NAME¶

std::strstreambuf::overflow - std::strstreambuf::overflow

Synopsis¶

protected:
virtual int_type overflow (int_type c = EOF);

Appends the character c to the put area of the buffer, reallocating if possible.

1) If c==EOF, does nothing
2) Otherwise, if the put area has a write position available (pptr() < epptr()),
stores the character as if by *pptr()++ = c
3) Otherwise, if the stream buffer mode is not dynamic or the stream buffer is
currently frozen, the function fails and returns EOF
4) Otherwise, the function reallocates (or initially allocates) a dynamic array
large enough to hold the contents of the current dynamic array (if any) plus at
least one additional write position. If a pointer to the allocating function palloc
was used in the constructor, that function is called with (*palloc)(n) where n is
the number of bytes to allocate, otherwise new char[n] is used. If a pointer to the
deallocating function pfree was used in the constructor, that function is called
with (*pfree)(p) to deallocate the previous array, if needed, otherwise delete[] p
is used. If allocation fails, the function fails and returns EOF.

Parameters¶

c - the character to store in the put area

Return value¶

If c==EOF, returns some value other than EOF. Otherwise, returns (unsigned char)(c)
on success, EOF on failure.

Example¶

// Run this code

#include <strstream>
#include <iostream>

struct mybuf : std::strstreambuf
{
int_type overflow(int_type c)
{
std::cout << "Before overflow(): size of the put area is " << epptr()-pbase()
<< " with " << epptr()-pptr() << " write positions available\n";
int_type rc = std::strstreambuf::overflow(c);
std::cout << "After overflow(): size of the put area is " << epptr()-pbase()
<< " with " << epptr()-pptr() << " write positions available\n";
return rc;
}
};

int main()
{
mybuf sbuf; // read-write dynamic strstreambuf
std::iostream stream(&sbuf);

stream << "Sufficiently long string to overflow the initial allocation, at least "
<< " on some systems.";
}

Possible output:¶

Before overflow(): size of the put area is 16 with 0 write positions available
After overflow(): size of the put area is 32 with 15 write positions available
Before overflow(): size of the put area is 32 with 0 write positions available
After overflow(): size of the put area is 64 with 31 write positions available
Before overflow(): size of the put area is 64 with 0 write positions available
After overflow(): size of the put area is 128 with 63 write positions available

See also¶

overflow writes characters to the associated output sequence from the put area
[virtual] (virtual protected member function of std::basic_streambuf<CharT,Traits>)
overflow appends a character to the output sequence
[virtual] (virtual protected member function of
std::basic_stringbuf<CharT,Traits,Allocator>)
overflow writes characters to the associated file from the put area
[virtual] (virtual protected member function of std::basic_filebuf<CharT,Traits>)
sputc writes one character to the put area and advances the next pointer
(public member function of std::basic_streambuf<CharT,Traits>)
put inserts a character
(public member function of std::basic_ostream<CharT,Traits>)