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