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(iostream-295.info)Extending

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Extended data fields
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   A related collection of methods allows you to extend this collection
of flags and parameters for your own applications, without risk of
conflict between them:

 - Method: static fmtflags ios::bitalloc ()
     Reserve a bit (the single bit on in the result) to use as a flag.
     Using `bitalloc' guards against conflict between two packages that
     use `ios' objects for different purposes.

     This method is available for upward compatibility, but is not in
     the ANSI working paper.  The number of bits available is limited; a
     return value of `0' means no bit is available.

 - Method: static int ios::xalloc ()
     Reserve space for a long integer or pointer parameter.  The result
     is a unique nonnegative integer.  You can use it as an index to
     `ios::iword' or `ios::pword'.  Use `xalloc' to arrange for
     arbitrary special-purpose data in your `ios' objects, without risk
     of conflict between packages designed for different purposes.

 - Method: long& ios::iword (int INDEX)
     Return a reference to arbitrary data, of long integer type, stored
     in an `ios' instance.  INDEX, conventionally returned from
     `ios::xalloc', identifies what particular data you need.

 - Method: long ios::iword (int INDEX) const
     Return the actual value of a long integer stored in an `ios'.

 - Method: void*& ios::pword (int INDEX)
     Return a reference to an arbitrary pointer, stored in an `ios'
     instance.  INDEX, originally returned from `ios::xalloc',
     identifies what particular pointer you need.

 - Method: void* ios::pword (int INDEX) const
     Return the actual value of a pointer stored in an `ios'.