module Netpagebuffer:Buffer for page-aligned I/Osig
..end
The idea of this buffer is that input data is added to the last
page of the buffer only (with add_inplace
). If then all previous
input was already a multiple of the page size, it is ensured that
the new input is added at a page boundary. This kind of input operation
can often be accelerated by the OS ("zero copy network I/O").
type
t
val create : int -> t
blocksize
: creates new buffer with this blocksize
, which must
be a whole multiple of the page size of the OS
The blocksize
is normally either
val contents : t -> string
val length : t -> int
val sub : t -> int -> int -> string
val blit_to_string : t -> int -> string -> int -> int -> unit
val blit_to_memory : t -> int -> Netsys_mem.memory -> int -> int -> unit
val add_string : t -> string -> unit
val add_sub_string : t -> string -> int -> int -> unit
val add_sub_memory : t -> Netsys_mem.memory -> int -> int -> unit
val add_inplace : t -> (Netsys_mem.memory -> int -> int -> int) -> int
add_inplace b f
: Calls f m pos len
where m
is the last page
of the buffer, and pos
is the first free byte on the page, and
len
is the number of free bytes on the page. The function f
is
expected to store new data in m
from pos
to pos+n-1
and to
return n
. The number n
is also returned as final result.
It is ensured that f
is called with a value of len>=1
.
val page_for_additions : t -> Netsys_mem.memory * int * int
let (m,pos,len) = page_for_additions b
: Returns the last page
in m
, the first free byte on the page in pos
, and
the number of free bytes on the page in len
. (The same values
the function f
would have got as arguments in add_inplace
.)val advance : t -> int -> unit
advance b n
: Marks further n
bytes in the last page of the
buffer as used. These bytes are not modified in any way - it is
expected that the user calls page_for_additions
first, and sets
these n
bytes to new values directly.val page_for_consumption : t -> Netsys_mem.memory * int * int
let (m,pos,len) = page_for_consumption b
: Returns the first page
in m
, the first used byte on the page in pos
, and
the number of used bytes on the page in len
.val delete_hd : t -> int -> unit
delete_hd b n
: Deletes n
bytes from the beginning of the bufferval clear : t -> unit
val index_from : t -> int -> char -> int
index_from nb k c
: Searches the character c
in the buffer beginning
at position k
. If found, the position of the left-most occurence is
returned. Otherwise, Not_found
is raised.