CS代考计算机代写 #include “filesys/directory.h”
#include “filesys/directory.h”
#include
#include
#include
#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 == ‘ ’ || 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;
}
