// Copyright 2018 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 ashmem implements Android ashmem module (Anonymus Shared Memory).
package ashmem

import (
	"gvisor.dev/gvisor/pkg/abi/linux"
	"gvisor.dev/gvisor/pkg/sentry/context"
	"gvisor.dev/gvisor/pkg/sentry/fs"
	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
	"gvisor.dev/gvisor/pkg/sentry/usermem"
)

// Device implements fs.InodeOperations.
//
// +stateify savable
type Device struct {
	fsutil.InodeGenericChecker       `state:"nosave"`
	fsutil.InodeNoExtendedAttributes `state:"nosave"`
	fsutil.InodeNoopAllocate         `state:"nosave"`
	fsutil.InodeNoopRelease          `state:"nosave"`
	fsutil.InodeNoopTruncate         `state:"nosave"`
	fsutil.InodeNoopWriteOut         `state:"nosave"`
	fsutil.InodeNotDirectory         `state:"nosave"`
	fsutil.InodeNotMappable          `state:"nosave"`
	fsutil.InodeNotSocket            `state:"nosave"`
	fsutil.InodeNotSymlink           `state:"nosave"`
	fsutil.InodeVirtual              `state:"nosave"`

	fsutil.InodeSimpleAttributes
}

var _ fs.InodeOperations = (*Device)(nil)

// NewDevice creates and initializes a Device structure.
func NewDevice(ctx context.Context, owner fs.FileOwner, fp fs.FilePermissions) *Device {
	return &Device{
		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fp, linux.ANON_INODE_FS_MAGIC),
	}
}

// GetFile implements fs.InodeOperations.GetFile.
func (ad *Device) GetFile(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
	return fs.NewFile(ctx, d, flags, &Area{
		ad:        ad,
		tmpfsFile: nil,
		perms:     usermem.AnyAccess,
	}), nil
}