LooksReaderImpl.mesa; written by Bill Paxton, March 1981
edited by McGregor, February 8, 1983 11:37 am
edited by Bill Paxton, July 8, 1983 2:18 pm
DIRECTORY
RunReader,
LooksReader;
LooksReaderImpl:
CEDAR MONITOR
IMPORTS RunReader, LooksReader
EXPORTS LooksReader
SHARES LooksReader =
BEGIN OPEN LooksReader;
Create:
PUBLIC
PROC []
RETURNS [new: Ref] = {
create a reader for chars and looks
new ← NEW[Body]; new^ ← [0,0,noLooks,RunReader.Create[]] };
lksrdr1, lksrdr2, lksrdr3: Ref; -- shared looks readers
GetLooksReader:
PUBLIC
ENTRY
PROC
RETURNS [reader: Ref] = {
IF lksrdr3 # NIL THEN { reader ← lksrdr3; lksrdr3 ← NIL }
ELSE IF lksrdr2 # NIL THEN { reader ← lksrdr2; lksrdr2 ← NIL }
ELSE IF lksrdr1 # NIL THEN { reader ← lksrdr1; lksrdr1 ← NIL }
ELSE reader ← Create[] };
FreeLooksReader:
PUBLIC
ENTRY
PROC [reader: Ref] = {
SetPosition[reader, NIL];
IF lksrdr3 = reader OR lksrdr2 = reader OR lksrdr1 = reader THEN ERROR;
IF lksrdr3 = NIL THEN lksrdr3 ← reader
ELSE IF lksrdr2 = NIL THEN lksrdr2 ← reader
ELSE IF lksrdr1 = NIL THEN lksrdr1 ← reader };
END.