Clean up HID backend and API.

device/hid/hid_platform_resource_bidi_map.h

Index: device/hid/hid_platform_resource_bidi_map.h
diff --git a/device/hid/hid_platform_resource_bidi_map.h b/device/hid/hid_platform_resource_bidi_map.h
new file mode 100644
index 0000000000000000000000000000000000000000..05330a49b6cb5906ed9fb3cd61551baec79771bc
--- /dev/null
+++ b/device/hid/hid_platform_resource_bidi_map.h
@@ -0,0 +1,107 @@
+// 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 DEVICE_HID_HID_DEVICE_RESOURCE_BIDI_MAP_H_
+#define DEVICE_HID_HID_DEVICE_RESOURCE_BIDI_MAP_H_
+
+#include <map>
+
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "device/hid/hid_device_info.h"
+
+namespace device {
+
+// This is a utility class which platform implementations can use to manage
+// a 1:1 mapping between a generic HidService-generated device ID and some
+// platform-dependent resource identifier.
+template <typename PlatformResourceType>
+class HidPlatformResourceBidiMap {
+ public:
+  // Add a unique (ID, resource) entry to the map. Iff either the ID or the
+  // given resource is already stored in the map, the map will remain
+  // unchanged and this will return |false|.
+  bool Add(HidDeviceId device_id, PlatformResourceType resource) {
+    if (ContainsKey(device_resources_, device_id) ||
+        ContainsKey(device_ids_, resource)) {
+      return false;
+    }
+    device_resources_[device_id] = resource;
+    device_ids_[resource] = device_id;
+    return true;
+  }
+
+  // Remove an entry by its resource value. Returns |false| if the resource was
+  // not present in the map.
+  bool RemoveByResource(PlatformResourceType resource) {
+    typename DeviceResourceToIdMap::iterator id_iter =
+        device_ids_.find(resource);
+    if (id_iter == device_ids_.end())
+      return false;
+
+    HidDeviceId device_id = id_iter->second;
+    typename DeviceIdToResourceMap::iterator resource_iter =
+        device_resources_.find(device_id);
+
+    // This should never fail if the corresponding resource was found.
+    DCHECK(resource_iter != device_resources_.end());
+
+    device_ids_.erase(id_iter);
+    device_resources_.erase(resource_iter);
+    return true;
+  }
+
+  // Remove an entry by its device ID. Returns |false| if the ID was not present
+  // in the map.
+  bool RemoveById(HidDeviceId device_id) {
+    typename DeviceIdToResourceMap::iterator resource_iter =
+        device_resources_.find(device_id);
+    if (resource_iter == device_resources_.end())
+      return false;
+
+    PlatformResourceType resource = resource_iter->second;
+    typename DeviceResourceToIdMap::iterator id_iter =
+        device_ids_.find(resource);
+
+    // This should never fail if the corresponding ID was found.
+    DCHECK(id_iter != device_ids_.end());
+
+    device_ids_.erase(id_iter);
+    device_resources_.erase(resource_iter);
+    return true;
+  }
+
+  // Get a device ID by its resource value. Returns |false| if the resource was
+  // not present in the map.
+  bool GetIdByResource(PlatformResourceType resource, HidDeviceId* device_id) {
+    typename DeviceResourceToIdMap::iterator id_iter =
+        device_ids_.find(resource);
+    if (id_iter == device_ids_.end())
+      return false;
+    *device_id = id_iter->second;
+    return true;
+  }
+
+  // Get a resource value by its device ID. Returns |false| if the ID was not
+  // present in the map.
+  bool GetResourceById(HidDeviceId device_id, PlatformResourceType* resource) {
+    typename DeviceIdToResourceMap::iterator resource_iter =
+        device_resources_.find(device_id);
+    if (resource_iter == device_resources_.end())
+      return false;
+    *resource = resource_iter->second;
+    return true;
+  }
+
+ private:
+  typedef std::map<HidDeviceId, PlatformResourceType> DeviceIdToResourceMap;
+  DeviceIdToResourceMap device_resources_;
+
+  typedef std::map<PlatformResourceType, HidDeviceId> DeviceResourceToIdMap;
+  DeviceResourceToIdMap device_ids_;
+};
+
+}  // namespace device
+
+#endif  // DEVICE_HID_HID_DEVICE_RESOURCE_BIDI_MAP_H_