9654f72016-04-12Henrik Grubbström (Grubba) //! Module for handling multiple concurrent events.
c60ad22016-04-13Henrik Grubbström (Grubba) /* * Inspired by https://github.com/couchdeveloper/FutureLib */
9654f72016-04-12Henrik Grubbström (Grubba) protected enum State { STATE_PENDING = 0, STATE_FULFILLED, STATE_REJECTED, }; protected Thread.Mutex mux = Thread.Mutex(); protected Thread.Condition cond = Thread.Condition(); //! Value that will be provided asynchronously //! sometime in the future. //! //! @seealso //! @[Promise] class Future { mixed result = UNDEFINED; State state; protected function(mixed:void) success_cb; protected array(mixed) success_ctx; protected function(mixed:void) failure_cb; protected array(mixed) failure_ctx; //! Wait for fullfillment and return the value. //! //! @throws //! Throws on rejection. mixed get() { State s = state; mixed res = result; if (!s) { object key = mux->lock(); while (!state) { cond->wait(key); } s = state; res = result; key = 0; } if (s == STATE_REJECTED) { throw(res); } return res; } //! Register a callback that is to be called on fulfillment. void on_success(function(mixed, mixed ... : void) cb, mixed ... extra) { object key = mux->lock(); success_cb = cb; success_ctx = extra; State s = state; mixed res = result; key = 0; if (s == STATE_FULFILLED) { call_out(cb, 0, res, @extra); } } //! Register a callback that is to be called on failure. void on_failure(function(mixed, mixed ... : void) cb, mixed ... extra) { object key = mux->lock(); failure_cb = cb; failure_ctx = extra; State s = state; mixed res = result; key = 0; if (s == STATE_REJECTED) { call_out(cb, 0, res, @extra); } }
c60ad22016-04-13Henrik Grubbström (Grubba)  //! Apply @[fun] with @[val] followed by the contents of @[ctx], //! and update @[p] with the result. protected void apply(mixed val, Promise p, function(mixed, mixed ... : mixed) fun, array(mixed) ctx) { mixed err = catch { p->success(fun(val, @ctx)); return; }; p->failure(err); } //! Apply @[fun] with @[val] followed by the contents of @[ctx], //! and update @[p] with the eventual result. protected void apply_flat(mixed val, Promise p, function(mixed, mixed ... : Future) fun, array(mixed) ctx) { mixed err = catch { Future f = fun(val, @ctx); if (!objectp(f) || !f->on_failure || !f->on_success) { error("Expected %O to return a Future. Got: %O.\n", fun, f); } f->on_failure(p->failure); f->on_success(p->success); return; }; p->failure(err); } //! Apply @[fun] with @[val] followed by the contents of @[ctx], //! and update @[p] with @[val] if @[fun] didn't return false. //! If @[fun] returned false fail @[p] with @[UNDEFINED]. protected void apply_filter(mixed val, Promise p, function(mixed, mixed ... : int(0..1)) fun, array(mixed) ctx) { mixed err = catch { if (fun(val, @ctx)) { p->success(val); } else { p->failure(UNDEFINED); } return; }; p->failure(err); } //! Return a @[Future] that will be fulfilled with the result //! of applying @[fun] with the fulfilled result of this @[Future] //! followed by @[extra]. this_program map(function(mixed, mixed ... : mixed) fun, mixed ... extra) { Promise p = Promise(); on_failure(p->failure); on_success(apply, p, fun, extra); return p->future(); } //! Return a @[Future] that will be fulfilled with the fulfilled result //! of applying @[fun] with the fulfilled result of this @[Future] //! followed by @[extra]. this_program flat_map(function(mixed, mixed ... : this_program) fun, mixed ... extra) { Promise p = Promise(); on_failure(p->failure); on_success(apply_flat, p, fun, extra); return p->future(); } //! Return a @[Future] that will be fulfilled with either //! the fulfiled result of this @[Future], or the result //! of applying @[fun] with the failed result followed //! by @[extra]. this_program recover(function(mixed, mixed ... : mixed) fun, mixed ... extra) { Promise p = Promise(); on_success(p->success); on_failure(apply, p, fun, extra); return p->future(); } //! Return a @[Future] that will be fulfilled with either //! the fulfiled result of this @[Future], or the fulfilled result //! of applying @[fun] with the failed result followed //! by @[extra]. this_program recover_with(function(mixed, mixed ... : this_program) fun, mixed ... extra) { Promise p = Promise(); on_success(p->success); on_failure(apply_flat, p, fun, extra); return p->future(); } //! Return a @[Future] that either will by fulfilled by the //! fulfilled result of this @[Future] if applying @[fun] //! with the result followed by @[extra] returns true, //! or will fail with @[UNDEFINED] if it returns false. this_program filter(function(mixed, mixed ... : int(0..1)) fun, mixed ... extra) { Promise p = Promise(); on_failure(p->failure); on_success(apply_filter, p, fun, extra); return p->future(); } //! Return a @[Future] that will be fulfilled with either //! the result of applying @[success] with the fulfilled result //! followed by @[extra], or the result of applying @[failure] //! with the failed result followed by @[extra]. //! //! @[failure] defaults to @[success]. //! //! @seealso //! @[map] this_program transform(function(mixed, mixed ... : mixed) success, function(mixed, mixed ... : mixed)|void failure, mixed ... extra) { Promise p = Promise(); on_success(apply, p, success, extra); on_failure(apply, p, failure || success, extra); return p->future(); } //! Return a @[Future] that will be fulfilled with either //! the fulfilled result of applying @[success] with the fulfilled result //! followed by @[extra], or the fulfilled result of applying @[failure] //! with the failed result followed by @[extra]. //! //! @[failure] defaults to @[success]. //! //! @seealso //! @[flat_map] this_program transform_with(function(mixed, mixed ... : Future) success, function(mixed, mixed ... : Future)|void failure, mixed ... extra) { Promise p = Promise(); on_success(apply_flat, p, success, extra); on_failure(apply_flat, p, failure || success, extra); return p->future(); }
9654f72016-04-12Henrik Grubbström (Grubba) } //! Promise to provide a @[Future] value. //!
c60ad22016-04-13Henrik Grubbström (Grubba) //! Objects of this class are typically kept internal to the //! code that provides the @[Future] value. The only thing //! that is directly returned to the user is the return //! value from @[future()]. //!
9654f72016-04-12Henrik Grubbström (Grubba) //! @seealso
c60ad22016-04-13Henrik Grubbström (Grubba) //! @[Future], @[future()]
9654f72016-04-12Henrik Grubbström (Grubba) class Promise { inherit Future; //! The future value that we promise. Future future() { return Future::this; } //! Fulfill the @[Future] value. void success(mixed value) { object key = mux->lock(); if (state < STATE_REJECTED) { result = value; state = STATE_FULFILLED; function cb = success_cb; array(mixed) extra = success_ctx; cond->broadcast(); key = 0; if (cb) { call_out(cb, 0, value, @extra); } } } //! Reject the @[Future] value. void failure(mixed value) { object key = mux->lock(); state = STATE_REJECTED; result = value; function cb = failure_cb; array(mixed) extra = failure_ctx; cond->broadcast(); key = 0; if (cb) { call_out(cb, 0, value, @extra); } } protected void destroy() { if (!state) { failure(({ "Promise broken.\n", backtrace() })); } } }