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//+build ignore
// compression_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 look to see if there are (compressible) names, if so it will add that
// type to compressionLenHelperType and comressionLenSearchType which "fake" the
// compression so that Len() is fast.
package main
import (
"bytes"
"fmt"
"go/format"
"go/importer"
"go/types"
"log"
"os"
)
var packageHdr = `
// Code generated by "go run compress_generate.go"; DO NOT EDIT.
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()
var domainTypes []string // Types that have a domain name in them (either compressible or not).
var cdomainTypes []string // Types that have a compressible domain name in them (subset of domainType)
Names:
for _, name := range scope.Names() {
o := scope.Lookup(name)
if o == nil || !o.Exported() {
continue
}
st, _ := getTypeStruct(o.Type(), scope)
if st == nil {
continue
}
if name == "PrivateRR" {
continue
}
if scope.Lookup("Type"+o.Name()) == nil && o.Name() != "RFC3597" {
log.Fatalf("Constant Type%s does not exist.", o.Name())
}
for i := 1; i < st.NumFields(); i++ {
if _, ok := st.Field(i).Type().(*types.Slice); ok {
if st.Tag(i) == `dns:"domain-name"` {
domainTypes = append(domainTypes, o.Name())
continue Names
}
if st.Tag(i) == `dns:"cdomain-name"` {
cdomainTypes = append(cdomainTypes, o.Name())
domainTypes = append(domainTypes, o.Name())
continue Names
}
continue
}
switch {
case st.Tag(i) == `dns:"domain-name"`:
domainTypes = append(domainTypes, o.Name())
continue Names
case st.Tag(i) == `dns:"cdomain-name"`:
cdomainTypes = append(cdomainTypes, o.Name())
domainTypes = append(domainTypes, o.Name())
continue Names
}
}
}
b := &bytes.Buffer{}
b.WriteString(packageHdr)
// compressionLenHelperType - all types that have domain-name/cdomain-name can be used for compressing names
fmt.Fprint(b, "func compressionLenHelperType(c map[string]int, r RR) {\n")
fmt.Fprint(b, "switch x := r.(type) {\n")
for _, name := range domainTypes {
o := scope.Lookup(name)
st, _ := getTypeStruct(o.Type(), scope)
fmt.Fprintf(b, "case *%s:\n", name)
for i := 1; i < st.NumFields(); i++ {
out := func(s string) { fmt.Fprintf(b, "compressionLenHelper(c, x.%s)\n", st.Field(i).Name()) }
if _, ok := st.Field(i).Type().(*types.Slice); ok {
switch st.Tag(i) {
case `dns:"domain-name"`:
fallthrough
case `dns:"cdomain-name"`:
// For HIP we need to slice over the elements in this slice.
fmt.Fprintf(b, `for i := range x.%s {
compressionLenHelper(c, x.%s[i])
}
`, st.Field(i).Name(), st.Field(i).Name())
}
continue
}
switch {
case st.Tag(i) == `dns:"cdomain-name"`:
fallthrough
case st.Tag(i) == `dns:"domain-name"`:
out(st.Field(i).Name())
}
}
}
fmt.Fprintln(b, "}\n}\n\n")
// compressionLenSearchType - search cdomain-tags types for compressible names.
fmt.Fprint(b, "func compressionLenSearchType(c map[string]int, r RR) (int, bool) {\n")
fmt.Fprint(b, "switch x := r.(type) {\n")
for _, name := range cdomainTypes {
o := scope.Lookup(name)
st, _ := getTypeStruct(o.Type(), scope)
fmt.Fprintf(b, "case *%s:\n", name)
j := 1
for i := 1; i < st.NumFields(); i++ {
out := func(s string, j int) {
fmt.Fprintf(b, "k%d, ok%d := compressionLenSearch(c, x.%s)\n", j, j, st.Field(i).Name())
}
// There are no slice types with names that can be compressed.
switch {
case st.Tag(i) == `dns:"cdomain-name"`:
out(st.Field(i).Name(), j)
j++
}
}
k := "k1"
ok := "ok1"
for i := 2; i < j; i++ {
k += fmt.Sprintf(" + k%d", i)
ok += fmt.Sprintf(" && ok%d", i)
}
fmt.Fprintf(b, "return %s, %s\n", k, ok)
}
fmt.Fprintln(b, "}\nreturn 0, false\n}\n\n")
// gofmt
res, err := format.Source(b.Bytes())
if err != nil {
b.WriteTo(os.Stderr)
log.Fatal(err)
}
f, err := os.Create("zcompress.go")
fatalIfErr(err)
defer f.Close()
f.Write(res)
}
func fatalIfErr(err error) {
if err != nil {
log.Fatal(err)
}
}
|
