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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <config.h>
include <fio.h>
define SWAPI {tempi=$1;$1=$2;$2=tempi}
define SWAPL {templ=$1;$1=$2;$2=templ}
define SWAPP {tempp=$1;$1=$2;$2=tempp}
# FSWAPFD -- Swap the file descriptors of two open files. All i/o to file
# fd1 is redirected to fd2 and vice versa, until the swap is reversed.
# We are used by FREDIR to temporarily redirect i/o (normally to one of the
# standard streams) to a special file. If CLOSE is called to close a
# redirected file, we are called to unswap the two streams and then the
# redirection file is closed. All the i/o pointers, buffer pointers, and
# so on of the original stream are restored to exactly the condition they
# were in before (unless i/o has occurred on the other file during the
# interim).
procedure fswapfd (fd1, fd2)
int fd1, fd2 # file descriptors to be swapped.
int tempi
long templ
pointer tempp
include <fio.com>
begin
SWAPL (boffset[fd1], boffset[fd2])
SWAPP (bufptr[fd1], bufptr[fd2])
SWAPP (buftop[fd1], buftop[fd2])
SWAPP (iop[fd1], iop[fd2])
SWAPP (itop[fd1], itop[fd2])
SWAPP (otop[fd1], otop[fd2])
SWAPP (fiodes[fd1], fiodes[fd2])
SWAPI (redir_fd[fd1], redir_fd[fd2])
end
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