--- /dev/null
+package dns
+
+import (
+ "bytes"
+ "fmt"
+ "io"
+ "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.
+func (zp *ZoneParser) generate(l lex) (RR, bool) {
+ token := l.token
+ step := 1
+ if i := strings.IndexByte(token, '/'); i >= 0 {
+ if i+1 == len(token) {
+ return zp.setParseError("bad step in $GENERATE range", l)
+ }
+
+ s, err := strconv.Atoi(token[i+1:])
+ if err != nil || s <= 0 {
+ return zp.setParseError("bad step in $GENERATE range", l)
+ }
+
+ step = s
+ token = token[:i]
+ }
+
+ sx := strings.SplitN(token, "-", 2)
+ if len(sx) != 2 {
+ return zp.setParseError("bad start-stop in $GENERATE range", l)
+ }
+
+ start, err := strconv.Atoi(sx[0])
+ if err != nil {
+ return zp.setParseError("bad start in $GENERATE range", l)
+ }
+
+ end, err := strconv.Atoi(sx[1])
+ if err != nil {
+ return zp.setParseError("bad stop in $GENERATE range", l)
+ }
+ if end < 0 || start < 0 || end < start {
+ return zp.setParseError("bad range in $GENERATE range", l)
+ }
+
+ zp.c.Next() // _BLANK
+
+ // Create a complete new string, which we then parse again.
+ var s string
+ for l, ok := zp.c.Next(); ok; l, ok = zp.c.Next() {
+ if l.err {
+ return zp.setParseError("bad data in $GENERATE directive", l)
+ }
+ if l.value == zNewline {
+ break
+ }
+
+ s += l.token
+ }
+
+ r := &generateReader{
+ s: s,
+
+ cur: start,
+ start: start,
+ end: end,
+ step: step,
+
+ file: zp.file,
+ lex: &l,
+ }
+ zp.sub = NewZoneParser(r, zp.origin, zp.file)
+ zp.sub.includeDepth, zp.sub.includeAllowed = zp.includeDepth, zp.includeAllowed
+ zp.sub.SetDefaultTTL(defaultTtl)
+ return zp.subNext()
+}
+
+type generateReader struct {
+ s string
+ si int
+
+ cur int
+ start int
+ end int
+ step int
+
+ mod bytes.Buffer
+
+ escape bool
+
+ eof bool
+
+ file string
+ lex *lex
+}
+
+func (r *generateReader) parseError(msg string, end int) *ParseError {
+ r.eof = true // Make errors sticky.
+
+ l := *r.lex
+ l.token = r.s[r.si-1 : end]
+ l.column += r.si // l.column starts one zBLANK before r.s
+
+ return &ParseError{r.file, msg, l}
+}
+
+func (r *generateReader) Read(p []byte) (int, error) {
+ // NewZLexer, through NewZoneParser, should use ReadByte and
+ // not end up here.
+
+ panic("not implemented")
+}
+
+func (r *generateReader) ReadByte() (byte, error) {
+ if r.eof {
+ return 0, io.EOF
+ }
+ if r.mod.Len() > 0 {
+ return r.mod.ReadByte()
+ }
+
+ if r.si >= len(r.s) {
+ r.si = 0
+ r.cur += r.step
+
+ r.eof = r.cur > r.end || r.cur < 0
+ return '\n', nil
+ }
+
+ si := r.si
+ r.si++
+
+ switch r.s[si] {
+ case '\\':
+ if r.escape {
+ r.escape = false
+ return '\\', nil
+ }
+
+ r.escape = true
+ return r.ReadByte()
+ case '$':
+ if r.escape {
+ r.escape = false
+ return '$', nil
+ }
+
+ mod := "%d"
+
+ if si >= len(r.s)-1 {
+ // End of the string
+ fmt.Fprintf(&r.mod, mod, r.cur)
+ return r.mod.ReadByte()
+ }
+
+ if r.s[si+1] == '$' {
+ r.si++
+ return '$', nil
+ }
+
+ var offset int
+
+ // Search for { and }
+ if r.s[si+1] == '{' {
+ // Modifier block
+ sep := strings.Index(r.s[si+2:], "}")
+ if sep < 0 {
+ return 0, r.parseError("bad modifier in $GENERATE", len(r.s))
+ }
+
+ var errMsg string
+ mod, offset, errMsg = modToPrintf(r.s[si+2 : si+2+sep])
+ if errMsg != "" {
+ return 0, r.parseError(errMsg, si+3+sep)
+ }
+ if r.start+offset < 0 || r.end+offset > 1<<31-1 {
+ return 0, r.parseError("bad offset in $GENERATE", si+3+sep)
+ }
+
+ r.si += 2 + sep // Jump to it
+ }
+
+ fmt.Fprintf(&r.mod, mod, r.cur+offset)
+ return r.mod.ReadByte()
+ default:
+ if r.escape { // Pretty useless here
+ r.escape = false
+ return r.ReadByte()
+ }
+
+ return r.s[si], nil
+ }
+}
+
+// Convert a $GENERATE modifier 0,0,d to something Printf can deal with.
+func modToPrintf(s string) (string, int, string) {
+ // Modifier is { offset [ ,width [ ,base ] ] } - provide default
+ // values for optional width and type, if necessary.
+ var offStr, widthStr, base string
+ switch xs := strings.Split(s, ","); len(xs) {
+ case 1:
+ offStr, widthStr, base = xs[0], "0", "d"
+ case 2:
+ offStr, widthStr, base = xs[0], xs[1], "d"
+ case 3:
+ offStr, widthStr, base = xs[0], xs[1], xs[2]
+ default:
+ return "", 0, "bad modifier in $GENERATE"
+ }
+
+ switch base {
+ case "o", "d", "x", "X":
+ default:
+ return "", 0, "bad base in $GENERATE"
+ }
+
+ offset, err := strconv.Atoi(offStr)
+ if err != nil {
+ return "", 0, "bad offset in $GENERATE"
+ }
+
+ width, err := strconv.Atoi(widthStr)
+ if err != nil || width < 0 || width > 255 {
+ return "", 0, "bad width in $GENERATE"
+ }
+
+ if width == 0 {
+ return "%" + base, offset, ""
+ }
+
+ return "%0" + widthStr + base, offset, ""
+}
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