/**
* Record resignation.
* <p>
* <I>Note: this method should only be called by an AltingBarrier synchronised
* on this AltingBarrierBase.</I>
* <p>
*/
internal void resign()
{
enrolled--;
countdown--;
if (countdown == 0)
{
countdown = enrolled;
if (enrolled > 0)
{
AltingBarrierCoordinate.startEnable();
AltingBarrierCoordinate.startDisable(enrolled);
AltingBarrier fe = frontEnds;
while (fe != null)
{
fe.schedule();
fe = fe.next;
}
}
}
}
/**
* Record the offer to synchronise.
* <P>
* <I>Note: this method should only be called by an AltingBarrier synchronised
* on this AltingBarrierBase.</I>
* <p>
*
* @return true if all the offers are in.
*/
internal Boolean enable()
{
countdown--;
if (countdown == 0)
{
countdown = enrolled;
AltingBarrierCoordinate.startDisable(enrolled);
AltingBarrier fe = frontEnds;
while (fe != null)
{
fe.schedule();
fe = fe.next;
}
return(true);
}
else
{
return(false);
}
}
/**
* This removes the given <i>front-end</i> chained to this <i>alting</i> barrier.
* It also nulls its reference to this base - to prevent any attempted reuse!
* <p>
* <i>Note: this method should only be called by an AltingBarrier synchronised
* on this AltingBarrierBase.</I>
* <p>
*
* @param ab the <i>front-end</i> being discarded from this barrier.
* This array must be unaltered from one previously delivered by
* an {@link #expand expand}.
*/
internal void contract(AltingBarrier ab)
{
// assume: (ab != null)
AltingBarrier fa = null;
AltingBarrier fb = frontEnds;
while ((fb != null) && (fb != ab))
{
fa = fb;
fb = fb.next;
}
if (fb == null)
{
throw new AltingBarrierError(
"\n*** Could not find front-end in AltingBarrier contract."
);
}
// deduce: (fb == ab) && (fb != null)
// deduce: (fa == null) || (fa.next == fb)
// deduce: (fa == null) <==> (frontEnds == ab)
// deduce: (fa != null) <==> (fa.next == ab)
if (fa == null)
{
frontEnds = fb.next;
}
else
{
fa.next = fb.next;
}
ab.baseClass = null;
if (ab.enrolled)
{
enrolled--;
countdown--;
}
if (countdown == 0)
{
countdown = enrolled;
if (enrolled > 0)
{
AltingBarrierCoordinate.startEnable();
AltingBarrierCoordinate.startDisable(enrolled);
AltingBarrier fe = frontEnds;
while (fe != null)
{
fe.schedule();
fe = fe.next;
}
}
}
else if (countdown < 0)
{
throw new JCSP_InternalError(
"Please report the circumstances to [email protected] - thanks!"
);
}
}
/**
* This removes the given <i>front-ends</i> chained to this <i>alting</i> barrier.
* It also nulls all of them - to prevent any attempted reuse!
* <p>
* <i>Note: this method should only be called by an AltingBarrier synchronised
* on this AltingBarrierBase.</I>
* <p>
*
* @param ab the <i>front-ends</i> being discarded from this barrier.
* This array must be unaltered from one previously delivered by
* an {@link #expand expand}.
*/
internal void contract(AltingBarrier[] ab)
{
// assume: (ab != null) && (ab.Length > 0)
AltingBarrier first = ab[0];
// counts the number of front-ends whose (hopefully terminated) processes
// were still enrolled.
int discard = 0;
AltingBarrier fa = null;
AltingBarrier fb = frontEnds;
while ((fb != null) && (fb != first))
{
fa = fb;
fb = fb.next;
}
if (fb == null)
{
throw new AltingBarrierError(
"\n*** Could not find first front-end in AltingBarrier contract."
);
}
// Below, we will null elements of "ab" as we pass though the array.
// However, the formal "deduce" and "invariant" comments that follow
// relate to code that does not do this. This is safe since the logic
// of the code does not depend on values of "ab", subsequent to their
// anullment.
ab[0].baseClass = null;
ab[0] = null;
// deduce: (fb == ab[0]) && (fb != null)
// deduce: (fa == null) || (fa.next == fb)
// deduce: (fa == null) <==> (frontEnds == ab[0])
// deduce: (fa != null) <==> (fa.next == ab[0])
for (int i = 1; i < ab.Length; i++)
{
// invariant: (fb == ab[i-1]) && (fb != null)
if (fb.enrolled)
{
discard++;
}
fb = fb.next;
if (fb == null)
{
throw new AltingBarrierError(
"\n*** Could not find second (or later) front-end in AltingBarrier contract."
);
}
if (fb != ab[i])
{
throw new AltingBarrierError(
"\n*** Removal array in AltingBarrier contract not one delivered by expand."
);
}
// deduce: (fb == ab[i]) && (fb != null)
ab[i].baseClass = null;
ab[i] = null;
}
// deduce: (fb == ab[(ab.Length) - 1]) && (fb != null)
if (fb.enrolled)
{
discard++;
}
// deduce: (fa == null) <==> (frontEnds == ab[0]) [NO CHANGE]
// deduce: (fa != null) <==> (fa.next == ab[0]) [NO CHANGE]
if (fa == null)
{
frontEnds = fb.next;
}
else
{
fa.next = fb.next;
}
enrolled -= discard;
countdown -= discard;
if (countdown == 0)
{
countdown = enrolled;
if (enrolled > 0)
{
AltingBarrierCoordinate.startEnable();
AltingBarrierCoordinate.startDisable(enrolled);
AltingBarrier fe = frontEnds;
while (fe != null)
{
fe.schedule();
fe = fe.next;
}
}
}
else if (countdown < 0)
{
throw new JCSP_InternalError(
"Please report the circumstances to [email protected] - thanks!"
);
}
}
