osu-lazer/osu.Game/IO/Archives/ZipArchiveReader.cs

// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.

#nullable disable

using System.Buffers;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Microsoft.Toolkit.HighPerformance;
using osu.Framework.IO.Stores;
using SharpCompress.Archives.Zip;
using SixLabors.ImageSharp.Memory;

namespace osu.Game.IO.Archives
{
    public sealed class ZipArchiveReader : ArchiveReader
    {
        private readonly Stream archiveStream;
        private readonly ZipArchive archive;

        public ZipArchiveReader(Stream archiveStream, string name = null)
            : base(name)
        {
            this.archiveStream = archiveStream;
            archive = ZipArchive.Open(archiveStream);
        }

        public override Stream GetStream(string name)
        {
            ZipArchiveEntry entry = archive.Entries.SingleOrDefault(e => e.Key == name);
            if (entry == null)
                return null;

            var owner = MemoryAllocator.Default.Allocate<byte>((int)entry.Size);

            using (Stream s = entry.OpenEntryStream())
                s.ReadExactly(owner.Memory.Span);

            return new MemoryOwnerMemoryStream(owner);
        }

        public override void Dispose()
        {
            archive.Dispose();
            archiveStream.Dispose();
        }

        public override IEnumerable<string> Filenames => archive.Entries.Where(e => !e.IsDirectory).Select(e => e.Key).ExcludeSystemFileNames();

        private class MemoryOwnerMemoryStream : Stream
        {
            private readonly IMemoryOwner<byte> owner;
            private readonly Stream stream;

            public MemoryOwnerMemoryStream(IMemoryOwner<byte> owner)
            {
                this.owner = owner;

                stream = owner.Memory.AsStream();
            }

            protected override void Dispose(bool disposing)
            {
                owner?.Dispose();
                base.Dispose(disposing);
            }

            public override void Flush() => stream.Flush();

            public override int Read(byte[] buffer, int offset, int count) => stream.Read(buffer, offset, count);

            public override long Seek(long offset, SeekOrigin origin) => stream.Seek(offset, origin);

            public override void SetLength(long value) => stream.SetLength(value);

            public override void Write(byte[] buffer, int offset, int count) => stream.Write(buffer, offset, count);

            public override bool CanRead => stream.CanRead;

            public override bool CanSeek => stream.CanSeek;

            public override bool CanWrite => stream.CanWrite;

            public override long Length => stream.Length;

            public override long Position
            {
                get => stream.Position;
                set => stream.Position = value;
            }
        }
    }
}