README
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HDLC for Go
Simple implementation of an Encoder/Decoder for the High-Level Data Link Control as used in the PPP (Point-to-Point Protocol).
Implements validations of frames based on the standard CRC16 checksum.
Tested and working with pppd.
Documentation
Please read the godocs here.
Documentation
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Overview ¶
Package hdlc provides a simple implementation of an Encoder/Decoder for the High-Level Data Link Control as used in the PPP (Point-to-Point Protocol).
Example ¶
conn1, conn2 := net.Pipe()
// Decode
frameCh := make(chan *hdlc.Frame)
go func() {
decoder := hdlc.NewDecoder(conn2)
frame, err := decoder.ReadFrame()
if err != nil {
panic(err)
}
frameCh <- frame
}()
// Encode
{
encoder := hdlc.NewEncoder(conn1)
frame := hdlc.Encapsulate([]byte("hello world"), false)
if _, err := encoder.WriteFrame(frame); err != nil {
panic(err)
}
}
frame := <-frameCh
fmt.Printf("%s", frame.Payload)
Output: hello world
Example (Accm) ¶
Register the Line Feed and Horizontal Tab characters in the Async-Control-Character-Map.
conn1, conn2 := net.Pipe()
accm := hdlc.CharHT | hdlc.CharLF
// Decode
frameCh := make(chan *hdlc.Frame)
go func() {
decoder := hdlc.NewDecoder(conn2).SetACCM(accm)
frame, err := decoder.ReadFrame()
if err != nil {
panic(err)
}
frameCh <- frame
}()
// Encode
{
encoder := hdlc.NewEncoder(conn1).SetACCM(accm)
frame := hdlc.Encapsulate([]byte("hello\n\tworld"), false)
if _, err := encoder.WriteFrame(frame); err != nil {
panic(err)
}
}
frame := <-frameCh
fmt.Printf("%s", frame.Payload)
Output: hello world
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var ( // ErrInvalidFrame represents any decoding error where the data received // doesn't respect the HDLC spec. ErrInvalidFrame = errors.New("invalid frame") // ErrEmptyFrame is returned every time there's an empty frame on the stream, // ie. when decoding. ErrEmptyFrame = errors.New("empty frame") )
Functions ¶
This section is empty.
Types ¶
type ControlChar ¶ added in v1.2.0
type ControlChar uint32
ControlChar is an ASCII control character, which is a character less than 0x20.
https://en.wikipedia.org/wiki/ASCII#Control_code_chart
const ( CharNUL ControlChar = 1 << iota // Null CharSOH // Start of Head CharSTX // Start of Text CharETX // End of Text CharEOT // End of Transmission CharENQ // Enquiry CharACK // Acknowledgement CharBEL // Bell CharBS // Backspace CharHT // Horizontal Tab CharLF // Line Feed CharVT // vertical Tab CharFF // Form Feed CharCR // Carriage Return CharSO // Shift Out CharSI // Shift In CharDLE // Data Link Escape CharDC1 // Device Control 1 (XON) CharDC2 // Device Control 2 CharDC3 // Device Control 3 (XOFF) CharDC4 // Device Control 4 CharNAK // Negative Acknowledgement CharSYN // Synchronous Idle CharETB // End of Transmission Block CharCAN // Cancel CharEM // End of Medium CharSUB // Substitute CharESC // Escape CharFS // File Separator CharGS // Group Separator CharRS // Record Separator CharUS // Unit Separator // All control characters CharALL = CharNUL | CharSOH | CharSTX | CharETX | CharEOT | CharENQ | CharACK | CharBEL | CharBS | CharHT | CharLF | CharVT | CharFF | CharCR | CharSO | CharSI | CharDLE | CharDC1 | CharDC2 | CharDC3 | CharDC4 | CharNAK | CharSYN | CharETB | CharCAN | CharEM | CharSUB | CharESC | CharFS | CharGS | CharRS | CharUS )
type Decoder ¶
type Decoder struct {
// contains filtered or unexported fields
}
A Decoder reads HDLC frames from an input stream.
func NewDecoder ¶
NewDecoder returns a new decoder that reads from r. The decoder introduces its own buffering and may read data from r beyond the requested frames.
func (*Decoder) ReadFrame ¶
ReadFrame re-syncs the Decoder if necessary and reads the next frame. Returns ErrInvalidFrame if the decoding fails. Returns ErrEmptyFrame when the frame has no content to decode.
func (*Decoder) SetACCM ¶ added in v1.2.0
func (fd *Decoder) SetACCM(chars ControlChar) *Decoder
SetACCM sets the decoder's Async-Control-Character-Map (ACCM). The default ACCM value is 0, meaning that the decoder does not escape any control characters.
Note that this implementation does not negotiate the ACCM with the peer.
type Encoder ¶
type Encoder struct {
// contains filtered or unexported fields
}
An Encoder writes HDLC frames to an output stream.
func NewEncoder ¶
NewEncoder returns a new encoder that writes to w.
func (*Encoder) SetACCM ¶ added in v1.2.0
func (e *Encoder) SetACCM(chars ControlChar) *Encoder
SetACCM sets the encoder's Async-Control-Character-Map (ACCM). The default ACCM value is 0, meaning that the encoder does not escape any control characters.
Note that this implementation does not negotiate the ACCM with the peer.
type Frame ¶
A Frame is an HDLC frame. Use Encapsulate to create a new one starting from a payload.
func Encapsulate ¶
Encapsulate takes a payload p and some configuration and creates a frame that can be written with an Encoder.
Source Files