diff --git a/VolumeBase.h b/VolumeBase.h
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+/*
+ * Copyright (C) 2008 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 ANDROID_VOLD_VOLUME_BASE_H
+#define ANDROID_VOLD_VOLUME_BASE_H
+
+#include "Utils.h"
+
+#include <utils/Errors.h>
+
+#include <sys/types.h>
+#include <list>
+#include <string>
+
+namespace android {
+namespace vold {
+
+enum class VolumeState {
+    kUnmounted,
+    kMounting,
+    kMounted,
+    kCorrupt,
+    kFormatting,
+    kUnmounting,
+};
+
+enum class VolumeType {
+    kPublic,
+    kPrivate,
+    kEmulated,
+    kAsec,
+    kObb,
+};
+
+// events:
+// volume_created private:127:4
+// volume_state private:127:4 mounted
+// volume_meta private:127:4 [fsGuid] [label]
+// volume_destroyed public:127:4
+
+// commands:
+// volume mount public:127:4 [primary]
+// volume unmount public:127:4
+// volume bind_user public:127:4 [userId]
+// volume unbind_user public:127:4 [userId]
+// volume bind_package private:4:1 [userId] [package]
+// volume unbind_package private:4:1 [userId] [package]
+
+/*
+ * Representation of a mounted volume ready for presentation.
+ *
+ * Various subclasses handle the different mounting prerequisites, such as
+ * encryption details, etc.  Volumes can also be "stacked" above other
+ * volumes to help communicate dependencies.  For example, an ASEC volume
+ * can be stacked on a vfat volume.
+ *
+ * Mounted volumes can be asked to manage bind mounts to present themselves
+ * to specific users on the device.
+ *
+ * When an unmount is requested, the volume recursively unmounts any stacked
+ * volumes and removes any bind mounts before finally unmounting itself.
+ */
+class VolumeBase {
+public:
+    virtual ~VolumeBase();
+
+    VolumeType getType() { return mType; }
+    const std::string& getId() { return mId; }
+    VolumeState getState() { return mState; }
+
+    void stackVolume(const std::shared_ptr<VolumeBase>& volume);
+    void unstackVolume(const std::shared_ptr<VolumeBase>& volume);
+
+    status_t mount();
+    status_t unmount();
+    status_t format();
+
+protected:
+    explicit VolumeBase(VolumeType type);
+
+    /* ID that uniquely references this disk */
+    std::string mId;
+
+    /* Manage bind mounts for this volume */
+    status_t mountBind(const std::string& source, const std::string& target);
+    status_t unmountBind(const std::string& target);
+
+    virtual status_t doMount() = 0;
+    virtual status_t doUnmount() = 0;
+    virtual status_t doFormat();
+
+private:
+    /* Volume type */
+    VolumeType mType;
+    /* Current state of volume */
+    VolumeState mState;
+
+    /* Volumes stacked on top of this volume */
+    std::list<std::shared_ptr<VolumeBase>> mStacked;
+    /* Currently active bind mounts */
+    std::list<std::string> mBindTargets;
+
+    void setState(VolumeState state);
+
+    DISALLOW_COPY_AND_ASSIGN(VolumeBase);
+};
+
+}  // namespace vold
+}  // namespace android
+
+#endif