1 files changed, 119 insertions, 0 deletions
diff --git a/vendor/golang.org/x/net/http2/writesched_roundrobin.go b/vendor/golang.org/x/net/http2/writesched_roundrobin.go
new file mode 100644
index 00000000..54fe8632
--- /dev/null
+++ b/vendor/golang.org/x/net/http2/writesched_roundrobin.go
@@ -0,0 +1,119 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http2
+
+import (
+	"fmt"
+	"math"
+)
+
+type roundRobinWriteScheduler struct {
+	// control contains control frames (SETTINGS, PING, etc.).
+	control writeQueue
+
+	// streams maps stream ID to a queue.
+	streams map[uint32]*writeQueue
+
+	// stream queues are stored in a circular linked list.
+	// head is the next stream to write, or nil if there are no streams open.
+	head *writeQueue
+
+	// pool of empty queues for reuse.
+	queuePool writeQueuePool
+}
+
+// newRoundRobinWriteScheduler constructs a new write scheduler.
+// The round robin scheduler priorizes control frames
+// like SETTINGS and PING over DATA frames.
+// When there are no control frames to send, it performs a round-robin
+// selection from the ready streams.
+func newRoundRobinWriteScheduler() WriteScheduler {
+	ws := &roundRobinWriteScheduler{
+		streams: make(map[uint32]*writeQueue),
+	}
+	return ws
+}
+
+func (ws *roundRobinWriteScheduler) OpenStream(streamID uint32, options OpenStreamOptions) {
+	if ws.streams[streamID] != nil {
+		panic(fmt.Errorf("stream %d already opened", streamID))
+	}
+	q := ws.queuePool.get()
+	ws.streams[streamID] = q
+	if ws.head == nil {
+		ws.head = q
+		q.next = q
+		q.prev = q
+	} else {
+		// Queues are stored in a ring.
+		// Insert the new stream before ws.head, putting it at the end of the list.
+		q.prev = ws.head.prev
+		q.next = ws.head
+		q.prev.next = q
+		q.next.prev = q
+	}
+}
+
+func (ws *roundRobinWriteScheduler) CloseStream(streamID uint32) {
+	q := ws.streams[streamID]
+	if q == nil {
+		return
+	}
+	if q.next == q {
+		// This was the only open stream.
+		ws.head = nil
+	} else {
+		q.prev.next = q.next
+		q.next.prev = q.prev
+		if ws.head == q {
+			ws.head = q.next
+		}
+	}
+	delete(ws.streams, streamID)
+	ws.queuePool.put(q)
+}
+
+func (ws *roundRobinWriteScheduler) AdjustStream(streamID uint32, priority PriorityParam) {}
+
+func (ws *roundRobinWriteScheduler) Push(wr FrameWriteRequest) {
+	if wr.isControl() {
+		ws.control.push(wr)
+		return
+	}
+	q := ws.streams[wr.StreamID()]
+	if q == nil {
+		// This is a closed stream.
+		// wr should not be a HEADERS or DATA frame.
+		// We push the request onto the control queue.
+		if wr.DataSize() > 0 {
+			panic("add DATA on non-open stream")
+		}
+		ws.control.push(wr)
+		return
+	}
+	q.push(wr)
+}
+
+func (ws *roundRobinWriteScheduler) Pop() (FrameWriteRequest, bool) {
+	// Control and RST_STREAM frames first.
+	if !ws.control.empty() {
+		return ws.control.shift(), true
+	}
+	if ws.head == nil {
+		return FrameWriteRequest{}, false
+	}
+	q := ws.head
+	for {
+		if wr, ok := q.consume(math.MaxInt32); ok {
+			ws.head = q.next
+			return wr, true
+		}
+		q = q.next
+		if q == ws.head {
+			break
+		}
+	}
+	return FrameWriteRequest{}, false
+}