Aaru/Aaru.Filters/GZip.cs

// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : GZip.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Filters.
//
// --[ Description ] ----------------------------------------------------------
//
//     Allow to open files that are compressed using gzip.
//
// --[ License ] --------------------------------------------------------------
//
//     This library is free software; you can redistribute it and/or modify
//     it under the terms of the GNU Lesser General Public License as
//     published by the Free Software Foundation; either version 2.1 of the
//     License, or (at your option) any later version.
//
//     This library is distributed in the hope that it will be useful, but
//     WITHOUT ANY WARRANTY; without even the implied warranty of
//     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
//     Lesser General Public License for more details.
//
//     You should have received a copy of the GNU Lesser General Public
//     License along with this library; if not, see <http://www.gnu.org/licenses/>.
//
// ----------------------------------------------------------------------------
// Copyright © 2011-2021 Natalia Portillo
// ****************************************************************************/

using System;
using System.IO;
using System.IO.Compression;
using Aaru.CommonTypes.Enums;
using Aaru.CommonTypes.Interfaces;
using Aaru.Helpers;

namespace Aaru.Filters
{
    /// <inheritdoc />
    /// <summary>Decompress gzip files while reading</summary>
    public sealed class GZip : IFilter
    {
        Stream _dataStream;
        uint   _decompressedSize;
        Stream _zStream;

        /// <inheritdoc />
        public string Name => "GZip";
        /// <inheritdoc />
        public Guid Id => new("F4996661-4A29-42C9-A2C7-3904EF40F3B0");
        /// <inheritdoc />
        public string Author => "Natalia Portillo";

        /// <inheritdoc />
        public void Close()
        {
            _dataStream?.Close();
            _dataStream = null;
            BasePath    = null;
        }

        /// <inheritdoc />
        public string BasePath { get; private set; }

        /// <inheritdoc />
        public Stream GetDataForkStream() => _zStream;

        /// <inheritdoc />
        public string Path => BasePath;

        /// <inheritdoc />
        public Stream GetResourceForkStream() => null;

        /// <inheritdoc />
        public bool HasResourceFork => false;

        /// <inheritdoc />
        public bool Identify(byte[] buffer) => buffer[0] == 0x1F && buffer[1] == 0x8B && buffer[2] == 0x08;

        /// <inheritdoc />
        public bool Identify(Stream stream)
        {
            byte[] buffer = new byte[3];

            stream.Seek(0, SeekOrigin.Begin);
            stream.Read(buffer, 0, 3);
            stream.Seek(0, SeekOrigin.Begin);

            return buffer[0] == 0x1F && buffer[1] == 0x8B && buffer[2] == 0x08;
        }

        /// <inheritdoc />
        public bool Identify(string path)
        {
            if(!File.Exists(path))
                return false;

            var    stream = new FileStream(path, FileMode.Open, FileAccess.Read);
            byte[] buffer = new byte[3];

            stream.Seek(0, SeekOrigin.Begin);
            stream.Read(buffer, 0, 3);
            stream.Seek(0, SeekOrigin.Begin);

            return buffer[0] == 0x1F && buffer[1] == 0x8B && buffer[2] == 0x08;
        }

        /// <inheritdoc />
        public ErrorNumber Open(byte[] buffer)
        {
            byte[] mtimeB = new byte[4];
            byte[] isizeB = new byte[4];

            _dataStream = new MemoryStream(buffer);
            BasePath    = null;

            _dataStream.Seek(4, SeekOrigin.Begin);
            _dataStream.Read(mtimeB, 0, 4);
            _dataStream.Seek(-4, SeekOrigin.End);
            _dataStream.Read(isizeB, 0, 4);
            _dataStream.Seek(0, SeekOrigin.Begin);

            uint mtime = BitConverter.ToUInt32(mtimeB, 0);
            uint isize = BitConverter.ToUInt32(isizeB, 0);

            _decompressedSize = isize;
            CreationTime      = DateHandlers.UnixUnsignedToDateTime(mtime);
            LastWriteTime     = CreationTime;

            _zStream = new ForcedSeekStream<GZipStream>(_decompressedSize, _dataStream, CompressionMode.Decompress);

            return ErrorNumber.NoError;
        }

        /// <inheritdoc />
        public ErrorNumber Open(Stream stream)
        {
            byte[] mtimeB = new byte[4];
            byte[] isizeB = new byte[4];

            _dataStream = stream;
            BasePath    = null;

            _dataStream.Seek(4, SeekOrigin.Begin);
            _dataStream.Read(mtimeB, 0, 4);
            _dataStream.Seek(-4, SeekOrigin.End);
            _dataStream.Read(isizeB, 0, 4);
            _dataStream.Seek(0, SeekOrigin.Begin);

            uint mtime = BitConverter.ToUInt32(mtimeB, 0);
            uint isize = BitConverter.ToUInt32(isizeB, 0);

            _decompressedSize = isize;
            CreationTime      = DateHandlers.UnixUnsignedToDateTime(mtime);
            LastWriteTime     = CreationTime;

            _zStream = new ForcedSeekStream<GZipStream>(_decompressedSize, _dataStream, CompressionMode.Decompress);

            return ErrorNumber.NoError;
        }

        /// <inheritdoc />
        public ErrorNumber Open(string path)
        {
            byte[] mtimeB = new byte[4];
            byte[] isizeB = new byte[4];

            _dataStream = new FileStream(path, FileMode.Open, FileAccess.Read);
            BasePath    = System.IO.Path.GetFullPath(path);

            _dataStream.Seek(4, SeekOrigin.Begin);
            _dataStream.Read(mtimeB, 0, 4);
            _dataStream.Seek(-4, SeekOrigin.End);
            _dataStream.Read(isizeB, 0, 4);
            _dataStream.Seek(0, SeekOrigin.Begin);

            uint mtime = BitConverter.ToUInt32(mtimeB, 0);
            uint isize = BitConverter.ToUInt32(isizeB, 0);

            _decompressedSize = isize;
            var fi = new FileInfo(path);
            CreationTime = fi.CreationTimeUtc;
            LastWriteTime = DateHandlers.UnixUnsignedToDateTime(mtime);
            _zStream = new ForcedSeekStream<GZipStream>(_decompressedSize, _dataStream, CompressionMode.Decompress);

            return ErrorNumber.NoError;
        }

        /// <inheritdoc />
        public DateTime CreationTime { get; private set; }

        /// <inheritdoc />
        public long DataForkLength => _decompressedSize;

        /// <inheritdoc />
        public DateTime LastWriteTime { get; private set; }

        /// <inheritdoc />
        public long Length => _decompressedSize;

        /// <inheritdoc />
        public long ResourceForkLength => 0;

        /// <inheritdoc />
        public string Filename
        {
            get
            {
                if(BasePath?.EndsWith(".gz", StringComparison.InvariantCultureIgnoreCase) == true)
                    return BasePath.Substring(0, BasePath.Length - 3);

                return BasePath?.EndsWith(".gzip", StringComparison.InvariantCultureIgnoreCase) == true
                           ? BasePath.Substring(0, BasePath.Length - 5) : BasePath;
            }
        }

        /// <inheritdoc />
        public string ParentFolder => System.IO.Path.GetDirectoryName(BasePath);
    }
}