chore: vendor

vendor/go.opentelemetry.io/otel/sdk/metric/cache.go

@@ -0,0 +1,83 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package metric // import "go.opentelemetry.io/otel/sdk/metric"
+
+import (
+	"sync"
+)
+
+// cache is a locking storage used to quickly return already computed values.
+//
+// The zero value of a cache is empty and ready to use.
+//
+// A cache must not be copied after first use.
+//
+// All methods of a cache are safe to call concurrently.
+type cache[K comparable, V any] struct {
+	sync.Mutex
+	data map[K]V
+}
+
+// Lookup returns the value stored in the cache with the associated key if it
+// exists. Otherwise, f is called and its returned value is set in the cache
+// for key and returned.
+//
+// Lookup is safe to call concurrently. It will hold the cache lock, so f
+// should not block excessively.
+func (c *cache[K, V]) Lookup(key K, f func() V) V {
+	c.Lock()
+	defer c.Unlock()
+
+	if c.data == nil {
+		val := f()
+		c.data = map[K]V{key: val}
+		return val
+	}
+	if v, ok := c.data[key]; ok {
+		return v
+	}
+	val := f()
+	c.data[key] = val
+	return val
+}
+
+// HasKey returns true if Lookup has previously been called with that key
+//
+// HasKey is safe to call concurrently.
+func (c *cache[K, V]) HasKey(key K) bool {
+	c.Lock()
+	defer c.Unlock()
+	_, ok := c.data[key]
+	return ok
+}
+
+// cacheWithErr is a locking storage used to quickly return already computed values and an error.
+//
+// The zero value of a cacheWithErr is empty and ready to use.
+//
+// A cacheWithErr must not be copied after first use.
+//
+// All methods of a cacheWithErr are safe to call concurrently.
+type cacheWithErr[K comparable, V any] struct {
+	cache[K, valAndErr[V]]
+}
+
+type valAndErr[V any] struct {
+	val V
+	err error
+}
+
+// Lookup returns the value stored in the cacheWithErr with the associated key
+// if it exists. Otherwise, f is called and its returned value is set in the
+// cacheWithErr for key and returned.
+//
+// Lookup is safe to call concurrently. It will hold the cacheWithErr lock, so f
+// should not block excessively.
+func (c *cacheWithErr[K, V]) Lookup(key K, f func() (V, error)) (V, error) {
+	combined := c.cache.Lookup(key, func() valAndErr[V] {
+		val, err := f()
+		return valAndErr[V]{val: val, err: err}
+	})
+	return combined.val, combined.err
+}