53 lines
1.4 KiB
Go
53 lines
1.4 KiB
Go
package channel
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import (
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"encoding/json"
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"io"
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)
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const bufSize = 2048
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// RawJSON is a framing that transmits and receives records on r and wc, in which
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// each record is defined by being a complete JSON value. No padding or other
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// separation is added.
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func RawJSON(r io.Reader, wc io.WriteCloser) Channel {
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return jsonc{wc: wc, dec: json.NewDecoder(r), buf: make([]byte, bufSize)}
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}
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// A jsonc implements channel.Channel. Messages sent on a raw channel are not
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// explicitly framed, and messages received are framed by JSON syntax.
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type jsonc struct {
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wc io.WriteCloser
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dec *json.Decoder
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buf json.RawMessage
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}
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// Send implements part of the Channel interface.
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func (c jsonc) Send(msg []byte) error {
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if len(msg) == 0 {
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_, err := io.WriteString(c.wc, "null\n")
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return err
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}
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_, err := c.wc.Write(msg)
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return err
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}
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// Recv implements part of the Channel interface. It reports an error if the
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// message is not a structurally valid JSON value. It is safe for the caller to
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// treat any record returned as a json.RawMessage.
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func (c jsonc) Recv() ([]byte, error) {
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c.buf = c.buf[:0] // reset
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err := c.dec.Decode(&c.buf)
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if err == nil && isNull(c.buf) {
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return nil, nil
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}
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return c.buf, err
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}
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// Close implements part of the Channel interface.
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func (c jsonc) Close() error { return c.wc.Close() }
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func isNull(msg json.RawMessage) bool {
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return len(msg) == 4 && msg[0] == 'n' && msg[1] == 'u' && msg[2] == 'l' && msg[3] == 'l'
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}
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