From d13d8a046838ce3d0e2643bb5b49f2ff77d679ca Mon Sep 17 00:00:00 2001
From: Marc Horowitz <marc@mit.edu>
Date: Wed, 1 Nov 1989 20:02:01 +0000
Subject: Initial revision

---
 zwgc/mux.c | 138 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 zwgc/mux.c

(limited to 'zwgc/mux.c')

diff --git a/zwgc/mux.c b/zwgc/mux.c
new file mode 100644
index 0000000..e19067c
--- /dev/null
+++ b/zwgc/mux.c
@@ -0,0 +1,138 @@
+/****************************************************************************/
+/*                                                                          */
+/*        Module containing code to wait on multiple file descriptors:      */
+/*                                                                          */
+/****************************************************************************/
+
+#include <sys/types.h>
+#include <sys/time.h>
+#include <errno.h>
+#include <stdio.h>
+#include "mux.h"
+#include "error.h"
+#include "zwgc.h"
+
+/*
+ * mux_end_loop_p - Setting this to true during a mux_loop causes the mux_loop
+ *                  to be exited.
+ */
+
+int mux_end_loop_p;
+
+/*
+ * max_source - the maximum file descriptor that a handler was ever
+ *              registered for:
+ */
+
+static int max_source = -1;
+
+/*
+ * Which file descriptors we're waiting on for input & the accompanying
+ * input handlers & their arguments:
+ */
+
+static fd_set input_sources;
+static void (*input_handler[MAX_SOURCES])();
+static void *input_handler_arg[MAX_SOURCES];
+
+/*
+ *    void mux_init()
+ *        Requires: mux_init has never been called before
+ *        Effects: Initializes the mux module.  Must be called before
+ *                 any other mux call.
+ */
+
+void mux_init()
+{
+    int i;
+
+    FD_ZERO(&input_sources);
+    
+    for (i=0; i<MAX_SOURCES; i++)
+      input_handler[i] = NULL;
+}
+
+/*
+ *    void mux_add_input_source(int descriptior; void (*handler)(); void *arg)
+ *        Requires: 0<=descriptor<MAX_SOURCES, mux_init has been called
+ *        Modifies: Removes the previous input handler if any for descriptor
+ *        Effects: Registers handler as the input handler for file descriptor
+ *                 descriptor.  When mux_loop() is running and input is
+ *                 available on descriptor, handler will be called with
+ *                 argument arg.
+ */
+
+void mux_add_input_source(descriptor, handler, arg)
+     int descriptor;
+     void (*handler)();
+     void *arg;
+{
+#ifdef DEBUG
+    if(descriptor < 0 || descriptor >= MAX_SOURCES)
+      abort(); /* <<<>>> */
+#endif
+    
+    input_handler[descriptor] = handler;
+    input_handler_arg[descriptor] = arg;
+    FD_SET(descriptor, &input_sources);
+    if(descriptor > max_source)
+      max_source = descriptor;
+}
+
+/*
+ *    void mux_loop()
+ *        Requires: mux_init has been called.
+ *        Effects: Loops until mux_end_loop_p becomes true.  (Sets
+ *                 mux_end_loop_p false to start).  Whenever input is
+ *                 available on an input source which has a registered
+ *                 handler (see mux_add_input_source), that handler is
+ *                 called with its argument.  It is guarenteed that if
+ *                 input is available on a source, its respective input
+ *                 handler, if any, will eventually be called.  No other
+ *                 ordering guarentees are made.  When some signal handler
+ *                 or input handler eventually sets mux_end_loop_p to
+ *                 true, we return.
+ */
+
+void mux_loop()
+{
+    int i;
+    fd_set input_sources_copy;
+
+    mux_end_loop_p = 0;
+
+    for (;;) {
+	/*
+	 * Exit if mux_end_loop_p has been set to true by a handler:
+	 */
+	if (mux_end_loop_p)
+	  break;
+
+	/*
+	 * Do a select on all the file descriptors we care about to
+	 * wait until at least one of them has input available:
+	 */
+	input_sources_copy = input_sources;
+	if ( select(max_source+1, &input_sources_copy, (fd_set *)NULL,
+		   (fd_set *)NULL, (struct timeval *)NULL) == -1 )
+	  if (errno == EINTR)
+	    continue;    /* on a signal restart checking mux_loop_end_p */
+	  else
+	    FATAL_TRAP( errno, "while selecting" );
+
+	/*
+	 * Call all input handlers whose corresponding file descriptors have
+	 * input:
+	 */
+	for(i=0; i<=max_source; i++)
+	  if (FD_ISSET(i, &input_sources_copy) && input_handler[i]) {
+#ifdef DEBUG
+	      if (zwgc_debug)
+		fprintf(stderr,
+			"mux_loop...activity on fd %d, calling %x(%x)\n",
+			i,input_handler[i],input_handler_arg[i]);
+#endif
+	      input_handler[i](input_handler_arg[i]);
+	  }
+    }
+}
-- 
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