PKHeX/PKHeX.Core/Saves/Blocks/BlockInfo3DS.cs

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using System;
using static System.Buffers.Binary.BinaryPrimitives;
namespace PKHeX.Core
{
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/// <summary>
/// Gen6+ Block Info (inside BEEF chunk)
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/// </summary>
public abstract class BlockInfo3DS : BlockInfo
{
private readonly int BlockInfoOffset;
// ==chunk def== @ BlockInfoOffset
// u64 timestamp1
// u64 timestamp2
// u8[4] BEEF magic
// n*{blockInfo}, where n varies per sav type
// ==block info def==
// u32 length
// u16 id
// u16 checksum
// when stored, each block size is rounded up to nearest 0x200, and the next chunk is immediately after
protected BlockInfo3DS(int bo, uint id, int ofs, int len)
{
BlockInfoOffset = bo;
ID = id;
Offset = ofs;
Length = len;
}
private int ChecksumOffset => BlockInfoOffset + 0x14 + ((int)ID * 8) + 6;
protected abstract ushort GetChecksum(Span<byte> data);
protected override bool ChecksumValid(Span<byte> data)
{
ushort chk = GetChecksum(data);
var old = ReadUInt16LittleEndian(data[ChecksumOffset..]);
return chk == old;
}
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protected override void SetChecksum(Span<byte> data)
{
ushort chk = GetChecksum(data);
WriteUInt16LittleEndian(data[ChecksumOffset..], chk);
}
}
public sealed class BlockInfo6 : BlockInfo3DS
{
public BlockInfo6(int bo, uint id, int ofs, int len) : base(bo, id, ofs, len) { }
protected override ushort GetChecksum(Span<byte> data) => Checksums.CRC16_CCITT(data.Slice(Offset, Length));
}
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public sealed class BlockInfo7 : BlockInfo3DS
{
public BlockInfo7(int bo, uint id, int ofs, int len) : base(bo, id, ofs, len) { }
protected override ushort GetChecksum(Span<byte> data) => Checksums.CRC16Invert(data.Slice(Offset, Length));
}
public sealed class BlockInfo7b : BlockInfo3DS
{
public BlockInfo7b(int bo, uint id, int ofs, int len) : base(bo, id, ofs, len) { }
protected override ushort GetChecksum(Span<byte> data) => Checksums.CRC16NoInvert(data.Slice(Offset, Length));
}
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}