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Module Netpagebuffer

module Netpagebuffer: sig .. end
Buffer for page-aligned I/O

This kind of buffer uses page-aligned bigarrays. Data can only be added to the end, or deleted at the beginning of the buffer.

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
crea pagesize: creates new buffer with this pagesize, which must be a whole multiple of the page size of the OS
val contents : t -> string
Returns the contents as string
val length : t -> int
The length
val sub : t -> int -> int -> string
Returns a substring
val blit_to_string : t -> int -> string -> int -> int -> unit
Blits contents to a string
val blit_to_memory : t -> int -> Netsys_mem.memory -> int -> int -> unit
Blits contents to another memory buffer
val add_string : t -> string -> unit
Adds a string to the end of the buffer
val add_sub_string : t -> string -> int -> int -> unit
Adds a sub string to the end of the buffer
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 delete_hd : t -> int -> unit
delete_hd b n: Deletes n bytes from the beginning of the buffer
val clear : t -> unit
Deletes all contents of the buffer
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