package octez-libs

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package octez-libs
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Module Tezos_stdlib_unix.Stored_dataSource

Persistent data manager.

Every data read/write operation is protected by a mutex preventing concurrent data-races.

Sourcetype 'a file = private {
  1. encoding : 'a Data_encoding.t;
  2. eq : 'a -> 'a -> bool;
  3. path : string;
  4. json : bool;
}

A data structure that represents files via their paths and encodings.

type 'a eq := 'a -> 'a -> bool
Sourcetype 'a t

The type for the (persistent) data of a file.

Sourcetype Tezos_error_monad.Error_monad.error +=
  1. | Missing_stored_data of string

This error is returned when the requested data is not found.

Sourceval make_file : ?json:bool -> filepath:string -> 'a Data_encoding.t -> 'a eq -> 'a file

make_file ?(json=false) ~filepath encoding represents a file located at filepath. The content of this value is encoded using encoding. By default, the content is encoded in binary content except if json=true. eq is used internally to test whether the contents of the file should be updated when calling write or update_with.

Warning It is the caller responsability to ensure that the base directory of the filepath exists; otherwise, reading and writing will fail.

Sourceval get : 'a t -> 'a Lwt.t

get data accesses the data (cached).

Sourceval write : 'a t -> 'a -> unit Tezos_error_monad.Error_monad.tzresult Lwt.t

write data value overwrites the previous data with the new value. The cache is only updated if the write succeeds. If the write fails, it is up to the user to retry.

Sourceval write_file : 'a file -> 'a -> unit Tezos_error_monad.Error_monad.tzresult Lwt.t

write_file encoded_file value raw writes the encoded_file with the value.

Warning this function should not be used in a normal context as it aims to overwrite the target without avoiding data races. Favour the usage of write.

Sourceval update_with : 'a t -> ('a -> 'a Lwt.t) -> unit Tezos_error_monad.Error_monad.tzresult Lwt.t

update_with data f atomically updates data with the result of the application of f. Concurrent accesses to the data will block until the value is updated.

The cache is only updated if the write succeeds. If the write fails, it is up to the user to retry.

Warning Calling read/write in f will result in a deadlock.

load encoded_file loads and decode a data from an encoded_file.

Sourceval init : 'a file -> initial_data:'a -> 'a t Tezos_error_monad.Error_monad.tzresult Lwt.t

init encoded_file eq ~initial_data creates or load an on-disk data. If the file already exists, then the data is read from the file. Otherwise, initial_data is used.

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