CS3871/assignments/sync: Initial Commit

4 files changed, 212 insertions, 0 deletions

diff --git a/sync/assign.rst b/sync/assign.rst
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+================
+Syncronization 1
+================
+
+Write a program that uses semaphores to implement a readers/writers solution. Your program should:
+
+    - be written in C and use the standard kernel IPC mechanisms (semget,semop,shmget etc)
+    - be written as a single top level source file compiled as:  gcc –o myprog  myprog.c
+    - take two arguments on the command line:   myprog NR NW  where NR,NW are each integers specifying the number of reader/writer processes respectively
+    - use fork/exec to create the readers/writers
+
+The shared memory segment should be 16k bytes in size, with all bytes initialized to 0x30
+
+Reader:
+
+.. code ::
+
+  open a file (for append) named reader.N, where N is the reader number
+  while (1) {
+        for (i=0; i<16k; i++) {
+                  read the next byte of the shared memory segment
+                  write that byte to the file
+                  flush the file
+        }
+        sleep a random number of seconds, between 0 and N inclusive
+  }
+
+Writer:
+
+.. code ::
+
+        while (1) {
+	        for (i=0; i<16k; i++)
+	        	shared memory segment[i] = N + 0x30;
+        	sleep a random number of seconds between 0 and 2*N inclusive
+        }
+
+readers and writers should be mutually exclusive
+multiple concurrent readers are allowed
+writers have priority over readers
+writers are mutually exclusive relative to each other
diff --git a/sync/reader.c b/sync/reader.c
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+++ b/sync/reader.c
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+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+	int shmid, i, pid, id;
+	char *mem, filename[50];
+	FILE fd;
+	timeval *s;
+
+	if (argc != 1) {
+		printf("usage: reader [id]\n");
+		exit(1);
+	}
+
+	id = atoi(argv[1]);
+
+	if (argc < 2) {
+		printf("usage: sync [number readers] [number writers]\n");
+		exit(1);
+	}
+
+	if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
+		perror("shmget: shmget failed");
+		exit(1);
+	}
+
+	if ((mem = shmat(shmid, NULL, 0)) == (char *) -1) {
+		perror("shmat");
+		exit(1);
+	}
+
+	sprintf(filename, "reader.%d", id);
+	
+	fd = fopen(filename, "a");
+
+	if (!fd) {
+		perror("fopen: ");
+		exit(1);
+	}
+	srand(time(NULL));
+
+	while (1) {
+		s->tv_sec = rand() % id;
+		for (i = 0; i < 1<<14; i++) {
+			fprintf(fd, "%c", *(mem + i));
+			fflush(fd);
+		}
+
+		select(0, NULL, NULL, NULL, s);
+	}
+}
diff --git a/sync/sync.c b/sync/sync.c
new file mode 100644
index 0000000..e1fbc4c
--- /dev/null
+++ b/sync/sync.c
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+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+	int shmid, i, pid, n_read, n_write;
+	char *mem, **arg_r, **arg_w;
+
+	if (argc < 2) {
+		printf("usage: sync [number readers] [number writers]\n");
+		exit(1);
+	}
+	n_read = atoi(argv[1]);
+	n_write = atoi(argv[2]);
+
+	if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
+		perror("shmget: shmget failed");
+		exit(1);
+	}
+
+	if ((mem = shmat(shmid, NULL, 0)) == (char *) -1) {
+		perror("shmat");
+		exit(1);
+	}
+
+	for (i = 0; i < 1<<14; i++) {
+		*(mem + i) = 0x30;
+	}
+
+	arg_r = malloc(sizeof(char*) * 2);
+	arg_w = malloc(sizeof(char*) * 2);
+
+	*(arg_r + 1) = NULL;
+	*(arg_w + 1) = NULL;
+
+	for (i = 0; i < n_read; i++){
+		sprintf(*arg_r, "%d", i);
+		if (pid = fork()) {
+			printf("starting reader %d...\n", i);
+		} else {
+			execvp("./reader", arg_r);
+		}
+	}
+
+	for (i = 0; i < n_write; i++) {
+		sprintf(*arg_w, "%d", i);
+		if (pid = fork()) {
+			printf("starting writer %d...\n", i);
+		} else {
+			execvp("./writer", arg_w);
+		}
+		
+	}
+}
diff --git a/sync/writer.c b/sync/writer.c
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+++ b/sync/writer.c
@@ -0,0 +1,51 @@
+
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <types.h>
+
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+	int shmid, i, pid, id;
+	char *mem;
+	timeval *s;
+
+	if (argc != 1) {
+		printf("usage: reader [id]\n");
+		exit(1);
+	}
+
+	id = atoi(argv[1]);
+
+	if (argc < 2) {
+		printf("usage: sync [number readers] [number writers]\n");
+		exit(1);
+	}
+
+	if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
+		perror("shmget: shmget failed");
+		exit(1);
+	}
+
+	if ((mem = shmat(shmid, NULL, 0)) == (char *) -1) {
+		perror("shmat");
+		exit(1);
+	}
+	
+	srand(time(NULL));
+
+
+	while (1) {
+		s->tv_sec = rand() % (id * 2;
+		for (i = 0; i < 1<<14; i++) {
+			mem[i]= 0x30 + id;
+			select(0, NULL, NULL, NULL, s);
+		}
+	}
+}