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diff --git a/include/kdbinder/binder/PermissionCache.h b/include/kdbinder/binder/PermissionCache.h
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+++ b/include/kdbinder/binder/PermissionCache.h
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+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef INCLUDE_KDBINDER_BINDER_PERMISSIONCACHE_H_
+#define INCLUDE_KDBINDER_BINDER_PERMISSIONCACHE_H_
+
+#include <stdint.h>
+#include <unistd.h>
+
+#include <utils/String16.h>
+#include <utils/Singleton.h>
+#include <utils/SortedVector.h>
+
+namespace android {
+
+/*
+ * PermissionCache caches permission checks for a given uid.
+ *
+ * Currently the cache is not updated when there is a permission change,
+ * for instance when an application is uninstalled.
+ *
+ * IMPORTANT: for the reason stated above, only system permissions are safe
+ * to cache. This restriction may be lifted at a later time.
+ *
+ */
+
+class PermissionCache : Singleton<PermissionCache> {
+  struct Entry {
+    String16 name;
+    uid_t uid;
+    bool granted;
+    inline bool operator < (const Entry& e) const {
+      return (uid == e.uid) ? (name < e.name) : (uid < e.uid);
+    }
+  };
+
+  mutable Mutex mLock;
+  // we pool all the permission names we see, as many permissions checks
+  // will have identical names
+  SortedVector< String16 > mPermissionNamesPool;
+  // this is our cache per say. it stores pooled names.
+  SortedVector< Entry > mCache;
+
+  // free the whole cache, but keep the permission name pool
+  void purge();
+
+  status_t check(bool* granted, const String16& permission, uid_t uid) const;
+
+  void cache(const String16& permission, uid_t uid, bool granted);
+
+ public:
+  PermissionCache();
+
+  static bool checkCallingPermission(const String16& permission);
+
+  static bool checkCallingPermission(const String16& permission,
+                                     int32_t* outPid, int32_t* outUid);
+
+  static bool checkPermission(const String16& permission, pid_t pid, uid_t uid);
+};
+
+}  // namespace android
+
+#endif  // INCLUDE_KDBINDER_BINDER_PERMISSIONCACHE_H_