gotosocial/vendor/github.com/miekg/dns/generate.go

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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 := int64(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.ParseInt(token[i+1:], 10, 64)
if err != nil || s <= 0 {
return zp.setParseError("bad step in $GENERATE range", l)
}
step = s
token = token[:i]
}
startStr, endStr, ok := strings.Cut(token, "-")
if !ok {
return zp.setParseError("bad start-stop in $GENERATE range", l)
}
start, err := strconv.ParseInt(startStr, 10, 64)
if err != nil {
return zp.setParseError("bad start in $GENERATE range", l)
}
end, err := strconv.ParseInt(endStr, 10, 64)
if err != nil {
return zp.setParseError("bad stop in $GENERATE range", l)
}
if end < 0 || start < 0 || end < start || (end-start)/step > 65535 {
return zp.setParseError("bad range in $GENERATE range", l)
}
// _BLANK
l, ok = zp.c.Next()
if !ok || l.value != zBlank {
return zp.setParseError("garbage after $GENERATE range", l)
}
// 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 $GENERATE directive", l)
}
if l.value == zNewline {
break
}
s += l.token
}
r := &generateReader{
s: s,
cur: start,
start: start,
end: end,
step: step,
file: zp.file,
lex: &l,
}
zp.sub = NewZoneParser(r, zp.origin, zp.file)
zp.sub.includeDepth, zp.sub.includeAllowed = zp.includeDepth, zp.includeAllowed
zp.sub.generateDisallowed = true
zp.sub.SetDefaultTTL(defaultTtl)
return zp.subNext()
}
type generateReader struct {
s string
si int
cur int64
start int64
end int64
step int64
mod bytes.Buffer
escape bool
eof bool
file string
lex *lex
}
func (r *generateReader) parseError(msg string, end int) *ParseError {
r.eof = true // Make errors sticky.
l := *r.lex
l.token = r.s[r.si-1 : end]
l.column += r.si // l.column starts one zBLANK before r.s
return &ParseError{r.file, msg, l}
}
func (r *generateReader) Read(p []byte) (int, error) {
// NewZLexer, through NewZoneParser, should use ReadByte and
// not end up here.
panic("not implemented")
}
func (r *generateReader) ReadByte() (byte, error) {
if r.eof {
return 0, io.EOF
}
if r.mod.Len() > 0 {
return r.mod.ReadByte()
}
if r.si >= len(r.s) {
r.si = 0
r.cur += r.step
r.eof = r.cur > r.end || r.cur < 0
return '\n', nil
}
si := r.si
r.si++
switch r.s[si] {
case '\\':
if r.escape {
r.escape = false
return '\\', nil
}
r.escape = true
return r.ReadByte()
case '$':
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 int64
// 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, int64, string) {
// Modifier is { offset [ ,width [ ,base ] ] } - provide default
// values for optional width and type, if necessary.
offStr, s, ok0 := strings.Cut(s, ",")
widthStr, s, ok1 := strings.Cut(s, ",")
base, _, ok2 := strings.Cut(s, ",")
if !ok0 {
widthStr = "0"
}
if !ok1 {
base = "d"
}
if ok2 {
return "", 0, "bad modifier in $GENERATE"
}
switch base {
case "o", "d", "x", "X":
default:
return "", 0, "bad base in $GENERATE"
}
offset, err := strconv.ParseInt(offStr, 10, 64)
if err != nil {
return "", 0, "bad offset in $GENERATE"
}
width, err := strconv.ParseUint(widthStr, 10, 8)
if err != nil {
return "", 0, "bad width in $GENERATE"
}
if width == 0 {
return "%" + base, offset, ""
}
return "%0" + widthStr + base, offset, ""
}