Module Mirage_flow_combinators

This module define flow-related devices for MirageOS, using lwt for I/O.

Release v4.0.2

Copy stats

type stats = {
  1. read_bytes : int64;
  2. read_ops : int64;
  3. write_bytes : int64;
  4. write_ops : int64;
  5. duration : int64;
}

The type for I/O statistics from a copy operation.

val pp_stats : stats Fmt.t

pp_stats is the pretty-printer for flow stats.

module type CONCRETE = Mirage_flow.S with type error = [ `Msg of string ] and type write_error = [ Mirage_flow.write_error | `Msg of string ]

CONCRETE expose the private row as `Msg str errors, using pp_error and pp_write_error.

module Concrete (S : Mirage_flow.S) : CONCRETE with type flow = S.flow

Functor to transform a flow signature using private rows for errors into concrete error types.

module Copy (Clock : Mirage_clock.MCLOCK) (A : Mirage_flow.S) (B : Mirage_flow.S) : sig ... end
module Proxy (Clock : Mirage_clock.MCLOCK) (A : Mirage_flow.S) (B : Mirage_flow.S) : sig ... end
module F : sig ... end

In-memory, function-based flows.

type t

The type for first-class flows.

include Mirage_flow.S with type flow = t
type error

The type for flow errors.

val pp_error : error Fmt.t

pp_error is the pretty-printer for errors.

type nonrec write_error = private [>
  1. | Mirage_flow.write_error
]

The type for write errors.

val pp_write_error : write_error Fmt.t

pp_write_error is the pretty-printer for write errors.

type flow = t

The type for flows. A flow represents the state of a single reliable stream that is connected to an endpoint.

val read : flow -> (Cstruct.t Mirage_flow.or_eof, error) Stdlib.result Lwt.t

read flow blocks until some data is available and returns a fresh buffer containing it.

The returned buffer will be of a size convenient to the flow implementation, but will always have at least 1 byte.

When read returns `Eof or an error, close (or shutdown) should be called on the flow by the client. Once read returned `Eof or an error, no subsequent read call will be successful.

val write : flow -> Cstruct.t -> (unit, write_error) Stdlib.result Lwt.t

write flow buffer writes a buffer to the flow. There is no indication when the buffer has actually been sent and, therefore, it must not be reused. The contents may be transmitted in separate packets, depending on the underlying transport. The result Ok () indicates success, Error `Closed indicates that the connection is now closed and therefore the data could not be written. Other errors are possible.

The promise is resolved when the buffer has been accepted by the implementation (if a partial write occured, write will wait until the remainder of the buffer has been accepted by the implementation).

If write returns an error, close (or shutdown) should be called on the flow by the client. Once write returned an error, no subsequent write or writev call will be successful.

val writev : flow -> Cstruct.t list -> (unit, write_error) Stdlib.result Lwt.t

writev flow buffers writes a sequence of buffers to the flow. There is no indication when the buffers have actually been sent and, therefore, they must not be reused. The result Ok () indicates success, Error `Closed indicates that the connection is now closed and therefore the data could not be written. Other errors are possible.

The promise is resolved when the buffers have been accepted by the implementation (if a partial write occured, writev will wait until all buffers have been accepted by the implementation).

If writev returns an error, close (or shutdown) should be called on the flow by the client. Once writev returned an error, no subsequent writev or write call will be successful.

val shutdown : flow -> [ `read | `write | `read_write ] -> unit Lwt.t

shutdown flow mode shuts down the flow for the specific mode: A flow which is shutdown `read (or `read_write) will never be read again (subsequent calls will return `Eof); a flow which is shutdown `write (or `read_write) flushes all pending writes and signals the remote endpoint there won't be any future write or writev calls (subsequent calls will return `Closed). E.g. in TCP, the signalling is done by sending a segment with the FIN flag.

If this flow is layered upon another flow' (e.g. TLS over TCP), and the internal state after shutdown is `Closed, close on the underlying flow' is executed.

val close : flow -> unit Lwt.t

close flow terminates the flow and frees all associated data. Any subsequent read or write will return an error. A subsequent close will not do anything (esp. not raising an exception), but it may log an error.

If this flow is layered upon another flow' (e.g. TLS over TCP), close on the underlying flow' is executed.

val create : (module Mirage_flow.S with type flow = 'a) -> 'a -> string -> t

create (module M) t name is the flow representing t using the function defined in M.

val pp : t Fmt.t

pp is the pretty-printer for IO flows.

val forward : ?verbose:bool -> src:t -> dst:t -> unit -> unit Lwt.t

forward ?verbose ~src ~dst () forwards writes from src to dst. Block until either src or dst is closed. If verbose is set (by default it is not), show the full flow contents in the debug messages.

val proxy : ?verbose:bool -> t -> t -> unit Lwt.t

proxy ?verbose x y is the same as forward x y <*> forward y x. Block until both flows are closed. If verbose is set (by default it is not), show the full flow contents in the debug messages.