75 lines
1.9 KiB
C#
75 lines
1.9 KiB
C#
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using System;
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using System.IO;
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namespace LCLib.Asn1Processor
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{
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/// <summary>
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/// Summary description for Util.
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/// </summary>
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internal class Asn1Util
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{
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public static int BytePrecision(ulong value)
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{
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int i;
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for (i = sizeof(ulong); i > 0; --i)
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if ((value >> (i - 1) * 8) != 0)
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break;
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return i;
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}
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public static int DERLengthEncode(Stream xdata, ulong length)
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{
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int i = 0;
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if (length <= 0x7f)
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{
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xdata.WriteByte((byte)length);
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i++;
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}
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else
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{
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xdata.WriteByte((byte)(BytePrecision(length) | 0x80));
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i++;
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for (int j = BytePrecision((ulong)length); j > 0; --j)
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{
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xdata.WriteByte((byte)(length >> (j - 1) * 8));
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i++;
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}
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}
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return i;
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}
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public static long DerLengthDecode(Stream bt)
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{
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long length = 0;
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byte b;
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b = (byte)bt.ReadByte();
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if ((b & 0x80) == 0)
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{
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length = b;
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}
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else
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{
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long lengthBytes = b & 0x7f;
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if (lengthBytes == 0)
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{
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throw new Exception("Indefinite length.");
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}
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length = 0;
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while (lengthBytes-- > 0)
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{
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if ((length >> (8 * (sizeof(long) - 1))) > 0)
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throw new Exception("Length overflow.");
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b = (byte)bt.ReadByte();
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length = (length << 8) | b;
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}
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}
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return length;
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}
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private Asn1Util()
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{
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}
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}
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}
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