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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 ramfs
import (
"io"
"sync"
"gvisor.googlesource.com/gvisor/pkg/secio"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
"gvisor.googlesource.com/gvisor/pkg/syserror"
)
// File represents a unique file. It uses a simple byte slice as storage, and
// thus should only be used for small files.
//
// A File is not mappable.
//
// +stateify savable
type File struct {
Entry
// mu protects the fields below.
mu sync.Mutex `state:"nosave"`
// data tracks backing data for the file.
data []byte
}
// InitFile initializes a file.
func (f *File) InitFile(ctx context.Context, owner fs.FileOwner, perms fs.FilePermissions) {
f.InitEntry(ctx, owner, perms)
}
// UnstableAttr returns unstable attributes of this ramfs file.
func (f *File) UnstableAttr(ctx context.Context, inode *fs.Inode) (fs.UnstableAttr, error) {
f.mu.Lock()
defer f.mu.Unlock()
uattr, _ := f.Entry.UnstableAttr(ctx, inode)
uattr.Size = int64(len(f.data))
uattr.Usage = f.usageLocked()
return uattr, nil
}
// usageLocked returns the disk usage. Caller must hold f.mu.
func (f *File) usageLocked() int64 {
return int64(len(f.data))
}
// Append appends the given data. This is for internal use.
func (f *File) Append(data []byte) {
f.mu.Lock()
defer f.mu.Unlock()
f.data = append(f.data, data...)
}
// Truncate truncates this node.
func (f *File) Truncate(ctx context.Context, inode *fs.Inode, l int64) error {
f.mu.Lock()
defer f.mu.Unlock()
if l < int64(len(f.data)) {
// Remove excess bytes.
f.data = f.data[:l]
return nil
} else if l > int64(len(f.data)) {
// Create a new slice with size l, and copy f.data into it.
d := make([]byte, l)
copy(d, f.data)
f.data = d
}
f.Entry.NotifyModification(ctx)
return nil
}
// ReadAt implements io.ReaderAt.
func (f *File) ReadAt(data []byte, offset int64) (int, error) {
if offset < 0 {
return 0, ErrInvalidOp
}
if offset >= int64(len(f.data)) {
return 0, io.EOF
}
n := copy(data, f.data[offset:])
// Did we read past the end?
if offset+int64(len(data)) >= int64(len(f.data)) {
return n, io.EOF
}
return n, nil
}
// DeprecatedPreadv reads into a collection of slices from a given offset.
func (f *File) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
f.mu.Lock()
defer f.mu.Unlock()
if offset >= int64(len(f.data)) {
return 0, io.EOF
}
n, err := dst.CopyOut(ctx, f.data[offset:])
if n > 0 {
f.Entry.NotifyAccess(ctx)
}
return int64(n), err
}
// WriteAt implements io.WriterAt.
func (f *File) WriteAt(data []byte, offset int64) (int, error) {
if offset < 0 {
return 0, ErrInvalidOp
}
newLen := offset + int64(len(data))
if newLen < 0 {
// Overflow.
return 0, syserror.EINVAL
}
if newLen > int64(len(f.data)) {
// Copy f.data into new slice with expanded length.
d := make([]byte, newLen)
copy(d, f.data)
f.data = d
}
return copy(f.data[offset:], data), nil
}
// DeprecatedPwritev writes from a collection of slices at a given offset.
func (f *File) DeprecatedPwritev(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) {
f.mu.Lock()
defer f.mu.Unlock()
n, err := src.CopyInTo(ctx, safemem.FromIOWriter{secio.NewOffsetWriter(f, offset)})
if n > 0 {
f.Entry.NotifyModification(ctx)
}
return n, err
}
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