feat[OS/lab5]: completed part A

OSs/lab5/part-A/Makefile

@@ -0,0 +1,12 @@
+targets = main
+all: $(targets)
+
+main: main.o
+	$(CC) -o $@ $^ $(CFLAGS)
+
+%.o: %.c
+	$(CC) -c $^ -o $@ $(CFLAGS)
+
+clean:
+	rm -f $(targets)
+	rm -f *.o

OSs/lab5/part-A/main.c

@@ -0,0 +1,132 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <string.h>
+#include <ctype.h>
+
+#define PIPE_READ_IDX   0
+#define PIPE_WRITE_IDX  1
+
+int client(int fd_read, int fd_write);
+int server(int fd_read, int fd_write);
+
+#define DO_OR_FAIL(cond) if (cond) return EXIT_FAILURE
+int main()
+{
+    int pipe_to_server[2], pipe_to_client[2];
+    DO_OR_FAIL(pipe(pipe_to_server) < 0);
+    DO_OR_FAIL(pipe(pipe_to_client) < 0);
+
+    pid_t client_pid;
+    if ((client_pid = fork()) == 0) { // server
+        DO_OR_FAIL(close(pipe_to_server[PIPE_WRITE_IDX]));
+        DO_OR_FAIL(close(pipe_to_client[PIPE_READ_IDX]));
+
+        DO_OR_FAIL(
+                server(
+                    pipe_to_server[PIPE_READ_IDX],
+                    pipe_to_client[PIPE_WRITE_IDX]
+                    )
+                );
+    }
+    // client
+    DO_OR_FAIL(close(pipe_to_server[PIPE_READ_IDX]));
+    DO_OR_FAIL(close(pipe_to_client[PIPE_WRITE_IDX]));
+
+    DO_OR_FAIL(
+            client(
+                pipe_to_client[PIPE_READ_IDX],
+                pipe_to_server[PIPE_WRITE_IDX]
+                )
+            );
+
+    return 0;
+}
+
+char *ltrim(char *s)
+{
+    while(isspace(*s)) s++;
+    return s;
+}
+
+char *rtrim(char *s)
+{
+    char* back = s + strlen(s);
+    while(isspace(*--back));
+    *(back+1) = '\0';
+    return s;
+}
+
+char *trim(char *s)
+{
+    return rtrim(ltrim(s)); 
+}
+
+#define BUF_SIZE 256
+
+#define DO_OR_PROPAGATE(call, expected, tmp_var) \
+    if ((tmp_var = (call)) != expected)) return tmp_var
+
+/**
+ * Performs client actions
+ *
+ * @fd_read - pipe to read from
+ * @fd_write - pipe to write t\no
+ * 
+ * returns 0 on success or -errno on fail
+ */
+int client(int fd_read, int fd_write)
+{
+    char buf[BUF_SIZE] = {0};
+    if (!fgets(buf, BUF_SIZE, stdin)) return -EFAULT;
+    const char *s = trim(buf);
+    size_t len = strlen(s);
+    ssize_t n_written = write(fd_write, s, len);
+    if (n_written < 0 || n_written < len) {
+        return -EFAULT;
+    }
+    memset(buf, 0, BUF_SIZE);
+    size_t n;
+    while ((n = read(fd_read, buf, BUF_SIZE)) > 0) {
+        len = strlen(buf);
+        n_written = fwrite(buf, sizeof(buf[0]), strlen(buf), stdout);
+        if (n_written < 0 || n_written < len) {
+            return -EFAULT;
+        }
+        memset(buf, 0, sizeof(buf));
+    }
+    return 0;
+}
+
+/**
+ * Performs server actions
+ *
+ * @fd_read - pipe to read from
+ * @fd_write - pipe to write to
+ *
+ * returns 0 on success or -errno on fail
+ */
+int server(int fd_read, int fd_write)
+{
+    char buf[BUF_SIZE] = {0};
+    size_t n = read(fd_read, buf, BUF_SIZE);
+    if (n == 0) return -EFAULT;
+    FILE *f = fopen(buf, "r");
+    // не 100% правильно, но наиболее вероятно
+    if (f == NULL) {
+        const char error_msg[] = "Can't open requested file\n";
+        write(fd_write, error_msg, sizeof(error_msg));
+        goto epilog;
+    }
+
+    while ((n = fread(buf, sizeof(buf[0]), BUF_SIZE, f)) > 0) {
+        write(fd_write, buf, n);
+        memset(buf, 0, sizeof(buf));
+    }
+
+epilog:
+    fclose(f);
+    return 0;
+}