// Copyright 2017 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.

library fuchsia.mem;

/// A buffer for data whose size is not necessarily a multiple of the page
/// size.
///
/// VMO objects have a physical size that is always a multiple of the page
/// size. As such, VMO alone cannot serve as a buffer for arbitrarly sized
/// data. `fuchsia.mem.Buffer` is a standard struct that aggregate the VMO
/// and its size.
struct Buffer {
    /// The vmo that contains the buffer.
    handle<vmo> vmo;

    /// The number of bytes in the buffer.
    ///
    /// The content of the buffer begin at the start of the VMO and continue
    /// for `size` bytes. To specify a range of bytes that do not start at
    /// the beginning of the VMO, use `Range` rather than buffer.
    ///
    /// This size must not be greater than the physical size of the VMO.
    uint64 size;
};

/// Binary data that might be stored inline or in a VMO.
///
/// Useful for performance-sensitive protocols that sometimes receive small
/// amounts of binary data (i.e., which is more efficient to provide using
/// `bytes`) but also need to support arbitrary amounts of data (i.e., which
/// need to be provided out-of-line in a `Buffer`).
flexible union Data {
    /// The binary data provided inline in the message.
    1: bytes bytes;

    /// The binary data provided out-of-line in a `Buffer`.
    2: Buffer buffer;
};