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 allocator 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
#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
| [virtual] | writes characters to the associated output sequence from the put area (virtual protected member function of std::basic_streambuf) |
| [virtual] | appends a character to the output sequence (virtual protected member function of std::basic_stringbuf) |
| [virtual] | writes characters to the associated file from the put area (virtual protected member function of std::basic_filebuf) |
| writes one character to the put area and advances the next pointer (public member function of std::basic_streambuf) | |
| inserts a character (public member function of std::basic_ostream) |
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