From 043fc465c4208b46515bb5287c919d2fdff81c5e Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Mon, 5 Jul 2021 19:21:46 +0200
Subject: os: add homework 2

---
 Year_2/OS/hw/hw2.c | 119 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 Year_2/OS/hw/hw2.c

(limited to 'Year_2/OS')

diff --git a/Year_2/OS/hw/hw2.c b/Year_2/OS/hw/hw2.c
new file mode 100644
index 0000000..2245f15
--- /dev/null
+++ b/Year_2/OS/hw/hw2.c
@@ -0,0 +1,119 @@
+/*
+    Homework n.2
+
+    Estendere l'esempio 'move.c' visto a lezione per supportare i 2 casi speciali:
+    - spostamento cross-filesystem: individuato tale caso, il file deve essere
+      spostato utilizzando la strategia "copia & cancella";
+    - spostamento di un link simbolico: individuato tale caso, il link simbolico
+      deve essere ricreato a destinazione con lo stesso contenuto (ovvero il percorso
+      che denota l'oggetto referenziato); notate come tale spostamento potrebbe
+      rendere il nuovo link simbolico non effettivamente valido.
+
+    La sintassi da supportare e' la seguente:
+     $ homework-2 <pathname sorgente> <pathname destinazione>
+*/
+#include <fcntl.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+/* Function from the homework 1 */
+int copyfile(int*, int*);
+
+int main(int argc, char** argv)
+{
+    struct stat src, dst;
+    char buffer[1024];
+    int fd_src, fd_dst;
+    int size;
+
+    if (argc < 3) {
+        fprintf(stderr, "Usage: %s <src> <dst>", argv[0]);
+        exit(1);
+    }
+
+    if (lstat(argv[1], &src) == -1) {
+        perror("lstat");
+        exit(1);
+    }
+
+    switch (src.st_mode & S_IFMT) {
+    case S_IFREG:
+        strncpy(buffer, argv[2], 1024);
+        stat(dirname(buffer), &dst);
+
+        /* Destination's father must be a directory */
+        if (!S_ISDIR(dst.st_mode)) {
+            fprintf(stderr, "Destination is not a directory");
+        }
+
+        if (dst.st_dev == src.st_dev) {
+            if (link(argv[1], argv[2]) == -1) {
+                perror("link");
+                exit(1);
+            }
+
+        } else {
+            if ((fd_src = open(argv[1], O_RDONLY)) == -1) {
+                perror("Error opening source");
+                exit(1);
+            }
+
+            if ((fd_dst = open(argv[2], O_CREAT | O_TRUNC | O_WRONLY, (src.st_mode & 0777))) == -1) {
+                perror("Error opening destination");
+                exit(1);
+            }
+
+            copyfile(&fd_src, &fd_dst);
+
+            close(fd_src);
+            close(fd_dst);
+        }
+        break;
+    case S_IFLNK:
+        if ((size = readlink(argv[1], buffer, 1024)) == -1) {
+            perror("readlink");
+            exit(1);
+        }
+
+        buffer[size] = '\0';
+        if (symlink(buffer, argv[2]) == -1) {
+            perror("symlink");
+            exit(1);
+        }
+        break;
+    default:
+        fprintf(stderr, "Source file type not supported");
+    }
+
+    if (unlink(argv[1]) == -1) {
+        perror("ulink");
+        exit(1);
+    }
+
+    return 0;
+}
+
+int copyfile(int* src, int* dst)
+{
+    int n;
+    char buffer[1024];
+
+    do {
+        if ((n = read(*src, buffer, 1024)) == -1) {
+            perror("read");
+            exit(1);
+        }
+
+        if (write(*dst, buffer, n) == -1) {
+            perror("write");
+            exit(1);
+        }
+    } while (n > 0);
+
+    return n;
+}
-- 
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