49 lines
1.3 KiB
C#
49 lines
1.3 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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namespace libsharperang {
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public class CRC32 {
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private uint _Initial = 0xFFFFFFFF;
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public uint Initial { get => ~_Initial; private set => _Initial=~value; }
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private uint Polynomial = 0xedb88320;
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private uint[] Table;
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public bool Initialised=false;
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public CRC32(uint Initial) => this.Initial=Initial;
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public CRC32() { }
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public void Initialise() {
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Table=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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? (Polynomial^(e>>1))
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: (e>>1);
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}
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return e;
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}).ToArray();
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Initialised=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 bit=(iv>>i)&1;
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ivr |= (bit<<(31-i));
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}
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return ~ivr;
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}
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public uint GetChecksum<T>(IEnumerable<T> bytes) {
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if (!Initialised) Initialise();
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try {
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return ~bytes.Aggregate(_Initial,
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(csR, cB) => Table[(csR & 0xFF) ^ Convert.ToByte(cB)] ^ (csR>>8));
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} catch (FormatException e) {
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throw new Exception("Could not read stream as bytes", e);
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} catch (InvalidCastException e) {
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throw new Exception("Could not read stream as bytes", e);
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} catch (OverflowException e) {
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throw new Exception("Could not read stream as bytes", e);
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}
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}
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}
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}
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