108 lines
3.5 KiB
C#
108 lines
3.5 KiB
C#
using System;
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using System.Text;
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namespace XWorld.Framework.Protocol
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{
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// 与 PacketWriter 对偶；任何越界/畸形长度抛 FormatException（容错入口统一）
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public sealed class PacketReader
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{
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private readonly byte[] _buf;
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private int _pos;
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public PacketReader(byte[] data)
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{
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_buf = data ?? Array.Empty<byte>();
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_pos = 0;
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}
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public int Position => _pos;
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public bool HasMore => _pos < _buf.Length;
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public byte ReadByte()
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{
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if (_pos >= _buf.Length) throw new FormatException("PacketReader: read past end");
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return _buf[_pos++];
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}
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public bool ReadBool() => ReadByte() != 0;
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public ushort ReadUInt16()
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{
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byte lo = ReadByte();
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byte hi = ReadByte();
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return (ushort)(lo | (hi << 8));
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}
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public uint ReadVarUInt()
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{
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uint result = 0;
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int shift = 0;
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while (true)
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{
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if (shift > 28) throw new FormatException("PacketReader: varuint too long");
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byte b = ReadByte();
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// 第 5 字节(shift==28)只有低 4 位有效，超出即为越界 varuint
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if (shift == 28 && (b & 0x70) != 0)
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throw new FormatException("PacketReader: varuint overflow");
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result |= (uint)(b & 0x7F) << shift;
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if ((b & 0x80) == 0) break;
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shift += 7;
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}
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return result;
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}
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public int ReadVarInt()
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{
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uint zig = ReadVarUInt();
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return (int)(zig >> 1) ^ -(int)(zig & 1); // zigzag decode
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}
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public long ReadVarLong()
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{
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ulong result = 0;
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int shift = 0;
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while (true)
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{
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if (shift > 63) throw new FormatException("PacketReader: varlong too long");
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byte b = ReadByte();
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// 第 10 字节(shift==63)只有最低 1 位有效，超出即为越界 varlong
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if (shift == 63 && (b & 0x7E) != 0)
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throw new FormatException("PacketReader: varlong overflow");
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result |= (ulong)(b & 0x7F) << shift;
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if ((b & 0x80) == 0) break;
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shift += 7;
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}
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return (long)(result >> 1) ^ -(long)(result & 1);
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}
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public float ReadSingle()
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{
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byte[] b = new byte[4];
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b[0] = ReadByte(); b[1] = ReadByte(); b[2] = ReadByte(); b[3] = ReadByte();
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if (!BitConverter.IsLittleEndian) Array.Reverse(b);
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return BitConverter.ToSingle(b, 0);
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}
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public byte[] ReadBytes()
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{
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uint len = ReadVarUInt();
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if (len == 0) return Array.Empty<byte>();
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if (_pos + len > _buf.Length) throw new FormatException("PacketReader: bytes length exceeds buffer");
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byte[] outv = new byte[len];
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Array.Copy(_buf, _pos, outv, 0, (int)len);
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_pos += (int)len;
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return outv;
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}
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public string ReadString()
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{
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uint len = ReadVarUInt();
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if (len == 0) return string.Empty;
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if (_pos + len > _buf.Length) throw new FormatException("PacketReader: string length exceeds buffer");
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string s = Encoding.UTF8.GetString(_buf, _pos, (int)len);
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_pos += (int)len;
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return s;
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}
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}
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}
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