//
// Writes the specified number of data items to the
// stream blocking queue, activating the specified cancellers.
//
public int Write(T[] buffer, int offset, int count, StCancelArgs cargs)
{
//
// If this is a zero length write, return immediately.
//
if (count == 0)
{
return(0);
}
//
// Initialize the local variables.
//
int remaining = count;
WaitNodeQueue <T> wl = new WaitNodeQueue <T>();
int toCopy;
//
// Acquire the queue's lock.
//
slock.Enter();
//
// If the queue's buffer is full, check if the current
// thread must wait.
//
if (available == length)
{
goto CheckForWait;
}
//
// If there are waiting readers (i.e., the buffer is empty),
// transfer data items transferring directly to the waiting
// readers' buffers.
//
if (!waitQueue.IsEmpty)
{
do
{
WaitNode <T> rdw = waitQueue.head;
//
// Compute the number of data items to transfer to the
// waiting reader's buffer and perform the transfer.
//
if ((toCopy = rdw.remaining) > remaining)
{
toCopy = remaining;
}
Array.Copy(buffer, offset, rdw.buffer, rdw.offset, toCopy);
rdw.remaining -= toCopy;
rdw.offset += toCopy;
remaining -= toCopy;
offset += toCopy;
//
// If the waiting reader completes its read operation,
// remove its wait node from the wait list and try to
// lock the associated parker.
//
if (rdw.remaining == 0)
{
waitQueue.Dequeue();
if (rdw.TryLock() && !rdw.UnparkInProgress(StParkStatus.Success))
{
wl.Add(rdw);
}
}
else
{
//
// The data items are not enough to satisfy the waiting
// reader that is at front of wait queue, so break the loop.
//
break;
}
} while (remaining != 0 && !waitQueue.IsEmpty);
}
//
// If we have still data items to write and there is free space
// in the queue's buffer, transfer the appropriate number of data
// items the queue's buffer.
//
if (remaining != 0 && available < length)
{
//
// Compute the number of data items that can be copied
// to the queue's buffer and perform the transfer.
//
if ((toCopy = remaining) > (length - available))
{
toCopy = length - available;
}
int t = tail;
int tillEnd;
if ((tillEnd = length - t) >= toCopy)
{
Array.Copy(buffer, offset, items, t, toCopy);
if ((t += toCopy) >= length)
{
t = 0;
}
}
else
{
int fromBegin = toCopy - tillEnd;
Array.Copy(buffer, offset, items, t, tillEnd);
Array.Copy(buffer, offset + tillEnd, items, 0, fromBegin);
t = fromBegin;
}
//
// Update counters and indexes.
//
tail = t;
available += toCopy;
remaining -= toCopy;
offset += toCopy;
}
CheckForWait:
//
// If there are still data items to write, the current thread must
// wait if a null timeout wasn't specified.
//
WaitNode <T> wn = null;
bool mustWait;
if (mustWait = (remaining != 0 && cargs.Timeout != 0))
{
waitQueue.Enqueue(wn = new WaitNode <T>(buffer, offset, remaining));
}
//
// Release the queue's lock and unpark the readers threads
// release above.
//
slock.Exit();
wl.UnparkAll();
//
// If the current thread doesn't need to wait, return the
// number of written data items.
//
if (!mustWait)
{
return(count - remaining);
}
//
// Park the current thread, activating the specified cancellers.
//
int ws = wn.Park(cargs);
//
// If the write was completed, return the number of written
// data items.
//
if (ws == StParkStatus.Success)
{
return(count);
}
//
// The write was cancelled due to timeout, alert or interrupt.
// If the wait node is still inserted in the wait queue, acquire
// the queue's lock and unlink it.
//
if (wn.next != wn)
{
slock.Enter();
waitQueue.Remove(wn);
slock.Exit();
}
//
// If at least a data item was written, ignore the cancellation
// and return the number of transferred data items.
//
int c;
if ((c = count - wn.remaining) != 0)
{
StCancelArgs.PostponeCancellation(ws);
return(c);
}
//
// No data items were written; so, report the failure appropriately.
//
StCancelArgs.ThrowIfException(ws);
return(0);
}
//
// Tries to enter the write lock, activating the specified
// cancellers.
//
public bool TryEnterWrite(StCancelArgs cargs)
{
int tid = Thread.CurrentThread.ManagedThreadId;
if (!isReentrant)
{
if (tid == writer)
{
throw new StLockRecursionException("Recursive enter write not allowed");
}
if (rdCounts.Lookup(tid) != null)
{
throw new StLockRecursionException("Write after read not allowed");
}
}
else
{
//
// If this is a recursive enter, increment the recursive acquisition
// counter and return success.
//
if (tid == writer)
{
wrCount++;
return(true);
}
}
//
// Acquire the spinlock that protects the r/w lock shared state.
//
slock.Enter();
//
// If the write lock can be entered - this is, there are no lock
// readers, no lock writer or upgrader or the current thread is the
// upgrader -, enter the write lock, release the spinlock and
// return success.
//
if (readers == 0 && writer == UNOWNED && (upgrader == tid || upgrader == UNOWNED))
{
writer = tid;
slock.Exit();
wrCount = 1;
return(true);
}
//
// If the current thread isn't the current upgrader but is reader,
// release the spinlock and throw the appropriate exception.
//
if (tid != upgrader && rdCounts.Lookup(tid) != null)
{
slock.Exit();
throw new StLockRecursionException("Write after read not allowed");
}
//
// The write lock can't be entered immediately. So, if a null timeout
// was specified, release the spinlock and return failure.
//
if (cargs.Timeout == 0)
{
slock.Exit();
return(false);
}
//
// Create a wait node and insert it in the writers queue.
// If the current thread isn't the current upgrader, the wait
// node is inserted in the writer's queue; otherwise, the wait
// node becomes referenced by the *upgradeToWriteWaiter* field.
//
int sc;
WaitNode wn = new WaitNode(tid);
if (tid == upgrader)
{
upgToWrWaiter = wn;
sc = spinCount;
}
else
{
sc = wrQueue.IsEmpty ? spinCount : 0;
wrQueue.Enqueue(wn);
}
//
// Release spin the lock and park the current thread, activating
// the specified cancellers and spinning, if appropriate.
//
slock.Exit();
int ws = wn.Park(sc, cargs);
//
// If the thread entered the write lock, initialize the recursive
// acquisition counter and return success.
//
if (ws == StParkStatus.Success)
{
wrCount = 1;
return(true);
}
//
// The enter attempted was cancelled. So, if the wait node was
// already remove from the respective queue, report the failure
// appropriately. Otherwise, unlink the wait node and, if appropriate,
// taking into account the other waiters.
//
if (wn.next == wn)
{
goto ReportFailure;
}
slock.Enter();
if (wn.next != wn)
{
if (wn == upgToWrWaiter)
{
upgToWrWaiter = null;
}
else
{
wrQueue.Remove(wn);
//
// If the writers queue becomes empty, it is possible that there
// is a waiting upgrader or waiting reader threads that can now
// proceed.
//
if (writer == UNOWNED && upgrader == UNOWNED && wrQueue.IsEmpty &&
TryWakeupUpgraderAndReaders())
{
goto ReportFailure;
}
}
}
slock.Exit();
ReportFailure:
StCancelArgs.ThrowIfException(ws);
return(false);
}
//
// Tries to enter the lock in upgrade read mode, activating
// the specified cancellers.
//
public bool TryEnterUpgradeableRead(StCancelArgs cargs)
{
int tid = Thread.CurrentThread.ManagedThreadId;
ReaderCounter rc = rdCounts.Lookup(tid);
if (!isReentrant)
{
if (tid == upgrader)
{
throw new StLockRecursionException("Recursive upgrade not allowed");
}
if (tid == writer)
{
throw new StLockRecursionException("Upgrade after write not allowed");
}
if (rc != null)
{
throw new StLockRecursionException("Upgrade after read not allowed");
}
}
else
{
//
// If the current thread is the current upgrader, increment the
// recursive acquisition counter and return.
//
if (tid == upgrader)
{
upCount++;
return(true);
}
//
// If the current thread is the current writer, it can also
// becomes the upgrader. If it is also a reader, it will be
// accounted as reader on the *upgraderIsReader* flag.
//
if (tid == writer)
{
upgrader = tid;
upCount = 1;
if (rc != null)
{
upgraderIsReader = true;
}
return(true);
}
if (rc != null)
{
throw new StLockRecursionException("Upgrade after read not allowed");
}
}
//
// Acquire the spinlock that protects the r/w lock shared state.
//
slock.Enter();
//
// If the lock isn't in write or upgrade read mode, the
// current thread becomes the current upgrader. Then, release
// the spinlock and return success.
//
if (writer == UNOWNED && upgrader == UNOWNED)
{
upgrader = tid;
slock.Exit();
upgraderIsReader = false;
upCount = 1;
return(true);
}
//
// The upgrade read lock can't be acquired immediately.
// So, if a null timeout was specified, return failure.
//
if (cargs.Timeout == 0)
{
slock.Exit();
return(false);
}
//
// Create a wait node and insert it in the upgrader's queue.
//
int sc = (upQueue.IsEmpty && wrQueue.IsEmpty) ? spinCount : 0;
WaitNode wn;
upQueue.Enqueue(wn = new WaitNode(tid));
//
// Release the spinlock and park the current thread activating
// the specified cancellers and spinning, if appropriate.
//
slock.Exit();
int ws = wn.Park(sc, cargs);
//
// If we acquired the upgrade lock, initialize the recursive
// acquisition count and the *upgraderIsReader flag and return
// success.
//
if (ws == StParkStatus.Success)
{
upCount = 1;
upgraderIsReader = false;
return(true);
}
//
// The acquire attemptwas cancelled. So, ensure that the
// wait node is unlinked from the wait queue and report
// the failure appropriately.
//
if (wn.next != wn)
{
slock.Enter();
upQueue.Remove(wn);
slock.Exit();
}
StCancelArgs.ThrowIfException(ws);
return(false);
}
//
// Tries to enter the read lock, activating the
// specified cancellers.
//
public bool TryEnterRead(StCancelArgs cargs)
{
int tid = Thread.CurrentThread.ManagedThreadId;
ReaderCounter rc = rdCounts.Lookup(tid);
if (!isReentrant)
{
if (tid == writer)
{
throw new StLockRecursionException("Read after write not allowed");
}
if (rc != null)
{
throw new StLockRecursionException("Recursive read not allowed");
}
}
else
{
//
// If this is a recursive enter, increment the recursive
// acquisition counter and return.
//
if (rc != null)
{
rc.count++;
return(true);
}
}
//
// Acquire the spinlock that protected the r/u/w lock shared state.
//
slock.Enter();
//
// If the current thread is the upgrader, it can also enter
// the read lock. So, add an entry to the readers table,
// release the spinlock and return success.
//
if (tid == upgrader)
{
rdCounts.Add(tid);
slock.Exit();
upgraderIsReader = true;
return(true);
}
//
// The read lock can be entered, if the r/w lock isn't in write
// mode and no thread is waiting to enter the writer mode.
// If these conditions are met, increment the number of lock
// readers, add an entry to the readers table, release the
// spinlock and return success.
//
if (writer == UNOWNED && wrQueue.IsEmpty && upgToWrWaiter == null)
{
readers++;
rdCounts.Add(tid);
slock.Exit();
return(true);
}
//
// If the r/w lock is reentrant and the current thread is the
// current writer, it can also to become a reader. So, increment
// the number of lock readers, add an entry to the readers table,
// release the spinlock and return success.
//
if (isReentrant && tid == writer)
{
readers++;
rdCounts.Add(tid);
slock.Exit();
return(true);
}
//
// The current thread can't enter the read lock immediately.
// So, if a null timeout was specified, release the spinlock
// and return failure.
//
if (cargs.Timeout == 0)
{
slock.Exit();
return(false);
}
//
// Create a wait node and insert it in the readers queue.
// Compute also the amount of spinning.
//
int sc = rdQueue.IsEmpty ? spinCount : 0;
WaitNode wn;
rdQueue.Enqueue(wn = new WaitNode(tid));
//
// Release the spinlock and park the current thread, activating
// the specified cancellers and spinning if appropriate.
//
slock.Exit();
int ws = wn.Park(sc, cargs);
//
// If we entered the read lock, return success.
//
if (ws == StParkStatus.Success)
{
return(true);
}
//
// The enter attempt was cancelled. So, ensure that the wait node
// is unlinked from the queue and report the failure appropriately.
//
if (wn.next != wn)
{
slock.Enter();
rdQueue.Remove(wn);
slock.Exit();
}
StCancelArgs.ThrowIfException(ws);
return(false);
}
