1 files changed, 95 insertions, 0 deletions
diff --git a/vendor/go.opentelemetry.io/otel/sdk/metric/exemplar/storage.go b/vendor/go.opentelemetry.io/otel/sdk/metric/exemplar/storage.go
new file mode 100644
index 000000000..0e2e26dfb
--- /dev/null
+++ b/vendor/go.opentelemetry.io/otel/sdk/metric/exemplar/storage.go
@@ -0,0 +1,95 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
+
+import (
+	"context"
+	"time"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// storage is an exemplar storage for [Reservoir] implementations.
+type storage struct {
+	// store are the measurements sampled.
+	//
+	// This does not use []metricdata.Exemplar because it potentially would
+	// require an allocation for trace and span IDs in the hot path of Offer.
+	store []measurement
+}
+
+func newStorage(n int) *storage {
+	return &storage{store: make([]measurement, n)}
+}
+
+// Collect returns all the held exemplars.
+//
+// The Reservoir state is preserved after this call.
+func (r *storage) Collect(dest *[]Exemplar) {
+	*dest = reset(*dest, len(r.store), len(r.store))
+	var n int
+	for _, m := range r.store {
+		if !m.valid {
+			continue
+		}
+
+		m.exemplar(&(*dest)[n])
+		n++
+	}
+	*dest = (*dest)[:n]
+}
+
+// measurement is a measurement made by a telemetry system.
+type measurement struct {
+	// FilteredAttributes are the attributes dropped during the measurement.
+	FilteredAttributes []attribute.KeyValue
+	// Time is the time when the measurement was made.
+	Time time.Time
+	// Value is the value of the measurement.
+	Value Value
+	// SpanContext is the SpanContext active when a measurement was made.
+	SpanContext trace.SpanContext
+
+	valid bool
+}
+
+// newMeasurement returns a new non-empty Measurement.
+func newMeasurement(ctx context.Context, ts time.Time, v Value, droppedAttr []attribute.KeyValue) measurement {
+	return measurement{
+		FilteredAttributes: droppedAttr,
+		Time:               ts,
+		Value:              v,
+		SpanContext:        trace.SpanContextFromContext(ctx),
+		valid:              true,
+	}
+}
+
+// exemplar returns m as an [Exemplar].
+func (m measurement) exemplar(dest *Exemplar) {
+	dest.FilteredAttributes = m.FilteredAttributes
+	dest.Time = m.Time
+	dest.Value = m.Value
+
+	if m.SpanContext.HasTraceID() {
+		traceID := m.SpanContext.TraceID()
+		dest.TraceID = traceID[:]
+	} else {
+		dest.TraceID = dest.TraceID[:0]
+	}
+
+	if m.SpanContext.HasSpanID() {
+		spanID := m.SpanContext.SpanID()
+		dest.SpanID = spanID[:]
+	} else {
+		dest.SpanID = dest.SpanID[:0]
+	}
+}
+
+func reset[T any](s []T, length, capacity int) []T {
+	if cap(s) < capacity {
+		return make([]T, length, capacity)
+	}
+	return s[:length]
+}