[ViewVC] Diff of: cvs/IO-AIO/README

Comparing IO-AIO/README (file contents):
Revision 1.32 by root, Thu Oct 2 11:35:03 2008 UTC vs.
Revision 1.39 by root, Wed Aug 5 11:53:16 2009 UTC

      # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
      use AnyEvent::AIO;
      # EV integration
-     my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
+     my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
      # Event integration
      Event->io (fd => IO::AIO::poll_fileno,
                 poll => 'r',
                 cb => \&IO::AIO::poll_cb);
      Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
                                  \&IO::AIO::poll_cb);
 DESCRIPTION
     This module implements asynchronous I/O using whatever means your
-    operating system supports.
+    operating system supports. It is implemented as an interface to "libeio"
+    (<http://software.schmorp.de/pkg/libeio.html>).
     Asynchronous means that operations that can normally block your program
     (e.g. reading from disk) will be done asynchronously: the operation will
     still block, but you can do something else in the meantime. This is
     extremely useful for programs that need to stay interactive even when
     operations concurrently.
     While most of this works on all types of file descriptors (for example
     sockets), using these functions on file descriptors that support
     nonblocking operation (again, sockets, pipes etc.) is very inefficient.
-    Use an event loop for that (such as the Event module): IO::AIO will
+    Use an event loop for that (such as the EV module): IO::AIO will
     naturally fit into such an event loop itself.
     In this version, a number of threads are started that execute your
     requests and signal their completion. You don't need thread support in
     perl, and the threads created by this module will not be visible to
     it is currently not reentrant in any way, so use appropriate locking
     yourself, always call "poll_cb" from within the same thread, or never
     call "poll_cb" (or other "aio_" functions) recursively.
   EXAMPLE
-    This is a simple example that uses the Event module and loads
+    This is a simple example that uses the EV module and loads /etc/passwd
-    /etc/passwd asynchronously:
+    asynchronously:
        use Fcntl;
-       use Event;
+       use EV;
        use IO::AIO;
-       # register the IO::AIO callback with Event
+       # register the IO::AIO callback with EV
-       Event->io (fd => IO::AIO::poll_fileno,
+       my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
-                  poll => 'r',
-                  cb => \&IO::AIO::poll_cb);
        # queue the request to open /etc/passwd
        aio_open "/etc/passwd", O_RDONLY, 0, sub {
           my $fh = shift
              or die "error while opening: $!";
              # file contents now in $contents
              print $contents;
              # exit event loop and program
-             Event::unloop;
+             EV::unloop;
           };
        };
        # possibly queue up other requests, or open GUI windows,
        # check for sockets etc. etc.
        # process events as long as there are some:
-       Event::loop;
+       EV::loop;
 REQUEST ANATOMY AND LIFETIME
     Every "aio_*" function creates a request. which is a C data structure
     not directly visible to Perl.
         Or in other words: the file descriptor will be closed, but it will
         not be free for reuse until the perl filehandle is closed.
     aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
     aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
-        Reads or writes $length bytes from the specified $fh and $offset
+        Reads or writes $length bytes from or to the specified $fh and
-        into the scalar given by $data and offset $dataoffset and calls the
+        $offset into the scalar given by $data and offset $dataoffset and
-        callback without the actual number of bytes read (or -1 on error,
+        calls the callback without the actual number of bytes read (or -1 on
-        just like the syscall).
+        error, just like the syscall).
+        "aio_read" will, like "sysread", shrink or grow the $data scalar to
+        offset plus the actual number of bytes read.
         If $offset is undefined, then the current file descriptor offset
         will be used (and updated), otherwise the file descriptor offset
         will not be changed by these calls.
     aio_readdir $pathname, $callback->($entries)
         Unlike the POSIX call of the same name, "aio_readdir" reads an
         entire directory (i.e. opendir + readdir + closedir). The entries
         will not be sorted, and will NOT include the "." and ".." entries.
-        The callback a single argument which is either "undef" or an
+        The callback is passed a single argument which is either "undef" or
-        array-ref with the filenames.
+        an array-ref with the filenames.
+    aio_readdirx $pathname, $flags, $callback->($entries, $flags)
+        Quite similar to "aio_readdir", but the $flags argument allows to
+        tune behaviour and output format. In case of an error, $entries will
+        be "undef".
+        The flags are a combination of the following constants, ORed
+        together (the flags will also be passed to the callback, possibly
+        modified):
+        IO::AIO::READDIR_DENTS
+            When this flag is off, then the callback gets an arrayref with
+            of names only (as with "aio_readdir"), otherwise it gets an
+            arrayref with "[$name, $type, $inode]" arrayrefs, each
+            describing a single directory entry in more detail.
+            $name is the name of the entry.
+            $type is one of the "IO::AIO::DT_xxx" constants:
+            "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
+            "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
+            "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
+            "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
+            you need to know, you have to run stat yourself. Also, for speed
+            reasons, the $type scalars are read-only: you can not modify
+            them.
+            $inode is the inode number (which might not be exact on systems
+            with 64 bit inode numbers and 32 bit perls). This field has
+            unspecified content on systems that do not deliver the inode
+            information.
+        IO::AIO::READDIR_DIRS_FIRST
+            When this flag is set, then the names will be returned in an
+            order where likely directories come first. This is useful when
+            you need to quickly find directories, or you want to find all
+            directories while avoiding to stat() each entry.
+            If the system returns type information in readdir, then this is
+            used to find directories directly. Otherwise, likely directories
+            are files beginning with ".", or otherwise files with no dots,
+            of which files with short names are tried first.
+        IO::AIO::READDIR_STAT_ORDER
+            When this flag is set, then the names will be returned in an
+            order suitable for stat()'ing each one. That is, when you plan
+            to stat() all files in the given directory, then the returned
+            order will likely be fastest.
+            If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
+            specified, then the likely dirs come first, resulting in a less
+            optimal stat order.
+        IO::AIO::READDIR_FOUND_UNKNOWN
+            This flag should not be set when calling "aio_readdirx".
+            Instead, it is being set by "aio_readdirx", when any of the
+            $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
+            flag therefore indicates that all $type's are known, which can
+            be used to speed up some algorithms.
     aio_load $path, $data, $callback->($status)
         This is a composite request that tries to fully load the given file
         into memory. Status is the same as with aio_read.
     aio_move $srcpath, $dstpath, $callback->($status)
         Try to move the *file* (directories not supported as either source
         or destination) from $srcpath to $dstpath and call the callback with
         the 0 (error) or -1 ok.
-        This is a composite request that tries to rename(2) the file first.
+        This is a composite request that tries to rename(2) the file first;
-        If rename files with "EXDEV", it copies the file with "aio_copy"
+        if rename fails with "EXDEV", it copies the file with "aio_copy"
-        and, if that is successful, unlinking the $srcpath.
+        and, if that is successful, unlinks the $srcpath.
     aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
         Scans a directory (similar to "aio_readdir") but additionally tries
         to efficiently separate the entries of directory $path into two sets
         of names, directories you can recurse into (directories), and ones
         Implementation notes.
         The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
         can.
+        If readdir returns file type information, then this is used directly
+        to find directories.
-        After reading the directory, the modification time, size etc. of the
+        Otherwise, after reading the directory, the modification time, size
-        directory before and after the readdir is checked, and if they match
+        etc. of the directory before and after the readdir is checked, and
-        (and isn't the current time), the link count will be used to decide
+        if they match (and isn't the current time), the link count will be
-        how many entries are directories (if >= 2). Otherwise, no knowledge
+        used to decide how many entries are directories (if >= 2).
-        of the number of subdirectories will be assumed.
+        Otherwise, no knowledge of the number of subdirectories will be
+        assumed.
-        Then entries will be sorted into likely directories (everything
+        Then entries will be sorted into likely directories a non-initial
-        without a non-initial dot currently) and likely non-directories
+        dot currently) and likely non-directories (see "aio_readdirx"). Then
-        (everything else). Then every entry plus an appended "/." will be
+        every entry plus an appended "/." will be "stat"'ed, likely
-        "stat"'ed, likely directories first. If that succeeds, it assumes
+        directories first, in order of their inode numbers. If that
-        that the entry is a directory or a symlink to directory (which will
+        succeeds, it assumes that the entry is a directory or a symlink to
-        be checked seperately). This is often faster than stat'ing the entry
+        directory (which will be checked seperately). This is often faster
-        itself because filesystems might detect the type of the entry
+        than stat'ing the entry itself because filesystems might detect the
-        without reading the inode data (e.g. ext2fs filetype feature).
+        type of the entry without reading the inode data (e.g. ext2fs
+        filetype feature), even on systems that cannot return the filetype
+        information on readdir.
         If the known number of directories (link count - 2) has been
         reached, the rest of the entries is assumed to be non-directories.
         This only works with certainty on POSIX (= UNIX) filesystems, which
         Asynchronously call fdatasync on the given filehandle and call the
         callback with the fdatasync result code.
         If this call isn't available because your OS lacks it or it couldn't
         be detected, it will be emulated by calling "fsync" instead.
+    aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
+        Sync the data portion of the file specified by $offset and $length
+        to disk (but NOT the metadata), by calling the Linux-specific
+        sync_file_range call. If sync_file_range is not available or it
+        returns ENOSYS, then fdatasync or fsync is being substituted.
+        $flags can be a combination of
+        "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
+        "IO::AIO::SYNC_FILE_RANGE_WRITE" and
+        "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
+        manpage for details.
     aio_pathsync $path, $callback->($status)
         This request tries to open, fsync and close the given path. This is
         a composite request intended to sync directories after directory
         operations (E.g. rename). This might not work on all operating
         systems or have any specific effect, but usually it makes sure that
         directory changes get written to disc. It works for anything that
         can be opened for read-only, not just directories.
+        Future versions of this function might fall back to other methods
+        when "fsync" on the directory fails (such as calling "sync").
         Passes 0 when everything went ok, and -1 on error.
     aio_group $callback->(...)
         This is a very special aio request: Instead of doing something, it
         is a container for other aio requests, which is useful if you want
     cancel $req
         Cancels the request, if possible. Has the effect of skipping
         execution when entering the execute state and skipping calling the
         callback when entering the the result state, but will leave the
-        request otherwise untouched. That means that requests that currently
+        request otherwise untouched (with the exception of readdir). That
-        execute will not be stopped and resources held by the request will
+        means that requests that currently execute will not be stopped and
-        not be freed prematurely.
+        resources held by the request will not be freed prematurely.
     cb $req $callback->(...)
         Replace (or simply set) the callback registered to the request.
   IO::AIO::GRP CLASS
         does not impose any limits).
         If the feed does not queue more requests when called, it will be
         automatically removed from the group.
-        If the feed limit is 0, it will be set to 2 automatically.
+        If the feed limit is 0 when this method is called, it will be set to
+        2 automatically.
         Example:
            # stat all files in @files, but only ever use four aio requests concurrently:
         Sets the feeder limit for the group: The feeder will be called
         whenever the group contains less than this many requests.
         Setting the limit to 0 will pause the feeding process.
+        The default value for the limit is 0, but note that setting a feeder
+        automatically bumps it up to 2.
   SUPPORT FUNCTIONS
    EVENT PROCESSING AND EVENT LOOP INTEGRATION
     $fileno = IO::AIO::poll_fileno
         Return the *request result pipe file descriptor*. This filehandle
         must be polled for reading by some mechanism outside this module
-        (e.g. Event or select, see below or the SYNOPSIS). If the pipe
+        (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
-        becomes readable you have to call "poll_cb" to check the results.
+        pipe becomes readable you have to call "poll_cb" to check the
+        results.
         See "poll_cb" for an example.
     IO::AIO::poll_cb
         Process some outstanding events on the result pipe. You have to call
         If not all requests were processed for whatever reason, the
         filehandle will still be ready when "poll_cb" returns, so normally
         you don't have to do anything special to have it called later.
         Example: Install an Event watcher that automatically calls
-        IO::AIO::poll_cb with high priority:
+        IO::AIO::poll_cb with high priority (more examples can be found in
+        the SYNOPSIS section, at the top of this document):
            Event->io (fd => IO::AIO::poll_fileno,
                       poll => 'r', async => 1,
                       cb => \&IO::AIO::poll_cb);
     IO::AIO::npending
         Returns the number of requests currently in the pending state
         (executed, but not yet processed by poll_cb).
+   MISCELLANEOUS FUNCTIONS
+    IO::AIO implements some functions that might be useful, but are not
+    asynchronous.
+    IO::AIO::sendfile $ofh, $ifh, $offset, $count
+        Calls the "eio_sendfile_sync" function, which is like
+        "aio_sendfile", but is blocking (this makes most sense if you know
+        the input data is likely cached already and the output filehandle is
+        set to non-blocking operations).
+        Returns the number of bytes copied, or -1 on error.
+    IO::AIO::fadvise $fh, $offset, $len, $advice
+        Simply calls the "posix_fadvise" function (see it's manpage for
+        details). The following advice constants are avaiable:
+        "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
+        "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
+        "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
+        On systems that do not implement "posix_fadvise", this function
+        returns ENOSYS, otherwise the return value of "posix_fadvise".
   FORK BEHAVIOUR
     This module should do "the right thing" when the process using it forks:
     Before the fork, IO::AIO enters a quiescent state where no requests can
     be added in other threads and no results will be processed. After the

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Comparing IO-AIO/README (file contents): Revision 1.32 by root, Thu Oct 2 11:35:03 2008 UTC vs. Revision 1.39 by root, Wed Aug 5 11:53:16 2009 UTC

Diff Legend

Comparing IO-AIO/README (file contents):
Revision 1.32 by root, Thu Oct 2 11:35:03 2008 UTC vs.
Revision 1.39 by root, Wed Aug 5 11:53:16 2009 UTC