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// Copyright 2020 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
package tool
import (
"bytes"
"encoding/hex"
"flag"
"fmt"
"strings"
"github.com/google/syzkaller/pkg/log"
)
type Flag struct {
Name string
Value string
}
// OptionalFlags produces command line flag value that encapsulates the given flags as optional.
// This is intended for programmatic use only when we invoke older versions of binaries with new unsupported flags.
// Use tool.Init to support optional flags in the binary.
// The format keeps flags reasonably readable ("-optional=foo=bar:baz=123"), not subject to accidental splitting
// into multiple arguments due to spaces and supports bool/non-bool flags.
func OptionalFlags(flags []Flag) string {
return fmt.Sprintf("-%v=%v", optionalFlag, serializeFlags(flags))
}
func ParseFlags(set *flag.FlagSet, args []string) error {
flagOptional := set.String(optionalFlag, "", "optional flags for programmatic use only")
if err := set.Parse(args); err != nil {
return err
}
flags, err := deserializeFlags(*flagOptional)
if err != nil {
return err
}
for _, f := range flags {
ff := set.Lookup(f.Name)
if ff == nil {
log.Logf(0, "ignoring optional flag %q=%q", f.Name, f.Value)
continue
}
if err := ff.Value.Set(f.Value); err != nil {
return err
}
}
return nil
}
const optionalFlag = "optional"
func serializeFlags(flags []Flag) string {
if len(flags) == 0 {
return ""
}
buf := new(bytes.Buffer)
for _, f := range flags {
fmt.Fprintf(buf, ":%v=%v", flagEscape(f.Name), flagEscape(f.Value))
}
return buf.String()[1:]
}
func deserializeFlags(value string) ([]Flag, error) {
if value == "" {
return nil, nil
}
var flags []Flag
for _, arg := range strings.Split(value, ":") {
eq := strings.IndexByte(arg, '=')
if eq == -1 {
return nil, fmt.Errorf("failed to parse flags %q: no eq", value)
}
name, err := flagUnescape(arg[:eq])
if err != nil {
return nil, fmt.Errorf("failed to parse flags %q: %v", value, err)
}
value, err := flagUnescape(arg[eq+1:])
if err != nil {
return nil, fmt.Errorf("failed to parse flags %q: %v", value, err)
}
flags = append(flags, Flag{name, value})
}
return flags, nil
}
func flagEscape(s string) string {
buf := new(bytes.Buffer)
for i := 0; i < len(s); i++ {
ch := s[i]
if ch <= 0x20 || ch >= 0x7f || ch == ':' || ch == '=' || ch == '\\' {
buf.Write([]byte{'\\', 'x'})
buf.WriteString(hex.EncodeToString([]byte{ch}))
continue
}
buf.WriteByte(ch)
}
return buf.String()
}
func flagUnescape(s string) (string, error) {
buf := new(bytes.Buffer)
for i := 0; i < len(s); i++ {
ch := s[i]
if ch <= 0x20 || ch >= 0x7f || ch == ':' || ch == '=' {
return "", fmt.Errorf("unescaped char %v", ch)
}
if ch == '\\' {
if i+4 > len(s) || s[i+1] != 'x' {
return "", fmt.Errorf("truncated escape sequence")
}
res, err := hex.DecodeString(s[i+2 : i+4])
if err != nil {
return "", err
}
buf.WriteByte(res[0])
i += 3
continue
}
buf.WriteByte(ch)
}
return buf.String(), nil
}
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