1 files changed, 39 insertions, 0 deletions
diff --git a/sys/gio/cursor/gtrtrunc.x b/sys/gio/cursor/gtrtrunc.x
new file mode 100644
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--- /dev/null
+++ b/sys/gio/cursor/gtrtrunc.x
@@ -0,0 +1,39 @@
+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<gio.h>
+include	<gki.h>
+include	"gtr.h"
+
+# GTR_TRUNCATE -- Truncate the frame buffer, which has grown larger than
+# the limit set by the user (or the system default).  This is done by moving
+# the metacode data at the end of the buffer (beginning with the word pointed
+# to by gki) to the maximum upper limit of the buffer and adjusting the input
+# and output pointers accordingly.
+
+procedure gtr_truncate (tr, gki)
+
+pointer	tr			# giotr descriptor
+pointer	gki			# pointer to first word to be preserved
+pointer	top
+int	nwords
+
+begin
+	# Find the first instruction preceding the soft upper limit on the
+	# size of the buffer.
+
+	top = TR_FRAMEBUF(tr) + TR_MAXLENFRAMEBUF(tr)
+	while (Mems[top] != BOI && top > TR_FRAMEBUF(tr))
+	    top = top - 1
+
+	# Move the partial instruction likely to be at the end of the buffer
+	# to the new "top".  Note that we can only truncate (discard)
+	# instructions which have already been executed, hence the partial
+	# instruction at the end of the buffer must be preserved.
+
+	if (gki != top) {
+	    nwords = TR_OP(tr) - gki
+	    call amovs (Mems[gki], Mems[top], nwords)
+	    TR_IP(tr) = top
+	    TR_OP(tr) = top + nwords
+	}
+end