/usr/share/gocode/src/github.com/miekg/dns/msg_generate.go is in golang-github-miekg-dns-dev 0.0~git20170501.0.f282f80-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// msg_generate.go is meant to run with go generate. It will use
// go/{importer,types} to track down all the RR struct types. Then for each type
// it will generate pack/unpack methods based on the struct tags. The generated source is
// written to zmsg.go, and is meant to be checked into git.
package main
import (
"bytes"
"fmt"
"go/format"
"go/importer"
"go/types"
"log"
"os"
"strings"
)
var packageHdr = `
// *** DO NOT MODIFY ***
// AUTOGENERATED BY go generate from msg_generate.go
package dns
`
// getTypeStruct will take a type and the package scope, and return the
// (innermost) struct if the type is considered a RR type (currently defined as
// those structs beginning with a RR_Header, could be redefined as implementing
// the RR interface). The bool return value indicates if embedded structs were
// resolved.
func getTypeStruct(t types.Type, scope *types.Scope) (*types.Struct, bool) {
st, ok := t.Underlying().(*types.Struct)
if !ok {
return nil, false
}
if st.Field(0).Type() == scope.Lookup("RR_Header").Type() {
return st, false
}
if st.Field(0).Anonymous() {
st, _ := getTypeStruct(st.Field(0).Type(), scope)
return st, true
}
return nil, false
}
func main() {
// Import and type-check the package
pkg, err := importer.Default().Import("github.com/miekg/dns")
fatalIfErr(err)
scope := pkg.Scope()
// Collect actual types (*X)
var namedTypes []string
for _, name := range scope.Names() {
o := scope.Lookup(name)
if o == nil || !o.Exported() {
continue
}
if st, _ := getTypeStruct(o.Type(), scope); st == nil {
continue
}
if name == "PrivateRR" {
continue
}
// Check if corresponding TypeX exists
if scope.Lookup("Type"+o.Name()) == nil && o.Name() != "RFC3597" {
log.Fatalf("Constant Type%s does not exist.", o.Name())
}
namedTypes = append(namedTypes, o.Name())
}
b := &bytes.Buffer{}
b.WriteString(packageHdr)
fmt.Fprint(b, "// pack*() functions\n\n")
for _, name := range namedTypes {
o := scope.Lookup(name)
st, _ := getTypeStruct(o.Type(), scope)
fmt.Fprintf(b, "func (rr *%s) pack(msg []byte, off int, compression map[string]int, compress bool) (int, error) {\n", name)
fmt.Fprint(b, `off, err := rr.Hdr.pack(msg, off, compression, compress)
if err != nil {
return off, err
}
headerEnd := off
`)
for i := 1; i < st.NumFields(); i++ {
o := func(s string) {
fmt.Fprintf(b, s, st.Field(i).Name())
fmt.Fprint(b, `if err != nil {
return off, err
}
`)
}
if _, ok := st.Field(i).Type().(*types.Slice); ok {
switch st.Tag(i) {
case `dns:"-"`: // ignored
case `dns:"txt"`:
o("off, err = packStringTxt(rr.%s, msg, off)\n")
case `dns:"opt"`:
o("off, err = packDataOpt(rr.%s, msg, off)\n")
case `dns:"nsec"`:
o("off, err = packDataNsec(rr.%s, msg, off)\n")
case `dns:"domain-name"`:
o("off, err = packDataDomainNames(rr.%s, msg, off, compression, compress)\n")
default:
log.Fatalln(name, st.Field(i).Name(), st.Tag(i))
}
continue
}
switch {
case st.Tag(i) == `dns:"-"`: // ignored
case st.Tag(i) == `dns:"cdomain-name"`:
o("off, err = PackDomainName(rr.%s, msg, off, compression, compress)\n")
case st.Tag(i) == `dns:"domain-name"`:
o("off, err = PackDomainName(rr.%s, msg, off, compression, false)\n")
case st.Tag(i) == `dns:"a"`:
o("off, err = packDataA(rr.%s, msg, off)\n")
case st.Tag(i) == `dns:"aaaa"`:
o("off, err = packDataAAAA(rr.%s, msg, off)\n")
case st.Tag(i) == `dns:"uint48"`:
o("off, err = packUint48(rr.%s, msg, off)\n")
case st.Tag(i) == `dns:"txt"`:
o("off, err = packString(rr.%s, msg, off)\n")
case strings.HasPrefix(st.Tag(i), `dns:"size-base32`): // size-base32 can be packed just like base32
fallthrough
case st.Tag(i) == `dns:"base32"`:
o("off, err = packStringBase32(rr.%s, msg, off)\n")
case strings.HasPrefix(st.Tag(i), `dns:"size-base64`): // size-base64 can be packed just like base64
fallthrough
case st.Tag(i) == `dns:"base64"`:
o("off, err = packStringBase64(rr.%s, msg, off)\n")
case strings.HasPrefix(st.Tag(i), `dns:"size-hex:SaltLength`):
// directly write instead of using o() so we get the error check in the correct place
field := st.Field(i).Name()
fmt.Fprintf(b, `// Only pack salt if value is not "-", i.e. empty
if rr.%s != "-" {
off, err = packStringHex(rr.%s, msg, off)
if err != nil {
return off, err
}
}
`, field, field)
continue
case strings.HasPrefix(st.Tag(i), `dns:"size-hex`): // size-hex can be packed just like hex
fallthrough
case st.Tag(i) == `dns:"hex"`:
o("off, err = packStringHex(rr.%s, msg, off)\n")
case st.Tag(i) == `dns:"octet"`:
o("off, err = packStringOctet(rr.%s, msg, off)\n")
case st.Tag(i) == "":
switch st.Field(i).Type().(*types.Basic).Kind() {
case types.Uint8:
o("off, err = packUint8(rr.%s, msg, off)\n")
case types.Uint16:
o("off, err = packUint16(rr.%s, msg, off)\n")
case types.Uint32:
o("off, err = packUint32(rr.%s, msg, off)\n")
case types.Uint64:
o("off, err = packUint64(rr.%s, msg, off)\n")
case types.String:
o("off, err = packString(rr.%s, msg, off)\n")
default:
log.Fatalln(name, st.Field(i).Name())
}
default:
log.Fatalln(name, st.Field(i).Name(), st.Tag(i))
}
}
// We have packed everything, only now we know the rdlength of this RR
fmt.Fprintln(b, "rr.Header().Rdlength = uint16(off-headerEnd)")
fmt.Fprintln(b, "return off, nil }\n")
}
fmt.Fprint(b, "// unpack*() functions\n\n")
for _, name := range namedTypes {
o := scope.Lookup(name)
st, _ := getTypeStruct(o.Type(), scope)
fmt.Fprintf(b, "func unpack%s(h RR_Header, msg []byte, off int) (RR, int, error) {\n", name)
fmt.Fprintf(b, "rr := new(%s)\n", name)
fmt.Fprint(b, "rr.Hdr = h\n")
fmt.Fprint(b, `if noRdata(h) {
return rr, off, nil
}
var err error
rdStart := off
_ = rdStart
`)
for i := 1; i < st.NumFields(); i++ {
o := func(s string) {
fmt.Fprintf(b, s, st.Field(i).Name())
fmt.Fprint(b, `if err != nil {
return rr, off, err
}
`)
}
// size-* are special, because they reference a struct member we should use for the length.
if strings.HasPrefix(st.Tag(i), `dns:"size-`) {
structMember := structMember(st.Tag(i))
structTag := structTag(st.Tag(i))
switch structTag {
case "hex":
fmt.Fprintf(b, "rr.%s, off, err = unpackStringHex(msg, off, off + int(rr.%s))\n", st.Field(i).Name(), structMember)
case "base32":
fmt.Fprintf(b, "rr.%s, off, err = unpackStringBase32(msg, off, off + int(rr.%s))\n", st.Field(i).Name(), structMember)
case "base64":
fmt.Fprintf(b, "rr.%s, off, err = unpackStringBase64(msg, off, off + int(rr.%s))\n", st.Field(i).Name(), structMember)
default:
log.Fatalln(name, st.Field(i).Name(), st.Tag(i))
}
fmt.Fprint(b, `if err != nil {
return rr, off, err
}
`)
continue
}
if _, ok := st.Field(i).Type().(*types.Slice); ok {
switch st.Tag(i) {
case `dns:"-"`: // ignored
case `dns:"txt"`:
o("rr.%s, off, err = unpackStringTxt(msg, off)\n")
case `dns:"opt"`:
o("rr.%s, off, err = unpackDataOpt(msg, off)\n")
case `dns:"nsec"`:
o("rr.%s, off, err = unpackDataNsec(msg, off)\n")
case `dns:"domain-name"`:
o("rr.%s, off, err = unpackDataDomainNames(msg, off, rdStart + int(rr.Hdr.Rdlength))\n")
default:
log.Fatalln(name, st.Field(i).Name(), st.Tag(i))
}
continue
}
switch st.Tag(i) {
case `dns:"-"`: // ignored
case `dns:"cdomain-name"`:
fallthrough
case `dns:"domain-name"`:
o("rr.%s, off, err = UnpackDomainName(msg, off)\n")
case `dns:"a"`:
o("rr.%s, off, err = unpackDataA(msg, off)\n")
case `dns:"aaaa"`:
o("rr.%s, off, err = unpackDataAAAA(msg, off)\n")
case `dns:"uint48"`:
o("rr.%s, off, err = unpackUint48(msg, off)\n")
case `dns:"txt"`:
o("rr.%s, off, err = unpackString(msg, off)\n")
case `dns:"base32"`:
o("rr.%s, off, err = unpackStringBase32(msg, off, rdStart + int(rr.Hdr.Rdlength))\n")
case `dns:"base64"`:
o("rr.%s, off, err = unpackStringBase64(msg, off, rdStart + int(rr.Hdr.Rdlength))\n")
case `dns:"hex"`:
o("rr.%s, off, err = unpackStringHex(msg, off, rdStart + int(rr.Hdr.Rdlength))\n")
case `dns:"octet"`:
o("rr.%s, off, err = unpackStringOctet(msg, off)\n")
case "":
switch st.Field(i).Type().(*types.Basic).Kind() {
case types.Uint8:
o("rr.%s, off, err = unpackUint8(msg, off)\n")
case types.Uint16:
o("rr.%s, off, err = unpackUint16(msg, off)\n")
case types.Uint32:
o("rr.%s, off, err = unpackUint32(msg, off)\n")
case types.Uint64:
o("rr.%s, off, err = unpackUint64(msg, off)\n")
case types.String:
o("rr.%s, off, err = unpackString(msg, off)\n")
default:
log.Fatalln(name, st.Field(i).Name())
}
default:
log.Fatalln(name, st.Field(i).Name(), st.Tag(i))
}
// If we've hit len(msg) we return without error.
if i < st.NumFields()-1 {
fmt.Fprintf(b, `if off == len(msg) {
return rr, off, nil
}
`)
}
}
fmt.Fprintf(b, "return rr, off, err }\n\n")
}
// Generate typeToUnpack map
fmt.Fprintln(b, "var typeToUnpack = map[uint16]func(RR_Header, []byte, int) (RR, int, error){")
for _, name := range namedTypes {
if name == "RFC3597" {
continue
}
fmt.Fprintf(b, "Type%s: unpack%s,\n", name, name)
}
fmt.Fprintln(b, "}\n")
// gofmt
res, err := format.Source(b.Bytes())
if err != nil {
b.WriteTo(os.Stderr)
log.Fatal(err)
}
// write result
f, err := os.Create("zmsg.go")
fatalIfErr(err)
defer f.Close()
f.Write(res)
}
// structMember will take a tag like dns:"size-base32:SaltLength" and return the last part of this string.
func structMember(s string) string {
fields := strings.Split(s, ":")
if len(fields) == 0 {
return ""
}
f := fields[len(fields)-1]
// f should have a closing "
if len(f) > 1 {
return f[:len(f)-1]
}
return f
}
// structTag will take a tag like dns:"size-base32:SaltLength" and return base32.
func structTag(s string) string {
fields := strings.Split(s, ":")
if len(fields) < 2 {
return ""
}
return fields[1][len("\"size-"):]
}
func fatalIfErr(err error) {
if err != nil {
log.Fatal(err)
}
}
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