Add ability to retrieve a thread_name given a thread_id.

base/threading/thread_id_name_manager.cc

Index: base/threading/thread_id_name_manager.cc
diff --git a/base/threading/thread_id_name_manager.cc b/base/threading/thread_id_name_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8b55af4229f526a980cc5c0e0971ca10c7018fa6
--- /dev/null
+++ b/base/threading/thread_id_name_manager.cc
@@ -0,0 +1,64 @@
+// Copyright (c) 2012 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 "base/threading/thread_id_name_manager.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "base/logging.h"
+#include "base/memory/singleton.h"
+
+namespace base {
+
+ThreadIdNameManager::ThreadIdNameManager()
+    : current_version_(1) {
+}
+
+ThreadIdNameManager::~ThreadIdNameManager() {
+}
+
+ThreadIdNameManager* ThreadIdNameManager::GetInstance() {
+  return Singleton<ThreadIdNameManager,
+      LeakySingletonTraits<ThreadIdNameManager> >::get();
+}
+
+const char* ThreadIdNameManager::GetNameForId(PlatformThreadId id) {
+  base::AutoLock locked(lock_);
+  DCHECK(id_to_name_.count(id));
+  return id_to_name_[id];
+}
+
+void ThreadIdNameManager::SetNameForId(PlatformThreadId id, const char* name) {
+  base::AutoLock locked(lock_);
+  if (id_to_name_.count(id))
+    free(id_to_name_[id]);
+
+  id_to_name_[id] = strdup(name);

[jar (doing other things), 2012/12/21 00:17:00]

It is always good form to do as little work inside a lock as possible.  Hence
better would be:
a) strdup the argument
b) get lock
c) extract current name if any, into a temp variable.
d) set current name to the result of (a)
e) release lock
f) free result of (c).

[dsinclair, 2012/12/21 16:28:59]

Done.

+  id_to_version_[id] = current_version_++;
+}
+
+void ThreadIdNameManager::RemoveNameForId(PlatformThreadId id) {
+  if (id == base::kInvalidThreadId)
+    return;
+
+  base::AutoLock locked(lock_);
+  DCHECK(id_to_name_.count(id));
+
+  char* old_name = id_to_name_[id];
+  id_to_name_.erase(id);
+  id_to_version_.erase(id);
+  free(old_name);

[jar (doing other things), 2012/12/21 00:17:00]

Here again, you can do the free after you release the lock

[dsinclair, 2012/12/21 16:28:59]

Done.

+}
+
+uint32 ThreadIdNameManager::GetVersionForId(PlatformThreadId id) {
+  if (id == base::kInvalidThreadId)
+    return 0;
+
+  base::AutoLock locked(lock_);
+  DCHECK(id_to_version_.count(id));
+  return id_to_version_[id];
+}
+
+}  // namespace base