int_type overflow(int_type c = EOF) override;
Effects:
Appends the character designated by
c to the output
sequence, if possible, in one of two ways:
If
c != EOF
and if either the output sequence has a write position available or
the function makes a write position available
(as described below),
assigns
c to
*pnext++.Returns
(unsigned char)c.If
c == EOF,
there is no character to append
.Returns a value other than
EOF.
Returns
EOF
to indicate failure
.Remarks:
The function can alter the number of write positions available as a
result of any call
. To make a write position available, the function reallocates
(or initially allocates)
an array object with a sufficient number of elements
n to hold the current array object (if any),
plus at least one additional write position
.How many additional write positions are made
available is otherwise unspecified
.
If
palloc is not a null pointer, the function calls
(*palloc)(n)
to allocate the new dynamic array object
.Otherwise, it evaluates the expression
new charT[n].In either case, if the allocation fails, the function returns
EOF.Otherwise, it sets
allocated in
strmode.To free a previously existing dynamic array object whose first
element address is
p:
If
pfree is not a null pointer,
the function calls
(*pfree)(p).Otherwise, it evaluates the expression
delete[]p.If
(strmode & dynamic) == 0,
or if
(strmode & frozen) != 0,
the function cannot extend the array (reallocate it with greater length) to make a write position available
.int_type pbackfail(int_type c = EOF) override;
Puts back the character designated by
c to the input
sequence, if possible, in one of three ways:
If
c != EOF,
if the input sequence has a putback position available, and if
(char)c == gnext[-1],
assigns
gnext - 1
to
gnext.If
c != EOF,
if the input sequence has a putback position available, and if
strmode & constant is zero,
assigns
c to
*--gnext.If
c == EOF
and if the input sequence has a putback position available,
assigns
gnext - 1
to
gnext.Returns a value other than
EOF.
Returns
EOF
to indicate failure
.Remarks:
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 underflow() override;
Effects:
Reads a character from the
input sequence,
if possible, without moving the stream position past it, as follows:
If the input sequence has a read position available, the function
signals success by returning
(unsigned char)*gnext.Otherwise, if
the current write next pointer
pnext is not a null pointer and
is greater than the current read end pointer
gend,
makes a
read position
available by
assigning to
gend a value greater than
gnext and
no greater than
pnext.Returns
(unsigned char)*gnext.
Returns
EOF
to indicate failure
.Remarks:
The function can alter the number of read positions available as a
result of any call
. pos_type seekoff(off_type off, seekdir way, openmode which = in | out) override;
Effects:
Alters the stream position within one of the
controlled sequences, if possible, as indicated in Table
140. Table
140 —
seekoff positioning
Conditions | Result |
(which & ios::in) != 0 | positions the input sequence |
(which & ios::out) != 0 | positions the output sequence |
(which & (ios::in |
ios::out)) == (ios::in |
ios::out)) and
way == either
ios::beg or
ios::end | positions both the input and the output sequences |
Otherwise | the positioning operation fails . |
For a sequence to be positioned, if its next pointer is a null pointer,
the positioning operation fails
.Otherwise, the function determines
newoff as indicated in
Table
141.Table
141 —
newoff values
Condition | newoff Value |
way == ios::beg | 0 |
way == ios::cur | the next pointer minus the beginning pointer ( xnext - xbeg) . |
way == ios::end | seekhigh minus the beginning pointer ( seekhigh - xbeg) . |
If
(newoff + off) < (seeklow - xbeg)
or
(seekhigh - xbeg) < (newoff + off),
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:
Alters the stream position within one of the
controlled sequences, if possible, to correspond to the
stream position stored in
sp
(as described below)
. If
(which & ios::in) != 0,
positions the input sequence
.If
(which & ios::out) != 0,
positions the output sequence
.If the function positions neither sequence, the positioning operation fails
.
For a sequence to be positioned, if its next pointer is a null pointer,
the positioning operation fails
.Otherwise, the function determines
newoff from
sp.offset():
If newoff is an invalid stream position,
has a negative value, or
has a value greater than (seekhigh - seeklow),
the positioning operation fails
Otherwise, the function
adds
newoff to the beginning pointer
xbeg and
stores the result in 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)).streambuf<char>* setbuf(char* s, streamsize n) override;
Effects:
Implementation defined, except that
setbuf(0, 0)
has no effect
.