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// Copyright 2014 Manu Martinez-Almeida. All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.
package sse
import (
type decoder struct {
events []Event
func Decode(r io.Reader) ([]Event, error) {
var dec decoder
return dec.decode(r)
func (d *decoder) dispatchEvent(event Event, data string) {
dataLength := len(data)
if dataLength > 0 {
//If the data buffer's last character is a U+000A LINE FEED (LF) character, then remove the last character from the data buffer.
data = data[:dataLength-1]
if dataLength == 0 && event.Event == "" {
if event.Event == "" {
event.Event = "message"
event.Data = data = append(, event)
func (d *decoder) decode(r io.Reader) ([]Event, error) {
buf, err := ioutil.ReadAll(r)
if err != nil {
return nil, err
var currentEvent Event
var dataBuffer *bytes.Buffer = new(bytes.Buffer)
// TODO (and unit tests)
// Lines must be separated by either a U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pair,
// a single U+000A LINE FEED (LF) character,
// or a single U+000D CARRIAGE RETURN (CR) character.
lines := bytes.Split(buf, []byte{'\n'})
for _, line := range lines {
if len(line) == 0 {
// If the line is empty (a blank line). Dispatch the event.
d.dispatchEvent(currentEvent, dataBuffer.String())
// reset current event and data buffer
currentEvent = Event{}
if line[0] == byte(':') {
// If the line starts with a U+003A COLON character (:), ignore the line.
var field, value []byte
colonIndex := bytes.IndexRune(line, ':')
if colonIndex != -1 {
// If the line contains a U+003A COLON character character (:)
// Collect the characters on the line before the first U+003A COLON character (:),
// and let field be that string.
field = line[:colonIndex]
// Collect the characters on the line after the first U+003A COLON character (:),
// and let value be that string.
value = line[colonIndex+1:]
// If value starts with a single U+0020 SPACE character, remove it from value.
if len(value) > 0 && value[0] == ' ' {
value = value[1:]
} else {
// Otherwise, the string is not empty but does not contain a U+003A COLON character character (:)
// Use the whole line as the field name, and the empty string as the field value.
field = line
value = []byte{}
// The steps to process the field given a field name and a field value depend on the field name,
// as given in the following list. Field names must be compared literally,
// with no case folding performed.
switch string(field) {
case "event":
// Set the event name buffer to field value.
currentEvent.Event = string(value)
case "id":
// Set the event stream's last event ID to the field value.
currentEvent.Id = string(value)
case "retry":
// If the field value consists of only characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9),
// then interpret the field value as an integer in base ten, and set the event stream's reconnection time to that integer.
// Otherwise, ignore the field.
currentEvent.Id = string(value)
case "data":
// Append the field value to the data buffer,
// then append a single U+000A LINE FEED (LF) character to the data buffer.
//Otherwise. The field is ignored.
// Once the end of the file is reached, the user agent must dispatch the event one final time.
d.dispatchEvent(currentEvent, dataBuffer.String())
return, nil
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