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
|
/*
* Copyright (C) 2012 Typesafe Inc. <http://www.typesafe.com>
*/
package scala.async
import scala.language.higherKinds
import scala.reflect.macros.Context
/**
* An abstraction over a future system.
*
* Used by the macro implementations in [[scala.async.AsyncBase]] to
* customize the code generation.
*
* The API mirrors that of `scala.concurrent.Future`, see the instance
* [[scala.async.ScalaConcurrentFutureSystem]] for an example of how
* to implement this.
*/
trait FutureSystem {
/** A container to receive the final value of the computation */
type Prom[A]
/** A (potentially in-progress) computation */
type Fut[A]
/** Result of an asynchronous computation */
type Result[A]
/** An execution context, required to create or register an on completion callback on a Future. */
type ExecContext
trait Ops {
val c: reflect.macros.Context
import c.universe._
/** Lookup the execution context, typically with an implicit search */
def execContext: Expr[ExecContext]
def promType[A: WeakTypeTag]: Type
def resultType[A: WeakTypeTag]: Type
def stateMachineType[A: WeakTypeTag]: Type
def execContextType: Type
/** Create an empty promise */
def createProm[A: WeakTypeTag]: Expr[Prom[A]]
/** Extract a future from the given promise. */
def promiseToFuture[A: WeakTypeTag](prom: Expr[Prom[A]]): Expr[Fut[A]]
/** Construct a future to asynchronously compute the given expression */
def future[A: WeakTypeTag](a: Expr[A])(execContext: Expr[ExecContext]): Expr[Fut[A]]
/** Register an call back to run on completion of the given future */
def onComplete[A, U](future: Expr[Fut[A]], fun: Expr[Result[A] => U],
execContext: Expr[ExecContext]): Expr[Unit]
/** Complete a promise with a value */
def completeProm[A: WeakTypeTag](prom: Expr[Prom[A]], value: Expr[A]): Expr[Unit]
/** Complete a promise with an exception */
def completePromWithExceptionTopLevel[A: WeakTypeTag](prom: Expr[Prom[A]], exception: Expr[Throwable]): Expr[Unit]
/** Complete a promise with a failed result */
def completePromWithFailedResult[A: WeakTypeTag](prom: Expr[Prom[A]], resultName: TermName): Expr[Unit]
/** Test if the given result is failed */
def isFailedResult(name: TermName): Expr[Boolean]
/** Result value of a completion */
def resultValue(name: TermName, resultType: Type): Tree
def spawn(tree: Tree): Tree =
future(c.Expr[Unit](tree))(execContext).tree
def castTo[A: WeakTypeTag](future: Expr[Fut[Any]]): Expr[Fut[A]]
}
def mkOps(ctx: Context): Ops { val c: ctx.type }
}
trait TryBasedFutureSystem extends FutureSystem {
type Result[A] = scala.util.Try[A]
trait OpsWithTry extends Ops {
import c.universe._
def resultType[A: WeakTypeTag]: Type = c.weakTypeOf[scala.util.Try[A]]
protected def completePromWithTry[A: WeakTypeTag](prom: Expr[Prom[A]], value: Expr[scala.util.Try[A]]): Expr[Unit]
def completeProm[A: WeakTypeTag](prom: Expr[Prom[A]], value: Expr[A]): Expr[Unit] =
completePromWithTry(prom, reify(scala.util.Success(value.splice)))
def completePromWithExceptionTopLevel[A: WeakTypeTag](prom: Expr[Prom[A]], exception: Expr[Throwable]): Expr[Unit] =
completePromWithTry(prom, reify(scala.util.Failure(exception.splice)))
def completePromWithFailedResult[A: WeakTypeTag](prom: Expr[Prom[A]], resultName: TermName): Expr[Unit] = {
val result = c.Expr[scala.util.Try[A]](
TypeApply(Select(Ident(resultName), newTermName("asInstanceOf")),
List(TypeTree(weakTypeOf[scala.util.Try[A]]))))
completePromWithTry(prom, result)
}
/** `methodSym( (_: Foo).bar(null: A, null: B)` will return the symbol of `bar`, after overload resolution. */
private def methodSym(apply: c.Expr[Any]): Symbol = {
val tree2: Tree = c.typeCheck(apply.tree)
tree2.collect {
case s: SymTree if s.symbol.isMethod => s.symbol
}.headOption.getOrElse(sys.error(s"Unable to find a method symbol in ${apply.tree}"))
}
lazy val Try_isFailure = methodSym(reify((null: scala.util.Try[Any]).isFailure))
lazy val Try_get = methodSym(reify((null: scala.util.Try[Any]).get))
def isFailedResult(name: TermName): Expr[Boolean] =
c.Expr[Boolean](Select(Ident(name), Try_isFailure))
def resultValue(name: TermName, resultType: Type): Tree =
TypeApply(Select(Select(Ident(name), Try_get), newTermName("asInstanceOf")), List(TypeTree(resultType)))
}
}
object ScalaConcurrentFutureSystem extends TryBasedFutureSystem {
import scala.concurrent._
type Prom[A] = Promise[A]
type Fut[A] = Future[A]
type ExecContext = ExecutionContext
def mkOps(ctx: Context): Ops { val c: ctx.type } = new OpsWithTry {
val c: ctx.type = ctx
import c.universe._
def execContext: Expr[ExecContext] = c.Expr(c.inferImplicitValue(c.weakTypeOf[ExecutionContext]) match {
case EmptyTree => c.abort(c.macroApplication.pos, "Unable to resolve implicit ExecutionContext")
case context => context
})
def promType[A: WeakTypeTag]: Type = c.weakTypeOf[Promise[A]]
def stateMachineType[A: WeakTypeTag]: Type = c.weakTypeOf[scala.async.StateMachine[Promise[A], ExecutionContext]]
def execContextType: Type = c.weakTypeOf[ExecutionContext]
def createProm[A: WeakTypeTag]: Expr[Prom[A]] = reify {
Promise[A]()
}
def promiseToFuture[A: WeakTypeTag](prom: Expr[Prom[A]]) = reify {
prom.splice.future
}
def future[A: WeakTypeTag](a: Expr[A])(execContext: Expr[ExecContext]) = reify {
Future(a.splice)(execContext.splice)
}
def onComplete[A, U](future: Expr[Fut[A]], fun: Expr[scala.util.Try[A] => U],
execContext: Expr[ExecContext]): Expr[Unit] = reify {
future.splice.onComplete(fun.splice)(execContext.splice)
}
protected def completePromWithTry[A: WeakTypeTag](prom: Expr[Prom[A]], value: Expr[scala.util.Try[A]]): Expr[Unit] = reify {
prom.splice.complete(value.splice)
c.literalUnit.splice
}
def castTo[A: WeakTypeTag](future: Expr[Fut[Any]]): Expr[Fut[A]] = reify {
future.splice.asInstanceOf[Fut[A]]
}
}
}
/**
* A trivial implementation of [[scala.async.FutureSystem]] that performs computations
* on the current thread. Useful for testing.
*/
object IdentityFutureSystem extends TryBasedFutureSystem {
class Prom[A](var a: A)
type Fut[A] = A
type ExecContext = Unit
def mkOps(ctx: Context): Ops { val c: ctx.type } = new OpsWithTry {
val c: ctx.type = ctx
import c.universe._
def execContext: Expr[ExecContext] = c.literalUnit
def promType[A: WeakTypeTag]: Type = c.weakTypeOf[Prom[A]]
def stateMachineType[A: WeakTypeTag]: Type = c.weakTypeOf[scala.async.StateMachine[Prom[A], ExecContext]]
def execContextType: Type = c.weakTypeOf[Unit]
def createProm[A: WeakTypeTag]: Expr[Prom[A]] = reify {
new Prom(null.asInstanceOf[A])
}
def promiseToFuture[A: WeakTypeTag](prom: Expr[Prom[A]]) = reify {
prom.splice.a
}
def future[A: WeakTypeTag](t: Expr[A])(execContext: Expr[ExecContext]) = t
def onComplete[A, U](future: Expr[Fut[A]], fun: Expr[scala.util.Try[A] => U],
execContext: Expr[ExecContext]): Expr[Unit] = reify {
fun.splice.apply(util.Success(future.splice))
c.literalUnit.splice
}
protected def completePromWithTry[A: WeakTypeTag](prom: Expr[Prom[A]], value: Expr[scala.util.Try[A]]): Expr[Unit] = reify {
prom.splice.a = value.splice.get
c.literalUnit.splice
}
def castTo[A: WeakTypeTag](future: Expr[Fut[Any]]): Expr[Fut[A]] = ???
}
}
|
