// Push is used to issue a server push to the client. Note that this cannot be performed
// by clients.
func (c *Conn) Push(resource string, origin common.Stream) (common.PushStream, error) {
c.goawayLock.Lock()
goaway := c.goawayReceived || c.goawaySent
c.goawayLock.Unlock()
if goaway {
return nil, common.ErrGoaway
}
if c.server == nil {
return nil, errors.New("Error: Only servers can send pushes.")
}
// Parse and check URL.
url, err := url.Parse(resource)
if err != nil {
return nil, err
}
if url.Scheme == "" || url.Host == "" {
return nil, errors.New("Error: Incomplete path provided to resource.")
}
resource = url.String()
// Ensure the resource hasn't been pushed on the given stream already.
if c.pushedResources[origin] == nil {
c.pushedResources[origin] = map[string]struct{}{
resource: struct{}{},
}
} else if _, ok := c.pushedResources[origin][url.String()]; !ok {
c.pushedResources[origin][resource] = struct{}{}
} else {
return nil, errors.New("Error: Resource already pushed to this stream.")
}
// Check stream limit would allow the new stream.
if !c.pushStreamLimit.Add() {
return nil, errors.New("Error: Max concurrent streams limit exceeded.")
}
// Verify that path is prefixed with / as required by spec.
path := url.Path
if !strings.HasPrefix(path, "/") {
path = "/" + path
}
// Prepare the SYN_STREAM.
push := new(frames.SYN_STREAM)
push.Flags = common.FLAG_UNIDIRECTIONAL
push.AssocStreamID = origin.StreamID()
push.Priority = 3
push.Header = make(http.Header)
push.Header.Set("scheme", url.Scheme)
push.Header.Set("host", url.Host)
push.Header.Set("url", path)
push.Header.Set("version", "HTTP/1.1")
// Send.
c.streamCreation.Lock()
defer c.streamCreation.Unlock()
c.lastPushStreamIDLock.Lock()
c.lastPushStreamID += 2
newID := c.lastPushStreamID
c.lastPushStreamIDLock.Unlock()
if newID > common.MAX_STREAM_ID {
return nil, errors.New("Error: All server streams exhausted.")
}
push.StreamID = newID
c.output[0] <- push
// Create the PushStream.
out := NewPushStream(c, newID, origin, c.output[3])
// Store in the connection map.
c.streamsLock.Lock()
c.streams[newID] = out
c.streamsLock.Unlock()
return out, nil
}
