Inter-thread data transfer

Data can be passed between threads. The threads can be in the same process or in different processes.

The mechanism for copying data between threads is called inter-thread data transfer and is handled by the four functions provided by the RThread handle:

• ReadL()

• WriteL()

• GetDesLength()

• GetDesMaxLength()

The functions are used in the implementation of the RMessage class which, in turn, is used for passing information between clients and servers.

The ReadL() and WriteL() functions, which transfer data, assume that both source and target data are descriptors.

Typically, code executing in the current thread will have a handle to another thread. The code in the current thread copies data from the other thread, represented by an RThread handle, by calling its ReadL() function. Copying data to the other thread is similar, but is done using the WriteL() function. The following diagram illustrates this:

The source or target location in the other thread is identified by pointer. The pointer only has meaning within the context of that thread; attempting to reference the pointer directly from within the current thread is meaningless and may cause an exception.