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# std::strstreambuf::overflow

From cppreference.com
< cpp‎ | io‎ | strstreambuf

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.

### [edit] Parameters

c | - | the character to store in the put area

### [edit] Return value

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

### [edit] 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

### [edit] See also

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

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