Package channel defines a communications channel that can encode/transmit and decode/receive data records with a configurable framing discipline, and provides some simple framing implementations.


A Channel represents the ability to send and received framed records, comprising the methods:

Send([]byte) error      // send a single complete record
Recv() ([]byte, error)  // receive a single complete record
Close() error           // close the channel

Each record passed to Send is available for Recv. Record contents are not interpreted (except as noted below), and it is up to the implementation to decide how records are framed for transport. A channel must support use by one sender and one receiver concurrently, but is not otherwise required to be safe for concurrent use.


A Framing function adapts a pair of io.Reader and io.WriteCloser to a Channel by imposing a particular message-framing discipline. This package provides several framing implementations, for example:

ch := channel.LSP(r, wc)

creates a channel that reads from r and writes to wc using the Language Server Protocol (LSP) framing defined by



This section is empty.


View Source
var LSP = Header("application/vscode-jsonrpc; charset=utf-8")

    LSP is a header framing (see Header) that transmits and receives messages on r and wc using the MIME type application/vscode-jsonrpc. This is the format preferred by the Language Server Protocol (LSP), defined by

    View Source
    var Line = Split('\n')

      Line is a framing discipline for messages terminated by a Unicode LF (10). This framing has the constraint that records may not contain LF.


      func IsErrClosing

      func IsErrClosing(err error) bool

        IsErrClosing reports whether err is the internal error returned by a read from a pipe or socket that is closed. This is false for err == nil.


        type Channel

        type Channel interface {
        	// Close shuts down the channel, after which no further records may be
        	// sent or received.
        	Close() error

          A Channel represents the ability to transmit and receive data records. A channel does not interpret the contents of a record, but may add and remove framing so that records can be embedded in higher-level protocols.

          One sender and one receiver may use a Channel concurrently, but the methods of a Channel are not otherwise required to be safe for concurrent use.

          func Direct

          func Direct() (client, server Channel)

            Direct returns a pair of synchronous connected channels that pass message buffers directly in memory without framing or encoding. Sends to client will be received by server, and vice versa.

            func RawJSON

            func RawJSON(r io.Reader, wc io.WriteCloser) Channel

              RawJSON is a framing that transmits and receives records on r and wc, in which each record is defined by being a complete JSON value. No padding or other separation is added.

              func Varint

              func Varint(r io.Reader, wc io.WriteCloser) Channel

                Varint is a framing that transmits and receives messages on r and wc, with each message prefixed by its length encoded in a varint as defined by the encoding/binary package.

                func WithTrigger

                func WithTrigger(ch Channel, trigger func()) Channel

                  WithTrigger returns a Channel that delegates I/O operations to ch, and when a Recv operation on ch returns io.EOF it synchronously calls the trigger.

                  type ContentTypeMismatchError

                  type ContentTypeMismatchError struct {
                  	Got, Want string // the observed and expected content type values

                    A ContentTypeMismatchError is reported by the Recv method of a Header framing when the content type of the message does not match the type expected by the channel.

                    func (*ContentTypeMismatchError) Error

                    func (c *ContentTypeMismatchError) Error() string

                    type Framing

                    type Framing func(io.Reader, io.WriteCloser) Channel

                      A Framing converts a reader and a writer into a Channel with a particular message-framing discipline.

                      func Header(mimeType string) Framing

                        Header returns a framing that behaves as StrictHeader, but allows received messages to omit the Content-Type header without error. An error will still be reported if a content-type is set but does not match.

                        func Split

                        func Split(b byte) Framing

                          Split returns a framing in which each message is terminated by the specified byte value. The framing has the constraint that outbound records may not contain the split byte internally.

                          func StrictHeader

                          func StrictHeader(mimeType string) Framing

                            StrictHeader defines a framing that transmits and receives messages using a header prefix similar to HTTP, in which mimeType describes the content type.

                            Specifically, each message is sent in the format:

                            Content-Type: <mime-type>\r\n
                            Content-Length: <nbytes>\r\n

                            The length (nbytes) is encoded as decimal digits. For example, given a mimeType value "application/json", the message "123\n" is transmitted as:

                            Content-Type: application/json\r\n
                            Content-Length: 4\r\n

                            If mimeType == "", the Content-Type header is omitted when sending.

                            If the content type of an otherwise-valid received message does not match the expected value, Recv returns the decoded message along with an error of concrete type *ContentTypeMismatchError.

                            Note: The framing returned by StrictHeader does not verify the encoding of a message matches the declared mimeType.

                            type Receiver

                            type Receiver interface {
                            	// Recv returns the next available record from the channel.  If no further
                            	// messages are available, it returns nil, io.EOF.  Each call to Recv
                            	// fetches a single complete record.
                            	Recv() ([]byte, error)

                              A Receiver represents the ability to receive a message from a channel.

                              type Sender

                              type Sender interface {
                              	// Send transmits a record on the channel. Each call to Send transmits one
                              	// complete record.
                              	Send([]byte) error

                                A Sender represents the ability to transmit a message on a channel.


                                Path Synopsis
                                Package chanutil exports helper functions for working with channels and framing defined by the package.
                                Package chanutil exports helper functions for working with channels and framing defined by the package.