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feat: implement symmetric coroutines with fiber.call and fiber.run distinction

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Add new `fiber.call` method that remembers the calling fiber for symmetric transfer, while `fiber.run` now performs tail-call style switching without preserving the caller. Introduce re-entrancy guards preventing a fiber from being called multiple times, update all test fixtures to use the new API, and add comprehensive test coverage for call semantics including direct/indirect re-entrancy, value passing, and finished fiber errors.
This commit is contained in:
Bob Nystrom
2014-04-14 14:23:05 +00:00
parent 71783400ae
commit 10b19d969b
31 changed files with 276 additions and 63 deletions
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src/wren_core.c
+71 -17
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@@ -224,18 +224,13 @@ DEF_NATIVE(fiber_new)
RETURN_OBJ(newFiber);
}
DEF_NATIVE(fiber_isDone)
{
ObjFiber* runFiber = AS_FIBER(args[0]);
RETURN_BOOL(runFiber->numFrames == 0);
}
DEF_NATIVE(fiber_run)
DEF_NATIVE(fiber_call)
{
ObjFiber* runFiber = AS_FIBER(args[0]);
if (runFiber->numFrames == 0) RETURN_ERROR("Cannot run a finished fiber.");
if (runFiber->numFrames == 0) RETURN_ERROR("Cannot call a finished fiber.");
if (runFiber->caller != NULL) RETURN_ERROR("Fiber has already been called.");
// Remember who ran it.
runFiber->caller = fiber;
@@ -248,11 +243,12 @@ DEF_NATIVE(fiber_run)
return PRIM_RUN_FIBER;
}
DEF_NATIVE(fiber_run1)
DEF_NATIVE(fiber_call1)
{
ObjFiber* runFiber = AS_FIBER(args[0]);
if (runFiber->numFrames == 0) RETURN_ERROR("Cannot run a finished fiber.");
if (runFiber->numFrames == 0) RETURN_ERROR("Cannot call a finished fiber.");
if (runFiber->caller != NULL) RETURN_ERROR("Fiber has already been called.");
// Remember who ran it.
runFiber->caller = fiber;
@@ -273,15 +269,69 @@ DEF_NATIVE(fiber_run1)
return PRIM_RUN_FIBER;
}
DEF_NATIVE(fiber_isDone)
{
ObjFiber* runFiber = AS_FIBER(args[0]);
RETURN_BOOL(runFiber->numFrames == 0);
}
DEF_NATIVE(fiber_run)
{
ObjFiber* runFiber = AS_FIBER(args[0]);
if (runFiber->numFrames == 0) RETURN_ERROR("Cannot run a finished fiber.");
// If the fiber was yielded, make the yield call return null.
if (runFiber->caller == NULL && runFiber->stackSize > 0)
{
runFiber->stack[runFiber->stackSize - 1] = NULL_VAL;
}
// Unlike run, this does not remember the calling fiber. Instead, it
// remember's *that* fiber's caller. You can think of it like tail call
// elimination. The switched-from fiber is discarded and when the switched
// to fiber completes or yields, control passes to the switched-from fiber's
// caller.
runFiber->caller = fiber->caller;
return PRIM_RUN_FIBER;
}
DEF_NATIVE(fiber_run1)
{
ObjFiber* runFiber = AS_FIBER(args[0]);
if (runFiber->numFrames == 0) RETURN_ERROR("Cannot run a finished fiber.");
// If the fiber was yielded, make the yield call return the value passed to
// run.
if (runFiber->caller == NULL && runFiber->stackSize > 0)
{
runFiber->stack[runFiber->stackSize - 1] = args[1];
}
// Unlike run, this does not remember the calling fiber. Instead, it
// remember's *that* fiber's caller. You can think of it like tail call
// elimination. The switched-from fiber is discarded and when the switched
// to fiber completes or yields, control passes to the switched-from fiber's
// caller.
runFiber->caller = fiber->caller;
return PRIM_RUN_FIBER;
}
DEF_NATIVE(fiber_yield)
{
if (fiber->caller == NULL) RETURN_ERROR("No fiber to yield to.");
ObjFiber* caller = fiber->caller;
fiber->caller = NULL;
// Make the caller's run method return null.
fiber->caller->stack[fiber->caller->stackSize - 1] = NULL_VAL;
caller->stack[caller->stackSize - 1] = NULL_VAL;
// Return the fiber to resume.
args[0] = OBJ_VAL(fiber->caller);
args[0] = OBJ_VAL(caller);
return PRIM_RUN_FIBER;
}
@@ -289,8 +339,11 @@ DEF_NATIVE(fiber_yield1)
{
if (fiber->caller == NULL) RETURN_ERROR("No fiber to yield to.");
ObjFiber* caller = fiber->caller;
fiber->caller = NULL;
// Make the caller's run method return the argument passed to yield.
fiber->caller->stack[fiber->caller->stackSize - 1] = args[1];
caller->stack[caller->stackSize - 1] = args[1];
// When the yielding fiber resumes, we'll store the result of the yield call
// in its stack. Since Fiber.yield(value) has two arguments (the Fiber class
@@ -299,7 +352,7 @@ DEF_NATIVE(fiber_yield1)
fiber->stackSize--;
// Return the fiber to resume.
args[0] = OBJ_VAL(fiber->caller);
args[0] = OBJ_VAL(caller);
return PRIM_RUN_FIBER;
}
@@ -966,16 +1019,17 @@ void wrenInitializeCore(WrenVM* vm)
NATIVE(vm->boolClass, "toString", bool_toString);
NATIVE(vm->boolClass, "!", bool_not);
// TODO: Make fibers inherit Sequence and be iterable.
vm->fiberClass = defineClass(vm, "Fiber");
NATIVE(vm->fiberClass->metaclass, " instantiate", fiber_instantiate);
NATIVE(vm->fiberClass->metaclass, "new ", fiber_new);
NATIVE(vm->fiberClass->metaclass, "yield", fiber_yield);
NATIVE(vm->fiberClass->metaclass, "yield ", fiber_yield1);
NATIVE(vm->fiberClass, "call", fiber_call);
NATIVE(vm->fiberClass, "call ", fiber_call1);
NATIVE(vm->fiberClass, "isDone", fiber_isDone);
NATIVE(vm->fiberClass, "run", fiber_run);
NATIVE(vm->fiberClass, "run ", fiber_run1);
// TODO: Primitives for switching to a fiber without setting the caller.
// (I.e. symmetric coroutines.)
vm->fnClass = defineClass(vm, "Fn");