provided code

src/filesys/directory.c

@@ -0,0 +1,236 @@
+#include "filesys/directory.h"
+#include <stdio.h>
+#include <string.h>
+#include <list.h>
+#include "filesys/filesys.h"
+#include "filesys/inode.h"
+#include "threads/malloc.h"
+
+/* A directory. */
+struct dir 
+  {
+    struct inode *inode;                /* Backing store. */
+    off_t pos;                          /* Current position. */
+  };
+
+/* A single directory entry. */
+struct dir_entry 
+  {
+    block_sector_t inode_sector;        /* Sector number of header. */
+    char name[NAME_MAX + 1];            /* Null terminated file name. */
+    bool in_use;                        /* In use or free? */
+  };
+
+/* Creates a directory with space for ENTRY_CNT entries in the
+   given SECTOR.  Returns true if successful, false on failure. */
+bool
+dir_create (block_sector_t sector, size_t entry_cnt)
+{
+  return inode_create (sector, entry_cnt * sizeof (struct dir_entry));
+}
+
+/* Opens and returns the directory for the given INODE, of which
+   it takes ownership.  Returns a null pointer on failure. */
+struct dir *
+dir_open (struct inode *inode) 
+{
+  struct dir *dir = calloc (1, sizeof *dir);
+  if (inode != NULL && dir != NULL)
+    {
+      dir->inode = inode;
+      dir->pos = 0;
+      return dir;
+    }
+  else
+    {
+      inode_close (inode);
+      free (dir);
+      return NULL; 
+    }
+}
+
+/* Opens the root directory and returns a directory for it.
+   Return true if successful, false on failure. */
+struct dir *
+dir_open_root (void)
+{
+  return dir_open (inode_open (ROOT_DIR_SECTOR));
+}
+
+/* Opens and returns a new directory for the same inode as DIR.
+   Returns a null pointer on failure. */
+struct dir *
+dir_reopen (struct dir *dir) 
+{
+  return dir_open (inode_reopen (dir->inode));
+}
+
+/* Destroys DIR and frees associated resources. */
+void
+dir_close (struct dir *dir) 
+{
+  if (dir != NULL)
+    {
+      inode_close (dir->inode);
+      free (dir);
+    }
+}
+
+/* Returns the inode encapsulated by DIR. */
+struct inode *
+dir_get_inode (struct dir *dir) 
+{
+  return dir->inode;
+}
+
+/* Searches DIR for a file with the given NAME.
+   If successful, returns true, sets *EP to the directory entry
+   if EP is non-null, and sets *OFSP to the byte offset of the
+   directory entry if OFSP is non-null.
+   otherwise, returns false and ignores EP and OFSP. */
+static bool
+lookup (const struct dir *dir, const char *name,
+        struct dir_entry *ep, off_t *ofsp) 
+{
+  struct dir_entry e;
+  size_t ofs;
+  
+  ASSERT (dir != NULL);
+  ASSERT (name != NULL);
+
+  for (ofs = 0; inode_read_at (dir->inode, &e, sizeof e, ofs) == sizeof e;
+       ofs += sizeof e) 
+    if (e.in_use && !strcmp (name, e.name)) 
+      {
+        if (ep != NULL)
+          *ep = e;
+        if (ofsp != NULL)
+          *ofsp = ofs;
+        return true;
+      }
+  return false;
+}
+
+/* Searches DIR for a file with the given NAME
+   and returns true if one exists, false otherwise.
+   On success, sets *INODE to an inode for the file, otherwise to
+   a null pointer.  The caller must close *INODE. */
+bool
+dir_lookup (const struct dir *dir, const char *name,
+            struct inode **inode) 
+{
+  struct dir_entry e;
+
+  ASSERT (dir != NULL);
+  ASSERT (name != NULL);
+
+  if (lookup (dir, name, &e, NULL))
+    *inode = inode_open (e.inode_sector);
+  else
+    *inode = NULL;
+
+  return *inode != NULL;
+}
+
+/* Adds a file named NAME to DIR, which must not already contain a
+   file by that name.  The file's inode is in sector
+   INODE_SECTOR.
+   Returns true if successful, false on failure.
+   Fails if NAME is invalid (i.e. too long) or a disk or memory
+   error occurs. */
+bool
+dir_add (struct dir *dir, const char *name, block_sector_t inode_sector)
+{
+  struct dir_entry e;
+  off_t ofs;
+  bool success = false;
+
+  ASSERT (dir != NULL);
+  ASSERT (name != NULL);
+
+  /* Check NAME for validity. */
+  if (*name == '\0' || strlen (name) > NAME_MAX)
+    return false;
+
+  /* Check that NAME is not in use. */
+  if (lookup (dir, name, NULL, NULL))
+    goto done;
+
+  /* Set OFS to offset of free slot.
+     If there are no free slots, then it will be set to the
+     current end-of-file.
+     
+     inode_read_at() will only return a short read at end of file.
+     Otherwise, we'd need to verify that we didn't get a short
+     read due to something intermittent such as low memory. */
+  for (ofs = 0; inode_read_at (dir->inode, &e, sizeof e, ofs) == sizeof e;
+       ofs += sizeof e) 
+    if (!e.in_use)
+      break;
+
+  /* Write slot. */
+  e.in_use = true;
+  strlcpy (e.name, name, sizeof e.name);
+  e.inode_sector = inode_sector;
+  success = inode_write_at (dir->inode, &e, sizeof e, ofs) == sizeof e;
+
+ done:
+  return success;
+}
+
+/* Removes any entry for NAME in DIR.
+   Returns true if successful, false on failure,
+   which occurs only if there is no file with the given NAME. */
+bool
+dir_remove (struct dir *dir, const char *name) 
+{
+  struct dir_entry e;
+  struct inode *inode = NULL;
+  bool success = false;
+  off_t ofs;
+
+  ASSERT (dir != NULL);
+  ASSERT (name != NULL);
+
+  /* Find directory entry. */
+  if (!lookup (dir, name, &e, &ofs))
+    goto done;
+
+  /* Open inode. */
+  inode = inode_open (e.inode_sector);
+  if (inode == NULL)
+    goto done;
+
+  /* Erase directory entry. */
+  e.in_use = false;
+  if (inode_write_at (dir->inode, &e, sizeof e, ofs) != sizeof e) 
+    goto done;
+
+  /* Remove inode. */
+  inode_remove (inode);
+  success = true;
+
+ done:
+  inode_close (inode);
+  return success;
+}
+
+/* Reads the next directory entry in DIR and stores the name in
+   NAME.  Returns true if successful, false if the directory
+   contains no more entries. */
+bool
+dir_readdir (struct dir *dir, char name[NAME_MAX + 1])
+{
+  struct dir_entry e;
+
+  while (inode_read_at (dir->inode, &e, sizeof e, dir->pos) == sizeof e) 
+    {
+      dir->pos += sizeof e;
+      if (e.in_use)
+        {
+          strlcpy (name, e.name, NAME_MAX + 1);
+          return true;
+        } 
+    }
+  return false;
+}