103 lines
3.5 KiB
C#
103 lines
3.5 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace Kneesocks {
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public class Frame {
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public enum kOpcode {
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Continuation = 0x0,
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TextFrame = 0x1,
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BinaryFrame = 0x2,
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Close = 0x8,
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Ping = 0x9,
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Pong = 0xA
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};
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public kOpcode Opcode { get; set; }
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public bool IsFinal { get; set; }
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public bool IsMasked { get; set; }
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public byte[] Mask { get; set; } = new byte[] { 0, 0, 0, 0 };
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public byte Reserved { get; set; }
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public byte[] Content { get; set; }
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public byte[] MaskedContent {
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get {
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byte[] returnValue = new byte[Content.Length];
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for(long i = 0; i < Content.LongLength; ++i)
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returnValue[i] = (byte)(Content[i] ^ Mask[i % 4]);
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return returnValue;
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}
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}
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public byte[] GetRaw() {
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var headerSize = 2L;
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var bodySize = Content.LongLength;
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if(bodySize >= 0x7E && bodySize <= 0xFFFF)
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headerSize += 2;
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else if(bodySize > 0xFFFF)
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headerSize += 8;
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if(IsMasked)
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headerSize += 4;
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var returnValue = new byte[headerSize + bodySize];
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return returnValue;
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}
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public static Frame FromRaw(byte[] raw) {
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if(raw.Length < 2)
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throw new FormatException("Websocket frame cannot be less than two bytes long");
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var rawOpcode = raw[0] & 0x0F;
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if(!Enum.IsDefined(typeof(kOpcode), rawOpcode))
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throw new FormatException("Opcode '"+ rawOpcode.ToString("0x{0:X}") +"' not understood");
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var returnFrame = new Frame {
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IsFinal = (raw[0] & 0x80) != 0,
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Opcode = (kOpcode)rawOpcode,
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IsMasked = (raw[1] & 0x80) != 0,
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Reserved = (byte)((raw[0] & 0x70) >> 4)
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};
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ulong bodyLength = raw[1] & 0x7Ful;
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int lengthOffset =
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bodyLength < 126
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? 1
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: (bodyLength == 126 ? 3 : 9);
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for(var i = lengthOffset - 1; i > 0; --i) {
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var bytePos = lengthOffset - 1 - i;
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bodyLength &= 0xFFul << bytePos;
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bodyLength |= (ulong)raw[2 + i] << bytePos;
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}
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if(returnFrame.IsMasked) {
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for(var i = 0; i < 4; ++i)
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returnFrame.Mask[i] = raw[i + 1 + lengthOffset];
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lengthOffset += 4;
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}
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ulong expectedFrameLength = bodyLength + (uint)lengthOffset + 1;
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if(expectedFrameLength < (ulong)raw.LongLength)
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throw new FormatException("Raw frame length ("+ expectedFrameLength +") is less than described size ("+ (ulong)raw.LongLength +")");
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ulong counter = 0;
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returnFrame.Content = raw.Skip(lengthOffset + 1)
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.TakeWhile(x => counter++ < bodyLength)
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.ToArray();
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if(returnFrame.IsMasked) {
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counter = 0;
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returnFrame.Content =
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returnFrame.Content.Select(
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x => (byte)(x ^ returnFrame.Mask[counter++ % 4])
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).ToArray();
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}
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return returnFrame;
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}
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}
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}
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