From e9d64ba213280139af9b4be2874bb867a856f5de Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Mon, 27 Sep 2021 18:00:55 +0200
Subject: os: add exercise 2021-01-22

---
 Year_2/OS/filter.c | 196 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 196 insertions(+)
 create mode 100644 Year_2/OS/filter.c

(limited to 'Year_2')

diff --git a/Year_2/OS/filter.c b/Year_2/OS/filter.c
new file mode 100644
index 0000000..2312667
--- /dev/null
+++ b/Year_2/OS/filter.c
@@ -0,0 +1,196 @@
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.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 MAX_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
+filter(int id_shm, int id_sem, int index, int n, char* expr)
+{
+    char* msg;
+    int quit;
+    char* token;
+    int action;
+    char* word;
+    char* j;
+    char k[MAX_LEN];
+    unsigned w;
+    char c[1];
+    char next_msg[MAX_LEN];
+    char *pre_word, *next_word;
+
+    char *token_str, *token_word;
+
+    if ((msg = (char*)shmat(id_shm, NULL, 0)) == (char*)-1) {
+        perror("shmat");
+        exit(1);
+    }
+
+    quit = 0;
+    while (!quit) {
+        WAIT(id_sem, index);
+        if (strcmp(msg, "{{EOF}}") == 0) {
+            quit = 1;
+        } else {
+            switch (expr[0]) {
+            case '^':
+                action = 0;
+                break;
+            case '_':
+                action = 1;
+                break;
+            case '%':
+                action = 2;
+                break;
+            }
+            word = expr + 1;
+
+            token = strtok_r(msg, " ", &token_str);
+            next_msg[0] = '\0';
+            while (token) {
+                if (action == 0 || action == 1) {
+                    j = strstr(token, word);
+                    if (j) {
+                        k[0] = '\0';
+                        for (w = 0; w < strlen(word); ++w) {
+                            if (action == 0)
+                                c[0] = toupper(word[w]);
+                            else
+                                c[0] = tolower(word[w]);
+
+                            strcat(k, c);
+                        }
+                        strncpy(j, k, strlen(word));
+                    }
+                } else {
+                    strcpy(pre_word, word);
+                    pre_word = strtok_r(pre_word, ",", &token_word);
+                    next_word = strtok_r(NULL, ",", &token_word);
+
+                    j = strstr(token, pre_word);
+                    if (j) {
+                        strcpy(j, next_word);
+                    }
+                }
+                strcat(next_msg, token);
+                strcat(next_msg, " ");
+
+                token = strtok_r(NULL, " ", &token_str);
+            }
+            strcpy(msg, next_msg);
+        }
+
+        SIGNAL(id_sem, 0);
+        if (index == n)
+            SIGNAL(id_sem, 0);
+    }
+}
+
+int
+main(int argc, char* argv[])
+{
+    int id_shm;
+    int id_sem;
+    int i;
+    pid_t pid;
+    char buffer[MAX_LEN];
+    char ch;
+    FILE* f;
+    char* msg;
+
+    if (argc < 3) {
+        fprintf(stderr, "Usage: %s <file.txt> <filter-1> [filter-2] [...]", argv[0]);
+        exit(1);
+    }
+
+    if ((f = fopen(argv[1], "r")) == NULL) {
+        perror("fopen");
+        exit(1);
+    }
+
+    if ((id_shm = shmget(IPC_PRIVATE, 1024, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
+        perror("shmget");
+        exit(1);
+    }
+
+    if ((id_sem = semget(IPC_PRIVATE, argc - 1, IPC_CREAT | IPC_EXCL | 0644)) == -1) {
+        perror("semget");
+        exit(1);
+    }
+
+    semctl(id_sem, 0, SETVAL, 1);
+
+    /* Create n process for n filters */
+    for (i = 0; i < argc - 2; ++i) {
+        semctl(id_sem, i + 1, SETVAL, 0);
+        pid = fork();
+        if (pid == -1) {
+            perror("fork");
+            exit(1);
+        }
+
+        if (pid == 0) {
+            filter(id_shm, id_sem, i + 1, argc - 2, argv[i + 2]);
+            exit(0);
+        }
+    }
+
+    i = 0;
+    if ((msg = (char*)shmat(id_shm, NULL, 0)) == (char*)-1) {
+        perror("shmat");
+        exit(1);
+    }
+
+    while ((ch = fgetc(f)) != EOF) {
+        buffer[i++] = ch;
+        if (ch == '\n') {
+            buffer[i - 1] = '\0';
+            WAIT(id_sem, 0);
+            strncpy(msg, buffer, strlen(buffer) + 1);
+            for (i = 0; i < argc - 2; ++i) {
+                SIGNAL(id_sem, i + 1);
+                WAIT(id_sem, 0);
+            }
+            printf("%s\n", msg);
+            i = 0;
+        }
+    }
+
+    WAIT(id_sem, 0);
+    strcpy(msg, "{{EOF}}");
+    for (i = 0; i < argc - 2; ++i) {
+        SIGNAL(id_sem, i + 1);
+        WAIT(id_sem, 0);
+    }
+
+    for (i = 0; i < argc - 2; ++i)
+        wait(NULL);
+
+    shmctl(id_shm, IPC_RMID, NULL);
+    semctl(id_sem, argc - 1, IPC_RMID);
+
+    return 0;
+}
-- 
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