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/*
*
* Copyright 2020 gRPC 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 certprovider
import (
"fmt"
"sync"
)
// provStore is the global singleton certificate provider store.
var provStore = &store{
providers: make(map[storeKey]*wrappedProvider),
}
// storeKey acts as the key to the map of providers maintained by the store. A
// combination of provider name and configuration is used to uniquely identify
// every provider instance in the store. Go maps need to be indexed by
// comparable types, so the provider configuration is converted from
// `interface{}` to string using the ParseConfig method while creating this key.
type storeKey struct {
// name of the certificate provider.
name string
// configuration of the certificate provider in string form.
config string
// opts contains the certificate name and other keyMaterial options.
opts Options
}
// wrappedProvider wraps a provider instance with a reference count.
type wrappedProvider struct {
Provider
refCount int
// A reference to the key and store are also kept here to override the
// Close method on the provider.
storeKey storeKey
store *store
}
// store is a collection of provider instances, safe for concurrent access.
type store struct {
mu sync.Mutex
providers map[storeKey]*wrappedProvider
}
// GetProvider returns a provider instance from which keyMaterial can be read.
//
// name is the registered name of the provider, config is the provider-specific
// configuration, opts contains extra information that controls the keyMaterial
// returned by the provider.
//
// Implementations of the Builder interface should clearly document the type of
// configuration accepted by them.
//
// If a provider exists for passed arguments, its reference count is incremented
// before returning. If no provider exists for the passed arguments, a new one
// is created using the registered builder. If no registered builder is found,
// or the provider configuration is rejected by it, a non-nil error is returned.
func GetProvider(name string, config interface{}, opts Options) (Provider, error) {
provStore.mu.Lock()
defer provStore.mu.Unlock()
builder := getBuilder(name)
if builder == nil {
return nil, fmt.Errorf("no registered builder for provider name: %s", name)
}
stableConfig, err := builder.ParseConfig(config)
if err != nil {
return nil, err
}
sk := storeKey{
name: name,
config: string(stableConfig.Canonical()),
opts: opts,
}
if wp, ok := provStore.providers[sk]; ok {
wp.refCount++
return wp, nil
}
provider := builder.Build(stableConfig, opts)
if provider == nil {
return nil, fmt.Errorf("certprovider.Build(%v) failed", sk)
}
wp := &wrappedProvider{
Provider: provider,
refCount: 1,
storeKey: sk,
store: provStore,
}
provStore.providers[sk] = wp
return wp, nil
}
// Close overrides the Close method of the embedded provider. It releases the
// reference held by the caller on the underlying provider and if the
// provider's reference count reaches zero, it is removed from the store, and
// its Close method is also invoked.
func (wp *wrappedProvider) Close() {
ps := wp.store
ps.mu.Lock()
defer ps.mu.Unlock()
wp.refCount--
if wp.refCount == 0 {
wp.Provider.Close()
delete(ps.providers, wp.storeKey)
}
}
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