81 lines
1.6 KiB
Go
81 lines
1.6 KiB
Go
package tableflip
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import (
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"encoding/gob"
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"io"
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"io/ioutil"
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"os"
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"github.com/pkg/errors"
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)
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const (
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sentinelEnvVar = "TABLEFLIP_HAS_PARENT_7DIU3"
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notifyReady = 42
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)
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type parent struct {
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wr *os.File
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result <-chan error
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exited <-chan struct{}
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}
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func newParent(env *env) (*parent, map[fileName]*file, error) {
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if env.getenv(sentinelEnvVar) == "" {
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return nil, make(map[fileName]*file), nil
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}
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wr := env.newFile(3, "write")
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rd := env.newFile(4, "read")
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var names [][]string
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dec := gob.NewDecoder(rd)
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if err := dec.Decode(&names); err != nil {
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return nil, nil, errors.Wrap(err, "can't decode names from parent process")
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}
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files := make(map[fileName]*file)
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for i, parts := range names {
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var key fileName
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copy(key[:], parts)
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// Start at 5 to account for stdin, etc. and write
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// and read pipes.
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fd := 5 + i
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env.closeOnExec(fd)
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files[key] = &file{
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env.newFile(uintptr(fd), key.String()),
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uintptr(fd),
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}
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}
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result := make(chan error, 1)
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exited := make(chan struct{})
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go func() {
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defer rd.Close()
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n, err := io.Copy(ioutil.Discard, rd)
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if n != 0 {
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err = errors.New("unexpected data from parent process")
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} else if err != nil {
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err = errors.Wrap(err, "unexpected error while waiting for parent to exit")
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}
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result <- err
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close(exited)
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}()
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return &parent{
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wr: wr,
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result: result,
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exited: exited,
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}, files, nil
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}
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func (ps *parent) sendReady() error {
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defer ps.wr.Close()
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if _, err := ps.wr.Write([]byte{notifyReady}); err != nil {
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return errors.Wrap(err, "can't notify parent process")
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}
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return nil
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}
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