From 9ad37f5ddea118ed12974156cd3cc46998267970 Mon Sep 17 00:00:00 2001
From: Alex Stratford <alexander3.stratford@live.uwe.ac.uk>
Date: Wed, 4 Dec 2019 00:59:03 +0000
Subject: [PATCH] Improved file_search function line 80..106: Added comments
and improved functionality
---
userprog/syscall.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/userprog/syscall.c b/userprog/syscall.c
index b2a467f..98fc8eb 100644
--- a/userprog/syscall.c
+++ b/userprog/syscall.c
@@ -4,7 +4,8 @@
#include "system_calls.h"
#include "threads/interrupt.h"
#include "threads/thread.h"
-#include "lib/kernel/list.h" // Dependencies for
+// Dependency for list_elem struct and list_next / is_tail functions
+#include "lib/kernel/list.h"
/* System call numbers. */
@@ -88,15 +89,30 @@ syscall_handler (struct intr_frame *f UNUSED)
static struct list *file_list;
-// Goes through all the files in the file_list and looks for the
+/* Goes through all the files in the file_list and looks for the given file
+ * Descriptor.
+ */
void file_search(struct file_map *f) {
+ // Creates a struct to hold the currently checked file
struct file_map *curr_file;
+ // Creates the list element to test for end of list
struct list_elem *list_element;
*list_element = *list_begin(file_list);
+
+ // Loop to check each file in the linked list in turn
while ((curr_file->file_descriptor != f->file_descriptor) &&
- (is_tail(curr_file->list_element) == false)
+ (is_tail(list_element) == false)
) {
- *list_element = curr_file->list_element;
+ // Swaps the list_element for the next one in place
list_next(list_element);
}
+ // Copies list_element to current file
+ curr_file->list_element = *list_element;
+ // Checks if file has been found returning NULL if not or the file if it has
+ if (curr_file->file_descriptor != f->file_descriptor) {
+ f->file = NULL;
+ }
+ else {
+ f = curr_file;
+ }
}
\ No newline at end of file
--
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