Ocsigen

Reference manual

Version 0.99.3

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Ocsigen

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Module Ocsipersist


module Ocsipersist: sig .. end
Persistent data on hard disk.

There are currently two implementations of this module, one using a DBM database, and the other using SQLITE. Link the one your want with your program.

Persistent references



When launching the program, if the value exists on hard disk, it is loaded, otherwise it is initialised to the default value
type 'a t
Type of persistent data
type store
Data are divided into stores. Create one store for your project, where you will save all your data.
val open_store : string -> store
Open a store (and create it if it does not exist)
val make_persistent : store:store ->
       name:string -> default:'a -> 'a t Lwt.t
make_persistent store name default find a persistent value named name in store store from database, or create it with the default value default if it does not exist.
val make_persistent_lazy : store:store ->
       name:string -> default:(unit -> 'a) -> 'a t Lwt.t
Same as make_persistent but the default value is evaluated only if needed
val get : 'a t -> 'a Lwt.t
get pv gives the value of pv
val set : 'a t -> 'a -> unit Lwt.t
set pv value sets a persistent value pv to value

Persistent tables


type 'a table
Type of persistent table
val open_table : string -> 'a table
Open a table (and create it if it does not exist)
val find : 'a table -> string -> 'a Lwt.t
find table key gives the value associated to key. Raises Not_found if not found.
val add : 'a table -> string -> 'a -> unit Lwt.t
add table key value associates value to key. If the database already contains data associated with key, that data is discarded and silently replaced by the new data.
val replace_if_exists : 'a table -> string -> 'a -> unit Lwt.t
replace_if_exists table key value associates value to key only if key is already bound. If the database does not contain any data associated with key, raises Not_found.
val remove : 'a table -> string -> unit Lwt.t
remove table key removes the entry in the table if it exists
val length : 'a table -> int Lwt.t
Size of a table.
val iter_step : (string -> 'a -> unit Lwt.t) -> 'a table -> unit Lwt.t
Important warning: this iterator may not iter on all data of the table if another thread is modifying it in the same time. Nonetheless, it should not miss more than a very few data from time to time, except if the table is very old (at least 9 223 372 036 854 775 807 insertions).
val iter_table : (string -> 'a -> unit Lwt.t) -> 'a table -> unit Lwt.t
Legacy interface for iter_step
val fold_step : (string -> 'a -> 'b -> 'b Lwt.t) -> 'a table -> 'b -> 'b Lwt.t
Important warning: this iterator may not iter on all data of the table if another thread is modifying it in the same time. Nonetheless, it should not miss more than a very few data from time to time, except if the table is very old (at least 9 223 372 036 854 775 807 insertions).
val fold_table : (string -> 'a -> 'b -> 'b Lwt.t) -> 'a table -> 'b -> 'b Lwt.t
Legacy interface for iter_step