[ANN] CoroutineReadStream

by Stephen Pair (see copyright and MIT license below)

I enable the use of a ReadStream interface in cases where enumeration protocol is available, but no read stream interface is available.  For example, I can adapt any object that supports #do: for enumeration:

CoroutineReadStream on: #(1 2 3) iterator: #do:

The implementation makes use of coroutines to avoid the need to create and schedule a separate Process.  Sending #close will abandon the coroutine and unwind all contexts in the coroutine.  The coroutine is not invoked until the first request for an object.  The iterator is finished when there is an attempt to read past the end (via #next or #peek), or when there is an #atEnd test after the last object was retrieved.

A CoroutineReadSteam is not particularly efficient due to it's use of thisContext and how stacks are optimized in most Smalltalk implementations.

Instance Variables:

nextValue <Object | noObjectMarker> Holds the next value to be answered when #next is called (needed to support #peek and #atEnd)...if it holds the noObjectMarker, it inticates that the coroutine needs to be invoked to get the next object.

suspendedContext <ContextPart> This is either the context of the iterating stack (when not actively retrieving the next object for a client) or the stack of the user of the stream (when of retrieving the next object)

homeContext <MethodContext> Holds the context of #initializeForBlock: called during instantiation and is used to ensure that exception propagation and handling works as one would expect.

Copyright (c) 2009 Stephen Pair

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