120 lines
3.4 KiB
C
120 lines
3.4 KiB
C
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/*
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File: reqchannel.H
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Author: R. Bettati
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Department of Computer Science
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Texas A&M University
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Date : 2012/07/11
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*/
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#ifndef _reqchannel_H_ // include file only once
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#define _reqchannel_H_
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/*--------------------------------------------------------------------------*/
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/* DEFINES */
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/*--------------------------------------------------------------------------*/
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/* -- (none) -- */
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/*--------------------------------------------------------------------------*/
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/* INCLUDES */
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/*--------------------------------------------------------------------------*/
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#include <iostream>
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#include <fstream>
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#include <string>
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using namespace std;
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/*--------------------------------------------------------------------------*/
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/* DATA STRUCTURES */
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/*--------------------------------------------------------------------------*/
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/* -- (none) -- */
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/*--------------------------------------------------------------------------*/
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/* FORWARDS */
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/*--------------------------------------------------------------------------*/
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/* -- (none) -- */
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/*--------------------------------------------------------------------------*/
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/* CLASS R e q u e s t C h a n n e l */
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/*--------------------------------------------------------------------------*/
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class RequestChannel {
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public:
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typedef enum {SERVER_SIDE, CLIENT_SIDE} Side;
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typedef enum {READ_MODE, WRITE_MODE} Mode;
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private:
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string my_name;
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Side my_side;
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/* The current implementation uses named pipes. */
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int wfd;
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int rfd;
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char * pipe_name(Mode _mode);
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void open_read_pipe(char * _pipe_name);
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void open_write_pipe(char * _pipe_name);
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public:
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/* -- CONSTRUCTOR/DESTRUCTOR */
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RequestChannel(const string _name, const Side _side);
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/* Creates a "local copy" of the channel specified by the given name.
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If the channel does not exist, the associated IPC mechanisms are
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created. If the channel exists already, this object is associated with the channel.
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The channel has two ends, which are conveniently called "SERVER_SIDE" and "CLIENT_SIDE".
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If two processes connect through a channel, one has to connect on the server side
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and the other on the client side. Otherwise the results are unpredictable.
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NOTE: If the creation of the request channel fails (typically happens when too many
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request channels are being created) and error message is displayed, and the program
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unceremoniously exits.
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NOTE: It is easy to open too many request channels in parallel. In most systems,
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limits on the number of open files per process limit the number of established
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request channels to 125.
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*/
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~RequestChannel();
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/* Destructor of the local copy of the bus. By default, the Server Side deletes any IPC
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mechanisms associated with the channel. */
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string send_request(string _request);
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/* Send a string over the channel and wait for a reply. */
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string cread();
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/* Blocking read of data from the channel. Returns a string of characters
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read from the channel. Returns NULL if read failed. */
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int cwrite(string _msg);
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/* Write the data to the channel. The function returns the number of characters written
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to the channel. */
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string name();
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/* Returns the name of the request channel. */
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int read_fd();
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/* Returns the file descriptor used to read from the channel. */
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int write_fd();
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/* Returns the file descriptor used to write to the channel. */
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};
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#endif
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