lib/sema.txt
author Mario de Sousa <msousa@fe.up.pt>
Wed, 25 Apr 2012 15:56:45 +0100
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Remove access to NULL pointer.
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(*
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 * (c) 2011 Edouard Tisserant
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 *
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 * Fake semaphore support, for non preemptive implementation.
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 *
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 *)
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FUNCTION_BLOCK SEMA
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  VAR_INPUT
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    CLAIM : BOOL;
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    RELEASE : BOOL;
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  END_VAR
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  VAR_OUTPUT
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    BUSY : BOOL;
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  END_VAR
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  VAR
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    Q_INTERNAL : BOOL;
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  END_VAR
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  Q_INTERNAL := CLAIM OR ( Q_INTERNAL AND (NOT RELEASE));
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  BUSY := Q_INTERNAL;
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END_FUNCTION_BLOCK
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