92 lines
1.7 KiB
Modula-2
92 lines
1.7 KiB
Modula-2
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MODULE StoreFetch;
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(* From: MODULA-2, An Introduction, by Daniel Thalmann, Springer-Verlag,
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New York, 1985
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Figure 20.3
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*)
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FROM InOut IMPORT ReadString, WriteString, WriteLn;
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FROM Processes IMPORT SIGNAL, StartProcess, SEND, WAIT, Awaited, Init;
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MODULE SharedBuffer;
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IMPORT SIGNAL, SEND, WAIT, Awaited, Init;
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EXPORT Deposit, Remove;
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CONST N = 16;
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VAR n, in, out: CARDINAL;
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NonFull, NonEmpty: SIGNAL;
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Buffer: ARRAY [0..N-1] OF INTEGER;
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PROCEDURE Deposit(integer: INTEGER);
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BEGIN
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IF n=N THEN WAIT(NonFull) END;
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INC(n);
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Buffer[in] := integer;
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in := (in+1) MOD N;
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IF Awaited(NonEmpty) THEN SEND(NonEmpty) END;
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END Deposit;
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PROCEDURE Remove(VAR integer: INTEGER);
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BEGIN
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IF n=0 THEN WAIT(NonEmpty) END;
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DEC(n);
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integer := Buffer[out];
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out := (out+1) MOD N;
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IF Awaited(NonFull) THEN SEND(NonFull) END;
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END Remove;
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BEGIN
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n := 0;
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in := 0;
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out := 0;
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Init(NonFull);
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Init(NonEmpty);
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END SharedBuffer;
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CONST Max = 80;
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eos = 0C;
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TYPE StringType = ARRAY[0..Max-1] OF CHAR;
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VAR EndOfTransfer: SIGNAL;
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PROCEDURE Store;
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VAR i: INTEGER;
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String: StringType;
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BEGIN
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WriteString("Enter a string: ");
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i := -1;
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ReadString(String);
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REPEAT
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INC(i);
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Deposit(ORD(String[i]));
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UNTIL String[i] = eos;
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WAIT(EndOfTransfer);
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END Store;
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PROCEDURE Fetch;
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VAR i, OrdOfChar: INTEGER;
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String: StringType;
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BEGIN
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i := -1;
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REPEAT
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INC(i);
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Remove(OrdOfChar);
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String[i] := CHR(OrdOfChar);
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UNTIL String[i] = eos;
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WriteLn;
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WriteString("After transfer: ");
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WriteString(String);
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WriteLn;
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END Fetch;
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BEGIN
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Init(EndOfTransfer);
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StartProcess(Store, 500);
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StartProcess(Fetch, 500);
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WAIT(EndOfTransfer);
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END StoreFetch.
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