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Refactor dequeue to return option #51

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Refactor dequeue to return option #51

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24 changes: 12 additions & 12 deletions lib/faraday.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -39,8 +39,6 @@ type 'a iovec =
; off : int
; len : int }

exception Dequeue_empty

module Deque(T:sig type t val sentinel : t end) : sig
type elem = T.t

Expand All @@ -51,7 +49,7 @@ module Deque(T:sig type t val sentinel : t end) : sig
val is_empty : t -> bool

val enqueue : elem -> t -> unit
val dequeue_exn : t -> elem
val dequeue: t -> elem option
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Using options will cause allocation, which is what the use of exceptions was avoiding.

val enqueue_front : elem -> t -> unit

val map_to_list : t -> f:(elem -> 'b) -> 'b list
Expand Down Expand Up @@ -94,14 +92,14 @@ end = struct
t.elements.(t.back) <- e;
t.back <- t.back + 1

let dequeue_exn t =
let dequeue t =
if is_empty t then
raise Dequeue_empty
None
else
let result = Array.unsafe_get t.elements t.front in
Array.unsafe_set t.elements t.front sentinel;
t.front <- t.front + 1;
result
Some(result)

let enqueue_front e t =
(* This is in general not true for Deque data structures, but the usage
Expand Down Expand Up @@ -367,22 +365,24 @@ let yield t =
t.yield <- true

let rec shift_buffers t written =
try
let { len; _ } as iovec = Buffers.dequeue_exn t.scheduled in
match Buffers.dequeue t.scheduled with
Some(elem) ->
let { len; _ } as iovec = elem in
if len <= written then begin
shift_buffers t (written - len)
end else
Buffers.enqueue_front (IOVec.shift iovec written) t.scheduled
with Dequeue_empty ->
| None ->
assert (written = 0);
if t.scheduled_pos = t.write_pos then begin
t.scheduled_pos <- 0;
t.write_pos <- 0
end

let rec shift_flushes t =
try
let (threshold, f) as flush = Flushes.dequeue_exn t.flushed in
match Flushes.dequeue t.flushed with
Some(elem) ->
let (threshold, f) as flush = elem in
(* Edited notes from @dinosaure:
*
* The quantities [t.bytes_written] and [threshold] are always going to be
Expand All @@ -401,7 +401,7 @@ let rec shift_flushes t =
if t.bytes_written - min_int >= threshold - min_int
then begin f (); shift_flushes t end
else Flushes.enqueue_front flush t.flushed
with Dequeue_empty ->
| None ->
()

let shift t written =
Expand Down