zircon/system/ulib/fs/include/fs/mount_channel.h

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <zircon/types.h>

#ifdef __Fuchsia__
#include <lib/zx/channel.h>
#include <fs/client.h>
#endif // __Fuchsia__

#include <utility>

namespace fs {

#ifdef __Fuchsia__

// MountChannel functions exactly the same as a channel, except that it
// intentionally destructs by sending a clean "shutdown" signal to the
// underlying filesystem. Up until the point that a remote handle is
// attached to a vnode, this wrapper guarantees not only that the
// underlying handle gets closed on error, but also that the sub-filesystem
// is released (which cleans up the underlying connection to the block
// device).
class MountChannel {
public:
    constexpr MountChannel() = default;
    explicit MountChannel(zx_handle_t handle)
        : channel_(handle) {}
    explicit MountChannel(zx::channel channel)
        : channel_(std::move(channel)) {}
    MountChannel(MountChannel&& other)
        : channel_(std::move(other.channel_)) {}

    zx::channel TakeChannel() { return std::move(channel_); }

    ~MountChannel() {
        if (channel_.is_valid()) {
            vfs_unmount_handle(channel_.release(), 0);
        }
    }

private:
    zx::channel channel_;
};

#endif // __Fuchsia__

} // namespace fs