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```{index} single: Coro::AIO
```

# Coro::AIO

truly asynchronous file and directory I/O

## SYNOPSIS

```perl
use Coro::AIO;

## can now use any of the aio requests your IO::AIO module supports.

## read 1MB of /etc/passwd, without blocking other coroutines
my $fh = aio_open "/etc/passwd", O_RDONLY, 0
   or die "/etc/passwd: $!";
aio_read $fh, 0, 1_000_000, my $buf, 0
   or die "aio_read: $!";
aio_close $fh;
```

## DESCRIPTION

This module is an [AnyEvent](../AnyEvent.md) user, you need to make sure that you use and
run a supported event loop.

This module implements a thin wrapper around [IO::AIO](https://metacpan.org/pod/IO::AIO). All of
the functions that expect a callback are being wrapped by this module.

The API is exactly the same as that of the corresponding IO::AIO
routines, except that you have to specify _all_ arguments, even the
ones optional in IO::AIO, _except_ the callback argument. Instead of
calling a callback, the routines return the values normally passed to the
callback. Everything else, including `$!` and perls stat cache, are set
as expected after these functions return.

You can mix calls to `IO::AIO` functions with calls to this module. You
_must not_, however, call these routines from within IO::AIO callbacks,
as this causes a deadlock. Start a coro inside the callback instead.

This module also loads [AnyEvent::AIO](https://metacpan.org/pod/AnyEvent::AIO) to integrate into the event loop
in use, so please refer to its (and [AnyEvent](../AnyEvent.md)'s) documentation on how it
selects an appropriate event module.

All other functions exported by default by IO::AIO (e.g. `aioreq_pri`)
will be exported by default by Coro::AIO, too.

Functions that can be optionally imported from IO::AIO can be imported
from Coro::AIO or can be called directly, e.g. `Coro::AIO::nreqs`.

You cannot specify priorities with `aioreq_pri` if your coroutine has a
non-zero priority, as this module overwrites the request priority with the
current coroutine priority in that case.

For your convenience, here are the changed function signatures for most
of the requests, for documentation of these functions please have a look
at [IO::AIO](https://metacpan.org/pod/the&#x20-IO-AIO-manual). Note that requests added by newer
versions of [IO::AIO](https://metacpan.org/pod/IO::AIO) will be automatically wrapped as well.

- @results = aio\_wait $req

    This is not originally an IO::AIO request: what it does is to wait for
    `$req` to finish and return the results. This is most useful with
    `aio_group` requests.

    Is currently implemented by replacing the `$req` callback (and is very
    much like a wrapper around `$req->cb ()`).

- $fh = aio\_open $pathname, $flags, $mode
- $status = aio\_close $fh
- $retval = aio\_read  $fh,$offset,$length, $data,$dataoffset
- $retval = aio\_write $fh,$offset,$length, $data,$dataoffset
- $retval = aio\_sendfile $out\_fh, $in\_fh, $in\_offset, $length
- $retval = aio\_readahead $fh,$offset,$length
- $status = aio\_stat $fh\_or\_path
- $status = aio\_lstat $fh
- $status = aio\_unlink $pathname
- $status = aio\_rmdir $pathname
- $entries = aio\_readdir $pathname
- ($dirs, $nondirs) = aio\_scandir $path, $maxreq
- $status = aio\_fsync $fh
- $status = aio\_fdatasync $fh
- ... = aio\_xxx ...

    Any additional aio requests follow the same scheme: same parameters except
    you must not specify a callback but instead get the callback arguments as
    return values.

## SEE ALSO

[Coro::Socket](Socket.md) and [Coro::Handle](Handle.md) for non-blocking socket operation.

## AUTHOR/SUPPORT/CONTACT

```perl
Marc A. Lehmann <schmorp@schmorp.de>
http://software.schmorp.de/pkg/Coro.html
```