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package dns
import (
"bytes"
"errors"
"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* occurrences
// 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, err := strconv.Atoi(l.token[i+1:]); err == nil {
if s < 0 {
return "bad step in $GENERATE range"
}
step = s
} else {
return "bad step in $GENERATE range"
}
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 $GENERATE range"
}
<-c // _BLANK
// Create a complete new string, which we then parse again.
s := ""
BuildRR:
l = <-c
if l.value != zNewline && l.value != zEOF {
s += l.token
goto BuildRR
}
for i := start; i <= end; i += step {
var (
escape bool
dom bytes.Buffer
mod string
err error
offset int
)
for j := 0; j < len(s); j++ { // No 'range' because we need to jump around
switch s[j] {
case '\\':
if escape {
dom.WriteByte('\\')
escape = false
continue
}
escape = true
case '$':
mod = "%d"
offset = 0
if escape {
dom.WriteByte('$')
escape = false
continue
}
escape = false
if j+1 >= len(s) { // End of the string
dom.WriteString(fmt.Sprintf(mod, i+offset))
continue
} else {
if s[j+1] == '$' {
dom.WriteByte('$')
j++
continue
}
}
// Search for { and }
if s[j+1] == '{' { // Modifier block
sep := strings.Index(s[j+2:], "}")
if sep == -1 {
return "bad modifier in $GENERATE"
}
mod, offset, err = modToPrintf(s[j+2 : j+2+sep])
if err != nil {
return err.Error()
}
j += 2 + sep // Jump to it
}
dom.WriteString(fmt.Sprintf(mod, i+offset))
default:
if escape { // Pretty useless here
escape = false
continue
}
dom.WriteByte(s[j])
}
}
// Re-parse the RR and send it on the current channel t
rx, err := NewRR("$ORIGIN " + o + "\n" + dom.String())
if err != nil {
return err.Error()
}
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, error) {
xs := strings.SplitN(s, ",", 3)
if len(xs) != 3 {
return "", 0, errors.New("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, errors.New("bad base in $GENERATE")
}
offset, err := strconv.Atoi(xs[0])
if err != nil || offset > 255 {
return "", 0, errors.New("bad offset in $GENERATE")
}
width, err := strconv.Atoi(xs[1])
if err != nil || width > 255 {
return "", offset, errors.New("bad width in $GENERATE")
}
switch {
case width < 0:
return "", offset, errors.New("bad width in $GENERATE")
case width == 0:
return "%" + xs[1] + xs[2], offset, nil
}
return "%0" + xs[1] + xs[2], offset, nil
}
|
