66 lines
1.7 KiB
Go
66 lines
1.7 KiB
Go
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package protocol
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import (
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"encoding/binary"
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"fmt"
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"io"
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)
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// MessageDecoder handles decoding of protocol message headers
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type MessageDecoder struct{}
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// NewMessageDecoder creates a new message decoder
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func NewMessageDecoder() *MessageDecoder {
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return &MessageDecoder{}
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}
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// Decode reads the message header and returns a Message with the payload stream
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func (d *MessageDecoder) Decode(r io.Reader) (*Message, error) {
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// Read message type (1 byte)
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var msgType MessageType
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if err := binary.Read(r, binary.BigEndian, &msgType); err != nil {
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if err == io.EOF {
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return nil, err
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}
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return nil, fmt.Errorf("failed to read message type: %w", err)
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}
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// Validate message type (only request types are valid for server)
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if !isValidRequestType(msgType) {
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return nil, fmt.Errorf("invalid message type: 0x%02x", msgType)
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}
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// Read payload length (4 bytes, big-endian)
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var payloadLength uint32
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if err := binary.Read(r, binary.BigEndian, &payloadLength); err != nil {
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return nil, fmt.Errorf("failed to read payload length: %w", err)
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}
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// Validate payload length
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if payloadLength > MaxPayloadSize {
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return nil, fmt.Errorf("payload length %d exceeds maximum %d", payloadLength, MaxPayloadSize)
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}
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// Create limited reader for the payload
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var payloadStream io.Reader
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if payloadLength > 0 {
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payloadStream = io.LimitReader(r, int64(payloadLength))
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}
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return &Message{
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Type: msgType,
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PayloadLength: payloadLength,
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PayloadStream: payloadStream,
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}, nil
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}
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// isValidRequestType checks if the message type is a valid request type
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func isValidRequestType(msgType MessageType) bool {
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switch msgType {
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case ChallengeRequestType, SolutionRequestType:
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return true
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default:
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return false
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}
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}
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