private async Task <node> getNodeAt(
long index, IAccessContext <CSScope> context)
{
return(await context.InChild(
new CSScope(valueScope : InfiniteIntervalScope.Create(
RWScope.Read, 0, index + 1),
name : $"scope for getNodeAt {index}"),
async subContext =>
{
await subContext.UntilAvailable(new CSScope(valueScope :
InfiniteIntervalScope.Create(RWScope.Read, 0, 1),
name : $"UntilAvailable scope in getNodeAt {index}"));
node currentNode = state.FirstNode;
for (long i = 1; i <= index; i++)
{
await subContext.UntilAvailable(new CSScope(
valueScope: InfiniteIntervalScope.Create(
RWScope.Read, i, i + 1),
name: "UntilAvailable scope in " +
$"getNodeAt {index}"));
currentNode = currentNode.Successor;
}
return currentNode;
}));
}
private async Task add(T value, IAccessContext <CSScope> context)
{
await TaskCollector.With(async tc =>
{
CSScope pessimisticScope =
new CSScope(RWScope.ReadWrite,
InfiniteIntervalScope.Create(
RWScope.ReadWrite, 0, null),
$"pessimistic scope for add-{value}");
await context.InChildWithin(pessimisticScope,
async childContext =>
{
Tuple <node, int> lastNodeInfo =
await getLastNode(childContext);
/* At this point, we don’t require write access
* to the nodes from 0 to count - 1 anymore,
* but IInfiniteIntervalScope is not granular enough
* to represent that.
* Read tasks for lower indexes could proceed. */
node newNode = new node
{
Successor = null,
Value = value
};
tc.Add(appendToLastNode(
newNode, lastNodeInfo, childContext));
});
});
}
private async Task <Tuple <node, int> > getLastNode(
node startNode, int startIndex, IAccessContext <CSScope> context)
{
return(await context.InChild(
new CSScope(valueScope : InfiniteIntervalScope.Create(
RWScope.Read, startIndex + 1, null)),
async subContext =>
{
node currentNode = startNode;
for (int index = startIndex + 1; ; index++)
{
/* read the node at position index */
await subContext.UntilAvailable(new CSScope(valueScope:
InfiniteIntervalScope.Create(
RWScope.Read, index, index + 1)));
if (currentNode.Successor == null)
{
return Tuple.Create(currentNode, index - 1);
}
currentNode = currentNode.Successor;
subContext.RequiredScope = new CSScope(valueScope:
InfiniteIntervalScope.Create(
RWScope.Read, index + 1, null));
}
}));
}
private async Task <Tuple <node, int> > getLastNode(
IAccessContext <CSScope> context,
node startNode = null, int startIndex = -1)
{
if (startNode == null)
{
startIndex = -1;
}
return(await context.InChild(new CSScope(
valueScope : InfiniteIntervalScope.Create(
RWScope.Read, startIndex + 1, null),
name : "scope for getLastNode"),
async subContext =>
{
if (startNode == null)
{
node firstNode = await getFirstNode(subContext);
if (firstNode == null)
{
return null;
}
startNode = firstNode;
startIndex = 0;
}
var t = getLastNode(startNode, startIndex, subContext);
subContext.Dispose();
return await t;
}));
}
/// <remarks>
/// No child context of <paramref name="context"/>
/// may be created und employed before
/// the invocation of this method because
/// this method itself does not create an own child context.
/// </remarks>
private async Task <node> getFirstNode(IAccessContext <CSScope> context)
{
await context.UntilAvailable(new CSScope(
valueScope : InfiniteIntervalScope.Create(
RWScope.Read, 0, 1)));
return(state.FirstNode);
}
public IReactive <bool> MoveNextAsync()
{
return(Reactive.From <bool>(async resultResolver =>
{
await TaskCollector.With(async tc =>
{
using (ContextualStream <T> childStream =
stream.CreateChildWithin(new CSScope(valueScope:
InfiniteIntervalScope.Create(
RWScope.Read, 0, null))))
using (IAccessContext <enumeratorScope> childEnumContext
= context.CreateChild(new enumeratorScope(
RWScope.ReadWrite, RWScope.ReadWrite)))
{
long curNextIndex =
await readNextIndex(childEnumContext);
CSScope readNextNodeScope = new CSScope(valueScope:
InfiniteIntervalScope.Create(RWScope.Read,
curNextIndex, curNextIndex + 1));
childStream.Context.RequiredScope =
readNextNodeScope;
node nextNode;
if (curNextIndex == 0)
{
/* Erste Iteration. */
tc.Add(incrementNextIndex(childEnumContext));
nextNode = await childStream.getFirstNode(
childStream.Context);
}
else
{
node curCurrentNode =
await readCurrentNode(childEnumContext);
if (curCurrentNode == null)
{
throw new InvalidOperationException(
"The stream has already " +
"been iterated through.");
}
tc.Add(incrementNextIndex(childEnumContext));
await childStream.Context.UntilAvailable();
nextNode = curCurrentNode.Successor;
}
resultResolver.Resolve(nextNode != null);
childStream.Dispose();
tc.Add(setCurrentNode(nextNode, childEnumContext));
}
});
}));
}
public CSScope(
RWScope countScope = RWScope.None,
IInfiniteIntervalScope <RWScope> valueScope = null,
string name = null)
{
if (valueScope == null)
{
valueScope = InfiniteIntervalScope.Create(RWScope.None);
}
CountScope = countScope;
ValueScope = valueScope;
Name = name;
}
private static async Task addFibonacciNumbers(
ContextualStream <BigInteger> stream, int count = 30)
{
await TaskCollector.With(async tc =>
{
await stream.InChild(new CSScope(
RWScope.ReadWrite,
InfiniteIntervalScope.Create(
RWScope.ReadWrite, 0, null)),
async childStream =>
{
await Task.Yield();
IAppender <BigInteger> appender =
childStream.GetAppender();
BigInteger a = 1, b = 1;
tc.Add(appender.Append(a));
/* FIXME: Users of appender generally don’t know
* the internals of ContextualStream.
* Poss. solution: IAppender.MaxRequiredScope.
* Then it would also be useful, if (the) access scopes
* could be merged. */
childStream.Context.RequiredScope = new CSScope(
RWScope.ReadWrite,
InfiniteIntervalScope.Create(
RWScope.ReadWrite, 1, null));
tc.Add(appender.Append(b));
childStream.Context.RequiredScope = new CSScope(
RWScope.ReadWrite,
InfiniteIntervalScope.Create(
RWScope.ReadWrite, 2, null));
for (int i = 2; i < count; i++)
{
BigInteger c = a + b;
await Task.Delay(250);
a = b;
b = c;
tc.Add(appender.Append(c));
childStream.Context.RequiredScope = new CSScope(
RWScope.ReadWrite,
InfiniteIntervalScope.Create(
RWScope.ReadWrite, i + 1, null));
}
});
});
}
private async Task appendToLastNode(
node newNode, Tuple <node, int> lastNodeInfo,
IAccessContext <CSScope> context)
{
await context.InChildWithin(async childContext =>
{
if (lastNodeInfo == null)
{
/* Setting first node */
/* Requires an IInfiniteIntervalScope from 0 to infinity,
* because setting the first node determines
* could also change all other nodes. */
var scope = new CSScope(
RWScope.ReadWrite,
InfiniteIntervalScope.Create(
RWScope.ReadWrite, 0, 1),
$"scope for appendToLastNode {newNode.Value}");
/* TRAP: Using context instead of childContext here
* may easily lead to a deadlock. */
childContext.RequiredScope = scope;
/* Wait for all required scope before writing. */
await childContext.UntilAvailable();
state.FirstNode = newNode;
}
else
{
/* Set the new node */
int newIndex = lastNodeInfo.Item2 + 1;
var scope = new CSScope(
RWScope.ReadWrite,
InfiniteIntervalScope.Create(
RWScope.ReadWrite, newIndex, newIndex + 1));
childContext.RequiredScope = scope;
await childContext.UntilAvailable();
lastNodeInfo.Item1.Successor = newNode;
}
state.Count++;
});
}
public async Task Append(T value)
{
await TaskCollector.With(async tc =>
{
using (var lknChild =
lastKnownNode.CreateChild(RWScope.ReadWrite))
using (var lknIndexChild =
lastKnownNodeIndex.CreateChild(RWScope.ReadWrite))
using (var streamChildContext =
stream.Context.CreateChildWithin(
new CSScope(
RWScope.ReadWrite,
InfiniteIntervalScope.Create(
RWScope.ReadWrite, 0, null))))
{
node lkn = await tc.Adding(lknChild.Get());
int lknIndex;
if (lkn == null)
{
lknIndex = -1;
}
else
{
lknIndex = await tc.Adding(lknIndexChild.Get());
}
Tuple <node, int> lastNodeInfo =
await stream.getLastNode(
streamChildContext, lkn, lknIndex);
node newNode = new node
{
Value = value,
Successor = null,
};
tc.Add(stream.appendToLastNode(
newNode, lastNodeInfo, streamChildContext));
streamChildContext.Dispose();
tc.Add(lknChild.Set(newNode.ToFuture()));
tc.Add(lknIndexChild.Set(
((lastNodeInfo?.Item2 ?? -1) + 1).ToFuture()));
}
});
}
public static async Task PrintValues <T>(IChildContextualCreator <
CSScope, ContextualStream <T> > subContextFactory)
{
await subContextFactory.InChild(new CSScope(valueScope:
InfiniteIntervalScope.Create(RWScope.Read, 0, null)),
async ints =>
{
await TaskCollector.With(async tc =>
{
IAsyncEnumerator <T> enumerator =
ints.GetAsyncEnumerator();
while (await tc.Adding(enumerator.MoveNextAsync()))
{
T value =
await tc.Adding(enumerator.GetCurrentAsync());
Console.WriteLine(value);
}
});
});
}
public IReactive <T> GetCurrentAsync()
{
return(Reactive.From <T>(async resultResolver =>
{
using (ContextualStream <T> childStream =
stream.CreateChildWithin(new CSScope(valueScope:
InfiniteIntervalScope.Create(
RWScope.Read, 0, null))))
using (IAccessContext <enumeratorScope> childEnumContext =
context.CreateChildWithin(new enumeratorScope(
RWScope.Read,
RWScope.Read)))
{
long curNextIndex =
await readNextIndex(childEnumContext);
childEnumContext.RequiredScope =
new enumeratorScope(RWScope.Read);
CSScope readValueScope = new CSScope(valueScope:
InfiniteIntervalScope.Create(
RWScope.Read, curNextIndex - 1, curNextIndex));
childStream.Context.RequiredScope = readValueScope;
node curNode =
await readCurrentNode(childEnumContext);
childEnumContext.Dispose();
if (curNode == null)
{
throw new InvalidOperationException(
"The enumerator is already disposed.");
}
await childStream.Context.UntilAvailable(
readValueScope);
resultResolver.Resolve(curNode.Value);
}
}));
}