Mojo: Move the handle table details out of CoreImpl into its own class.

mojo/system/handle_table.h

+// Copyright 2014 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.
+
+#ifndef MOJO_SYSTEM_HANDLE_TABLE_H_
+#define MOJO_SYSTEM_HANDLE_TABLE_H_
+
+#include <utility>
+#include <vector>
+
+#include "base/containers/hash_tables.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "mojo/public/c/system/core.h"
+#include "mojo/system/system_impl_export.h"
+
+namespace mojo {
+namespace system {
+
+class CoreImpl;
+class Dispatcher;
+class DispatcherTransport;
+
+// Test-only function (defined/used in embedder/test_embedder.cc). Declared here
+// so it can be friended.
+namespace internal {
+bool ShutdownCheckNoLeaks(CoreImpl*);
+}
+
+// This class provides the (global) handle table (owned by |CoreImpl|), which
+// maps (valid) |MojoHandle|s to |Dispatcher|s. This is abstracted so that,
+// e.g., caching may be added.
+//
+// This class is NOT thread-safe; locking is left to |CoreImpl| (since it may
+// need to make several changes -- "atomically" or in rapid successsion, in
+// which case the extra locking/unlocking would be unnecessary overhead).
+
+class MOJO_SYSTEM_IMPL_EXPORT HandleTable {
+ public:
+  HandleTable();
+  ~HandleTable();
+
+  // Gets the dispatcher for a given handle (which should not be
+  // |MOJO_HANDLE_INVALID|). Returns null if there's no dispatcher for the given
+  // handle.
+  // WARNING: For efficiency, this returns a dumb pointer. If you're going to
+  // use the result outside |CoreImpl|'s lock, you MUST take a reference (e.g.,
+  // by storing the result inside a |scoped_refptr|).
+  Dispatcher* GetDispatcher(MojoHandle handle);
+
+  // On success, gets the dispatcher for a given handle (which should not be
+  // |MOJO_HANDLE_INVALID|) and removes it. (On failure, returns an appropriate
+  // result (and leaves |dispatcher| alone), namely
+  // |MOJO_RESULT_INVALID_ARGUMENT| if there's no dispatcher for the given
+  // handle or |MOJO_RESULT_BUSY| if the handle is marked as busy.)
+  MojoResult GetAndRemoveDispatcher(MojoHandle handle,
+                                    scoped_refptr<Dispatcher>* dispatcher);
+
+  // Adds a dispatcher (which must be valid), returning the handle for it.
+  // Returns |MOJO_HANDLE_INVALID| on failure (if the handle table is full).
+  MojoHandle AddDispatcher(const scoped_refptr<Dispatcher>& dispatcher);
+
+  // Adds a pair of dispatchers (which must be valid), return a pair of handles
+  // for them. On failure (if the handle table is full), the first (and second)
+  // handles will be |MOJO_HANDLE_INVALID|, and neither dispatcher will be
+  // added.
+  std::pair<MojoHandle, MojoHandle> AddDispatcherPair(
+      const scoped_refptr<Dispatcher>& dispatcher0,
+      const scoped_refptr<Dispatcher>& dispatcher1);
+
+  // Adds the given vector of dispatchers (of size at most
+  // |kMaxMessageNumHandles|). |handles| must point to an array of size at least
+  // |dispatchers.size()|. Unlike the other |AddDispatcher...()| functions, some
+  // of the dispatchers may be invalid (null). Returns true on success and false
+  // on failure (if the handle table is full), in which case it leaves
+  // |handles[...]| untouched (and all dispatchers unadded).
+  bool AddDispatcherVector(
+      const std::vector<scoped_refptr<Dispatcher> >& dispatchers,
+      MojoHandle* handles);
+
+  // Tries to mark the given handles as busy and start transport on them (i.e.,
+  // take their dispatcher locks); |transports| must be sized to contain
+  // |num_handles| elements. On failure, returns them to their original
+  // (non-busy, unlocked state).
+  MojoResult MarkBusyAndStartTransport(
+      MojoHandle disallowed_handle,
+      const MojoHandle* handles,
+      uint32_t num_handles,
+      std::vector<DispatcherTransport>* transports);
+
+  // Remove the given handles, which must all be present and which should have
+  // previously been marked busy by |MarkBusyAndStartTransport()|.
+  void RemoveBusyHandles(const MojoHandle* handles, uint32_t num_handles);
+
+  // Restores the given handles, which must all be present and which should have
+  // previously been marked busy by |MarkBusyAndStartTransport()|, to a non-busy
+  // state.
+  void RestoreBusyHandles(const MojoHandle* handles, uint32_t num_handles);
+
+ private:
+  friend bool internal::ShutdownCheckNoLeaks(CoreImpl*);
+
+  struct Entry {
+    Entry();
+    explicit Entry(const scoped_refptr<Dispatcher>& dispatcher);
+    ~Entry();
+
+    scoped_refptr<Dispatcher> dispatcher;
+    bool busy;
+  };
+  typedef base::hash_map<MojoHandle, Entry> HandleToEntryMap;
+
+  // Adds the given dispatcher to the handle table, not doing any size checks.
+  MojoHandle AddDispatcherNoSizeCheck(
+      const scoped_refptr<Dispatcher>& dispatcher);
+
+  HandleToEntryMap handle_to_entry_map_;
+  MojoHandle next_handle_;  // Invariant: never |MOJO_HANDLE_INVALID|.
+
+  DISALLOW_COPY_AND_ASSIGN(HandleTable);
+};
+
+}  // namespace system
+}  // namespace mojo
+
+#endif  // MOJO_SYSTEM_HANDLE_TABLE_H_