1 files changed, 70 insertions, 0 deletions
diff --git a/vendor/go.opentelemetry.io/otel/sdk/metric/exemplar/histogram_reservoir.go b/vendor/go.opentelemetry.io/otel/sdk/metric/exemplar/histogram_reservoir.go
new file mode 100644
index 000000000..3b76cf305
--- /dev/null
+++ b/vendor/go.opentelemetry.io/otel/sdk/metric/exemplar/histogram_reservoir.go
@@ -0,0 +1,70 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package exemplar // import "go.opentelemetry.io/otel/sdk/metric/exemplar"
+
+import (
+	"context"
+	"slices"
+	"sort"
+	"time"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+// HistogramReservoirProvider is a provider of [HistogramReservoir].
+func HistogramReservoirProvider(bounds []float64) ReservoirProvider {
+	cp := slices.Clone(bounds)
+	slices.Sort(cp)
+	return func(_ attribute.Set) Reservoir {
+		return NewHistogramReservoir(cp)
+	}
+}
+
+// NewHistogramReservoir returns a [HistogramReservoir] that samples the last
+// measurement that falls within a histogram bucket. The histogram bucket
+// upper-boundaries are define by bounds.
+//
+// The passed bounds must be sorted before calling this function.
+func NewHistogramReservoir(bounds []float64) *HistogramReservoir {
+	return &HistogramReservoir{
+		bounds:  bounds,
+		storage: newStorage(len(bounds) + 1),
+	}
+}
+
+var _ Reservoir = &HistogramReservoir{}
+
+// HistogramReservoir is a [Reservoir] that samples the last measurement that
+// falls within a histogram bucket. The histogram bucket upper-boundaries are
+// define by bounds.
+type HistogramReservoir struct {
+	*storage
+
+	// bounds are bucket bounds in ascending order.
+	bounds []float64
+}
+
+// Offer accepts the parameters associated with a measurement. The
+// parameters will be stored as an exemplar if the Reservoir decides to
+// sample the measurement.
+//
+// The passed ctx needs to contain any baggage or span that were active
+// when the measurement was made. This information may be used by the
+// Reservoir in making a sampling decision.
+//
+// The time t is the time when the measurement was made. The v and a
+// parameters are the value and dropped (filtered) attributes of the
+// measurement respectively.
+func (r *HistogramReservoir) Offer(ctx context.Context, t time.Time, v Value, a []attribute.KeyValue) {
+	var x float64
+	switch v.Type() {
+	case Int64ValueType:
+		x = float64(v.Int64())
+	case Float64ValueType:
+		x = v.Float64()
+	default:
+		panic("unknown value type")
+	}
+	r.store[sort.SearchFloat64s(r.bounds, x)] = newMeasurement(ctx, t, v, a)
+}