57 lines
1.3 KiB
OCaml
57 lines
1.3 KiB
OCaml
(* (c) 2017 Hannes Mehnert, all rights reserved *)
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(* a ring buffer with N strings, dropping old ones *)
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type 'a t = {
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data : (Ptime.t * 'a) array ;
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mutable write : int ;
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size : int ;
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}
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let create ?(size = 1024) neutral () =
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{ data = Array.make 1024 (Ptime.min, neutral) ; write = 0 ; size }
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let inc t = (succ t.write) mod t.size
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let write t entry =
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Array.set t.data t.write entry ;
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t.write <- inc t
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let dec t n = (pred n + t.size) mod t.size
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let written (ts, _) = not (Ptime.equal ts Ptime.min)
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let read t =
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let rec go s acc idx =
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if idx = s then (* don't read it twice *)
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acc
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else
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let entry = Array.get t.data idx in
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if written entry then go s (entry :: acc) (dec t idx)
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else acc
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in
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let idx = dec t t.write in
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let s =
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let entry = Array.get t.data idx in
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if written entry then [entry] else []
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in
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go idx s (dec t idx)
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let earlier ts than =
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if ts = Ptime.min then true
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else Ptime.is_earlier ts ~than
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let read_history t than =
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let rec go s acc idx =
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if idx = s then (* don't read it twice *)
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acc
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else
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let ts, v = Array.get t.data idx in
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if earlier ts than then acc
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else go s ((ts, v) :: acc) (dec t idx)
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in
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let idx = dec t t.write in
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let ts, v = Array.get t.data idx in
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if earlier ts than then []
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else go idx [(ts,v)] (dec t idx)
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