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// Copyright (c) 2019-2023, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.
package tools
import (
"fmt"
"io"
"os"
"github.com/sylabs/singularity/v4/pkg/util/loop"
"golang.org/x/sys/unix"
)
// CreateLoop associates a file to loop device and returns
// path of loop device used and a closer to close the loop device
func CreateLoop(file *os.File, offset, size uint64) (string, io.Closer, error) {
loopDev := &loop.Device{
MaxLoopDevices: loop.GetMaxLoopDevices(),
Shared: true,
Info: &unix.LoopInfo64{
Sizelimit: size,
Offset: offset,
Flags: unix.LO_FLAGS_AUTOCLEAR | unix.LO_FLAGS_READ_ONLY,
},
}
idx := 0
if err := loopDev.AttachFromFile(file, os.O_RDONLY, &idx); err != nil {
return "", nil, fmt.Errorf("failed to attach image %s: %s", file.Name(), err)
}
return fmt.Sprintf("/dev/loop%d", idx), loopDev, nil
}
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