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 may support @file{.} and @file{..} for a small amount of extra
+credit.
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.
+Update the @code{open} system call so that it can also open directories.
+Passing @file{.} as the argument to @code{open} must open the current
+directory, regardless of whether @file{.} and @file{..} are fully
+implemented. Of the existing system calls, only @code{close} needs to
+accept a file descriptor for a directory.
+
Implement the following new system calls:
@deftypefn {System Call} bool chdir (const char *@var{dir})
@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},
+regardless of whether they are implemented.
+
+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
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. 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.
-
@node Buffer Cache
@subsection Buffer Cache
@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}?
+
+If you don't implement @file{.} and @file{..}, then this is not a
+special case. If you do, then it is equivalent to @samp{/x}. That is,
+the root directory is its own parent.
+@end table
+
@node Buffer Cache FAQ
@subsection Buffer Cache FAQ
projects / pintos-anon / blobdiff