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// Copyright 2019 The gVisor 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 vfs
import (
"gvisor.dev/gvisor/pkg/context"
)
// contextID is this package's type for context.Context.Value keys.
type contextID int
const (
// CtxMountNamespace is a Context.Value key for a MountNamespace.
CtxMountNamespace contextID = iota
// CtxRoot is a Context.Value key for a VFS root.
CtxRoot
)
// MountNamespaceFromContext returns the MountNamespace used by ctx. If ctx is
// not associated with a MountNamespace, MountNamespaceFromContext returns nil.
//
// A reference is taken on the returned MountNamespace.
func MountNamespaceFromContext(ctx context.Context) *MountNamespace {
if v := ctx.Value(CtxMountNamespace); v != nil {
return v.(*MountNamespace)
}
return nil
}
// RootFromContext returns the VFS root used by ctx. It takes a reference on
// the returned VirtualDentry. If ctx does not have a specific VFS root,
// RootFromContext returns a zero-value VirtualDentry.
func RootFromContext(ctx context.Context) VirtualDentry {
if v := ctx.Value(CtxRoot); v != nil {
return v.(VirtualDentry)
}
return VirtualDentry{}
}
type rootContext struct {
context.Context
root VirtualDentry
}
// WithRoot returns a copy of ctx with the given root.
func WithRoot(ctx context.Context, root VirtualDentry) context.Context {
return &rootContext{
Context: ctx,
root: root,
}
}
// Value implements Context.Value.
func (rc rootContext) Value(key interface{}) interface{} {
switch key {
case CtxRoot:
rc.root.IncRef()
return rc.root
default:
return rc.Context.Value(key)
}
}
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