53 lines
1.4 KiB
Go
53 lines
1.4 KiB
Go
|
package channel
|
||
|
|
|
||
|
|
import (
|
||
|
|
"encoding/json"
|
||
|
|
"io"
|
||
|
|
)
|
||
|
|
|
||
|
|
const bufSize = 2048
|
||
|
|
|
||
|
|
// 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 RawJSON(r io.Reader, wc io.WriteCloser) Channel {
|
||
|
|
return jsonc{wc: wc, dec: json.NewDecoder(r), buf: make([]byte, bufSize)}
|
||
|
|
}
|
||
|
|
|
||
|
|
// A jsonc implements channel.Channel. Messages sent on a raw channel are not
|
||
|
|
// explicitly framed, and messages received are framed by JSON syntax.
|
||
|
|
type jsonc struct {
|
||
|
|
wc io.WriteCloser
|
||
|
|
dec *json.Decoder
|
||
|
|
buf json.RawMessage
|
||
|
|
}
|
||
|
|
|
||
|
|
// Send implements part of the Channel interface.
|
||
|
|
func (c jsonc) Send(msg []byte) error {
|
||
|
|
if len(msg) == 0 {
|
||
|
|
_, err := io.WriteString(c.wc, "null\n")
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
_, err := c.wc.Write(msg)
|
||
|
|
return err
|
||
|
|
}
|
||
|
|
|
||
|
|
// Recv implements part of the Channel interface. It reports an error if the
|
||
|
|
// message is not a structurally valid JSON value. It is safe for the caller to
|
||
|
|
// treat any record returned as a json.RawMessage.
|
||
|
|
func (c jsonc) Recv() ([]byte, error) {
|
||
|
|
c.buf = c.buf[:0] // reset
|
||
|
|
err := c.dec.Decode(&c.buf)
|
||
|
|
if err == nil && isNull(c.buf) {
|
||
|
|
return nil, nil
|
||
|
|
}
|
||
|
|
return c.buf, err
|
||
|
|
}
|
||
|
|
|
||
|
|
// Close implements part of the Channel interface.
|
||
|
|
func (c jsonc) Close() error { return c.wc.Close() }
|
||
|
|
|
||
|
|
func isNull(msg json.RawMessage) bool {
|
||
|
|
return len(msg) == 4 && msg[0] == 'n' && msg[1] == 'u' && msg[2] == 'l' && msg[3] == 'l'
|
||
|
|
}
|