make Fiber#transfer compatible with CRuby

include/mruby.h

@@ -72,6 +72,7 @@ enum mrb_fiber_state {
   MRB_FIBER_RUNNING,
   MRB_FIBER_RESUMING,
   MRB_FIBER_SUSPENDED,
+  MRB_FIBER_TRANSFERRED,
   MRB_FIBER_TERMINATED,
 };
 

mrbgems/mruby-fiber/src/fiber.c

@@ -136,27 +136,10 @@ fiber_result(mrb_state *mrb, mrb_value *a, int len)
 /* mark return from context modifying method */
 #define MARK_CONTEXT_MODIFY(c) (c)->ci->target_class = NULL
 
-/*
- *  call-seq:
- *     fiber.resume(args, ...) -> obj
- *
- *  Resumes the fiber from the point at which the last <code>Fiber.yield</code>
- *  was called, or starts running it if it is the first call to
- *  <code>resume</code>. Arguments passed to resume will be the value of
- *  the <code>Fiber.yield</code> expression or will be passed as block
- *  parameters to the fiber's block if this is the first <code>resume</code>.
- *
- *  Alternatively, when resume is called it evaluates to the arguments passed
- *  to the next <code>Fiber.yield</code> statement inside the fiber's block
- *  or to the block value if it runs to completion without any
- *  <code>Fiber.yield</code>
- */
 static mrb_value
-fiber_resume(mrb_state *mrb, mrb_value self)
+fiber_switch(mrb_state *mrb, mrb_value self, int len, const mrb_value *a, mrb_bool resume)
 {
   struct mrb_context *c = fiber_check(mrb, self);
-  mrb_value *a;
-  int len;
   mrb_callinfo *ci;
 
   for (ci = c->ci; ci >= c->cibase; ci--) {
@@ -164,6 +147,9 @@ fiber_resume(mrb_state *mrb, mrb_value self)
       mrb_raise(mrb, E_FIBER_ERROR, "can't cross C function boundary");
     }
   }
+  if (resume && c->status == MRB_FIBER_TRANSFERRED) {
+    mrb_raise(mrb, E_FIBER_ERROR, "resuming transfered fiber");
+  }
   if (c->status == MRB_FIBER_RUNNING || c->status == MRB_FIBER_RESUMING) {
     mrb_raise(mrb, E_FIBER_ERROR, "double resume");
   }
@@ -171,7 +157,8 @@ fiber_resume(mrb_state *mrb, mrb_value self)
     mrb_raise(mrb, E_FIBER_ERROR, "resuming dead fiber");
   }
   mrb_get_args(mrb, "*", &a, &len);
-  mrb->c->status = MRB_FIBER_RESUMING;
+  mrb->c->status = resume ? MRB_FIBER_RESUMING : MRB_FIBER_TRANSFERRED;
+  c->prev = resume ? mrb->c : (c->prev ? c->prev : mrb->root_c);
   if (c->status == MRB_FIBER_CREATED) {
     mrb_value *b = c->stack+1;
     mrb_value *e = b + len;
@@ -180,7 +167,6 @@ fiber_resume(mrb_state *mrb, mrb_value self)
       *b++ = *a++;
     }
     c->cibase->argc = len;
-    c->prev = mrb->c;
     if (c->prev->fib) 
       mrb_field_write_barrier(mrb, (struct RBasic*)c->fib, (struct RBasic*)c->prev->fib);
     mrb_write_barrier(mrb, (struct RBasic*)c->fib);
@@ -191,7 +177,6 @@ fiber_resume(mrb_state *mrb, mrb_value self)
     return c->ci->proc->env->stack[0];
   }
   MARK_CONTEXT_MODIFY(c);
-  c->prev = mrb->c;
   if (c->prev->fib) 
     mrb_field_write_barrier(mrb, (struct RBasic*)c->fib, (struct RBasic*)c->prev->fib);
   mrb_write_barrier(mrb, (struct RBasic*)c->fib);
@@ -200,6 +185,30 @@ fiber_resume(mrb_state *mrb, mrb_value self)
   return fiber_result(mrb, a, len);
 }
 
+/*
+ *  call-seq:
+ *     fiber.resume(args, ...) -> obj
+ *
+ *  Resumes the fiber from the point at which the last <code>Fiber.yield</code>
+ *  was called, or starts running it if it is the first call to
+ *  <code>resume</code>. Arguments passed to resume will be the value of
+ *  the <code>Fiber.yield</code> expression or will be passed as block
+ *  parameters to the fiber's block if this is the first <code>resume</code>.
+ *
+ *  Alternatively, when resume is called it evaluates to the arguments passed
+ *  to the next <code>Fiber.yield</code> statement inside the fiber's block
+ *  or to the block value if it runs to completion without any
+ *  <code>Fiber.yield</code>
+ */
+static mrb_value
+fiber_resume(mrb_state *mrb, mrb_value self)
+{
+  mrb_value *a;
+  int len;
+  mrb_get_args(mrb, "*", &a, &len);
+  return fiber_switch(mrb, self, len, a, TRUE);
+}
+
 /*
  *  call-seq:
  *     fiber.alive? -> true or false
@@ -229,14 +238,25 @@ fiber_eq(mrb_state *mrb, mrb_value self)
 static mrb_value
 fiber_transfer(mrb_state *mrb, mrb_value self)
 {
-  mrb_value result = fiber_resume(mrb, self);
+  struct mrb_context *c = fiber_check(mrb, self);
+  mrb_value* a;
+  int len;
+
+  mrb_get_args(mrb, "*", &a, &len);
 
-  mrb_assert(mrb->c->prev);
-  mrb_assert(mrb->c->prev->prev);
-  mrb->c->prev->status = MRB_FIBER_SUSPENDED;
-  mrb->c->prev = mrb->c->prev->prev;
+  if (c == mrb->root_c) {
+    mrb->c->status = MRB_FIBER_TRANSFERRED;
+    mrb->c = c;
+    c->status = MRB_FIBER_RUNNING;
+    MARK_CONTEXT_MODIFY(c);
+    return fiber_result(mrb, a, len);
+  }
+
+  if (c == mrb->c) {
+    return fiber_result(mrb, a, len);
+  }
 
-  return result;
+  return fiber_switch(mrb, self, len, a, FALSE);
 }
 
 mrb_value

mrbgems/mruby-fiber/test/fiber.rb

@@ -9,22 +9,24 @@ assert('Fiber#resume') {
 }
 
 assert('Fiber#transfer') do
+  f2 = nil
   f1 = Fiber.new do |v|
-    assert_raise(FiberError) { Fiber.current.transfer }
     Fiber.yield v
+    f2.transfer
   end
   f2 = Fiber.new do
+    f1.transfer(1)
     f1.transfer(1)
     Fiber.yield 2
   end
   assert_equal 1, f2.resume
-  assert_equal 2, f2.resume
-  f1.resume
+  assert_raise(FiberError) { f2.resume }
+  assert_equal 2, f2.transfer
+  assert_raise(FiberError) { f1.resume }
+  f1.transfer
   f2.resume
   assert_false f1.alive?
   assert_false f2.alive?
-
-  assert_raise(FiberError) { Fiber.current.transfer }
 end
 
 assert('Fiber#alive?') {
@@ -133,3 +135,74 @@ end
 assert('Fiber without block') do
   assert_raise(ArgumentError) { Fiber.new }
 end
+
+
+assert('Transfer to self.') do
+  result = []
+  f = Fiber.new { result << :start; f.transfer; result << :end  }
+  f.transfer
+  assert_equal [:start, :end], result
+
+  result = []
+  f = Fiber.new { result << :start; f.transfer; result << :end  }
+  f.resume
+  assert_equal [:start, :end], result
+end
+
+assert('Resume transferred fiber') do
+  f = Fiber.new {
+    assert_raise(FiberError) { f.resume }
+  }
+  f.transfer
+end
+
+assert('Root fiber transfer.') do
+  result = nil
+  root = Fiber.current
+  f = Fiber.new {
+    result = :ok
+    root.transfer
+  }
+  f.resume
+  assert_true f.alive?
+  assert_equal :ok, result
+end
+
+assert('Break nested fiber with root fiber transfer') do
+  root = Fiber.current
+
+  result = nil
+  f2 = nil
+  f1 = Fiber.new {
+    Fiber.yield f2.resume
+    result = :f1
+  }
+  f2 = Fiber.new {
+    result = :to_root
+    root.transfer :from_f2
+    result = :f2
+  }
+  assert_equal :from_f2, f1.resume
+  assert_equal :to_root, result
+  assert_equal :f2, f2.transfer
+  assert_equal :f2, result
+  assert_false f2.alive?
+  assert_equal :f1, f1.resume
+  assert_equal :f1, result
+  assert_false f1.alive?
+end
+
+assert('CRuby Fiber#transfer test.') do
+  ary = []
+  f2 = nil
+  f1 = Fiber.new{
+    ary << f2.transfer(:foo)
+    :ok
+  }
+  f2 = Fiber.new{
+    ary << f1.transfer(:baz)
+    :ng
+  }
+  assert_equal :ok, f1.transfer
+  assert_equal [:baz], ary
+end