Update mmap to add an insert helper function to allocate and add new mmap entries to the hash table

src/vm/mmap.c

@@ -4,6 +4,7 @@
 static unsigned mmap_hash (const struct hash_elem *e, void *aux);
 static bool mmap_less (const struct hash_elem *a_, const struct hash_elem *b_,
                 void *aux);
+static void mmap_cleanup(struct hash_elem *e, void *aux);
 
 /* Initializes the mmap table for the current thread. Sets the counter to 0. */
 bool
@@ -14,6 +15,34 @@ mmap_init (void)
   return hash_init (&t->mmap_files, mmap_hash, mmap_less, NULL);
 }
 
+/* Inserts a new mmap entry into the mmap table for the current thread. Upage
+   is the start address of the file data in the user VM. */
+struct mmap_entry *
+mmap_insert (struct file *file, void *upage)
+{
+  if (file == NULL || upage == NULL)
+    return NULL;
+
+  struct mmap_entry *mmap = malloc (sizeof (struct mmap_entry));
+  if (mmap == NULL)
+    return NULL;
+
+  mmap->mapping = thread_current ()->mmap_counter++;
+  mmap->file = file;
+  mmap->upage = upage;
+
+  hash_insert (&thread_current ()->mmap_files, &mmap->elem);
+  return mmap;
+}
+
+/* Destroys the mmap table for the current thread. Frees all the memory
+   allocated for the mmap entries. */
+void
+mmap_destroy (void)
+{
+  hash_destroy (&thread_current ()->mmap_files, mmap_cleanup);
+}
+
 /* A hash function for the mmap table. Returns a hash for an entry, based on its
    mapping. */
 static unsigned
@@ -43,11 +72,3 @@ mmap_cleanup (struct hash_elem *e, void *aux UNUSED)
   file_close (mmap->file);
   free (mmap);
 }
-
-/* Destroys the mmap table for the current thread. Frees all the memory
-   allocated for the mmap entries. */
-void
-mmap_destroy (void)
-{
-  hash_destroy (&thread_current ()->mmap_files, mmap_cleanup);
-}

src/vm/mmap.h

@@ -18,6 +18,7 @@ struct mmap_entry {
 };
 
 bool mmap_init (void);
+struct mmap_entry *mmap_insert (struct file *file, void *upage);
 void mmap_destroy (void);
 
 #endif /* vm/mmap.h */