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Distributed operating systemsThe stub unpacks the result and returns to the client. The net effect of all these steps is to convert the local call by the client procedure to the client stub to a local call to the server procedure without either client or server being aware of the intermediate steps. 2.4.2. Parameter Passing The function of the client stub is to take its parameters, pack them into a message, and send it to the server stub. While this sounds straightforward, it is not quite as simple as it at first appears. In this section we will look at some of the issues concerned with parameter passing in RPC systems. Packing parameters into a message is called parameter marshaling. As the simplest possible example, consider a remote procedure, sum(i, j), that takes two integer parameters and returns their arithmetic sum. (As a practical matter, one would not normally make such a simple procedure remote due to the overhead, but as an example it will do.) The call to sum, with parameters 4 and 7, is shown in the left-hand portion of the client process in Fig. 2-19 ...» |
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