undocker/internal/cmdrootfs/cmdrootfs.go

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package cmdrootfs
import (
"errors"
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"fmt"
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"io"
"os"
goflags "github.com/jessevdk/go-flags"
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"github.com/motiejus/code/undocker/internal/cmd"
"github.com/motiejus/code/undocker/rootfs"
"go.uber.org/multierr"
)
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type (
rootfsFactory func(io.ReadSeeker) io.WriterTo
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// Command is "rootfs" command
Command struct {
cmd.BaseCommand
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PositionalArgs struct {
Infile goflags.Filename `long:"infile" description:"Input tarball"`
Outfile string `long:"outfile" description:"Output path, stdout is '-'"`
} `positional-args:"yes" required:"yes"`
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rootfsNew rootfsFactory
}
)
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// Execute executes rootfs Command
func (c *Command) Execute(args []string) (err error) {
if len(args) != 0 {
return errors.New("too many args")
}
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if c.rootfsNew == nil {
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c.init()
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}
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rd, err := os.Open(string(c.PositionalArgs.Infile))
if err != nil {
return err
}
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defer func() { err = multierr.Append(err, rd.Close()) }()
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var out io.Writer
if fname := string(c.PositionalArgs.Outfile); fname == "-" {
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out = c.Stdout
} else {
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outf, err := os.Create(fname)
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if err != nil {
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return fmt.Errorf("create: %w", err)
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}
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defer func() { err = multierr.Append(err, outf.Close()) }()
out = outf
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}
if _, err := c.rootfsNew(rd).WriteTo(out); err != nil {
return err
}
return nil
}
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// init() initializes Command with the default options.
//
// Since constructors for sub-commands requires lots of boilerplate,
// command will initialize itself.
func (c *Command) init() {
c.BaseCommand.Init()
c.rootfsNew = func(r io.ReadSeeker) io.WriterTo {
return rootfs.New(r)
}
}