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A helper class for parsing binary structures that are Big-Endian encoded (as is common for network protocols).
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| using System; | |
| using static System.Buffers.Binary.BinaryPrimitives; | |
| namespace BinaryStruct | |
| { | |
| public ref struct Reader | |
| { | |
| public enum Endian | |
| { | |
| Little, | |
| Big | |
| } | |
| private readonly ReadOnlySpan<byte> _buffer; | |
| public Reader(ReadOnlySpan<byte> buffer) | |
| { | |
| _buffer = buffer; | |
| Cursor = 0; | |
| } | |
| public int Cursor { get; set; } | |
| public int Length => _buffer.Length; | |
| public Endian Endianess { get; set; } = Endian.Big; | |
| public static implicit operator Reader(byte[] buffer) => new Reader(buffer); | |
| public void Skip(int n) | |
| { | |
| Cursor += n; | |
| } | |
| public bool Take(int n, out ReadOnlySpan<byte> value, int? cursor = default) | |
| { | |
| value = default; | |
| Cursor = (cursor ?? Cursor) + n; | |
| if (Cursor > Length) | |
| return false; | |
| value = _buffer.Slice(Cursor - n, n); | |
| return true; | |
| } | |
| public bool U8(out byte value, int? cursor = default) | |
| { | |
| value = default; | |
| Cursor = (cursor ?? Cursor) + 1; | |
| if (Cursor > Length) | |
| return false; | |
| value = _buffer[Cursor - 1]; | |
| return true; | |
| } | |
| public bool U16(out ushort value, int? cursor = default, Endian? endianness = default) | |
| { | |
| value = default; | |
| Cursor = (cursor ?? Cursor) + 2; | |
| if (Cursor > Length) | |
| return false; | |
| var slice = _buffer.Slice(Cursor - 2, 2); | |
| value = (endianness ?? Endianess) switch | |
| { | |
| Endian.Little => ReadUInt16LittleEndian(slice), | |
| Endian.Big => ReadUInt16BigEndian(slice), | |
| }; | |
| return true; | |
| } | |
| public bool U32(out uint value, int? cursor = default, Endian? endianness = default) | |
| { | |
| value = default; | |
| Cursor = (cursor ?? Cursor) + 4; | |
| if (Cursor > Length) | |
| return false; | |
| var slice = _buffer.Slice(Cursor - 4, 4); | |
| value = (endianness ?? Endianess) switch | |
| { | |
| Endian.Little => ReadUInt32LittleEndian(slice), | |
| Endian.Big => ReadUInt32BigEndian(slice), | |
| }; | |
| return true; | |
| } | |
| } | |
| } | |
| namespace BinaryStruct.Tests | |
| { | |
| public class ReaderTests | |
| { | |
| [Fact] | |
| public void Test1() | |
| { | |
| var reader = new Reader([0x00, 0x01, 0x02, 0x03]); | |
| reader.U8(out var zero); | |
| reader.U8(out var one); | |
| reader.U8(out var two); | |
| reader.U8(out var three); | |
| Assert.Equal(0, zero); | |
| Assert.Equal(1, one); | |
| Assert.Equal(2, two); | |
| Assert.Equal(3, three); | |
| } | |
| [Fact] | |
| public void Test2() | |
| { | |
| var reader = new Reader([0x00, 0x01, 0x02, 0x03]); | |
| reader.U16(out var x0001); | |
| reader.U16(out var x0203); | |
| Assert.Equal(0x00_01, x0001); | |
| Assert.Equal(0x02_03, x0203); | |
| } | |
| [Fact] | |
| public void Test3() | |
| { | |
| var reader = new Reader([0x00, 0x01, 0x02, 0x03]); | |
| reader.U32(out var x00010203); | |
| Assert.Equal((uint)0x00_01_02_03, x00010203); | |
| } | |
| [Fact] | |
| public void Test4() | |
| { | |
| var reader = new Reader([0x00, 0x01, 0x02, 0x03]); | |
| reader.Skip(1); | |
| reader.Take(2, out var slice); | |
| byte[] expected = [0x01, 0x02]; | |
| Assert.Equal(expected, slice.ToArray()); | |
| } | |
| [Fact] | |
| public void Test5() | |
| { | |
| var reader = new Reader([0x00, 0x01, 0x02, 0x03]); | |
| reader.Cursor += 4; | |
| var success = reader.U8(out _); | |
| Assert.False(success); | |
| } | |
| } | |
| } |
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