign to the putback position, decrements the next pointer for the input sequence, and stores c there.
Returns: c.
If traits::eq_int_type(c, traits::eof()) returns true, and if either the input sequence has a putback position available or the function makes a putback position available, decrements the next pointer for the input sequence, gptr().
Returns: traits::not_eof(c).
If the function can succeed in more than one of these ways, it is unspecified which way is chosen. The function can alter the number of putback positions available as a result of any call.
int_type overflow(int_type c = traits::eof()) override;
Effects: Behaves according to the description of basic_streambuf<charT, traits>::overflow(c), except that the behavior of “consuming characters” is performed by first converting as if by:
charT* b = pbase(); charT* p = pptr(); charT* end; char xbuf[XSIZE]; char* xbuf_end; codecvt_base::result r = a_codecvt.out(state, b, p, end, xbuf, xbuf+XSIZE, xbuf_end);
and then
If r == codecvt_base::error then fail.
If r == codecvt_base::noconv then output characters from b up to (and not including) p.
If r == codecvt_base::partial then output to the file characters from xbuf up to xbuf_end, and repeat using characters from end to p. If output fails, fail (without repeating).
Otherwise output from xbuf to xbuf_end, and fail if output fails. At this point if b != p and b == end (xbuf isn't large enough) then increase XSIZE and repeat from the beginning.
Returns: traits::not_eof(c) to indicate success, and traits::eof() to indicate failure. If is_open() == false, the function always fails.
basic_streambuf* setbuf(char_type* s, streamsize n) override;
pos_type seekoff(off_type off, ios_base::seekdir way,
ios_base::openmode which
= ios_base::in | ios_base::out) override;
Effects: Let width denote a_codecvt.encoding(). If is_open() == false, or off != 0 && width <= 0, then the positioning operation fails. Otherwise, if way != basic_ios::cur or off != 0, and if the last operation was output, then update the output sequence and write any unshift sequence. Next, seek to the new position: if width > 0, call fseek(file, width * off, whence), otherwise call fseek(file, 0, whence).
Remarks: “The last operation was output” means either the last virtual operation was overflow or the put buffer is non-empty. “Write any unshift sequence” means, if width if less than zero then call a_codecvt.unshift(state, xbuf, xbuf+XSIZE, xbuf_end) and output the resulting unshift sequence. The function determines one of three values for the argument whence, of type int, as indicated in Table 118.
| way Value | stdio Equivalent |
| basic_ios::beg | SEEK_SET |
| basic_ios::cur | SEEK_CUR |
| basic_ios::end | SEEK_END |
Returns: A newly constructed pos_type object that stores the resultant stream position, if possible. If the positioning operation fails, or if the object cannot represent the resultant stream position, returns pos_type(off_type(-1)).
pos_type seekpos(pos_type sp,
ios_base::openmode which
= ios_base::in | ios_base::out) override;
Alters the file position, if possible, to correspond to the position stored in sp (as described below). Altering the file position performs as follows:
1.if (om & ios_base::out) != 0, then update the output sequence and write any unshift sequence;
2.set the file position to sp as if by a call to fsetpos;
3.if (om & ios_base::in) != 0, then update the input sequence;
where om is the open mode passed to the last call to open(). The operation fails if is_open() returns false.
If sp is an invalid stream position, or if the function positions neither sequence, the positioning operation fails. If sp has not been obtained by a previous successful call to one of the positioning functions (seekoff or seekpos) on the same file the effects are undefined.
int sync() override;
void imbue(const locale& loc) override;
Requires: If the file is not positioned at its beginning and the encoding of the current locale as determined by a_codecvt.encoding() is state-dependent ([locale.codecvt.virtuals]) then that facet is the same as the corresponding facet of loc.
Effects: Causes characters inserted or extracted after this call to be converted according to loc until another call of imbue.