reloadedd · May 7, 2020 07:56 · May 7, 2020
diff --git a/supervisors_and_cooperating_workers.c b/supervisors_and_cooperating_workers.c
@@ -0,0 +1,140 @@
+/* Solution for 'Supervisor & cooperating workers' pattern #6
+ * The program creates 4 anonymous pipes (1 for reading, 1 for reading, for each process. You have 2 processes => 2 x 2 = 4 anoynmous pipes)
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#define MAX_SIZE 1024
+
+void handle_error(const char *msg) {
+    perror(msg);
+    exit(EXIT_FAILURE);
+}
+
+int count_occurrences(char ch, const char *str) {
+    int occurrences = 0;
+    for (int i = 0; str[i]; ++i)
+        if (ch == str[i])
+            occurrences++;
+    return occurrences;
+}
+
+int main()
+{
+    int pipe1_child1[2], pipe2_child1[2], pipe1_child2[2], pipe2_child2[2];
+    char ch;
+    pid_t child1, child2;
+
+    if (pipe(pipe1_child1) == -1)
+        handle_error("[Error] When creating the first anonymous pipe: ");
+
+    if (pipe(pipe2_child1) == -1)
+        handle_error("[Error] When creating the first anonymous pipe: ");
+
+    if ((child1 = fork()) == -1)
+        handle_error("[Error] When forking the first child: ");
+
+    if (child1 == 0) {
+        // Executed by the first child
+
+        char buffer[MAX_SIZE], i, ch;
+        int index = 0, occurrences;
+
+        close(pipe1_child1[1]);   // Close the writing end of the reading pipe
+        close(pipe2_child1[0]);  // Close the reading end of the writing pipe
+
+        read(pipe1_child1[0], &ch, 1);
+
+        while (read(pipe1_child1[0], &i, 1) != 0)
+            if(index < MAX_SIZE)
+                buffer[index++] = i;
+
+        buffer[ (index == MAX_SIZE) ? MAX_SIZE - 1 : index ] = '\0';
+        printf("[%d] Read: %s\n", getpid(), buffer);
+
+        occurrences = count_occurrences(ch, buffer);
+        write(pipe2_child1[1], &occurrences, sizeof(int));
+
+        close(pipe2_child1[1]);     // Close the writing end
+        close(pipe1_child1[0]);     // Close the reading end
+    }else{
+        // Executed by the parent
+
+        if (pipe(pipe1_child2) == -1)
+            handle_error("[Error] When creating the second anonymous pipe: ");
+
+        if (pipe(pipe2_child2) == -1)
+            handle_error("[Error] When creating the second anonymous pipe: ");
+
+        if ((child2 = fork()) == -1)
+            handle_error("[Error] When forking the first child: ");
+
+        if (child2 == 0) {
+            // Executed by the second child
+
+            char buffer[MAX_SIZE], i, ch;
+            int index = 0, occurrences;
+
+            close(pipe1_child2[1]);   // Close the writing end of the reading pipe
+            close(pipe2_child2[0]);  // Close the reading end of the writing pipe
+
+            read(pipe1_child2[0], &ch, 1);
+
+            while (read(pipe1_child2[0], &i, 1) != 0)
+                if(index < MAX_SIZE)
+                    buffer[index++] = i;
+
+            buffer[ (index == MAX_SIZE) ? MAX_SIZE - 1 : index ] = '\0';
+            printf("[%d] Read: %s\n", getpid(), buffer);
+
+            occurrences = count_occurrences(ch, buffer);
+            write(pipe2_child2[1], &occurrences, sizeof(int));
+
+            close(pipe2_child2[1]);     // Close the writing end
+            close(pipe1_child2[0]);     // Close the reading end
+        }else{
+            // Executed by the parent
+
+            close(pipe1_child1[0]);     // Close the reading end (int the parent) of the child1's reading pipe
+            close(pipe2_child1[1]);     // Close the writing end (in the parent) of the child1's writing pipe
+            close(pipe1_child2[0]);     // Close the reading end (int the parent) of the child2's reading pipe
+            close(pipe2_child2[1]);     // Close the writing end (in the parent) of the child2's writing pipe
+
+            int counter = 1, occurrences_child1, occurrences_child2;
+
+            printf("Enter a sequence of characters, ended by CTRL + D.\n");
+            ch = getchar();     // Reading the fist character and sending it to both childs
+            write(pipe1_child1[1], &ch, 1);
+            write(pipe1_child2[1], &ch, 1);
+
+            while ((ch = getchar()) != EOF) {
+                if (counter % 2 == 0)   // characters from even positions will be sent to the first child
+                    write(pipe1_child1[1], &ch, 1);
+                else                    // characters from even positions will be sent to the first child
+                    write(pipe1_child2[1], &ch, 1);
+                counter++;
+            }
+
+            // Closing the write end on the parent, so that the childs can receive EOF
+            close(pipe1_child1[1]);
+            close(pipe1_child2[1]);
+
+            read(pipe2_child1[0], &occurrences_child1, sizeof(int));
+            read(pipe2_child2[0], &occurrences_child2, sizeof(int));
+
+            printf("[PARENT] Received from the first child, with PID = %d: %d\n", child1, occurrences_child1);
+            printf("[PARENT] Received from the second child, with PID = %d: %d\n", child2, occurrences_child2);
+            printf("[PARENT] The sum of both occurrences is: %d\n", occurrences_child1 + occurrences_child2);
+
+            // Close the childs' reading ends on the parent
+            close(pipe2_child1[0]);
+            close(pipe2_child2[0]);
+        }
+    }
+
+    return 0;
+}
No results found