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authorSanto Cariotti <santo@dcariotti.me>2021-09-26 12:34:22 +0200
committerSanto Cariotti <santo@dcariotti.me>2021-09-26 12:34:22 +0200
commitb9224fe08d3541fa93933b555619479a68be7ba1 (patch)
tree7d939f6fbb6aca835f1da9e32d4a8243a6dee16d /Year_2
parentf6bf5e48ecaa499faaa1483e9d5c1e5718424eb9 (diff)
os: add exercise 2021-07-26
Diffstat (limited to 'Year_2')
-rw-r--r--Year_2/OS/my-dus-c.c204
1 files changed, 204 insertions, 0 deletions
diff --git a/Year_2/OS/my-dus-c.c b/Year_2/OS/my-dus-c.c
new file mode 100644
index 0000000..5961c77
--- /dev/null
+++ b/Year_2/OS/my-dus-c.c
@@ -0,0 +1,204 @@
+/*
+ * Test the equivalent execution of this propgram with `du`:
+ *
+ * du --block-size=512 -s <path>
+ *
+ */
+#include <dirent.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <sys/shm.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define MAX_PATH_LEN 1024
+
+int
+WAIT(int id_sem, int n)
+{
+ struct sembuf sops[1] = { { n, -1, 0 } };
+
+ return semop(id_sem, sops, 1);
+}
+
+int
+SIGNAL(int id_sem, int n)
+{
+ struct sembuf sops[1] = { { n, 1, 0 } };
+
+ return semop(id_sem, sops, 1);
+}
+
+void
+handle_scanner_end(int id_shm, int id_sem, int id_scanner, char* pathname)
+{
+ char* msg;
+
+ if ((msg = (char*)shmat(id_shm, NULL, 0)) == (char*)-1) {
+ perror("shmat");
+ exit(1);
+ }
+
+ WAIT(id_sem, 0);
+ sprintf(msg, "%d;END;%s", id_scanner, pathname);
+ SIGNAL(id_sem, 1);
+}
+
+void
+stater(int id_shm, int id_sem, int* scanners, int scanners_n)
+{
+ char* msg;
+ int n;
+ struct stat sb;
+ char* token;
+ char* pathname;
+ int sid;
+
+ if ((msg = (char*)shmat(id_shm, NULL, 0)) == (char*)-1) {
+ perror("shmat");
+ exit(1);
+ }
+
+ n = 0;
+ while (n < scanners_n) {
+ WAIT(id_sem, 1);
+ /* I previously opened the file with `open` so I know I can read
+ * that. So now I open that file with stat, because `msg` contains
+ * the patname as string.
+ * But first I have to parse the `msg` receiving the scanner id.
+ */
+ token = strtok(msg, ";");
+ sid = atoi(token);
+ pathname = strtok(NULL, ";");
+
+ if (strcmp(pathname, "END") == 0) {
+ pathname = strtok(NULL, ";");
+ printf("%d\t%s\n", scanners[sid], pathname);
+ n++;
+ } else {
+ stat(pathname, &sb);
+ scanners[sid] += sb.st_blocks;
+ }
+ SIGNAL(id_sem, 0);
+ }
+}
+
+void
+scanner(int id_shm, int id_sem, int scanner_id, char* pathname)
+{
+ char* msg;
+ struct stat sb;
+ struct dirent* db;
+ int fd;
+ DIR* dp;
+ char buffer[MAX_PATH_LEN];
+
+ if ((msg = (char*)shmat(id_shm, NULL, 0)) == (char*)-1) {
+ perror("shmat");
+ exit(1);
+ }
+
+ if ((fd = open(pathname, O_RDONLY)) == -1) {
+ perror("open");
+ exit(1);
+ }
+
+ fstat(fd, &sb);
+
+ if ((sb.st_mode & S_IFMT) == S_IFDIR) {
+ if ((dp = opendir(pathname)) == NULL) {
+ perror("opendir");
+ exit(1);
+ }
+
+ while ((db = readdir(dp)) != NULL) {
+ if ((strcmp(db->d_name, ".") == 0) || strcmp(db->d_name, "..") == 0)
+ continue;
+ sprintf(buffer, "%s/%s", pathname, db->d_name);
+ scanner(id_shm, id_sem, scanner_id, buffer);
+ }
+
+ closedir(dp);
+ }
+
+ WAIT(id_sem, 0);
+ sprintf(msg, "%d;%s", scanner_id, pathname);
+ SIGNAL(id_sem, 1);
+}
+
+int
+main(int argc, char* argv[])
+{
+ int id_shm;
+ int i;
+ pid_t pid;
+ pid_t pid_scanners[argc - 1];
+ int scanners[argc - 1];
+ int id_sem;
+
+ for (i = 0; i < argc - 1; ++i)
+ scanners[i] = 0;
+
+ if ((id_shm = shmget(IPC_PRIVATE, 1024, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
+ perror("shmget");
+ exit(1);
+ }
+
+ if ((id_sem = semget(IPC_PRIVATE, 2, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
+ perror("semget");
+ exit(1);
+ }
+
+ semctl(id_sem, 0, SETVAL, 1);
+ semctl(id_sem, 1, SETVAL, 0);
+
+ if (argc < 2) {
+ exit(0);
+ }
+
+ pid = fork();
+ if (pid == -1) {
+ perror("fork");
+ exit(1);
+ }
+
+ if (pid == 0) {
+ stater(id_shm, id_sem, scanners, argc - 1);
+ exit(0);
+ }
+
+ for (i = 1; i < argc; ++i) {
+ pid_scanners[i - 1] = fork();
+ if (pid_scanners[i - 1] == -1) {
+ perror("fork");
+ exit(1);
+ }
+
+ if (pid_scanners[i - 1] == 0) {
+ scanner(id_shm, id_sem, i - 1, argv[i]);
+ handle_scanner_end(id_shm, id_sem, i - 1, argv[i]);
+ exit(0);
+ }
+ }
+
+ for (i = 0; i < argc; ++i)
+ wait(NULL);
+
+ if (shmctl(id_shm, IPC_RMID, NULL) == -1) {
+ perror("shmctl");
+ exit(1);
+ }
+
+ if (semctl(id_sem, 2, IPC_RMID) == -1) {
+ perror("semctl");
+ exit(1);
+ }
+
+ return 0;
+}