package tezos-protocol-011-PtHangz2

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Tree provides immutable, in-memory partial mirror of the context, with lazy reads and delayed writes. The trees are Merkle trees that carry the same hash as the part of the context they mirror.

Trees are immutable and non-persistent (they disappear if the host crash), held in memory for efficiency, where reads are done lazily and writes are done only when needed, e.g. on Context.commit. If a key is modified twice, only the last value will be written to disk on commit.

type t

The type for context views.

type tree

The type for context trees.

include VIEW with type t := tree and type tree := tree
type key = string list

The type for context keys.

type value = bytes

The type for context values.

Getters

val mem : tree -> key -> bool Lwt.t

mem t k is an Lwt promise that resolves to true iff k is bound to a value in t.

val mem_tree : tree -> key -> bool Lwt.t

mem_tree t k is like mem but for trees.

val get : tree -> key -> (value, Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.error Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.trace) result Lwt.t

get t k is an Lwt promise that resolves to Ok v if k is bound to the value v in t and Storage_ErrorMissing_key otherwise.

val get_tree : tree -> key -> (tree, Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.error Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.trace) result Lwt.t

get_tree is like get but for trees.

val find : tree -> key -> value option Lwt.t

find t k is an Lwt promise that resolves to Some v if k is bound to the value v in t and None otherwise.

val find_tree : tree -> key -> tree option Lwt.t

find_tree t k is like find but for trees.

val list : tree -> ?offset:int -> ?length:int -> key -> (string * tree) list Lwt.t

list t key is the list of files and sub-nodes stored under k in t. The result order is not specified but is stable.

offset and length are used for pagination.

Setters

val init : tree -> key -> value -> (tree, Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.error Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.trace) result Lwt.t

init t k v is an Lwt promise that resolves to Ok c if:

  • k is unbound in t;
  • k is bound to v in c;
  • and c is similar to t otherwise.

It is Storage_errorExisting_key if k is already bound in t.

val init_tree : tree -> key -> tree -> (tree, Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.error Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.trace) result Lwt.t

init_tree is like init but for trees.

val update : tree -> key -> value -> (tree, Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.error Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.trace) result Lwt.t

update t k v is an Lwt promise that resolves to Ok c if:

  • k is bound in t;
  • k is bound to v in c;
  • and c is similar to t otherwise.

It is Storage_errorMissing_key if k is not already bound in t.

val update_tree : tree -> key -> tree -> (tree, Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.error Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.trace) result Lwt.t

update_tree is like update but for trees.

val add : tree -> key -> value -> tree Lwt.t

add t k v is an Lwt promise that resolves to c such that:

  • k is bound to v in c;
  • and c is similar to t otherwise.

If k was already bound in t to a value that is physically equal to v, the result of the function is a promise that resolves to t. Otherwise, the previous binding of k in t disappears.

val add_tree : tree -> key -> tree -> tree Lwt.t

add_tree is like add but for trees.

val remove : tree -> key -> tree Lwt.t

remove t k v is an Lwt promise that resolves to c such that:

  • k is unbound in c;
  • and c is similar to t otherwise.
val remove_existing : tree -> key -> (tree, Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.error Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.trace) result Lwt.t

remove_existing t k v is an Lwt promise that resolves to Ok c if:

  • k is bound in t to a value;
  • k is unbound in c;
  • and c is similar to t otherwise.
val remove_existing_tree : tree -> key -> (tree, Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.error Tezos_protocol_environment_011_PtHangz2__Environment.Error_monad.trace) result Lwt.t

remove_existing_tree t k v is an Lwt promise that reolves to Ok c if:

  • k is bound in t to a tree;
  • k is unbound in c;
  • and c is similar to t otherwise.
val add_or_remove : tree -> key -> value option -> tree Lwt.t

add_or_remove t k v is:

  • add t k x if v is Some x;
  • remove t k otherwise.
val add_or_remove_tree : tree -> key -> tree option -> tree Lwt.t

add_or_remove_tree t k v is:

  • add_tree t k x if v is Some x;
  • remove t k otherwise.

Folds

val fold : ?depth:[ `Eq of int | `Le of int | `Lt of int | `Ge of int | `Gt of int ] -> tree -> key -> init:'a -> f:(key -> tree -> 'a -> 'a Lwt.t) -> 'a Lwt.t

fold ?depth t root ~init ~f recursively folds over the trees and values of t. The f callbacks are called with a key relative to root. f is never called with an empty key for values; i.e., folding over a value is a no-op.

Elements are traversed in lexical order of keys.

The depth is 0-indexed. If depth is set (by default it is not), then f is only called when the conditions described by the parameter is true:

  • Eq d folds over nodes and contents of depth exactly d.
  • Lt d folds over nodes and contents of depth strictly less than d.
  • Le d folds over nodes and contents of depth less than or equal to d.
  • Gt d folds over nodes and contents of depth strictly more than d.
  • Ge d folds over nodes and contents of depth more than or equal to d.
val empty : t -> tree

empty _ is the empty tree.

val is_empty : tree -> bool

is_empty t is true iff t is empty _.

val kind : tree -> [ `Value | `Tree ]

kind t is t's kind. It's either a tree node or a leaf value.

val to_value : tree -> value option Lwt.t

to_value t is Some v is t is a leaf tree and None otherwise.

hash t is t's Merkle hash.

val equal : tree -> tree -> bool

equal x y is true iff x and y have the same Merkle hash.

Caches

val clear : ?depth:int -> tree -> unit

clear ?depth t clears all caches in the tree t for subtrees with a depth higher than depth. If depth is not set, all of the subtrees are cleared.

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