kc3-lang/libbsd/man/funopen.3

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  Date : 2013-10-21T05:07:56
  

  Add funopen() function This is a wrapper over the glibc fopencookie() function. We diverge from the FreeBSD, OpenBSD and DragonFlyBSD declarations, because seekfn() there wrongly uses fpos_t, assuming it's an integral type, and any code using that on a system where fpos_t is a struct (such as GNU-based systems or NetBSD) will fail to build. In which case, as the code has to be modified anyway, we might just as well use the correct declaration.

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• man/funopen.3

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  .\"     @(#)funopen.3	8.1 (Berkeley) 6/9/93
  .\" $FreeBSD$
  .\"
  .Dd March 19, 2004
  .Dt FUNOPEN 3
  .Os
  .Sh NAME
  .Nm funopen ,
  .Nm fropen ,
  .Nm fwopen
  .Nd open a stream
  .Sh LIBRARY
  .ds str-Lb-libbsd Utility functions from BSD systems (libbsd, \-lbsd)
  .Lb libbsd
  .Sh SYNOPSIS
  .In bsd/stdio.h
  .Ft FILE *
  .Fn funopen "const void *cookie" "int (*readfn)(void *, char *, int)" "int (*writefn)(void *, const char *, int)" "off_t (*seekfn)(void *, off_t, int)" "int (*closefn)(void *)"
  .Ft FILE *
  .Fn fropen "void *cookie" "int (*readfn)(void *, char *, int)"
  .Ft FILE *
  .Fn fwopen "void *cookie" "int (*writefn)(void *, const char *, int)"
  .Sh DESCRIPTION
  The
  .Fn funopen
  function
  associates a stream with up to four
  .Dq Tn I/O No functions .
  Either
  .Fa readfn
  or
  .Fa writefn
  must be specified;
  the others can be given as an appropriately-typed
  .Dv NULL
  pointer.
  These
  .Tn I/O
  functions will be used to read, write, seek and
  close the new stream.
  .Pp
  In general, omitting a function means that any attempt to perform the
  associated operation on the resulting stream will fail.
  If the close function is omitted, closing the stream will flush
  any buffered output and then succeed.
  .Pp
  The calling conventions of
  .Fa readfn ,
  .Fa writefn ,
  .Fa seekfn
  and
  .Fa closefn
  must match those, respectively, of
  .Xr read 2 ,
  .Xr write 2 ,
  .Xr lseek 2 ,
  and
  .Xr close 2
  with the single exception that they are passed the
  .Fa cookie
  argument specified to
  .Fn funopen
  in place of the traditional file descriptor argument.
  .Pp
  Read and write
  .Tn I/O
  functions are allowed to change the underlying buffer
  on fully buffered or line buffered streams by calling
  .Xr setvbuf 3 .
  They are also not required to completely fill or empty the buffer.
  They are not, however, allowed to change streams from unbuffered to buffered
  or to change the state of the line buffering flag.
  They must also be prepared to have read or write calls occur on buffers other
  than the one most recently specified.
  .Pp
  All user
  .Tn I/O
  functions can report an error by returning \-1.
  Additionally, all of the functions should set the external variable
  .Va errno
  appropriately if an error occurs.
  .Pp
  An error on
  .Fn closefn
  does not keep the stream open.
  .Pp
  As a convenience, the include file
  .In stdio.h
  defines the macros
  .Fn fropen
  and
  .Fn fwopen
  as calls to
  .Fn funopen
  with only a read or write function specified.
  .Sh RETURN VALUES
  Upon successful completion,
  .Fn funopen
  returns a
  .Dv FILE
  pointer.
  Otherwise,
  .Dv NULL
  is returned and the global variable
  .Va errno
  is set to indicate the error.
  .Sh ERRORS
  .Bl -tag -width Er
  .It Bq Er EINVAL
  The
  .Fn funopen
  function
  was called without either a read or write function.
  The
  .Fn funopen
  function
  may also fail and set
  .Va errno
  for any of the errors
  specified for the routine
  .Xr malloc 3 .
  .El
  .Sh SEE ALSO
  .Xr fcntl 2 ,
  .Xr open 2 ,
  .Xr fclose 3 ,
  .Xr fopen 3 ,
  .Xr fseek 3 ,
  .Xr setbuf 3
  .Sh HISTORY
  The
  .Fn funopen
  functions first appeared in
  .Bx 4.4 .
  .Sh BUGS
  The
  .Fn funopen
  function
  may not be portable to systems other than
  .Bx .
  .Pp
  On
  .Fx ,
  .Ox
  and
  .Dx
  the
  .Fn funopen
  interface erroneously assumes that
  .Vt fpos_t
  is an integral type, and uses it in the
  .Fa seekfn
  hook; but because code using a
  .Fa seekfn
  hook will fail to build on systems where
  .Vt fpos_t
  is a struct, and it will need to be slightly fixed anyway, the
  implementation provided by libbsd (in the same way as
  .Nx )
  uses the correct
  .Vt off_t
  types.
  

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