LibHac/LibHac.Nand/DiscUtils.Streams/MappedStream.cs

//
// Copyright (c) 2008-2011, Kenneth Bell
//
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// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
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// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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using System.Collections.Generic;
using System.IO;

namespace DiscUtils.Streams
{
    /// <summary>
    /// Base class for streams that are essentially a mapping onto a parent stream.
    /// </summary>
    /// <remarks>
    /// This class provides access to the mapping underlying the stream, enabling
    /// callers to convert a byte range in this stream into one or more ranges in
    /// the parent stream.
    /// </remarks>
    public abstract class MappedStream : SparseStream
    {
        /// <summary>
        /// Converts any stream into a non-linear stream.
        /// </summary>
        /// <param name="stream">The stream to convert.</param>
        /// <param name="takeOwnership"><c>true</c> to have the new stream dispose the wrapped
        /// stream when it is disposed.</param>
        /// <returns>A sparse stream.</returns>
        /// <remarks>The wrapped stream is assumed to be a linear stream (such that any byte range
        /// maps directly onto the parent stream).</remarks>
        public new static MappedStream FromStream(Stream stream, Ownership takeOwnership)
        {
            return new WrappingMappedStream<Stream>(stream, takeOwnership, null);
        }

        /// <summary>
        /// Converts any stream into a non-linear stream.
        /// </summary>
        /// <param name="stream">The stream to convert.</param>
        /// <param name="takeOwnership"><c>true</c> to have the new stream dispose the wrapped
        /// stream when it is disposed.</param>
        /// <param name="extents">The set of extents actually stored in <c>stream</c>.</param>
        /// <returns>A sparse stream.</returns>
        /// <remarks>The wrapped stream is assumed to be a linear stream (such that any byte range
        /// maps directly onto the parent stream).</remarks>
        public new static MappedStream FromStream(Stream stream, Ownership takeOwnership,
                                                  IEnumerable<StreamExtent> extents)
        {
            return new WrappingMappedStream<Stream>(stream, takeOwnership, extents);
        }

        /// <summary>
        /// Maps a logical range down to storage locations.
        /// </summary>
        /// <param name="start">The first logical range to map.</param>
        /// <param name="length">The length of the range to map.</param>
        /// <returns>One or more stream extents specifying the storage locations that correspond
        /// to the identified logical extent range.</returns>
        /// <remarks>
        /// <para>As far as possible, the stream extents are returned in logical disk order -
        /// however, due to the nature of non-linear streams, not all of the range may actually
        /// be stored, or some or all of the range may be compressed - thus reading the
        /// returned stream extents is not equivalent to reading the logical disk range.</para>
        /// </remarks>
        public abstract IEnumerable<StreamExtent> MapContent(long start, long length);
    }
}