/
8_sem.c
110 lines (105 loc) · 2.41 KB
/
8_sem.c
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#include <sys/sem.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <stdbool.h>
void
print_all_sems(int semid)
{
unsigned short values[3];
if (semctl(semid, -1, GETALL, values) == -1) {
printf("error = %s\n", strerror(errno));
} else {
printf("Values are %d %d %d\n", values[0], values[1],
values[2]);
}
}
void
init_sems(int semid)
{
unsigned short values[3] = {1, 2, 3};
semctl(semid, -1, SETALL, values);
printf("Sem array is initialized\n");
print_all_sems(semid);
}
int
main()
{
key_t key = ftok("./a.out", 0);
int semid = semget(key, 3, IPC_CREAT | IPC_EXCL | S_IRWXU | S_IRWXO);
if (semid == -1) {
if (errno != EEXIST) {
printf("error = %s\n", strerror(errno));
return -1;
}
printf("Sem array already exists\n");
semid = semget(key, 0, 0);
if (semid == -1) {
printf("error = %s\n", strerror(errno));
return -1;
}
printf("Connected to %d\n", semid);
} else {
printf("Created sems with id %d\n", semid);
init_sems(semid);
}
struct sembuf ops[100], *op;
int ops_count = 0, sem_num;
bool is_inside_txn = false;
char cmd, *line = NULL;
size_t line_size = 0;
while (1) {
getline(&line, &line_size, stdin);
if (line == NULL)
continue;
/* Trim '\n'. */
line[strlen(line) - 1] = 0;
if (strcmp(line, "begin") == 0) {
is_inside_txn = true;
} else if (strcmp(line, "commit") == 0) {
if (semop(semid, ops, ops_count) == -1) {
printf("error = %s\n", strerror(errno));
} else {
is_inside_txn = false;
ops_count = 0;
print_all_sems(semid);
}
} else if (strcmp(line, "rollback") == 0) {
is_inside_txn = false;
ops_count = 0;
} else if (strcmp(line, "delete") == 0) {
if (semctl(semid, -1, IPC_RMID) == -1)
printf("error = %s\n", strerror(errno));
return 0;
} else if (strcmp(line, "quit") == 0) {
return 0;
} else if (strcmp(line, "show") == 0) {
print_all_sems(semid);
} else {
sscanf(line, "%d %c", &sem_num, &cmd);
op = &ops[ops_count];
if (cmd == '-') {
op->sem_op = -1;
} else if (cmd == '+') {
op->sem_op = 1;
} else {
printf("Unknown operation\n");
continue;
}
op->sem_num = sem_num - 1;
op->sem_flg = SEM_UNDO;
if (! is_inside_txn) {
if (semop(semid, op, 1) == -1)
printf("error = %s\n", strerror(errno));
else
print_all_sems(semid);
} else {
ops_count++;
}
}
}
return 0;
}