Annex D (normative) Compatibility features [depr]

D.13 char* streams [depr.str.strstreams]

D.13.2 Class strstreambuf [depr.strstreambuf]

D.13.2.4 strstreambuf overridden virtual functions [depr.strstreambuf.virtuals]

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:

(1.1)
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.
(1.2)
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.

Recommended practice: An implementation should consider alsize in making the decision how many additional write positions to make available.

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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:

(8.1)
If c != EOF, if the input sequence has a putback position available, and if (char)c == gnext[-1], assigns gnext - 1 to gnext.
Returns c.
(8.2)
If c != EOF, if the input sequence has a putback position available, and if strmode & constant is zero, assigns c to *--gnext.
Returns c.
(8.3)
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.

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int_type underflow() override;

Effects: Reads a character from the input sequence, if possible, without moving the stream position past it, as follows:

(11.1)
If the input sequence has a read position available, the function signals success by returning (unsigned char)*gnext.
(11.2)
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.

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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 150 .

Table 150: seekoff positioning [tab:depr.strstreambuf.seekoff.pos]

🔗	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 either way == ios::beg or way == 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 151 .

Table 151: newoff values [tab:depr.strstreambuf.seekoff.newoff]

🔗	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)).

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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).

(18.1)
If (which & ios::in) != 0, positions the input sequence.
(18.2)
If (which & ios::out) != 0, positions the output sequence.
(18.3)
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():

(19.1)
If newoff is an invalid stream position, has a negative value, or has a value greater than (seekhigh - seeklow), the positioning operation fails
(19.2)
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)).

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streambuf<char>* setbuf(char* s, streamsize n) override;

Effects: Behavior is implementation-defined, except that setbuf(0, 0) has no effect.