101 lines
3 KiB
C++
101 lines
3 KiB
C++
// synchlist.cc
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// Routines for synchronized access to a list.
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//
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// Implemented by surrounding the List abstraction
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// with synchronization routines.
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//
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// Implemented in "monitor"-style -- surround each procedure with a
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// lock acquire and release pair, using condition signal and wait for
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// synchronization.
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//
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// Copyright (c) 1992-1993 The Regents of the University of California.
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// All rights reserved. See copyright.h for copyright notice and limitation
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// of liability and disclaimer of warranty provisions.
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#include "copyright.h"
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#include "synchlist.h"
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//----------------------------------------------------------------------
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// SynchList::SynchList
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// Allocate and initialize the data structures needed for a
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// synchronized list, empty to start with.
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// Elements can now be added to the list.
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//----------------------------------------------------------------------
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SynchList::SynchList ()
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{
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list = new List ();
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lock = new Lock ("list lock");
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listEmpty = new Condition ("list empty cond");
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}
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//----------------------------------------------------------------------
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// SynchList::~SynchList
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// De-allocate the data structures created for synchronizing a list.
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//----------------------------------------------------------------------
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SynchList::~SynchList ()
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{
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delete list;
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list = NULL;
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delete lock;
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lock = NULL;
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delete listEmpty;
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listEmpty = NULL;
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}
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//----------------------------------------------------------------------
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// SynchList::Append
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// Append an "item" to the end of the list. Wake up anyone
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// waiting for an element to be appended.
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//
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// "item" is the thing to put on the list, it can be a pointer to
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// anything.
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//----------------------------------------------------------------------
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void
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SynchList::Append (void *item)
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{
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lock->Acquire (); // enforce mutual exclusive access to the list
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list->Append (item);
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listEmpty->Signal (lock); // wake up a waiter, if any
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lock->Release ();
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}
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//----------------------------------------------------------------------
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// SynchList::Remove
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// Remove an "item" from the beginning of the list. Wait if
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// the list is empty.
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// Returns:
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// The removed item.
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//----------------------------------------------------------------------
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void *
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SynchList::Remove ()
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{
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void *item;
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lock->Acquire (); // enforce mutual exclusion
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while (list->IsEmpty ())
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listEmpty->Wait (lock); // wait until list isn't empty
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item = list->Remove ();
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ASSERT (item != NULL);
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lock->Release ();
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return item;
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}
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//----------------------------------------------------------------------
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// SynchList::Mapcar
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// Apply function to every item on the list. Obey mutual exclusion
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// constraints.
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//
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// "func" is the procedure to be applied.
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//----------------------------------------------------------------------
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void
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SynchList::Mapcar (VoidFunctionPtr func)
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{
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lock->Acquire ();
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list->Mapcar (func);
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lock->Release ();
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}
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