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// Copyright 2018 Google LLC
//
// 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 fs
import (
"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
"gvisor.googlesource.com/gvisor/pkg/waiter"
)
// FileOperations are operations on a File that diverge per file system.
//
// Operations that take a *File may use only the following interfaces:
//
// - File.UniqueID: Operations may only read this value.
// - File.Dirent: Operations must not take or drop a reference.
// - File.Offset(): This value is guaranteed to not change for the
// duration of the operation.
// - File.Flags(): This value may change during the operation.
type FileOperations interface {
// Release release resources held by FileOperations.
Release()
// Waitable defines how this File can be waited on for read and
// write readiness.
waiter.Waitable
// Seek seeks to offset based on SeekWhence. Returns the new
// offset or no change in the offset and an error.
Seek(ctx context.Context, file *File, whence SeekWhence, offset int64) (int64, error)
// Readdir reads the directory entries of file and serializes them
// using serializer.
//
// Returns the new directory offset or no change in the offset and
// an error. The offset returned must not be less than file.Offset().
//
// Serialization of directory entries must not happen asynchronously.
Readdir(ctx context.Context, file *File, serializer DentrySerializer) (int64, error)
// Read reads from file into dst at offset and returns the number
// of bytes read which must be greater than or equal to 0. File
// systems that do not support reading at an offset, (i.e. pipefs,
// sockfs) may ignore the offset. These file systems are expected
// to construct Files with !FileFlags.Pread.
//
// Read may return a nil error and only partially fill dst (at or
// before EOF). If the file represents a symlink, Read reads the target
// value of the symlink.
//
// Read does not check permissions nor flags.
//
// Read must not be called if !FileFlags.Read.
Read(ctx context.Context, file *File, dst usermem.IOSequence, offset int64) (int64, error)
// Write writes src to file at offset and returns the number of bytes
// written which must be greater than or equal to 0. Like Read, file
// systems that do not support writing at an offset (i.e. pipefs, sockfs)
// may ignore the offset. These file systems are expected to construct
// Files with !FileFlags.Pwrite.
//
// If only part of src could be written, Write must return an error
// indicating why (e.g. syserror.ErrWouldBlock).
//
// Write does not check permissions nor flags.
//
// Write must not be called if !FileFlags.Write.
Write(ctx context.Context, file *File, src usermem.IOSequence, offset int64) (int64, error)
// Fsync writes buffered modifications of file and/or flushes in-flight
// operations to backing storage based on syncType. The range to sync is
// [start, end]. The end is inclusive so that the last byte of a maximally
// sized file can be synced.
Fsync(ctx context.Context, file *File, start, end int64, syncType SyncType) error
// Flush this file's buffers/state (on close(2)).
Flush(ctx context.Context, file *File) error
// ConfigureMMap mutates opts to implement mmap(2) for the file. Most
// implementations can either embed fsutil.NoMMap (if they don't support
// memory mapping) or call fsutil.GenericConfigureMMap with the appropriate
// memmap.Mappable.
ConfigureMMap(ctx context.Context, file *File, opts *memmap.MMapOpts) error
// Ioctl implements the ioctl(2) linux syscall.
//
// io provides access to the virtual memory space to which pointers in args
// refer.
//
// Preconditions: The AddressSpace (if any) that io refers to is activated.
Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error)
}
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