Stream context block structure.

typedef struct DSStreamCB {
   Item creatorTask;
   uint32 creatorSignal;
   int32 creatorStatus;
   Item threadItem;
   void* threadStackBlock;
   Item acquirePort;
   long bufDataSize;
   DSDataBufPtr freeBufHead;
   unsigned long streamFlags;
   uint32 clockOffset;
   uint32 lastValidClock;
   uint32 branchDest;
   Item requestPort;
   uint32 requestPortSignal;
   Item acqReplyPort;
   uint32 acqReplyPortSignal;
   MemPoolPtr dataMsgPool;
   Item subsReplyPort;
   uint32 subsReplyPortSignal;
   MemPoolPtr subsMsgPool;
   DSDataBufPtr filledBufHead;
   DSDataBufPtr filledBufTail;
   long totalBufferCount;
   long currentFreeBufferCount;
   DSRequestMsgPtr endOfStreamMsg;
   int32 repliesPending;
   DSRequestMsgPtr requestMsgHead;
   DSRequestMsgPtr requestMsgTail;
   long numSubscribers;
   DSSubscriber subscriber[DS_MAX_SUBSCRIBERS];
} DSStreamCB,  *DSStreamCBPtr

This data structure contains all the contexts necessary to drive a stream, including a description of all subscribers and the information necessary to manage all memory buffers. One of these data structures exists for each open stream.

• creatorTask Task to signal when initialization complete.

• creatorSignal Signal to send for synchronous completion.

• creatorStatus Result code for creator.

• threadItem Thread Item for the server process.

• threadStackBlock Pointer to thread's stack memory block.

• acquirePort Acquisition module message port.

• bufDataSize Size of data buffers in BYTES.

• freeBufHead Pointer to list of free data buffers.

• streamFlags Stream state flags.

• clockOffset Offset to get relative stream clock.

• lastValidClock Set when stream stopped.

• branchDest Marker to branching to STRM_GO_INPROGRESS true.

• requestPort Work request message port.

• requestPortSignal Signal for request port.

• acqReplyPort Reply port for data acquisition communications.

• acqReplyPortSignal Signal for data acquisition reply port.

• dataMsgPool Pool of data message blocks.

• subsReplyPort Reply port for subscriber communication.

• subsReplyPortSignal Signal for subscriber reply port.

• subsMsgPool Pool of subscriber message blocks.

• filledBufHead Pointer to list of filled data buffers.

• filledBufTail Pointer to end of list of filled data buffers.

• repliesPending Number of replies needed before replying to request.

• requestMsgHead Pointer to first request message in queue.

• requestMsgTail Pointer to last request message in queue.

• numSubscribers Number of subscribers.

DataStream.h