PacketReader

Remarks

Nothing here throws, ever. Every read returns a Boolean, and the first one that fails sets Failed so that every read after it fails too. A decoder can therefore read a whole message as straight-line code and check once at the end, and a hostile packet takes the same path as a truncated one.

That is a security property, not a convenience. Inbound bytes come from a machine we do not control; an exception escaping a decoder is a denial of service if it unwinds a frame and a crash if it does not, and a try/catch around the whole of the receive path is how a parser bug becomes exploitable. The reader is the closed door: it never allocates on a length it was told (only TryReadString allocates at all, and only up to a cap the caller states), never indexes outside its span, and never believes a length field.

Fields and properties (5)

• public bool Failed

  Whether any read has failed. Once set, every later read fails too.

• public readonly int Position

  How many bytes have been read.

• public readonly int Remaining

  How many bytes are left.

• public readonly bool IsComplete

  Whether everything was read and nothing failed — what a well-formed packet looks like.

• public readonly ReadOnlySpan<byte> RemainingBytes

  Everything not yet read, for handing the rest of a packet to whoever owns that part of it.

Methods (14)

• public PacketReader(ReadOnlySpan<byte> buffer)

  Creates a reader over a packet.

• public bool TryReadByte(out byte value)

  Reads one byte.

• public bool TryReadBool(out bool value)

  Reads a boolean.

• public bool TryReadUInt16(out ushort value)

  Reads an unsigned 16-bit value, little-endian.

• public bool TryReadUInt32(out uint value)

  Reads an unsigned 32-bit value, little-endian.

• public bool TryReadInt32(out int value)

  Reads a signed 32-bit value, little-endian.

• public bool TryReadUInt64(out ulong value)

  Reads an unsigned 64-bit value, little-endian.

• public bool TryReadSingle(out float value)

  Reads a 32-bit float by its bits.

• public bool TryReadTick(out Tick value)

  Reads a tick.

• public bool TryReadVariable(out uint value)

  Reads a value written by WriteVariable.

• public bool TryReadRaw(int count, out ReadOnlySpan<byte> bytes)

  Reads a fixed number of bytes.

• public bool TryReadBlob(int maxBytes, out ReadOnlySpan<byte> bytes)

  Reads bytes written by WriteBlob.

• public bool TryReadString(int maxBytes, out string value)

  Reads a string written by WriteString.

• public bool Reject()

  Marks the read as failed, for a decoder that found something it does not accept.

Used by (4)

• MatchProtocolMultiplayer
• NetworkSessionVixen.Net
• PacketCodecTestsVixen.Net.Tests
• PacketReaderTargetVixen.Net.Fuzz