int_type underflow() override;
Returns:
If the input sequence has a read position available,
returns
traits::to_int_type(*gptr()). Otherwise, returns
traits::eof().Any character in the underlying buffer which has been initialized is considered
to be part of the input sequence
.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 input sequence has a putback position available, and
if
traits::eq(to_char_type(c), gptr()[-1])
returns
true,
assigns
gptr() - 1
to
gptr().If
traits::eq_int_type(c, traits::eof())
returns
false
and if the input sequence
has a putback position available, and
if
mode
&
ios_base::out is
nonzero,
assigns
c to
*--gptr().If
traits::eq_int_type(c, traits::eof())
returns
true
and if the input sequence has a putback position available,
assigns
gptr() - 1
to
gptr().Returns:
traits::not_eof(c).
Returns:
traits::eof()
to indicate failure
. Remarks:
If the function can succeed in more than one of these ways, it is
unspecified which way is chosen
. int_type overflow(int_type c = traits::eof()) override;
Effects:
Appends the character designated by
c to the output
sequence, if possible, in one of two ways:
If
traits::eq_int_type(c, traits::eof())
returns
false
and if either
the output sequence has a write position available or
the function makes a write position available
(as described below),
the function calls
sputc(c).Signals success by returning
c.If
traits::eq_int_type(c, traits::eof())
returns
true,
there is no character to append
.Signals success by returning a value other than
traits::eof().
Remarks:
The function can alter the number of write positions available as a
result of any call
. Returns:
traits::eof()
to indicate failure
. The function can make a write position available only if
(mode & ios_base::out) != 0.To make a write position available,
the function reallocates (or initially allocates) an array object
with a sufficient number of elements to hold
the current array object (if any), plus
at least
one additional write position
.If
(mode & ios_base::in) != 0,
the function alters the read end pointer
egptr()
to point just past the new write position
.pos_type seekoff(off_type off, ios_base::seekdir way,
ios_base::openmode which
= ios_base::in | ios_base::out) override;
Effects:
Alters the stream position within one of the
controlled sequences, if possible, as indicated in Table
110. Table
110 —
seekoff positioning
Conditions | Result |
(which & ios_base::in) == ios_base::in | positions the input sequence |
(which & ios_base::out) == ios_base::out | positions the output sequence |
(which & (ios_base::in |
ios_base::out)) ==
(ios_base::in) |
ios_base::out))
and way == either
ios_base::beg or
ios_base::end | positions both the input and the output sequences |
Otherwise | the positioning operation fails . |
For a sequence to be positioned, if its next pointer
(either
gptr()
or
pptr())
is a null pointer and the new offset
newoff is nonzero, the positioning
operation fails
.Otherwise, the function determines
newoff as indicated in
Table
111.Table
111 —
newoff values
Condition | newoff Value |
way == ios_base::beg | 0 |
way == ios_base::cur | the next pointer minus the beginning pointer ( xnext - xbeg) . |
way == ios_base::end | the high mark pointer minus the beginning pointer ( high_mark - xbeg) . |
If
(newoff + off) < 0,
or if
newoff + off refers to an uninitialized
character (
[stringbuf.members]),
the positioning operation fails
.Otherwise, the function assigns
xbeg + newoff + off
to the next pointer
xnext.Returns:
pos_type(newoff),
constructed from the resultant offset
newoff
(of type
off_type),
that stores the resultant stream position, if possible
. If the positioning operation fails, or
if the constructed object cannot represent the resultant stream position,
the return value is
pos_type(off_type(-1)).pos_type seekpos(pos_type sp,
ios_base::openmode which
= ios_base::in | ios_base::out) override;
Effects:
Equivalent to
seekoff(off_type(sp), ios_base::beg, which). Returns:
sp
to indicate success, or
pos_type(off_type(-1))
to indicate failure
. basic_streambuf<charT, traits>* setbuf(charT* s, streamsize n);
Effects:
implementation-defined,
except that
setbuf(0, 0)
has no effect
.