Initial QSfera import

Server/vendor/go.opentelemetry.io/contrib/zpages/bucket.go

@@ -0,0 +1,76 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package zpages // import "go.opentelemetry.io/contrib/zpages"
+
+import (
+	"time"
+
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+)
+
+const (
+	// defaultBucketCapacity is the default capacity for every bucket (latency or error based).
+	defaultBucketCapacity = 10
+	// samplePeriod is the minimum time between accepting spans in a single bucket.
+	samplePeriod = time.Second
+)
+
+// bucket is a container for a set of spans for latency buckets or errored spans.
+type bucket struct {
+	nextTime  time.Time               // next time we can accept a span
+	buffer    []sdktrace.ReadOnlySpan // circular buffer of spans
+	nextIndex int                     // location next ReadOnlySpan should be placed in buffer
+	overflow  bool                    // whether the circular buffer has wrapped around
+}
+
+// newBucket returns a new bucket with the given capacity.
+func newBucket(capacity uint) *bucket {
+	return &bucket{
+		buffer: make([]sdktrace.ReadOnlySpan, capacity),
+	}
+}
+
+// add adds a span to the bucket, if nextTime has been reached.
+func (b *bucket) add(s sdktrace.ReadOnlySpan) {
+	if s.EndTime().Before(b.nextTime) {
+		return
+	}
+	if len(b.buffer) == 0 {
+		return
+	}
+	b.nextTime = s.EndTime().Add(samplePeriod)
+	b.buffer[b.nextIndex] = s
+	b.nextIndex++
+	if b.nextIndex == len(b.buffer) {
+		b.nextIndex = 0
+		b.overflow = true
+	}
+}
+
+// len returns the number of spans in the bucket.
+func (b *bucket) len() int {
+	if b.overflow {
+		return len(b.buffer)
+	}
+	return b.nextIndex
+}
+
+// spans returns the spans in this bucket.
+func (b *bucket) spans() []sdktrace.ReadOnlySpan {
+	return append([]sdktrace.ReadOnlySpan(nil), b.buffer[0:b.len()]...)
+}