lwt

Promises and event-driven I/O
Library lwt.unix
Module Lwt_unix . IO_vectors
type t

Mutable sequences of I/O vectors. An I/O vector describes a slice of a bytes or Bigarray buffer. Each I/O vector is a triple containing a reference to the buffer, an offset into the buffer where the slice begins, and the length of the slice.

Type abbreviation equivalent to Lwt_bytes.t. Do not use this type name directly; use Lwt_bytes.t instead.

val create : unit -> t

Creates an empty I/O vector sequence.

val append_bytes : t -> bytes -> int -> int -> unit

append_bytes vs buffer offset length appends a slice of the bytes buffer buffer beginning at offset and with length length to the I/O vector sequence vs.

val append_bigarray : t -> _bigarray -> int -> int -> unit

append_bigarray vs buffer offset length appends a slice of the Bigarray buffer buffer beginning at offset and with length length to the I/O vector sequence vs.

val drop : t -> int -> unit

drop vs n adjusts the I/O vector sequence vs so that it no longer includes its first n bytes.

val is_empty : t -> bool

is_empty vs is true if and only if vs has no I/O vectors, or all I/O vectors in vs have zero bytes.

val byte_count : t -> int

byte_count vs is the total number of bytes in vs.

  • since 4.2.0
val system_limit : int option

Some systems limit the number of I/O vectors that can be passed in a single call to their writev or readv system calls. On those systems, if the limit is n, this value is equal to Some n. On systems without such a limit, the value is equal to None.

Unless you need atomic I/O operations, you can ignore this limit. The Lwt binding automatically respects it internally. See Lwt_unix.writev.

A typical limit is 1024 vectors.