Persistent store with Git semantics: lazy reads, delayed writes, content-addressing
irmin: add Heap.layer for overlay heaps
Reads fall through from top to bottom; writes and caches go to top.
This is the building block for lazy remote navigation: layer a local
cache over a remote heap so cursors transparently fetch on miss.
+22
-3
+1
-1
lib/dune
+1
-1
lib/dune
+16
lib/heap.ml
+16
lib/heap.ml
···
110
110
close = (fun () -> ());
111
111
to_seq = (fun () -> List.to_seq blocks);
112
112
}
113
+
114
+
let layer top bottom =
115
+
{
116
+
top with
117
+
find =
118
+
(fun h ->
119
+
match top.find h with
120
+
| Some _ as r -> r
121
+
| None -> (
122
+
match bottom.find h with
123
+
| Some data as r ->
124
+
top.put h data;
125
+
r
126
+
| None -> None));
127
+
mem = (fun h -> top.mem h || bottom.mem h);
128
+
}
+5
-2
lib/heap.mli
+5
-2
lib/heap.mli
···
89
89
val of_list : equal:('h -> 'h -> bool) -> ('h * 'v) list -> ('h, 'v, 'b) t
90
90
(** [of_list ~equal blocks] creates a heap backed by [blocks]. *)
91
91
92
+
val layer : ('h, 'v, _) t -> ('h, 'v, _) t -> ('h, 'v, _) t
93
+
(** [layer top bottom] reads from [top] first, then [bottom] on miss. Writes go
94
+
to [top]. Found blocks from [bottom] are cached in [top]. *)
95
+
92
96
val to_seq : ('h, 'v, _) t -> ('h * 'v) Seq.t
93
-
(** [to_seq heap] enumerates the heap's blocks. For proof subheaps (created by
94
-
{!of_list}), returns all blocks. For backend heaps, returns [Seq.empty]. *)
97
+
(** [to_seq heap] enumerates the heap's blocks. *)