64 lines
1.8 KiB
C#
64 lines
1.8 KiB
C#
using System;
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namespace NfcAime.Dll.PN532 {
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internal static class Pn532HsuFrame
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{
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public const byte Preamble = 0x00;
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public const byte StartCode1 = 0x00;
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public const byte StartCode2 = 0xFF;
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public const byte Postamble = 0x00;
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public const byte HostToPn532Tfi = 0xD4;
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public const byte Pn532ToHostTfi = 0xD5;
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public static readonly byte[] AckFrame =
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[
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0x00, 0x00, 0xFF, 0x00, 0xFF, 0x00
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];
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public static readonly byte[] NakFrame =
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[
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0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00
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];
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public static byte[] BuildDataFrame(byte tfi, ReadOnlySpan<byte> data)
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{
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if (data.Length + 1 > byte.MaxValue)
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{
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throw new ArgumentOutOfRangeException(nameof(data), "PN532 HSU frames must fit in 255 bytes.");
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}
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var length = (byte)(data.Length + 1);
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var lcs = ComputeLcs(length);
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var dcs = ComputeDcs(tfi, data);
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var frame = new byte[7 + length];
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frame[0] = Preamble;
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frame[1] = StartCode1;
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frame[2] = StartCode2;
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frame[3] = length;
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frame[4] = lcs;
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frame[5] = tfi;
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data.CopyTo(frame.AsSpan(6));
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frame[6 + data.Length] = dcs;
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frame[7 + data.Length] = Postamble;
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return frame;
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}
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public static byte ComputeLcs(byte length)
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=> (byte)((0x100 - length) & 0xFF);
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public static byte ComputeDcs(byte tfi, ReadOnlySpan<byte> data)
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{
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var sum = tfi;
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for (var index = 0; index < data.Length; index++)
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{
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sum += data[index];
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}
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return (byte)((0x100 - (sum & 0xFF)) & 0xFF);
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}
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}
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}
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