Region handles carving up a block of external memory into smaller chunks. This is currently just a slab allocator of a fixed size, on the basis that most IO operations operate on predictable chunks of memory. Since the block of memory in a region is contiguous, it can be used in Uring's fixed buffer model to map it into kernel space for more efficient IO.

'a t is a reference to an Io_uring structure.

A handle for a submitted job, which can be used to cancel it. If an operation returns None, this means that submission failed because the ring is full.

create ~queue_depth will return a fresh Io_uring structure t. Initially, t has no fixed buffer. Use set_fixed_buffer if you want one.

• parameter polling_timeout

  If given, use polling mode with the given idle timeout (in ms). This requires privileges.

queue_depth t returns the total number of submission slots for the uring t

exit t will shut down the uring t. Any subsequent requests will fail.

• raises Invalid_argument

  if there are any requests in progress

set_fixed_buffer t buf sets buf as the fixed buffer for t.

You will normally want to wrap this with Region.alloc or similar to divide the buffer into chunks.

If t already has a buffer set, the old one will be removed.

Returns `ENOMEM if insufficient kernel resources are available or the caller's RLIMIT_MEMLOCK resource limit would be exceeded.

• raises Invalid_argument

  if there are any requests in progress

buf t is the fixed internal memory buffer associated with uring t using set_fixed_buffer, or a zero-length buffer if none is set.

noop t d submits a no-op operation to uring t. The user data d will be returned by wait or peek upon completion.

Represents different Linux clocks.

timeout t clock ns d submits a timeout request to uring t.

absolute denotes how clock and ns relate to one another. Default value is false

ns is the timeout time in nanoseconds

Flags that can be passed to openat2.

Flags that can be passed to openat2 to control path resolution.

openat2 t ~access ~flags ~perm ~resolve ~fd path d opens path, which is resolved relative to fd (or the current directory if fd is not given). The user data d will be returned by wait or peek upon completion.

• parameter access

  controls whether the file is opened for reading, writing, or both

• parameter flags

  are the usual open flags

• parameter perm

  sets the access control bits for newly created files (subject to the process's umask)

• parameter resolve

  controls how the pathname is resolved.

linkat t ~flags ~old_path ~new_path creates a new hard link.

If new_path already exists then it is not overwritten.

• parameter old_dir_fd

  If provided and old_path is a relative path, it is interpreted relative to old_dir_fd.

• parameter new_dir_fd

  If provided and new_path is a relative path, it is interpreted relative to new_dir_fd.

• parameter old_path

  Path of the already-existing link.

• parameter new_path

  Path for the newly created link.

unlink t ~dir ~fd path removes the directory entry path, which is resolved relative to fd. If fd is not given, then the current working directory is used. If path is a symlink, the link is removed, not the target.

• parameter dir

  If true, this acts like rmdir (only removing empty directories). If false, it acts like unlink (only removing non-directories).

poll_add t fd mask d will submit a poll(2) request to uring t. It completes and returns d when an event in mask is ready on fd.

For files, give the absolute offset, or use Optint.Int63.minus_one for the current position. For sockets, use an offset of Optint.Int63.zero (minus_one is not allowed here).

read t ~file_offset fd buf d will submit a read(2) request to uring t. It reads from absolute file_offset on the fd file descriptor and writes the results into the memory pointed to by buf. The user data d will be returned by wait or peek upon completion.

write t ~file_offset fd buf d will submit a write(2) request to uring t. It writes to absolute file_offset on the fd file descriptor from the the memory pointed to by buf. The user data d will be returned by wait or peek upon completion.

The maximum length of the list that can be passed to readv and similar.

readv t ~file_offset fd iov d will submit a readv(2) request to uring t. It reads from absolute file_offset on the fd file descriptor and writes the results into the memory pointed to by iov. The user data d will be returned by wait or peek upon completion.

Requires List.length iov <= Uring.iov_max

writev t ~file_offset fd iov d will submit a writev(2) request to uring t. It writes to absolute file_offset on the fd file descriptor from the the memory pointed to by iov. The user data d will be returned by wait or peek upon completion.

Requires List.length iov <= Uring.iov_max

read t ~file_offset fd ~off ~len d will submit a read(2) request to uring t. It reads up to len bytes from absolute file_offset on the fd file descriptor and writes the results into the fixed memory buffer associated with uring t at offset off. The user data d will be returned by wait or peek upon completion.

read_chunk is like read_fixed, but gets the offset from chunk.

• parameter len

  Restrict the read to the first len bytes of chunk.

write t ~file_offset fd off d will submit a write(2) request to uring t. It writes up to len bytes into absolute file_offset on the fd file descriptor from the fixed memory buffer associated with uring t at offset off. The user data d will be returned by wait or peek upon completion.

write_chunk is like write_fixed, but gets the offset from chunk.

• parameter len

  Restrict the write to the first len bytes of chunk.

splice t ~src ~dst ~len d will submit a request to copy len bytes from src to dst. The operation returns the number of bytes transferred, or 0 for end-of-input. The result is EINVAL if the file descriptors don't support splicing.

statx t ?fd ~mask path stat flags stats path, which is resolved relative to fd (or the current directory if fd is not given).

connect t fd addr d will submit a request to connect fd to addr.

Holder for the peer's address in accept.

accept t fd addr d will submit a request to accept a new connection on fd. The new FD will be configured with SOCK_CLOEXEC. The remote address will be stored in addr.

cancel t job d submits a request to cancel job. The cancel job itself returns 0 on success, or ENOTFOUND if job had already completed by the time the kernel processed the cancellation request.

• raises Invalid_argument

  if the job has already been returned by e.g. wait.

send_msg t fd buffs d will submit a sendmsg(2) request. The Msghdr will be constructed from the FDs (fds), address (dst) and buffers (buffs).

Requires List.length buffs <= Uring.iov_max

• parameter dst

  Destination address.

• parameter fds

  Extra file descriptors to attach to the message.

recv_msg t fd msghdr d will submit a recvmsg(2) request. If the request is successful then the msghdr will contain the sender address and the data received.

fsync t ?off ?len fd d will submit an fsync(2) request, with the optional offset off and length len specifying the subset of the file to perform the synchronisation on.

fdatasync t ?off ?len fd d will submit an fdatasync(2) request, with the optional offset off and length len specifying the subset of the file to perform the synchronisation on.

submit t will submit all the outstanding queued requests on uring t to the kernel. Their results can subsequently be retrieved using wait or peek.

The type of results of calling wait and peek. None denotes that either there were no completions in the queue or an interrupt / timeout occurred. Some contains both the user data attached to the completed request and the integer syscall result.

wait ?timeout t will block indefinitely (the default) or for timeout seconds for any outstanding events to complete on uring t. This calls submit automatically.

get_cqe_nonblocking t returns the next completion entry from the uring t. It is like wait except that it returns None instead of blocking.

• deprecated Renamed to Uring.get_cqe_nonblocking

register_eventfd t fd will register an eventfd to the the uring t. See documentation for io_uring_register_eventfd

error_of_errno e converts the error code abs e to a Unix error type.

active_ops t returns the number of operations added to the ring (whether submitted or not) for which the completion event has not yet been collected.

sqe_ready t is the number of unconsumed (if SQPOLL) or unsubmitted entries in the SQ ring.

get_debug_stats t collects some metrics about the internal state of t.