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// Copyright (c) Contributors to the Apptainer project, established as
// Apptainer a Series of LF Projects LLC.
// For website terms of use, trademark policy, privacy policy and other
// project policies see https://lfprojects.org/policies
// Copyright (c) 2019, 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 image
import (
"fmt"
"io"
"os"
)
type readerError string
func (e readerError) Error() string { return string(e) }
const (
// ErrNoSection corresponds to an image section not found.
ErrNoSection = readerError("no section found")
// ErrNoPartition corresponds to an image partition not found.
ErrNoPartition = readerError("no partition found")
)
func checkImage(image *Image) error {
if image == nil {
return fmt.Errorf("image is nil")
}
if image.File == nil {
return fmt.Errorf("image is not open for read")
}
return nil
}
func getSectionReader(file *os.File, section Section) io.Reader {
return io.NewSectionReader(file, int64(section.Offset), int64(section.Size))
}
func commonSectionReader(partition bool, image *Image, name string, index int) (io.Reader, error) {
var err error
idx := -1
if err = checkImage(image); err != nil {
return nil, err
}
sectionName := "sections"
sections := image.Sections
err = ErrNoSection
if partition {
sectionName = "partitions"
sections = image.Partitions
err = ErrNoPartition
}
if index >= 0 {
l := len(sections)
if index > l-1 {
return nil, fmt.Errorf("index too large, image contains %d %s", l, sectionName)
}
idx = index
}
if name == "" && idx < 0 {
return nil, fmt.Errorf("no name or positive index provided")
}
for i, p := range sections {
if p.Name == name || i == idx {
return getSectionReader(image.File, p), nil
}
}
return nil, err
}
// NewPartitionReader searches and returns a reader for an image
// partition identified by name or by index, if index is less than 0
// only partition with provided name will be returned if a matching
// entry is found
func NewPartitionReader(image *Image, name string, index int) (io.Reader, error) {
return commonSectionReader(true, image, name, index)
}
// NewSectionReader searches and returns a reader for an image
// section identified by name or by index, if index is less than 0
// only section with provided name will be returned if a matching
// entry is found.
func NewSectionReader(image *Image, name string, index int) (io.Reader, error) {
return commonSectionReader(false, image, name, index)
}
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