98 lines
1.7 KiB
Go
98 lines
1.7 KiB
Go
|
package helper
|
||
|
|
|
||
|
|
import (
|
||
|
|
"bytes"
|
||
|
|
"errors"
|
||
|
|
"fmt"
|
||
|
|
"io"
|
||
|
|
"strings"
|
||
|
|
"sync"
|
||
|
|
)
|
||
|
|
|
||
|
|
var (
|
||
|
|
ErrContainsNull = errors.New("argument contains null character")
|
||
|
|
)
|
||
|
|
|
||
|
|
// Args is sealed with a slice of arguments for writing to the helper args FD.
|
||
|
|
// The sealing args is checked to not contain null characters.
|
||
|
|
// Attempting to seal an instance twice will cause a panic.
|
||
|
|
type Args interface {
|
||
|
|
Seal(args []string) error
|
||
|
|
io.WriterTo
|
||
|
|
fmt.Stringer
|
||
|
|
}
|
||
|
|
|
||
|
|
// argsFD implements Args for helpers expecting null terminated arguments to a file descriptor.
|
||
|
|
// argsFD must not be copied after first use.
|
||
|
|
type argsFD struct {
|
||
|
|
seal []byte
|
||
|
|
sync.RWMutex
|
||
|
|
}
|
||
|
|
|
||
|
|
func (a *argsFD) Seal(args []string) error {
|
||
|
|
a.Lock()
|
||
|
|
defer a.Unlock()
|
||
|
|
|
||
|
|
if a.seal != nil {
|
||
|
|
panic("args sealed twice")
|
||
|
|
}
|
||
|
|
|
||
|
|
seal := bytes.Buffer{}
|
||
|
|
|
||
|
|
n := 0
|
||
|
|
for _, arg := range args {
|
||
|
|
// reject argument strings containing null
|
||
|
|
if hasNull(arg) {
|
||
|
|
return ErrContainsNull
|
||
|
|
}
|
||
|
|
|
||
|
|
// accumulate buffer size
|
||
|
|
n += len(arg) + 1
|
||
|
|
}
|
||
|
|
seal.Grow(n)
|
||
|
|
|
||
|
|
// write null terminated arguments
|
||
|
|
for _, arg := range args {
|
||
|
|
seal.WriteString(arg)
|
||
|
|
seal.WriteByte('\x00')
|
||
|
|
}
|
||
|
|
|
||
|
|
a.seal = seal.Bytes()
|
||
|
|
return nil
|
||
|
|
}
|
||
|
|
|
||
|
|
func (a *argsFD) WriteTo(w io.Writer) (int64, error) {
|
||
|
|
if a.seal == nil {
|
||
|
|
panic("attempted to activate unsealed args")
|
||
|
|
}
|
||
|
|
|
||
|
|
n, err := w.Write(a.seal)
|
||
|
|
return int64(n), err
|
||
|
|
}
|
||
|
|
|
||
|
|
func (a *argsFD) String() string {
|
||
|
|
if a == nil {
|
||
|
|
return "(invalid helper args)"
|
||
|
|
}
|
||
|
|
|
||
|
|
if a.seal == nil {
|
||
|
|
return "(unsealed helper args)"
|
||
|
|
}
|
||
|
|
|
||
|
|
return strings.ReplaceAll(string(a.seal), "\x00", " ")
|
||
|
|
}
|
||
|
|
|
||
|
|
func hasNull(s string) bool {
|
||
|
|
for _, b := range s {
|
||
|
|
if b == '\x00' {
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewArgs returns a new instance of Args
|
||
|
|
func NewArgs() Args {
|
||
|
|
return new(argsFD)
|
||
|
|
}
|