// /***************************************************************************
// The Disc Image Chef
// ----------------------------------------------------------------------------
//
// Filename       : Structs.cs
// Author(s)      : Michael Drüing <michael@drueing.de>
//
// Component      : Disk image plugins.
//
// --[ Description ] ----------------------------------------------------------
//
//     Contains structures for d2f disk images.
//
// --[ 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 © 2018-2019 Michael Drüing
// Copyright © 2011-2019 Natalia Portillo
// ****************************************************************************/

using System.Runtime.InteropServices;

namespace DiscImageChef.DiscImages
{
    public partial class WCDiskImage
    {
        /// <summary>
        ///     The expected signature of a proper image file.
        /// </summary>
        const string fileSignature = "WC DISK IMAGE\x1a\x1a";

        /// <summary>
        ///     The global header of a WCDiskImage file
        /// </summary>
        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct WCDiskImageFileHeader
        {
            /// <summary>
            ///     The signature should be "WC DISK IMAGE\0x1a\0x1a\0x00"
            /// </summary>
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
            public byte[] signature;

            /// <summary>
            ///     Version (currently only version 0 and 1 is known)
            /// </summary>
            public byte version;

            /// <summary>
            ///     The number of heads. Only 1 or 2 is supported
            /// </summary>
            public byte heads;

            /// <summary>
            ///     Sectors per track, maximum is 18
            /// </summary>
            public byte sectorsPerTrack;

            /// <summary>
            ///     The number of tracks/cylinders. 80 is the maximum
            /// </summary>
            public byte cylinders;

            /// <summary>
            ///     The "extra tracks" that are present. What this means is that the
            ///     tracks 81 and 82 might contain data (on an 80-track disk) and that
            ///     this data was dumped too. The order is head0extra1, head1extra1,
            ///     head0extra2, head1extra2. 1 means track is present.
            /// </summary>
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
            public byte[] extraTracks;

            /// <summary>
            ///     Additional metadata present flags.
            /// </summary>
            public ExtraFlag extraFlags;

            /// <summary>
            ///     Padding to make the header 32 bytes.
            /// </summary>
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 7)]
            public byte[] reserved;
        }

        enum ExtraFlag : byte
        {
            /// <summary>
            ///     Set if a Comment is present after the image
            /// </summary>
            Comment = 0x01,

            /// <summary>
            ///     Set if a directory listing is present after the image
            /// </summary>
            Directory = 0x02,
        }

        /// <summary>
        ///     The Sector header that precedes each sector
        /// </summary>
        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        struct WCDiskImageSectorHeader
        {
            /// <summary>
            ///     The sector flag (i.e. type)
            /// </summary>
            public SectorFlag flag;

            /// <summary>
            ///     The head this sector belongs to.
            /// </summary>
            public byte head;

            /// <summary>
            ///     The sector number within the track. Must be consecutive.
            /// </summary>
            public byte sector;

            /// <summary>
            ///     The cylinder number this sector belongs to.
            /// </summary>
            public byte cylinder;


            /// <summary>
            ///     A simple CRC16 over the data, to detect errors.
            /// </summary>
            public short crc;
        }

        enum SectorFlag : byte
        {
            /// <summary>
            ///     A normal sector
            /// </summary>
            Normal = 0x00,

            /// <summary>
            ///     A bad sector that could not be read
            /// </summary>
            BadSector = 0x01,

            /// <summary>
            ///     A sector filled with a repeating byte value. The value
            ///     is encoded in the LSB of the <c>crc</c> field.
            /// </summary>
            RepeatByte = 0x02,

            /// <summary>
            ///     Not a sector but a comment. Must come after all user data.
            ///     The <c>crc</c> field is the length of the comment data.
            /// </summary>
            Comment = 0x03,

            /// <summary>
            ///     Not a sector but the directory information.
            ///     The <c>crc</c> field is the length of the data.
            /// </summary>
            Directory = 0x04,
        }
    }
}