package async_kernel
Monadic concurrency library
Install
Dune Dependency
Authors
Maintainers
Sources
async_kernel-v0.16.0.tar.gz
sha256=0eda59386235e967698834d71cb8924d7b466bc4fcbf26ae72797ad05ca6f8a9
doc/src/async_kernel/ivar0.ml.html
Source file ivar0.ml
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472
open! Core open! Import module Scheduler = Scheduler1 module Cell = Types.Cell type any = [ `Empty | `Empty_one_handler | `Empty_one_or_more_handlers | `Full | `Indir ] type 'a t = 'a Types.Ivar.t = { mutable cell : ('a, any) cell } (* The ['b] is used to encode the constructor. This allows us to write functions that take only one of the constructors, with no runtime test. We maintain the invariant that the directed graph with ivars as nodes and [Indir]s as edges is acyclic. The only functions that create an [Indir] are [squash] and [connect], and for those, the target of the [Indir] is always a non-[Indir]. Thus, the newly added edges are never part of a cycle. *) and ('a, 'b) cell = ('a, 'b) Types.Cell.t = | Empty_one_or_more_handlers : { (* [run] is mutable so we can set it to [ignore] when the handler is removed. This is used when we install a handler on a full ivar since it is immediately added to the scheduler. *) mutable run : 'a -> unit ; execution_context : Execution_context.t ; (* [prev] and [next] circularly doubly link all handlers of the same ivar. *) mutable prev : ('a, [ `Empty_one_or_more_handlers ]) cell ; mutable next : ('a, [ `Empty_one_or_more_handlers ]) cell } -> ('a, [> `Empty_one_or_more_handlers ]) cell | Empty_one_handler : ('a -> unit) * Execution_context.t -> ('a, [> `Empty_one_handler ]) cell | Empty : ('a, [> `Empty ]) cell | Full : 'a -> ('a, [> `Full ]) cell | Indir : 'a t -> ('a, [> `Indir ]) cell module Handler = struct type 'a t = ('a, [ `Empty_one_or_more_handlers ]) cell let run (Empty_one_or_more_handlers t : _ t) = t.run let execution_context (Empty_one_or_more_handlers t : _ t) = t.execution_context let prev (Empty_one_or_more_handlers t : _ t) = t.prev let next (Empty_one_or_more_handlers t : _ t) = t.next let set_run (Empty_one_or_more_handlers t : _ t) x = t.run <- x let set_prev (Empty_one_or_more_handlers t : _ t) x = t.prev <- x let set_next (Empty_one_or_more_handlers t : _ t) x = t.next <- x let create run execution_context = (* An optimized implementation of: {[ let rec t = Empty_one_or_more_handlers { run ; execution_context ; prev = t ; next = t } in h1 ]} However the compilation of recursive value in OCaml is not optimal: the value is allocated twice and copied once (with a loop calling caml_modify). This is not necessary for simple recursive definitions like this one. Instead we allocate the value with dummy fields and update them after. *) let t = Empty_one_or_more_handlers { run; execution_context; prev = Obj.magic None; next = Obj.magic None } in set_prev t t; set_next t t; t ;; let create2 run1 execution_context1 run2 execution_context2 = (* An optimized implementation of: {[ let rec t1 = { run = run1 ; execution_context = execution_context1 ; prev = t2 ; next = t2 } and t2 = { run = run2 ; execution_context = execution_context2 ; prev = t1 ; next = t1 } in t1 ]} *) let t1 = Empty_one_or_more_handlers { run = run1 ; execution_context = execution_context1 ; prev = Obj.magic None ; next = Obj.magic None } in let t2 = Empty_one_or_more_handlers { run = run2; execution_context = execution_context2; prev = t1; next = t1 } in set_prev t1 t2; set_next t1 t2; t1 ;; let invariant t = Execution_context.invariant (execution_context t); let r = ref (next t) in while not (phys_equal !r t) do let t1 = !r in assert (phys_equal (prev (next t1)) t1); Execution_context.invariant (execution_context t1); r := next !r done ;; let is_singleton t = phys_equal t (next t) let length t = let n = ref 1 in let r = ref (next t) in while not (phys_equal !r t) do incr n; r := next !r done; !n ;; let enqueue t scheduler v = Scheduler.enqueue scheduler (execution_context t) (run t) v let schedule_jobs t v = let scheduler = Scheduler.t () in enqueue t scheduler v; let r = ref (next t) in while not (phys_equal !r t) do enqueue !r scheduler v; r := next !r done ;; let unlink t = set_prev (next t) (prev t); set_next (prev t) (next t); set_prev t t; set_next t t ;; let add t run execution_context = let result = Empty_one_or_more_handlers { run; execution_context; prev = prev t; next = t } in set_next (prev t) result; set_prev t result; result ;; (* [splice t1 t2] creates: {v --> t1 <--> ... <--> last1 <--> t2 <--> ... <--> last2 <-- | | ---------------------------------------------------------- v} *) let splice t1 t2 = let last1 = prev t1 in let last2 = prev t2 in set_next last1 t2; set_next last2 t1; set_prev t1 last2; set_prev t2 last1 ;; let of_list l = match l with | [] -> None | (run, execution_context) :: l -> let first = create run execution_context in let rec loop prev l = match l with | [] -> set_prev first prev | (run, execution_context) :: l -> let t = Empty_one_or_more_handlers { run; execution_context; prev; next = first } in set_next prev t; loop t l in loop first l; Some first ;; let to_list first = let rec loop t acc = let acc = (run t, execution_context t) :: acc in if phys_equal t first then acc else loop (prev t) acc in loop (prev first) [] ;; let sexp_of_t _ (t : _ t) = let (Empty_one_or_more_handlers { run = _; execution_context; next = _; prev = _ }) = t in [%message (execution_context : Execution_context.t)] ;; end type 'a ivar = 'a t (* Compiled as the identity. *) let cell_of_handler : _ Handler.t -> _ = function | Empty_one_or_more_handlers _ as x -> (x :> (_, any) cell) ;; let equal (t : _ t) t' = phys_equal t t' let indir t = { cell = Indir t } include Scheduler.Ivar (* [squash t] returns the non-[Indir] ivar at the end of the (possibly empty) chain of [Indir]s starting with [t] and ensures that all [Indir]s along that chain are replaced with an [Indir] pointing to the end of the chain. *) let squash = let rec follow indir t = (* [indir = Indir t] *) match t.cell with | Indir t' as indir' -> follow indir' t' | _ -> indir in let rec update t indir = match t.cell with | Indir t' -> t.cell <- indir; update t' indir | _ -> t in fun t -> match t.cell with | Indir t' -> (match t'.cell with | Indir t'' as indir -> update t (follow indir t'') | _ -> t' (* nothing to do, since [t] is a chain with a single [Indir] *)) | _ -> t ;; (* nothing to do, since [t] isn't an [Indir]. *) let invariant a_invariant t = let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Full a -> a_invariant a | Empty -> () | Empty_one_handler (_, execution_context) -> Execution_context.invariant execution_context | Empty_one_or_more_handlers _ as handler -> Handler.invariant handler ;; let sexp_of_t sexp_of_a t : Sexp.t = let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Full a -> List [ Atom "Full"; sexp_of_a a ] | Empty | Empty_one_handler _ | Empty_one_or_more_handlers _ -> Atom "Empty" ;; let peek t = let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Full a -> Some a | Empty | Empty_one_handler _ | Empty_one_or_more_handlers _ -> None ;; let value t ~if_empty_then_failwith = let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Full a -> a | Empty | Empty_one_handler _ | Empty_one_or_more_handlers _ -> failwith if_empty_then_failwith ;; let value_exn t = value t ~if_empty_then_failwith:"Ivar.value_exn called on empty ivar" let is_empty t = let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Full _ -> false | Empty | Empty_one_handler _ | Empty_one_or_more_handlers _ -> true ;; let is_full t = not (is_empty t) let fill t v = let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Full _ -> raise_s [%message "Ivar.fill of full ivar" (t : _ t)] | Empty -> t.cell <- Full v | Empty_one_handler (run, execution_context) -> t.cell <- Full v; Scheduler.(enqueue (t ())) execution_context run v | Empty_one_or_more_handlers _ as handler -> t.cell <- Full v; Handler.schedule_jobs handler v ;; let remove_handler t (handler : _ Handler.t) = Handler.set_run handler ignore; let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Empty | Empty_one_handler _ -> (* These are only possible if [handler] was already removed. *) () | Full _ -> (* This is possible if [t] was filled before we try to remove the handler. E.g. [Deferred.choose] will do this. *) () | Empty_one_or_more_handlers _ as cell -> if Handler.is_singleton handler then t.cell <- Empty else ( if phys_equal handler cell then t.cell <- cell_of_handler (Handler.next handler); Handler.unlink handler) ;; let add_handler t run execution_context = let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Empty -> let handler = Handler.create run execution_context in t.cell <- cell_of_handler handler; handler | Empty_one_handler (run', execution_context') -> let handler = Handler.create2 run execution_context run' execution_context' in t.cell <- cell_of_handler handler; handler | Empty_one_or_more_handlers _ as handler -> Handler.add handler run execution_context | Full v -> let handler = Handler.create run execution_context in (* [run] calls [handler.run], which, if [handler] has been removed, has been changed to [ignore]. *) let run v = Handler.run handler v in Scheduler.(enqueue (t ())) execution_context run v; handler ;; let has_handlers t = let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Empty_one_handler _ | Empty_one_or_more_handlers _ -> true | Empty | Full _ -> false ;; let upon' t run = add_handler t run Scheduler.(current_execution_context (t ())) (* [upon] is conceptually the same as: {[ let upon t f = ignore (upon' t run) ]} However, below is a more efficient implementation, which is worth doing because [upon] is very widely used and is so much more common than [upon']. The below implementation avoids the use of the bag of handlers in the extremely common case of one handler for the deferred. *) let upon t run = let scheduler = Scheduler.t () in let execution_context = Scheduler.current_execution_context scheduler in let t = squash t in match t.cell with | Indir _ -> assert false (* fulfilled by [squash] *) | Full v -> Scheduler.enqueue scheduler execution_context run v | Empty -> t.cell <- Empty_one_handler (run, execution_context) | Empty_one_handler (run', execution_context') -> t.cell <- cell_of_handler (Handler.create2 run execution_context run' execution_context') | Empty_one_or_more_handlers _ as handler -> ignore (Handler.add handler run execution_context : _ Handler.t) ;; (* [connect] takes ivars [bind_result] and [bind_rhs], and makes [bind_rhs] be an [Indir] pointing to the non-indir cell reachable from [bind_result]. On entry to [connect], [bind_result] and [bind_rhs] may be chains, since [bind_rhs] is an arbitrary user-supplied deferred, and [bind_result] is returned to the user prior to being [connect]ed, and may have been converted to an indirection in the case of right-nested binds. The purpose of [connect] is to make tail-recursive bind loops use constant space. E.g.: {[ let rec loop i = if i = 0 then return () else ( let%bind () = after (sec 1.) in loop (i - 1)) ]} [connect] makes intermediate bind results all be [Indir]s pointing at the outermost bind, rather than being a linear-length chain, with each pointing to the previous one. Then, since the program is only holding on to the innermost and outermost binds all the intermediate ones can be garbage collected. [connect] works by squashing its arguments so that the [bind_rhs] always points at the ultimate result. *) let connect = (* [repoint_indirs ~ivar ~indir ~bind_result] repoints to [indir] all the ivars in the chain reachable from [ivar], and returns the non-[Indir] cell at the end of the chain. After repointing, we will merge the handlers in that cell with the handlers in [bind_result], and put the merged set of handlers in [bind_result]. *) let rec repoint_indirs ~ivar ~indir ~bind_result = let cell = ivar.cell in match cell with | Indir ivar' -> ivar.cell <- indir; repoint_indirs ~ivar:ivar' ~indir ~bind_result | Full _ -> cell | Empty | Empty_one_handler _ | Empty_one_or_more_handlers _ -> (* It is possible that [bind_result] and [bind_rhs] are not equal, but their chains of indirs lead to the same non-[Indir] cell, in which case we cannot set that cell to point to itself, because that would introduce a cycle. *) if not (phys_equal ivar bind_result) then ivar.cell <- indir; cell in fun ~bind_result ~bind_rhs -> if not (phys_equal bind_result bind_rhs) then ( let bind_result = squash bind_result in let indir = Indir bind_result in let bind_rhs_contents = repoint_indirs ~ivar:bind_rhs ~indir ~bind_result in (* update [bind_result] with the union of handlers in [bind_result] and [bind_rhs] *) match bind_result.cell, bind_rhs_contents with | Indir _, _ | _, Indir _ -> assert false (* fulfilled by [squash] and [repoint_indirs] *) (* [connect] is only used in bind, whose ivar is only ever exported as a read-only deferred. Thus, [bind_result] must be empty. *) | Full _, _ -> assert false | _, Empty -> () | Empty, _ -> bind_result.cell <- bind_rhs_contents | Empty_one_handler (run, execution_context), Full v -> bind_result.cell <- bind_rhs_contents; Scheduler.(enqueue (t ())) execution_context run v | (Empty_one_or_more_handlers _ as handler), Full v -> bind_result.cell <- bind_rhs_contents; Handler.schedule_jobs handler v | ( Empty_one_handler (run1, execution_context1) , Empty_one_handler (run2, execution_context2) ) -> let handler1 = Handler.create2 run1 execution_context1 run2 execution_context2 in bind_result.cell <- cell_of_handler handler1 | ( (Empty_one_or_more_handlers _ as handler1) , Empty_one_handler (run2, execution_context2) ) -> ignore (Handler.add handler1 run2 execution_context2 : _ Handler.t) | ( Empty_one_handler (run1, execution_context1) , (Empty_one_or_more_handlers _ as handler2) ) -> let handler1 = Handler.add handler2 run1 execution_context1 in bind_result.cell <- cell_of_handler handler1 | ( (Empty_one_or_more_handlers _ as handler1) , (Empty_one_or_more_handlers _ as handler2) ) -> Handler.splice handler1 handler2) ;;
sectionYPositions = computeSectionYPositions($el), 10)"
x-init="setTimeout(() => sectionYPositions = computeSectionYPositions($el), 10)"
>