Moves assignments to given course folder.

5 files changed, 326 insertions, 0 deletions

diff --git a/CS3871/sync/assign.rst b/CS3871/sync/assign.rst
new file mode 100644
index 0000000..ea4a566
--- /dev/null
+++ b/CS3871/sync/assign.rst
@@ -0,0 +1,41 @@
+================
+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/CS3871/sync/makefile b/CS3871/sync/makefile
new file mode 100644
index 0000000..dd9c463
--- /dev/null
+++ b/CS3871/sync/makefile
@@ -0,0 +1,5 @@
+sync: sync.c reader.c writer.c
+	cc -o sync sync.c
+	cc -o reader reader.c
+	cc -o writer writer.c
+
diff --git a/CS3871/sync/reader.c b/CS3871/sync/reader.c
new file mode 100644
index 0000000..929eba1
--- /dev/null
+++ b/CS3871/sync/reader.c
@@ -0,0 +1,86 @@
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ipc.h>
+#include <sys/select.h>
+#include <sys/sem.h>
+#include <sys/shm.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+
+#define NSEM 3
+#define KEY 52
+
+char *mem;
+
+void quit(signum)
+int signum;
+{
+	shmdt(mem);
+	exit(1);
+}
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+	int shmid, semid, i, pid, id;
+	char filename[50];
+	FILE *fd;
+	struct sembuf sb;
+
+	if (argc < 2) {
+		printf("usage: reader [id]\n");
+		exit(1);
+	}
+
+	id = atoi(argv[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);
+	}
+
+	if ((semid = semget(shmid, NSEM, 0)) == -1) {
+		perror("Rsemget: ");
+		exit(1);
+	}
+
+	signal(SIGQUIT, quit);
+
+	sprintf(filename, "reader.%d", id);
+	
+	fd = fopen(filename, "a");
+
+	if (!fd) {
+		perror("fopen: ");
+		exit(1);
+	}
+	srand(time(NULL));
+
+	while (1) {
+		sb.sem_num = 0; sb.sem_op = -1; sb.sem_flg = 0;
+		semop(semid, &sb, 1);
+
+		for (i = 0; i < 1<<14; i++) {
+			fprintf(fd, "%c", *(mem + i));
+			fflush(fd);
+		}
+		fprintf(fd, "\n");
+		fflush(fd);
+
+		sb.sem_op = 1;
+		semop(semid, &sb, 1);
+
+
+		sleep(rand() % (id + 1));
+	}
+}
diff --git a/CS3871/sync/sync.c b/CS3871/sync/sync.c
new file mode 100644
index 0000000..23d6ba1
--- /dev/null
+++ b/CS3871/sync/sync.c
@@ -0,0 +1,118 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <sys/shm.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define NSEM 3
+
+union semun {
+	int val;
+	struct semid_ds *buf;
+	ushort *array;
+};
+
+
+int shmid, semid;
+
+void quit(signum)
+int signum;
+{
+	shmctl(shmid, IPC_RMID, NULL);
+	semctl(semid, IPC_RMID, 0);
+}
+
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+	int i, pid, n_read, n_write, w;
+	char *mem, **arg_r, **arg_w;
+	union semun semarg;
+
+	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);
+	}
+printf("Sshmid: %x\n", shmid);
+	signal(SIGQUIT, quit);
+
+	for (i = 0; i < 1<<14; i++) {
+		*(mem + i) = 0x30;
+	}
+
+	if ((semid = semget(shmid, NSEM, 0666 | IPC_CREAT)) == -1) {
+		perror("Ssemget: ");
+		exit(1);
+	}
+
+	semarg.val = 1;
+	for (i = 0; i < NSEM; i++) {
+		if ((semctl(semid, i, SETVAL, semarg)) == -1) {
+			perror("semctl: ");
+			exit(1);
+		}
+	}
+
+
+	arg_r = malloc(sizeof(char*) * 3);
+	arg_w = malloc(sizeof(char*) * 3);
+	*arg_r = malloc(sizeof(char) * 10);
+	*arg_w = malloc(sizeof(char) * 10);
+
+	*(arg_r + 1) = malloc(sizeof(char) * 50);
+	*(arg_w + 1) = malloc(sizeof(char) * 50);
+
+	*arg_r = "reader";
+	*arg_w = "writer";
+
+	*(arg_r + 2) = NULL;
+	*(arg_w + 2) = NULL;
+
+	for (i = 0; i < n_read; i++){
+		sprintf(*(arg_r + 1), "%d", i);
+		if (pid = fork()) {
+			/* printf("starting reader %d...\n", i); */
+		} else {
+			int ret = execv("./reader", arg_r);
+			printf("exec retern %d", ret);
+		}
+	}
+
+	for (i = 0; i < n_write; i++) {
+		sprintf(*(arg_w + 1), "%d", i);
+		if (pid = fork()) {
+			/* printf("starting writer %d...\n", i); */
+		} else {
+			execvp("./writer", arg_w);
+		}
+		
+	}
+
+	shmdt(mem);
+printf("sync done...\n");
+/* TODO
+ * why is this returning 8
+ */
+	for (i = 0; i < (n_write + n_read); i++) {
+		wait(&w);
+		printf("\nReturned with code:%d\n", WEXITSTATUS(w));
+	}
+	quit();
+}
diff --git a/CS3871/sync/writer.c b/CS3871/sync/writer.c
new file mode 100644
index 0000000..d38dd70
--- /dev/null
+++ b/CS3871/sync/writer.c
@@ -0,0 +1,76 @@
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ipc.h>
+#include <sys/select.h>
+#include <sys/sem.h>
+#include <sys/shm.h>
+#include <sys/types.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+
+#define NSEM 3
+
+char *mem;
+
+void quit(signum)
+int signum;
+{
+	shmdt(mem);
+	exit(1);
+}
+
+int main(argc, argv)
+int argc;
+char **argv;
+{
+	int shmid, semid, i, pid, id;
+	char *mem;
+	struct sembuf sb;
+
+	if (argc < 2) {
+		printf("usage: writer [id]\n");
+		exit(1);
+	}
+
+	id = atoi(argv[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);
+	}
+printf("Wshmid: %x\n", shmid);
+
+	if ((semid = semget(shmid, NSEM, 0)) == -1) {
+		perror("Wsemget: ");
+		exit(1);
+	}
+
+	signal(SIGQUIT, quit);
+	
+	srand(time(NULL));
+
+	while (1) {
+		rand() % id;
+		
+		sb.sem_num = 0; sb.sem_op = -1; sb.sem_flg = 0;
+		semop(semid, &sb, 1);
+
+		for (i = 0; i < 1<<14; i++) {
+			mem[i]= 0x30 + id;
+		}
+		
+		sb.sem_op = 1;
+		semop(semid, &sb, 1);
+
+		sleep(rand() % ((id * 2) + 1));
+	}
+}