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|
```ocaml
# #require "eio";;
# #mod_use "dscheck/fake_sched.ml";;
module Fake_sched :
sig
val cancel : Eio.Cancel.t -> unit
val run : (unit -> unit) -> Eio.Cancel.t option
end
```
```ocaml
module T = Eio__Sync
module Fiber_context = Eio.Private.Fiber_context
let show t = Fmt.pr "%a@." T.dump t
let put t v =
Fake_sched.run
(fun () ->
match T.put t v with
| () -> Fmt.pr "Sent %s@." v
| exception (Eio.Cancel.Cancelled _) -> Fmt.pr "Send of %s was cancelled@." v
| exception (Invalid_argument msg) -> Fmt.pr "Error adding %s: %s@." v msg
)
|> Option.map (fun ctx ->
Fmt.pr "Waiting for a consumer for %s@." v;
ctx
)
let take t label =
Fake_sched.run
(fun () ->
match T.take t with
| Error `Closed -> Fmt.pr "%s: Stream was closed@." label
| Ok v -> Fmt.pr "%s: Took %s@." label v
| exception (Eio.Cancel.Cancelled _) -> Fmt.pr "%s: Take cancelled@." label
)
|> Option.map (fun ctx ->
Fmt.pr "%s: Waiting for producer@." label;
ctx
)
```
Initially there are no consumers or producers:
```ocaml
# let t : string T.t = T.create ();;
val t : string T.t = <abstr>
# show t;;
Sync (balance=0)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
- : unit = ()
```
Adding one consumer makes the balance go negative:
```ocaml
# take t "cons1";;
cons1: Waiting for producer
- : Eio.Cancel.t option = Some <abstr>
# show t;;
Sync (balance=-1)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Slot (resume)
In_transition (suspend)
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
- : unit = ()
```
Sending a value wakes it:
```ocaml
# put t "A";;
cons1: Took A
Sent A
- : Eio.Cancel.t option = None
# show t;;
Sync (balance=0)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Finished
In_transition (suspend) (resume)
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
- : unit = ()
```
Trying to send a second value waits on the producers queue, setting the balance to 1:
```ocaml
# put t "B";;
Waiting for a consumer for B
- : Eio.Cancel.t option = Some <abstr>
# show t;;
Sync (balance=1)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Finished
In_transition (suspend) (resume)
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Item (resume)
In_transition (suspend)
In_transition
In_transition
End
- : unit = ()
```
Sending a third value must also wait:
```ocaml
# put t "C";;
Waiting for a consumer for C
- : Eio.Cancel.t option = Some <abstr>
# show t;;
Sync (balance=2)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Finished
In_transition (suspend) (resume)
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Item (resume)
Item
In_transition (suspend)
In_transition
End
- : unit = ()
```
The next consumer reads the first value and wakes the first producer:
```ocaml
# take t "cons2";;
Sent B
cons2: Took B
- : Eio.Cancel.t option = None
# show t;;
Sync (balance=1)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Finished
In_transition (suspend) (resume)
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Finished
Item (resume)
In_transition (suspend)
In_transition
End
- : unit = ()
```
Finally, we collect the last value:
```ocaml
# take t "cons3";;
Sent C
cons3: Took C
- : Eio.Cancel.t option = None
```
## Cancellation
Cancelling a consumer restores the balance:
```ocaml
# let t : string T.t = T.create ();;
val t : string T.t = <abstr>
# let request = take t "cons1" |> Option.get;;
cons1: Waiting for producer
val request : Eio.Cancel.t = <abstr>
# show t;;
Sync (balance=-1)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Slot (resume)
In_transition (suspend)
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
- : unit = ()
```
```ocaml
# Fake_sched.cancel request;;
cons1: Take cancelled
- : unit = ()
# show t;;
Sync (balance=0)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=1):
Finished (resume)
In_transition (suspend)
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
- : unit = ()
```
Cancelling a producer restores the balance count:
```ocaml
# let t : string T.t = T.create ();;
val t : string T.t = <abstr>
# let a = put t "A" |> Option.get;;
Waiting for a consumer for A
val a : Eio.Cancel.t = <abstr>
# put t "B" |> Option.get;;
Waiting for a consumer for B
- : Eio.Cancel.t = <abstr>
# show t;;
Sync (balance=2)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Item (resume)
Item
In_transition (suspend)
In_transition
End
- : unit = ()
# Fake_sched.cancel a;;
Send of A was cancelled
- : unit = ()
# show t;;
Sync (balance=1)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=1):
Finished (resume)
Item
In_transition (suspend)
In_transition
End
- : unit = ()
```
The next consumer sees the second value:
```ocaml
# take t "cons4";;
Sent B
cons4: Took B
- : Eio.Cancel.t option = None
# show t;;
Sync (balance=0)
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=1):
Finished
Finished
In_transition (suspend) (resume)
In_transition
End
- : unit = ()
```
## Closing
Closing cancels any waiting producers:
```ocaml
# let t : string T.t = T.create ();;
val t : string T.t = <abstr>
# put t "A" |> Option.get;;
Waiting for a consumer for A
- : Eio.Cancel.t = <abstr>
# T.close t;;
Error adding A: Stream closed
- : unit = ()
# show t;;
Sync (balance=(closed))
Consumers:
Segment 0 (prev=None, pointers=2, cancelled=0):
In_transition (suspend) (resume)
In_transition
In_transition
In_transition
End
Producers:
Segment 0 (prev=None, pointers=2, cancelled=0):
Finished
In_transition (suspend) (resume)
In_transition
In_transition
End
- : unit = ()
# put t "B";;
Error adding B: Stream closed
- : Eio.Cancel.t option = None
```
Closing cancels any waiting consumers:
```ocaml
# let t : string T.t = T.create ();;
val t : string T.t = <abstr>
# take t "A";;
A: Waiting for producer
- : Eio.Cancel.t option = Some <abstr>
# T.close t;;
A: Stream was closed
- : unit = ()
# take t "B";;
B: Stream was closed
- : Eio.Cancel.t option = None
# T.take_nonblocking t;;
- : (string, [> `Closed | `Would_block ]) result = Error `Closed
```
|
