std::strstreambuf::overflow - cppreference.com (original) (raw)

| protected: virtual int_type overflow( int_type c = EOF ); | | (deprecated in C++98) (removed in C++26) | | ------------------------------------------------------------------------- | | ---------------------------------------- |

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.

[edit] Parameters

[edit] Return value

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

[edit] Example

#include #include   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

[edit] See also

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