/base/Drivers/S3Trio64/BitmapInfoHeader.cs

///////////////////////////////////////////////////////////////////////////////

//

//  Microsoft Research Singularity

//

//  Copyright (c) Microsoft Corporation.  All rights reserved.

//

//  File:   BitmapInfoHeader.cs

//

//  Note:

//



using System;

using System.Runtime.InteropServices;



using Microsoft.SingSharp;

using Microsoft.Singularity;

using Microsoft.Singularity.Channels;



namespace Microsoft.Singularity.Io

{

    [CLSCompliant(false)]

    [StructLayout(LayoutKind.Explicit)]

    public pointerfree struct BITMAPINFOHEADER {

        [FieldOffset( 0)] public uint     biSize;

        [FieldOffset( 4)] public int      biWidth;

        [FieldOffset( 8)] public int      biHeight;

        [FieldOffset(12)] public ushort   biPlanes;

        [FieldOffset(14)] public ushort   biBitCount;

        [FieldOffset(16)] public uint     biCompression;

        [FieldOffset(20)] public uint     biSizeImage;

        [FieldOffset(24)] public int      biXPelsPerMeter;

        [FieldOffset(28)] public int      biYPelsPerMeter;

        [FieldOffset(30)] public uint     biClrUsed;

        [FieldOffset(32)] public uint     biClrImportant;



        public static BITMAPINFOHEADER Read(byte[]! in ExHeap buffer,

                                            int offset, out int used)

        {

            if (buffer == null || offset < 0 ||

                offset + sizeof(BITMAPINFOHEADER) > buffer.Length) {

                unchecked {

                    Tracing.Log(Tracing.Error,

                                "BITMAPINFOHEADER Read(offset={0}, length={1})",

                                (UIntPtr)(uint)offset,

                                (UIntPtr)(uint)buffer.Length);

                }

                throw new OverflowException("Read source invalid.");

            }



            used = offset + sizeof(BITMAPINFOHEADER);



            ref BITMAPINFOHEADER bmih = ref buffer[offset];

            return bmih;

        }



        public RGB[] ReadPalette(byte[]! in ExHeap buffer, int offset, out int used)

        {

            if (biClrUsed == 0 && biBitCount >= 24) {

                used = offset;

                return null;

            }



            int count = (biClrUsed != 0) ? (int)biClrUsed : (1 << biBitCount);



            if (buffer == null || offset < 0 ||

                offset + count * sizeof(uint) > buffer.Length) {

                unchecked {

                    Tracing.Log(Tracing.Error,

                                "RGB Read(offset={0}, count={1}, length={2}",

                                (UIntPtr)(uint)offset,

                                (UIntPtr)(uint)count,

                                (UIntPtr)(uint)buffer.Length);

                }

                throw new OverflowException("Read source invalid.");

            }



            RGB[] values = new RGB [count];

            used = offset;

            offset += sizeof(uint);



            for (int i = 0; i < count; i++) {

                values[i] = new RGB(buffer[2+offset], buffer[1+offset], buffer[0+offset]);

                offset += sizeof(uint);

            }

            return values;

        }

    }

} // namespace Microsoft.Singularity.Io