1 files changed, 75 insertions, 0 deletions
diff --git a/sys/fio/ungetline.x b/sys/fio/ungetline.x
new file mode 100644
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--- /dev/null
+++ b/sys/fio/ungetline.x
@@ -0,0 +1,75 @@
+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<config.h>
+include	<syserr.h>
+include	<fio.h>
+
+# UNGETLINE -- Push an EOS delimited string back into the input stream.
+# The next getc will return the first char of the pushed back string,
+# followed by successive chars in the string until EOS is reached, at which
+# time input reverts to wherever it was before pushback.  Pushback is last
+# in first out, i.e., the last string pushed will be the first string scanned
+# when reading.  Multiple characters and strings may be pushed back into the
+# input until the push back buffer overflows.  Overflow is often an indication
+# of recursion in whatever routine is doing the pushback.
+#
+# N.B.: this routine really pushes a string, not a line, i.e. we don't give
+# a whiz about newline characters.
+
+procedure ungetline (fd, str)
+
+int	fd			# file
+char	str[ARB]		# string to be pushed back
+
+int	or()
+pointer	ip, pb_iop, pb_sp, iop_limit
+errchk	syserr, syserrs, fmkpbbuf
+include	<fio.com>
+
+begin
+	fp = fiodes[fd]
+	if (fd <= 0 || fp == NULL)
+	    call syserr (SYS_FILENOTOPEN)
+
+	if (str[1] == EOS)
+	    return
+	if (FPBBUF(fp) == NULL)
+	    call fmkpbbuf (fd)
+
+	# Push the old pb_iop, iop, itop and bufptr on the stack for later
+	# restoration of the interrupted input stream by filbuf.  Note bufptr
+	# must be changed to point to a value less than iop to avoid a buffer
+	# fault.
+
+	pb_sp  = FPBSP(fp) - 1
+	pb_iop = FPBIOP(fp)
+
+	Memi[pb_sp] = pb_iop
+	pb_sp = pb_sp - 1
+	Memi[pb_sp] = bufptr[fd]
+	pb_sp = pb_sp - 1
+	Memi[pb_sp] = itop[fd]
+	pb_sp = pb_sp - 1
+	Memi[pb_sp] = iop[fd]
+
+	# Copy the string into the buffer; abort if the buffer overflows.
+	# Set iop to point to first char of string.  Note: pushed back chars
+	# grow upward while the stacked i/o pointers grow downward.
+
+	bufptr[fd] = pb_iop
+	iop[fd] = pb_iop
+	iop_limit = (pb_sp - 1) * SZ_INT + 1
+
+	for (ip=1;  str[ip] != EOS;  ip=ip+1) {
+	    if (pb_iop >= iop_limit)
+		call syserrs (SYS_FPBOVFL, FNAME(fp))
+	    Memc[pb_iop] = str[ip]
+	    pb_iop = pb_iop + 1
+	}
+
+	itop[fd] = pb_iop
+	
+	FPBSP(fp) = pb_sp
+	FPBIOP(fp) = pb_iop
+	fflags[fd] = or (fflags[fd], FF_PUSHBACK)
+end