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◄streambuf►                                   ◄Up► ◄Contents► ◄Index► ◄Back►
──The Microsoft iostream Classes────────────────────────────────────────────
 
  virtual int overflow( int nCh = EOF ) = 0;
 
  Parameter   Description
 
  <nCh>       EOF or the character to output.
 
  Remarks
 
  The virtual overflow function, together with the sync and underflow
  functions, defines the characteristics of the streambuf-derived class.
  Each derived class might implement overflow differently, but the
  interface with the calling stream class is the same.
 
  The overflow function is most frequently called by public streambuf
  functions like sputc and sputn when they sense that the put area is
  full, but other classes, including the stream classes, can call overflow
  anytime.
 
  The function "consumes" the characters in the put area between the pbase
  and pptr pointers and then reinitializes the put area. The overflow
  function must also consume <nCh> (if <nCh> is not EOF), or it might
  choose to put that character in the new put area so that it will be
  consumed on the next call.
 
  The definition of "consume" varies among derived classes. The filebuf
  class, for example, writes its characters to a file. The strsteambuf
  class, on the other hand, keeps them in its buffer and (if the buffer is
  designated as dynamic) expands the buffer in response to a call to
  overflow. This expansion is achieved by freeing the old buffer and
  replacing it with a new, larger one. The pointers are adjusted as
  necessary.
 
  Default Implementation
 
  No default implementation. Derived classes must define this function.
 
  Return Value
 
  EOF to indicate an error.
 
  See Also
 
  ◄streambuf::pbase►, ◄streambuf::pptr►, ◄streambuf::setp►,
  ◄streambuf::sync►, ◄streambuf::underflow►
 
 
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