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// Copyright 2011 Miek Gieben. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package dns
import (
"fmt"
"strconv"
"strings"
)
// Parse the $GENERATE statement as used in BIND9 zones.
// See http://www.zytrax.com/books/dns/ch8/generate.html for instance.
// We are called after '$GENERATE '. After which we expect:
// * the range (12-24/2)
// * lhs (ownername)
// * [[ttl][class]]
// * type
// * rhs (rdata)
// But we are lazy here, only the range is parsed *all* occurences
// of $ after that are interpreted.
// Any error are returned as a string value, the empty string signals
// "no error".
func generate(l lex, c chan lex, t chan Token, o string) string {
step := 1
if i := strings.IndexAny(l.token, "/"); i != -1 {
if i+1 == len(l.token) {
return "bad step in $GENERATE range"
}
if s, e := strconv.Atoi(l.token[i+1:]); e != nil {
return "bad step in $GENERATE range"
} else {
if s < 0 {
return "bad step in $GENERATE range"
}
step = s
}
l.token = l.token[:i]
}
sx := strings.SplitN(l.token, "-", 2)
if len(sx) != 2 {
return "bad start-stop in $GENERATE range"
}
start, err := strconv.Atoi(sx[0])
if err != nil {
return "bad start in $GENERATE range"
}
end, err := strconv.Atoi(sx[1])
if err != nil {
return "bad stop in $GENERATE range"
}
if end < 0 || start < 0 || end <= start {
return "bad range in $GENERATE range"
}
<-c // _BLANK
// Create a complete new string, which we then parse again.
s := ""
BuildRR:
l = <-c
if l.value != _NEWLINE && l.value != _EOF {
s += l.token
goto BuildRR
}
for i := start; i <= end; i += step {
var (
escape bool
dom string
mod string
err string
offset int
)
for j := 0; j < len(s); j++ { // No 'range' because we need to jump around
switch s[j] {
case '\\':
if escape {
dom += "\\"
escape = false
continue
}
escape = true
case '$':
mod = "%d"
offset = 0
if escape {
dom += "$"
escape = false
continue
}
escape = false
if j+1 >= len(s) { // End of the string
dom += fmt.Sprintf(mod, i+offset)
continue
} else {
if s[j+1] == '$' {
dom += "$"
j++
continue
}
}
// Search for { and }
if s[j+1] == '{' { // Modifier block
sep := strings.Index(s[j+2:], "}")
if sep == -1 {
return "bad modifier in $GENERATE"
}
mod, offset, err = modToPrintf(s[j+2 : j+2+sep])
if err != "" {
return err
}
j += 2 + sep // Jump to it
}
dom += fmt.Sprintf(mod, i+offset)
default:
if escape { // Pretty useless here
escape = false
continue
}
dom += string(s[j])
}
}
// Re-parse the RR and send it on the current channel t
rx, e := NewRR("$ORIGIN " + o + "\n" + dom)
if e != nil {
return e.(*ParseError).err
}
t <- Token{RR: rx}
// Its more efficient to first built the rrlist and then parse it in
// one go! But is this a problem?
}
return ""
}
// Convert a $GENERATE modifier 0,0,d to something Printf can deal with.
func modToPrintf(s string) (string, int, string) {
xs := strings.SplitN(s, ",", 3)
if len(xs) != 3 {
return "", 0, "bad modifier in $GENERATE"
}
// xs[0] is offset, xs[1] is width, xs[2] is base
if xs[2] != "o" && xs[2] != "d" && xs[2] != "x" && xs[2] != "X" {
return "", 0, "bad base in $GENERATE"
}
offset, err := strconv.Atoi(xs[0])
if err != nil {
return "", 0, "bad offset in $GENERATE"
}
width, err := strconv.Atoi(xs[1])
if err != nil {
return "", offset, "bad width in $GENERATE"
}
switch {
case width < 0:
return "", offset, "bad width in $GENERATE"
case width == 0:
return "%" + xs[1] + xs[2], offset, ""
default:
return "%0" + xs[1] + xs[2], offset, ""
}
panic("dns: not reached")
}
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