NdsDsiHeader.cs

namespace NdsForge;

public sealed class NdsDsiHeader
{
    private readonly ReadOnlyMemory<byte> _rawHeader;
    internal NdsDsiHeader(ReadOnlyMemory<byte> rawHeader)
    {
        _rawHeader = rawHeader;
        ReadOnlySpan<byte> data = rawHeader.Span;
        RawData = rawHeader.Slice(0x180, 0xE80);
        MemoryBankSettings = rawHeader.Slice(0x180, 0x30);
        RegionFlags = NdsBinary.ReadUInt32(data, 0x1B0);
        AccessControl = NdsBinary.ReadUInt32(data, 0x1B4);
        ScfgExtMask = NdsBinary.ReadUInt32(data, 0x1B8);
        ApplicationFlags = data[0x1BF];
        Arm7DeviceListAddress = NdsBinary.ReadUInt32(data, 0x1D4);
        NtrDigest = ReadRegion(data, 0x1E0);
        TwlDigest = ReadRegion(data, 0x1E8);
        SectorHashTable = ReadRegion(data, 0x1F0);
        BlockHashTable = ReadRegion(data, 0x1F8);
        DigestSectorSize = NdsBinary.ReadUInt32(data, 0x200);
        DigestBlockSectorCount = NdsBinary.ReadUInt32(data, 0x204);
        BannerSize = NdsBinary.ReadUInt32(data, 0x208);
        TotalImageSize = NdsBinary.ReadUInt32(data, 0x210);
        ModcryptArea1 = ReadRegion(data, 0x220);
        ModcryptArea2 = ReadRegion(data, 0x228);
        uint titleIdLow = NdsBinary.ReadUInt32(data, 0x230);
        uint titleIdHigh = NdsBinary.ReadUInt32(data, 0x234);
        TitleId = ((ulong)titleIdHigh << 32) | titleIdLow;
        PublicSaveSize = NdsBinary.ReadUInt32(data, 0x238);
        PrivateSaveSize = NdsBinary.ReadUInt32(data, 0x23C);
        AgeRatings = rawHeader.Slice(0x2F0, 0x10);
        Arm9Hmac = rawHeader.Slice(0x300, 20);
        Arm7Hmac = rawHeader.Slice(0x314, 20);
        DigestMasterHmac = rawHeader.Slice(0x328, 20);
        BannerHmac = rawHeader.Slice(0x33C, 20);
        Arm9iHmac = rawHeader.Slice(0x350, 20);
        Arm7iHmac = rawHeader.Slice(0x364, 20);
        Arm9WithoutSecureAreaHmac = rawHeader.Slice(0x3A0, 20);
        DebugArguments = rawHeader.Slice(0xE00, 0x180);
        RsaSignature = rawHeader.Slice(0xF80, 0x80);
    }

    public ReadOnlyMemory<byte> RawData { get; }

    public ReadOnlyMemory<byte> MemoryBankSettings { get; }

    public uint RegionFlags { get; }

    public uint AccessControl { get; }

    public uint ScfgExtMask { get; }

    public byte ApplicationFlags { get; }

    public uint Arm7DeviceListAddress { get; }

    public NdsRegion NtrDigest { get; }

    public NdsRegion TwlDigest { get; }

    public NdsRegion SectorHashTable { get; }

    public NdsRegion BlockHashTable { get; }

    public uint DigestSectorSize { get; }

    public uint DigestBlockSectorCount { get; }

    public uint BannerSize { get; }

    public uint TotalImageSize { get; }

    public NdsRegion ModcryptArea1 { get; }

    public NdsRegion ModcryptArea2 { get; }

    public bool HasModcryptAreas => !ModcryptArea1.IsEmpty || !ModcryptArea2.IsEmpty;

    public bool UsesInsecureModcryptKey =>
        (_rawHeader.Span[0x1C] & 0x04) != 0 || (ApplicationFlags & 0x80) != 0;

    public NdsRegion GetModcryptArea(NdsModcryptArea area) => area switch
    {
        NdsModcryptArea.First => ModcryptArea1,
        NdsModcryptArea.Second => ModcryptArea2,
        _ => throw new ArgumentOutOfRangeException(nameof(area), area, "Unknown modcrypt area."),
    };

    public ulong TitleId { get; }

    public uint PublicSaveSize { get; }

    public uint PrivateSaveSize { get; }

    public ReadOnlyMemory<byte> AgeRatings { get; }

    public ReadOnlyMemory<byte> Arm9Hmac { get; }

    public ReadOnlyMemory<byte> Arm7Hmac { get; }

    public ReadOnlyMemory<byte> DigestMasterHmac { get; }

    public ReadOnlyMemory<byte> BannerHmac { get; }

    public ReadOnlyMemory<byte> Arm9iHmac { get; }

    public ReadOnlyMemory<byte> Arm7iHmac { get; }

    public ReadOnlyMemory<byte> Arm9WithoutSecureAreaHmac { get; }

    public ReadOnlyMemory<byte> DebugArguments { get; }

    public ReadOnlyMemory<byte> RsaSignature { get; }

    public bool VerifyRsaSignature(NdsDsiRsaPublicKey publicKey)
    {
        ArgumentNullException.ThrowIfNull(publicKey);
        return publicKey.VerifyHeader(_rawHeader.Span[..0xE00], RsaSignature.Span);
    }

    private static NdsRegion ReadRegion(ReadOnlySpan<byte> data, int offset) =>
        NdsRegion.FromUInt32(NdsBinary.ReadUInt32(data, offset), NdsBinary.ReadUInt32(data, offset + 4));
}