pkg/cdi: implement default cache.

The default cache is always available and implicitly created the
first time it is referenced. It is created with the default cache
options but can then be reconfigured explicitly if necessary.

Aso add package level variants of the most commonly used cache
functions, Refresh(), InjectDevices, and GetErrors(). These all
use the default cache.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

Author: klihub

pkg/cdi/default-cache.go

@@ -0,0 +1,70 @@
+/*
+   Copyright © 2024 The CDI 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 cdi
+
+import (
+	"sync"
+
+	oci "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+var (
+	defaultCache   *Cache
+	getDefaultOnce sync.Once
+)
+
+func getOrCreateDefaultCache(options ...Option) (*Cache, bool) {
+	var created bool
+	getDefaultOnce.Do(func() {
+		defaultCache = newCache(options...)
+		created = true
+	})
+	return defaultCache, created
+}
+
+// GetDefaultCache returns the default CDI cache instance.
+func GetDefaultCache() *Cache {
+	cache, _ := getOrCreateDefaultCache()
+	return cache
+}
+
+// Configure applies options to the default CDI cache. Updates and refreshes
+// the default cache if options are not empty.
+func Configure(options ...Option) {
+	cache, created := getOrCreateDefaultCache(options...)
+	if len(options) == 0 || created {
+		return
+	}
+	cache.Configure(options...)
+}
+
+// Refresh explicitly refreshes the default CDI cache instance.
+func Refresh() error {
+	return GetDefaultCache().Refresh()
+}
+
+// InjectDevices injects the given qualified devices to the given OCI Spec.
+// using the default CDI cache instance to resolve devices.
+func InjectDevices(ociSpec *oci.Spec, devices ...string) ([]string, error) {
+	return GetDefaultCache().InjectDevices(ociSpec, devices...)
+}
+
+// GetErrors returns all errors encountered during the last refresh of
+// the default CDI cache instance.
+func GetErrors() map[string][]error {
+	return GetDefaultCache().GetErrors()
+}

pkg/cdi/doc.go

@@ -29,6 +29,14 @@
 // the vast majority of CDI consumers need. The API should be usable both
 // by OCI runtime clients and runtime implementations.
 //
+// # Default CDI Cache
+//
+// There is a default CDI cache instance which is always implicitly
+// available and instantiated the first time it is referenced directly
+// or indirectly. The most frequently used cache functions are available
+// as identically named package level functions which operate on the
+// default cache instance.
+//
 // # CDI Registry
 //
 // The primary interface to interact with CDI devices is the Registry. It