Unify var tracking between webkit and the proxy.

ppapi/shared_impl/var_tracker.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ppapi/shared_impl/var_tracker.h"
+
+#include <limits>
+
+#include "base/logging.h"
+#include "ppapi/shared_impl/id_assignment.h"
+#include "ppapi/shared_impl/var.h"
+
+namespace ppapi {
+
+VarTracker::VarInfo::VarInfo()
+    : var(),
+      ref_count(0),
+      track_with_no_reference_count(0) {
+}
+
+VarTracker::VarInfo::VarInfo(Var* v, int input_ref_count)
+    : var(v),
+      ref_count(input_ref_count),
+      track_with_no_reference_count(0) {
+}
+
+VarTracker::VarTracker() : last_var_id_(0) {
+}
+
+VarTracker::~VarTracker() {
+}
+
+int32 VarTracker::AddVar(Var* var) {
+  return AddVarInternal(var, true);
+}
+
+Var* VarTracker::GetVar(int32 var_id) const {
+  VarMap::const_iterator result = live_vars_.find(var_id);
+  if (result == live_vars_.end())
+    return NULL;
+  return result->second.var.get();
+}
+
+Var* VarTracker::GetVar(const PP_Var& var) const {
+  if (!IsVarTypeRefcounted(var.type))
+    return NULL;
+  return GetVar(static_cast<int32>(var.value.as_id));
+}
+
+bool VarTracker::AddRefVar(int32 var_id) {
+  DLOG_IF(ERROR, !CheckIdType(var_id, PP_ID_TYPE_VAR))

[dmichael (off chromium), 2011/08/08 22:13:59]

I'm having trouble figuring out where the var type bits actually gets injected
in to the var ID...? At least in the plugin side, I'm not seeing it. In the ID
assignment portion of this class, it looks like a straight increment from the
last ID, and the IDs count from 0.

[brettw, 2011/08/09 17:08:09]

VarTracker::AddVarInternal calls MakeTypedId.

+      << var_id << " is not a PP_Var ID.";
+  VarMap::iterator found = live_vars_.find(var_id);
+  if (found == live_vars_.end()) {
+    NOTREACHED();  // Invalid var.
+    return false;
+  }
+
+  VarInfo& info = found->second;
+  if (info.ref_count == 0) {
+    // All live vars with no refcount should be tracked objects.
+    DCHECK(info.track_with_no_reference_count > 0);
+    DCHECK(info.var->GetType() == PP_VARTYPE_OBJECT);
+
+    TrackedObjectGettingOneRef(found);
+  }
+
+  // Basic refcount increment.
+  info.ref_count++;
+  return true;
+}
+
+bool VarTracker::AddRefVar(const PP_Var& var) {
+  if (!IsVarTypeRefcounted(var.type))
+    return false;
+  return AddRefVar(static_cast<int32>(var.value.as_id));
+}
+
+bool VarTracker::ReleaseVar(int32 var_id) {
+  DLOG_IF(ERROR, !CheckIdType(var_id, PP_ID_TYPE_VAR))
+      << var_id << " is not a PP_Var ID.";
+  VarMap::iterator found = live_vars_.find(var_id);
+  if (found == live_vars_.end()) {
+    NOTREACHED() << "Unref-ing an invalid var";
+    return false;
+  }
+
+  VarInfo& info = found->second;
+  if (info.ref_count == 0) {
+    NOTREACHED() << "Releasing an object with zero ref";
+    return false;
+  }
+  info.ref_count--;
+
+  if (info.ref_count == 0) {
+    if (info.var->GetType() == PP_VARTYPE_OBJECT) {
+      // Objects have special requirements and may not necessarily be released
+      // when the refcount goes to 0.
+      ObjectGettingZeroRef(found);
+    } else {
+      // All other var types can just be released.
+      DCHECK(info.track_with_no_reference_count == 0);
+      live_vars_.erase(found);
+    }
+  }
+  return true;
+}
+
+bool VarTracker::ReleaseVar(const PP_Var& var) {
+  if (!IsVarTypeRefcounted(var.type))
+    return false;
+  return ReleaseVar(static_cast<int32>(var.value.as_id));
+}
+
+int32 VarTracker::AddVarInternal(Var* var, bool take_ref) {
+  // If the plugin manages to create 1B strings...

[dmichael (off chromium), 2011/08/08 22:13:59]

This is splitting hairs, but I think it's more like 500M ;-)
max() = 0111...1 ~= 2B 
max() >> 2 = 0001...1 ~= 500M
Are you using the highest order 2 bits for the type? If so, you maybe should be
using unsigned?

+  if (last_var_id_ == std::numeric_limits<int32>::max() >> kPPIdTypeBits)
+    return 0;
+
+  // Add the resource with plugin use-count 1.

[dmichael (off chromium), 2011/08/08 22:13:59]

Update comment to account for take_ref? Or just remove? It's kind of
self-evident.

+  int32 new_id = MakeTypedId(++last_var_id_, PP_ID_TYPE_VAR);
+  live_vars_.insert(std::make_pair(new_id, VarInfo(var, take_ref ? 1 : 0)));
+
+  return new_id;
+}
+
+VarTracker::VarMap::iterator VarTracker::GetLiveVar(int32 id) {
+  return live_vars_.find(id);
+}
+
+VarTracker::VarMap::iterator VarTracker::GetLiveVar(const PP_Var& var) {
+  return live_vars_.find(static_cast<int32>(var.value.as_id));
+}
+
+VarTracker::VarMap::const_iterator VarTracker::GetLiveVar(
+    const PP_Var& var) const {
+  return live_vars_.find(static_cast<int32>(var.value.as_id));
+}
+
+bool VarTracker::IsVarTypeRefcounted(PP_VarType type) const {
+  return type == PP_VARTYPE_STRING || type == PP_VARTYPE_OBJECT;
+}
+
+void VarTracker::TrackedObjectGettingOneRef(VarMap::const_iterator obj) {
+  // Anybody using tracked objects should override this.
+  NOTREACHED();
+}
+
+void VarTracker::ObjectGettingZeroRef(VarMap::iterator iter) {
+  DeleteObjectInfoIfNecessary(iter);
+}
+
+bool VarTracker::DeleteObjectInfoIfNecessary(VarMap::iterator iter) {
+  if (iter->second.ref_count != 0 ||
+      iter->second.track_with_no_reference_count != 0)
+    return false;  // Object still alive.
+  live_vars_.erase(iter);
+  return true;
+}
+
+}  // namespace ppapi