53 lines
1.6 KiB
C#
53 lines
1.6 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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namespace libpaperang.Helpers {
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public class CRC {
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public uint iv { get => ~iv; private set => iv=~value; }
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public uint mv = 0x35769521;
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private uint poly = 0xedb88320;
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private uint[] crctable;
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public bool IsInitialised=false;
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public CRC() => iv = 0;
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public CRC(uint iv) => this.iv = iv;
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public void Initialise() {
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crctable=Enumerable.Range(0, 256).Select(i => {
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uint e=(uint)i;
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for (ushort eb = 0; eb<8; eb++)
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e=((e&1)!=0)
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? (poly^(e>>1))
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: (e>>1);
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return e;
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}).ToArray();
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IsInitialised=true;
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}
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public uint Reflect(uint iv) {
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uint ivr=0;
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for (int i = 0; i<32; i++) {
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uint b=(iv>>i)&1;
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ivr|=(b<<(31-i));
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}
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return ~ivr;
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}
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public uint GetChecksumUint<T>(IEnumerable<T> data) {
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if (!IsInitialised) throw new CrcNotAvailableException();
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try {
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return ~data.Aggregate(iv,
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(cti, cb) => crctable[(cti&0xFF)^Convert.ToByte(cb)]^(cti>>8));
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} catch (FormatException e) {
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throw new FormatException("Could not read input as a byte stream", e);
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} catch (InvalidCastException e) {
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throw new InvalidCastException("Could not read input as a byte stream", e);
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} catch (OverflowException e) {
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throw new OverflowException("Could not read input as a byte stream", e);
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}
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}
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public byte[] GetChecksumBytes<T>(IEnumerable<T> data) => BitConverter.GetBytes(GetChecksumUint(data));
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public uint GetCrcIv() => iv == mv
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? iv
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: iv ^ mv;
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public byte[] GetCrcIvBytes() => BitConverter.GetBytes(GetCrcIv());
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}
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}
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