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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package diskio
import (
"fmt"
"io"
"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
)
type File[A ~int64] interface {
Name() string
Size() (A, error)
ReadAt(p []byte, off A) (n int, err error)
WriteAt(p []byte, off A) (n int, err error)
}
var (
_ io.WriterAt = File[int64](nil)
_ io.ReaderAt = File[int64](nil)
)
type Ref[A ~int64, T any] struct {
File File[A]
Addr A
Data T
}
func (r *Ref[A, T]) Read() error {
size := binstruct.StaticSize(r.Data)
buf := make([]byte, size)
if _, err := r.File.ReadAt(buf, r.Addr); err != nil {
return err
}
n, err := binstruct.Unmarshal(buf, &r.Data)
if err != nil {
return err
}
if n != size {
return fmt.Errorf("util.Ref[%T].Read: left over data: read %v bytes but only consumed %v",
r.Data, size, n)
}
return nil
}
func (r *Ref[A, T]) Write() error {
buf, err := binstruct.Marshal(r.Data)
if err != nil {
return err
}
if _, err = r.File.WriteAt(buf, r.Addr); err != nil {
return err
}
return nil
}
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