From db58f5aa1e173fd185ff87ee95a06644f86c41b1 Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Mon, 27 Sep 2021 16:13:39 +0200
Subject: os: add exercise 2021-02-10

---
 Year_2/OS/alpha-stats.c | 214 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 214 insertions(+)
 create mode 100644 Year_2/OS/alpha-stats.c

(limited to 'Year_2')

diff --git a/Year_2/OS/alpha-stats.c b/Year_2/OS/alpha-stats.c
new file mode 100644
index 0000000..b9b0a07
--- /dev/null
+++ b/Year_2/OS/alpha-stats.c
@@ -0,0 +1,214 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/sem.h>
+#include <sys/shm.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+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
+al(int sh_char, int sh_stats, int id_sem)
+{
+    char* ch;
+    long* stats;
+    int index;
+
+    if ((ch = (char*)shmat(sh_char, NULL, 0)) == (char*)-1) {
+        perror("shmat");
+        exit(1);
+    }
+
+    if ((stats = (long*)shmat(sh_stats, NULL, 0)) == (long*)-1) {
+        perror("shmat");
+        exit(1);
+    }
+
+    while (1) {
+        WAIT(id_sem, 1);
+        if (strcmp(ch, "exit") == 0) {
+            break;
+        }
+
+        if (*ch >= 'A' && *ch <= 'Z')
+            *ch = *ch + 32;
+
+        index = *ch - 97;
+        stats[index]++;
+
+        SIGNAL(id_sem, 0);
+    }
+}
+
+void
+mz(int sh_char, int sh_stats, int id_sem)
+{
+    char* ch;
+    long* stats;
+    int index;
+
+    if ((ch = (char*)shmat(sh_char, NULL, 0)) == (char*)-1) {
+        perror("shmat");
+        exit(1);
+    }
+
+    if ((stats = (long*)shmat(sh_stats, NULL, 0)) == (long*)-1) {
+        perror("shmat");
+        exit(1);
+    }
+
+    while (1) {
+        WAIT(id_sem, 2);
+        if (strcmp(ch, "exit") == 0) {
+            break;
+        }
+
+        if (*ch >= 'A' && *ch <= 'Z')
+            *ch = *ch + 32;
+
+        index = *ch - 97;
+        stats[index]++;
+
+        SIGNAL(id_sem, 0);
+    }
+}
+
+int
+main(int argc, char* argv[])
+{
+    int fd;
+    struct stat sb;
+    char* addr;
+    int sh_char, sh_stats; /* segments CHAR and STATS */
+    long* msg_stats;
+    char* ch;
+    pid_t p_al, p_mz;
+    int id_sem;
+    int i;
+    int skip_wait_p;
+
+    if (argc < 2) {
+        fprintf(stderr, "Usage: %s <file.txt>", argv[0]);
+        exit(1);
+    }
+
+    if ((fd = open(argv[1], O_RDONLY)) == -1) {
+        perror("open");
+        exit(1);
+    }
+
+    fstat(fd, &sb);
+
+    if ((addr = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0)) == MAP_FAILED) {
+        perror("mmap");
+        exit(1);
+    }
+
+    if ((sh_char = shmget(IPC_PRIVATE, 1, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
+        perror("shmget");
+        exit(1);
+    }
+
+    if ((sh_stats = shmget(IPC_PRIVATE, sizeof(long) * 26, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
+        perror("shmget");
+        exit(1);
+    }
+
+    /* Set to 0 every stats element */
+    if ((msg_stats = (long*)shmat(sh_stats, NULL, 0)) == (long*)-1) {
+        perror("shmat");
+        exit(1);
+    }
+
+    for (i = 0; i < 26; ++i)
+        *(msg_stats + i) = 0;
+
+    /* Create 3 semaphores */
+    if ((id_sem = semget(IPC_PRIVATE, 3, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
+        perror("semget");
+        exit(1);
+    }
+
+    semctl(id_sem, 0, SETVAL, 1);
+    semctl(id_sem, 1, SETVAL, 0);
+    semctl(id_sem, 2, SETVAL, 0);
+
+    p_al = fork();
+    if (p_al == -1) {
+        perror("fork");
+        exit(1);
+    }
+
+    if (p_al == 0) {
+        al(sh_char, sh_stats, id_sem);
+        exit(0);
+    }
+
+    p_mz = fork();
+    if (p_mz == -1) {
+        perror("fork");
+        exit(1);
+    }
+
+    if (p_mz == 0) {
+        mz(sh_char, sh_stats, id_sem);
+        exit(0);
+    }
+
+    if ((ch = (char*)shmat(sh_char, NULL, 0)) == (char*)-1) {
+        perror("shmat");
+        exit(1);
+    }
+
+    skip_wait_p = 0;
+    for (i = 0; i < sb.st_size; ++i) {
+        if (!skip_wait_p)
+            WAIT(id_sem, 0);
+
+        strcpy(ch, addr + i);
+
+        skip_wait_p = 0;
+        if ((*ch >= 'a' && *ch <= 'l') || (*ch >= 'A' && *ch <= 'L')) {
+            SIGNAL(id_sem, 1);
+        } else if ((*ch >= 'm' && *ch <= 'z') || (*ch >= 'M' && *ch <= 'Z')) {
+            SIGNAL(id_sem, 2);
+        } else {
+            skip_wait_p = 1;
+        }
+    }
+
+    strcpy(ch, "exit");
+    SIGNAL(id_sem, 1);
+    SIGNAL(id_sem, 2);
+
+    wait(NULL);
+    wait(NULL);
+
+    for (i = 0; i < 26; ++i)
+        printf("%c = %ld\n", i + 97, msg_stats[i]);
+
+    shmctl(sh_char, IPC_RMID, NULL);
+    shmctl(sh_stats, IPC_RMID, NULL);
+    semctl(id_sem, 3, IPC_RMID);
+    munmap(addr, sb.st_size);
+
+    return 0;
+}
-- 
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