1//+build ignore
2
3// types_generate.go is meant to run with go generate. It will use
4// go/{importer,types} to track down all the RR struct types. Then for each type
5// it will generate conversion tables (TypeToRR and TypeToString) and banal
6// methods (len, Header, copy) based on the struct tags. The generated source is
7// written to ztypes.go, and is meant to be checked into git.
8package main
9
10import (
11	"bytes"
12	"fmt"
13	"go/format"
14	"go/types"
15	"log"
16	"os"
17
18	"golang.org/x/tools/go/packages"
19)
20
21var packageHdr = `
22// Code generated by "go run duplicate_generate.go"; DO NOT EDIT.
23
24package dns
25
26`
27
28func getTypeStruct(t types.Type, scope *types.Scope) (*types.Struct, bool) {
29	st, ok := t.Underlying().(*types.Struct)
30	if !ok {
31		return nil, false
32	}
33	if st.Field(0).Type() == scope.Lookup("RR_Header").Type() {
34		return st, false
35	}
36	if st.Field(0).Anonymous() {
37		st, _ := getTypeStruct(st.Field(0).Type(), scope)
38		return st, true
39	}
40	return nil, false
41}
42
43// loadModule retrieves package description for a given module.
44func loadModule(name string) (*types.Package, error) {
45	conf := packages.Config{Mode: packages.NeedTypes | packages.NeedTypesInfo}
46	pkgs, err := packages.Load(&conf, name)
47	if err != nil {
48		return nil, err
49	}
50	return pkgs[0].Types, nil
51}
52
53func main() {
54	// Import and type-check the package
55	pkg, err := loadModule("github.com/miekg/dns")
56	fatalIfErr(err)
57	scope := pkg.Scope()
58
59	// Collect actual types (*X)
60	var namedTypes []string
61	for _, name := range scope.Names() {
62		o := scope.Lookup(name)
63		if o == nil || !o.Exported() {
64			continue
65		}
66
67		if st, _ := getTypeStruct(o.Type(), scope); st == nil {
68			continue
69		}
70
71		if name == "PrivateRR" || name == "OPT" {
72			continue
73		}
74
75		namedTypes = append(namedTypes, o.Name())
76	}
77
78	b := &bytes.Buffer{}
79	b.WriteString(packageHdr)
80
81	// Generate the duplicate check for each type.
82	fmt.Fprint(b, "// isDuplicate() functions\n\n")
83	for _, name := range namedTypes {
84
85		o := scope.Lookup(name)
86		st, isEmbedded := getTypeStruct(o.Type(), scope)
87		if isEmbedded {
88			continue
89		}
90		fmt.Fprintf(b, "func (r1 *%s) isDuplicate(_r2 RR) bool {\n", name)
91		fmt.Fprintf(b, "r2, ok := _r2.(*%s)\n", name)
92		fmt.Fprint(b, "if !ok { return false }\n")
93		fmt.Fprint(b, "_ = r2\n")
94		for i := 1; i < st.NumFields(); i++ {
95			field := st.Field(i).Name()
96			o2 := func(s string) { fmt.Fprintf(b, s+"\n", field, field) }
97			o3 := func(s string) { fmt.Fprintf(b, s+"\n", field, field, field) }
98
99			// For some reason, a and aaaa don't pop up as *types.Slice here (mostly like because the are
100			// *indirectly* defined as a slice in the net package).
101			if _, ok := st.Field(i).Type().(*types.Slice); ok {
102				o2("if len(r1.%s) != len(r2.%s) {\nreturn false\n}")
103
104				if st.Tag(i) == `dns:"cdomain-name"` || st.Tag(i) == `dns:"domain-name"` {
105					o3(`for i := 0; i < len(r1.%s); i++ {
106						if !isDuplicateName(r1.%s[i], r2.%s[i]) {
107							return false
108						}
109					}`)
110
111					continue
112				}
113
114				if st.Tag(i) == `dns:"apl"` {
115					o3(`for i := 0; i < len(r1.%s); i++ {
116						if !r1.%s[i].equals(&r2.%s[i]) {
117							return false
118						}
119					}`)
120
121					continue
122				}
123
124				o3(`for i := 0; i < len(r1.%s); i++ {
125					if r1.%s[i] != r2.%s[i] {
126						return false
127					}
128				}`)
129
130				continue
131			}
132
133			switch st.Tag(i) {
134			case `dns:"-"`:
135				// ignored
136			case `dns:"a"`, `dns:"aaaa"`:
137				o2("if !r1.%s.Equal(r2.%s) {\nreturn false\n}")
138			case `dns:"cdomain-name"`, `dns:"domain-name"`:
139				o2("if !isDuplicateName(r1.%s, r2.%s) {\nreturn false\n}")
140			default:
141				o2("if r1.%s != r2.%s {\nreturn false\n}")
142			}
143		}
144		fmt.Fprintf(b, "return true\n}\n\n")
145	}
146
147	// gofmt
148	res, err := format.Source(b.Bytes())
149	if err != nil {
150		b.WriteTo(os.Stderr)
151		log.Fatal(err)
152	}
153
154	// write result
155	f, err := os.Create("zduplicate.go")
156	fatalIfErr(err)
157	defer f.Close()
158	f.Write(res)
159}
160
161func fatalIfErr(err error) {
162	if err != nil {
163		log.Fatal(err)
164	}
165}
166