@file{filesys/Make.vars} to enable VM functionality. You can receive up
to 5% extra credit if you do enable VM.
-The tests for project 4 (and later projects) will probably run faster if
+The tests for project 4 will probably run faster if
you use the qemu emulator, e.g.@: via @code{make check
PINTOSOPTS='--qemu'}.
also applies to the root directory file, which should now be allowed
to expand beyond its initial limit of 16 files.
-The user is allowed to seek beyond the current end-of-file (EOF). The
+User programs are allowed to seek beyond the current end-of-file (EOF). The
seek itself does not extend the file. Writing at a position past EOF
extends the file to the position being written, and any gap between the
previous EOF and the start of the write must be filled with zeros. A
Update the existing system calls so that, anywhere a file name is
provided by the caller, an absolute or relative path name may used.
The directory separator character is forward slash (@samp{/}).
+You must also support special file names @file{.} and @file{..}, which
+have the same meanings as they do in Unix.
Update the @code{remove} system call so that it can delete empty
-directories in addition to regular files. Directories can only be
-deleted if they do not contain any files or subdirectories.
+directories in addition to regular files. Directories may only be
+deleted if they do not contain any files or subdirectories (other than
+@file{.} and @file{..}).
+
+Update the @code{open} system call so that it can also open directories.
+Of the existing system calls, only @code{close} needs to accept a file
+descriptor for a directory.
Implement the following new system calls:
@file{/a/b/c} does not.
@end deftypefn
-@deftypefn {System Call} void lsdir (void)
-Prints a list of files in the current directory to @code{stdout}, one
-per line, in no particular order.
+@deftypefn {System Call} bool readdir (int @var{fd}, char *@var{name})
+Reads a directory entry from file descriptor @var{fd}, which must
+represent a directory. If successful, stores the null-terminated file
+name in @var{name}, which must have room for @code{READDIR_MAX_LEN + 1}
+bytes, and returns true. If no entries are left in the directory,
+returns false.
+
+@file{.} and @file{..} should not be returned by @code{readdir}.
+
+If the directory changes while it is open, then it is acceptable for
+some entries not to be read at all or to be read multiple times.
+Otherwise, each directory entry should be read once, in any order.
+
+@code{READDIR_MAX_LEN} is defined in @file{lib/user/syscall.h}. If your
+file system supports longer file names than the basic file system, you
+should increase this value from the default of 14.
+@end deftypefn
+
+@deftypefn {System Call} bool isdir (int @var{fd})
+Returns true if @var{fd} represents a directory,
+false if it represents an ordinary file.
+@end deftypefn
+
+@deftypefn {System Call} int inumber (int @var{fd})
+Returns the @dfn{inode number} of the inode associated with @var{fd}.
+Applicable to file descriptors for both files and directories.
+
+An inode number persistently identifies a file or directory. It is
+unique during the file's existence. In Pintos, the sector number of the
+inode is suitable for use as an inode number.
@end deftypefn
We have provided @command{ls} and @command{mkdir} user programs, which
-are straightforward once the above syscalls are implemented.
+are straightforward once the above syscalls are implemented.
+We have also provided @command{pwd}, which is not so straightforward.
+The @command{shell} program implements @command{cd} internally.
The @code{pintos} @option{put} and @option{get} commands should now
accept full path names, assuming that the directories used in the
-paths have already been created. This should not require any extra
-effort on your part.
-
-You may support @file{.} and @file{..} for a small amount of extra
-credit.
+paths have already been created. This should not require any significant
+extra effort on your part.
@node Buffer Cache
@subsection Buffer Cache
30 files changed, 2721 insertions(+), 286 deletions(-)
@end verbatim
-@item What extra credit opportunities are available?
-
-You may implement Unix-style support for @file{.} and @file{..} in
-relative paths in their projects.
-
-You may submit with VM enabled.
-
@item Can @code{DISK_SECTOR_SIZE} change?
No, @code{DISK_SECTOR_SIZE} is fixed at 512. This is a fixed property
@menu
* Indexed Files FAQ::
+* Subdirectories FAQ::
* Buffer Cache FAQ::
@end menu
You'll need to consider this when deciding your inode organization.
@end table
+@node Subdirectories FAQ
+@subsection Subdirectories FAQ
+
+@table @b
+@item How should a file name like @samp{a//b} be interpreted?
+
+Multiple consecutive slashes are equivalent to a single slash, so this
+file name is the same as @samp{a/b}.
+
+@item How about a file name like @samp{/../x}?
+
+The root directory is its own parent, so it is equivalent to @samp{/x}.
+
+@item How should a file name that ends in @samp{/} be treated?
+
+Most Unix systems allow a slash at the end of the name for a directory,
+and reject other names that end in slashes. We will allow this
+behavior, as well as simply rejecting a name that ends in a slash.
+@end table
+
@node Buffer Cache FAQ
@subsection Buffer Cache FAQ
projects / pintos-anon / blobdiff