- Add different types for persistent and weak persistent handles

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
===================================================================
--- runtime/include/dart_api.h	(revision 23191)
+++ runtime/include/dart_api.h	(working copy)
@@ -176,9 +176,12 @@
  * deallocated (see Dart_DeletePersistentHandle).
  */
 typedef struct _Dart_Handle* Dart_Handle;
+typedef struct _Dart_PersistentHandle* Dart_PersistentHandle;
+typedef struct _Dart_WeakPersistentHandle* Dart_WeakPersistentHandle;
 
-typedef void (*Dart_WeakPersistentHandleFinalizer)(Dart_Handle handle,
-                                                   void* peer);
+typedef void (*Dart_WeakPersistentHandleFinalizer)(
+    Dart_WeakPersistentHandle handle,
+    void* peer);
 typedef void (*Dart_PeerFinalizer)(void* peer);
 
 /**
@@ -361,6 +364,17 @@
 DART_EXPORT bool Dart_IdentityEquals(Dart_Handle obj1, Dart_Handle obj2);
 
 /**
+ * Allocates a handle in the current scope from a persistent handle.
+ */
+DART_EXPORT Dart_Handle Dart_HandleFromPersistent(Dart_PersistentHandle object);
+
+/**
+ * Allocates a handle in the current scope from a weak persistent handle.
+ */
+DART_EXPORT Dart_Handle Dart_HandleFromWeakPersistent(
+    Dart_WeakPersistentHandle object);
+
+/**
  * Allocates a persistent handle for an object.
  *
  * This handle has the lifetime of the current isolate unless it is
@@ -368,14 +382,14 @@
  *
  * Requires there to be a current isolate.
  */
-DART_EXPORT Dart_Handle Dart_NewPersistentHandle(Dart_Handle object);
+DART_EXPORT Dart_PersistentHandle Dart_NewPersistentHandle(Dart_Handle object);
 
 /**
  * Deallocates a persistent handle.
  *
  * Requires there to be a current isolate.
  */
-DART_EXPORT void Dart_DeletePersistentHandle(Dart_Handle object);
+DART_EXPORT void Dart_DeletePersistentHandle(Dart_PersistentHandle object);
 
 /**
  * Allocates a weak persistent handle for an object.
@@ -394,17 +408,12 @@
  * \return Success if the weak persistent handle was
  *   created. Otherwise, returns an error.
  */
-DART_EXPORT Dart_Handle Dart_NewWeakPersistentHandle(
+DART_EXPORT Dart_WeakPersistentHandle Dart_NewWeakPersistentHandle(
     Dart_Handle object,
     void* peer,
     Dart_WeakPersistentHandleFinalizer callback);
 
-/**
- * Is this object a weak persistent handle?
- *
- * Requires there to be a current isolate.
- */
-DART_EXPORT bool Dart_IsWeakPersistentHandle(Dart_Handle object);
+DART_EXPORT void Dart_DeleteWeakPersistentHandle(Dart_WeakPersistentHandle object);
 
 /**
  * Allocates a prologue weak persistent handle for an object.
@@ -432,7 +441,7 @@
  * \return Success if the prologue weak persistent handle was created.
  *   Otherwise, returns an error.
  */
-DART_EXPORT Dart_Handle Dart_NewPrologueWeakPersistentHandle(
+DART_EXPORT Dart_WeakPersistentHandle Dart_NewPrologueWeakPersistentHandle(
     Dart_Handle object,
     void* peer,
     Dart_WeakPersistentHandleFinalizer callback);
@@ -442,7 +451,8 @@
  *
  * Requires there to be a current isolate.
  */
-DART_EXPORT bool Dart_IsPrologueWeakPersistentHandle(Dart_Handle object);
+DART_EXPORT bool Dart_IsPrologueWeakPersistentHandle(
+    Dart_WeakPersistentHandle object);
 
 /**
  * Constructs a set of weak references from the Cartesian product of
@@ -459,10 +469,11 @@
  * \return Success if the weak reference set could be created.
  *   Otherwise, returns an error handle.
  */
-DART_EXPORT Dart_Handle Dart_NewWeakReferenceSet(Dart_Handle* keys,
-                                                 intptr_t num_keys,
-                                                 Dart_Handle* values,
-                                                 intptr_t num_values);
+DART_EXPORT Dart_Handle Dart_NewWeakReferenceSet(
+    Dart_WeakPersistentHandle* keys,

[Anton Muhin, 2013/05/27 15:45:49]

there was one fancy trick in our code which currently not applicable: we need to
render some weak persistent handles as strong for GC.  We did it by creating a
set with strong persistent handle.

I implemented trivial workaround for now: I create a weak persistent handle for
an object held by strong persistent handle, but if we can direct this case in
API directly, that'd be great.

One simple approach would be either add a function or add a special semantics
for references set with empty key sets.

[Ivan Posva, 2013/05/28 21:12:20]

I am not sure I understand your usage of this API function, but to me it sounds
like this:
Occasionally you have a bunch of weak handles, which need to be preserved during
a GC. You used to create one strong persistent handle, use that as the "keys"
and the to-be-preserved weak handles as the values. Do I understand that
correctly?

If that is the case, then I suggest that you create a weak persistent handle
using Dart_True for each of your isolates. Keep this weak persistent handle
around, so that you can pass it as the key. I am not sure, but it sort of sounds
like you are already doing something similar.

[Anton Muhin, 2013/05/29 07:43:13]

Yes, that's exactly what we do: weak persistent handle to always reachable
object.

On 2013/05/28 21:12:20, Ivan Posva wrote:

+    intptr_t num_keys,
+    Dart_WeakPersistentHandle* values,
+    intptr_t num_values);
 
 // --- Garbage Collection Callbacks ---
 
@@ -1766,20 +1777,11 @@
  *   WeakPersistentHandle which needs to be deleted in the specified callback
  *   using Dart_DeletePersistentHandle.
  */
-DART_EXPORT Dart_Handle Dart_NewExternalTypedData(
-    Dart_TypedData_Type type,
-    void* data,
-    intptr_t length,
-    void* peer,
-    Dart_WeakPersistentHandleFinalizer callback);
+DART_EXPORT Dart_Handle Dart_NewExternalTypedData(Dart_TypedData_Type type,
+                                                  void* data,
+                                                  intptr_t length);
 
 /**
- * Retrieves the peer pointer associated with an external TypedData object.
- */
-DART_EXPORT Dart_Handle Dart_ExternalTypedDataGetPeer(Dart_Handle object,

[Anton Muhin, 2013/05/27 15:45:49]

there still should be a way to fetch peer object associated with external typed
data.

For now I use Dart_SetPeer/Dart_GetPeer, but I recall that assumption was they
are not used too much which might be not the case for typed data.

[Ivan Posva, 2013/05/28 21:12:20]

For now, please use Dart_SetPeer and Dart_GetPeer if you need to have access to
a peer value.

-                                                      void** peer);
-
-/**
  * Acquires access to the internal data address of a TypedData object.
  *
  * \param object The typed data object whose internal data address is to