[WIP] Compliant bound instruments

attribute/set.go

@@ -265,6 +265,47 @@ func NewSetWithFiltered(kvs []KeyValue, filter Filter) (Set, []KeyValue) {
 	return newSet(kvs), nil
 }
 
+// NewDistinctWithFilter returns a Distinct identifier for the filtered attribute set,
+// and the sorted and de-duplicated slice of attributes. It modifies the input slice
+// in-place to sort and de-duplicate the attributes.
+//
+// The returned Distinct represents the equivalence class of the attribute set after
+// the filter is applied. The returned slice contains all unique attributes, including
+// those that did not pass the filter.
+func NewDistinctWithFilter(kvs []KeyValue, filter Filter) (Distinct, []KeyValue) {
+	if len(kvs) == 0 {
+		return Distinct{hash: emptyHash}, kvs
+	}
+
+	// Stable sort so the following de-duplication can implement
+	// last-value-wins semantics.
+	slices.SortStableFunc(kvs, func(a, b KeyValue) int {
+		return cmp.Compare(a.Key, b.Key)
+	})
+
+	position := len(kvs) - 1
+	offset := position - 1
+
+	// De-duplicate with last-value-wins semantics.
+	for ; offset >= 0; offset-- {
+		if kvs[offset].Key == kvs[position].Key {
+			continue
+		}
+		position--
+		kvs[offset], kvs[position] = kvs[position], kvs[offset]
+	}
+	kvs = kvs[position:]
+
+	h := xxhash.New()
+	for _, kv := range kvs {
+		if filter == nil || filter(kv) {
+			h = hashKV(h, kv)
+		}
+	}
+
+	return Distinct{hash: h.Sum64()}, kvs
+}
+
 // NewSetWithSortableFiltered returns a new Set.
 //
 // Duplicate keys are eliminated by taking the last value.  This

metric/x/bound.go

@@ -0,0 +1,27 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package x // import "go.opentelemetry.io/otel/metric/x"
+
+import (
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+)
+
+// Float64Binder is an interface that can be implemented by instruments that support
+// binding attributes ahead of time.
+type Float64Binder interface {
+	// Bind returns a metric.Float64Counter for the given attributes.
+	// The returned counter is bound to the attributes and should be optimized
+	// for performance by avoiding map lookups on every Add call.
+	Bind(attrs ...attribute.KeyValue) metric.Float64Counter
+}
+
+// Int64Binder is an interface that can be implemented by instruments that support
+// binding attributes ahead of time.
+type Int64Binder interface {
+	// Bind returns a metric.Int64Counter for the given attributes.
+	// The returned counter is bound to the attributes and should be optimized
+	// for performance by avoiding map lookups on every Add call.
+	Bind(attrs ...attribute.KeyValue) metric.Int64Counter
+}