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(* M2StackAddress.mod provides a generic stack for ADDRESS sized objects.
Copyright (C) 2001-2024 Free Software Foundation, Inc.
Contributed by Gaius Mulley <gaius.mulley@southwales.ac.uk>.
This file is part of GNU Modula-2.
GNU Modula-2 is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GNU Modula-2 is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Modula-2; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. *)
IMPLEMENTATION MODULE M2StackAddress ;
FROM Storage IMPORT ALLOCATE, DEALLOCATE ;
FROM M2Error IMPORT InternalError ;
FROM M2Debug IMPORT Assert ;
CONST
MaxBucket = 10 ;
TYPE
StackBucket = POINTER TO RECORD
bucket: ARRAY [0..MaxBucket-1] OF ADDRESS ;
items : CARDINAL ;
prev : StackBucket ;
END ;
StackOfAddress = POINTER TO RECORD
tail: StackBucket ;
END ;
(*
InitStackAddress - creates and returns a new stack.
*)
PROCEDURE InitStackAddress () : StackOfAddress ;
VAR
s: StackOfAddress ;
BEGIN
NEW (s) ;
WITH s^ DO
tail := NIL
END ;
RETURN s
END InitStackAddress ;
(*
KillBucket - destroys a StackBucket and returns, NIL.
*)
PROCEDURE KillBucket (b: StackBucket) : StackBucket ;
BEGIN
IF b # NIL
THEN
b := KillBucket (b^.prev) ;
DISPOSE (b)
END ;
RETURN NIL
END KillBucket ;
(*
KillStackAddress - destroys a stack, returning NIL.
*)
PROCEDURE KillStackAddress (s: StackOfAddress) : StackOfAddress ;
BEGIN
IF s#NIL
THEN
s^.tail := KillBucket (s^.tail) ;
DISPOSE (s)
END ;
RETURN NIL
END KillStackAddress ;
(*
InitBucket - returns an empty StackBucket.
*)
PROCEDURE InitBucket (l: StackBucket) : StackBucket ;
VAR
b: StackBucket ;
BEGIN
NEW(b) ;
WITH b^ DO
items := 0 ;
prev := l
END ;
RETURN( b )
END InitBucket ;
(*
PushAddress - pushes a word, w, onto, s.
*)
PROCEDURE PushAddress (s: StackOfAddress; w: ADDRESS) ;
BEGIN
IF s=NIL
THEN
InternalError ('stack has not been initialized')
ELSE
WITH s^ DO
IF (tail=NIL) OR (tail^.items=MaxBucket)
THEN
tail := InitBucket(tail)
END ;
WITH tail^ DO
IF items<MaxBucket
THEN
bucket[items] := w ;
INC(items)
END
END
END
END
END PushAddress ;
(*
PopAddress - pops an element from stack, s.
*)
PROCEDURE PopAddress (s: StackOfAddress) : ADDRESS ;
VAR
b: StackBucket ;
BEGIN
IF s=NIL
THEN
InternalError ('stack has not been initialized')
ELSE
IF s^.tail=NIL
THEN
InternalError ('stack underflow')
ELSE
IF s^.tail^.items=0
THEN
b := s^.tail ;
IF b=NIL
THEN
InternalError ('stack underflow')
ELSE
s^.tail := b^.prev
END ;
DISPOSE(b)
END ;
IF s^.tail = NIL
THEN
InternalError ('stack underflow')
ELSE
WITH s^.tail^ DO
DEC(items) ;
RETURN( bucket[items] )
END
END
END
END
END PopAddress ;
(*
IsEmptyAddress - returns TRUE if stack, s, is empty.
*)
PROCEDURE IsEmptyAddress (s: StackOfAddress) : BOOLEAN ;
BEGIN
RETURN( (s=NIL) OR (s^.tail=NIL) )
END IsEmptyAddress ;
(*
PeepAddress - returns the element at, n, items below in the stack.
Top of stack can be seen via Peep(s, 1)
*)
PROCEDURE PeepAddress (s: StackOfAddress; n: CARDINAL) : ADDRESS ;
VAR
b: StackBucket ;
BEGIN
IF s^.tail=NIL
THEN
InternalError ('stack underflow')
ELSE
IF s^.tail^.items=0
THEN
b := s^.tail ;
IF b=NIL
THEN
InternalError ('stack underflow')
ELSE
s^.tail := b^.prev
END ;
DISPOSE(b)
END ;
b := s^.tail ;
WHILE n>=1 DO
IF b=NIL
THEN
InternalError ('stack underflow')
ELSIF b^.items>=n
THEN
RETURN( b^.bucket[b^.items-n] )
ELSE
Assert(b^.items<n) ;
DEC(n, b^.items) ;
b := b^.prev
END
END ;
InternalError ('stack underflow')
END
END PeepAddress ;
(*
ReduceAddress - reduce the stack by n elements.
*)
PROCEDURE ReduceAddress (s: StackOfAddress; n: CARDINAL) ;
VAR
b: StackBucket ;
BEGIN
IF s^.tail=NIL
THEN
InternalError ('stack underflow')
ELSE
IF s^.tail^.items=0
THEN
b := s^.tail ;
IF b=NIL
THEN
InternalError ('stack underflow')
ELSE
s^.tail := b^.prev
END ;
DISPOSE(b)
END ;
LOOP
IF s^.tail=NIL
THEN
InternalError ('stack underflow')
ELSIF s^.tail^.items>=n
THEN
DEC( s^.tail^.items, n) ;
RETURN (* all done exit *)
ELSE
b := s^.tail ;
DEC(n, b^.items) ;
s^.tail := s^.tail^.prev ;
DISPOSE(b)
END
END
END
END ReduceAddress ;
(*
NoOfItemsInStackAddress - returns the number of items held in the stack, s.
*)
PROCEDURE NoOfItemsInStackAddress (s: StackOfAddress) : CARDINAL ;
VAR
b: StackBucket ;
n: CARDINAL ;
BEGIN
IF IsEmptyAddress(s)
THEN
RETURN( 0 )
ELSE
n := 0 ;
b := s^.tail ;
WHILE b#NIL DO
INC (n, b^.items) ;
b := b^.prev
END ;
RETURN( n )
END
END NoOfItemsInStackAddress ;
END M2StackAddress.
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