package fat-filesystem

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Module Fat.KV_ROSource

KV_RO is a read-only key=value store backed by a simple FAT filesystem on a block device.

Parameters

module B : Mirage_block.S

Signature

include Mirage_kv.RO

Read-only key-value stores

Sourcetype nonrec error = private [>
  1. | Mirage_kv.error
]

The type for errors.

Sourceval pp_error : error Fmt.t

pp_error is the pretty-printer for errors.

Sourcetype t

The type representing the internal state of the key-value store.

Sourceval disconnect : t -> unit Lwt.t

Disconnect from the key-value store. While this might take some time to complete, it can never result in an error.

The type for keys.

Sourceval exists : t -> key -> ([ `Value | `Dictionary ] option, error) result Lwt.t

exists t k is Some `Value if k is bound to a value in t, Some `Dictionary if k is a prefix of a valid key in t and None if no key with that prefix exists in t.

exists answers two questions: does the key exist and is it referring to a value or a dictionary.

An error occurs when the underlying storage layer fails.

Sourceval get : t -> key -> (string, error) result Lwt.t

get t k is the value bound to k in t.

The result is Error (`Value_expected k) if k refers to a dictionary in t.

Sourceval list : t -> key -> ((string * [ `Value | `Dictionary ]) list, error) result Lwt.t

list t k is the list of entries and their types in the dictionary referenced by k in t.

The result is Error (`Dictionary_expected k) if k refers to a value in t.

Sourceval last_modified : t -> key -> (int * int64, error) result Lwt.t

last_modified t k is the last time the value bound to k in t has been modified.

The modification time (d, ps) is a span for the signed POSIX picosecond span d * 86_400e12 + ps. d is a signed number of POSIX days and ps a number of picoseconds in the range [0;86_399_999_999_999_999L].

When the value bound to k is a dictionary, the modification time is the latest modification of all entries in that dictionary. This behaviour is only one level deep and not recursive.

Sourceval digest : t -> key -> (string, error) result Lwt.t

digest t k is the unique digest of the value bound to k in t.

When the value bound to k is a dictionary, the digest is a unique and deterministic digest of its entries.

Sourceval connect : B.t -> t Lwt.t

connect block creates a key=value store over a FAT filesystem on the block device>