gtsocial-umbx

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sanitize.go (2028B)

      1 package dns
      2 
      3 // Dedup removes identical RRs from rrs. It preserves the original ordering.
      4 // The lowest TTL of any duplicates is used in the remaining one. Dedup modifies
      5 // rrs.
      6 // m is used to store the RRs temporary. If it is nil a new map will be allocated.
      7 func Dedup(rrs []RR, m map[string]RR) []RR {
      8 
      9 	if m == nil {
     10 		m = make(map[string]RR)
     11 	}
     12 	// Save the keys, so we don't have to call normalizedString twice.
     13 	keys := make([]*string, 0, len(rrs))
     14 
     15 	for _, r := range rrs {
     16 		key := normalizedString(r)
     17 		keys = append(keys, &key)
     18 		if mr, ok := m[key]; ok {
     19 			// Shortest TTL wins.
     20 			rh, mrh := r.Header(), mr.Header()
     21 			if mrh.Ttl > rh.Ttl {
     22 				mrh.Ttl = rh.Ttl
     23 			}
     24 			continue
     25 		}
     26 
     27 		m[key] = r
     28 	}
     29 	// If the length of the result map equals the amount of RRs we got,
     30 	// it means they were all different. We can then just return the original rrset.
     31 	if len(m) == len(rrs) {
     32 		return rrs
     33 	}
     34 
     35 	j := 0
     36 	for i, r := range rrs {
     37 		// If keys[i] lives in the map, we should copy and remove it.
     38 		if _, ok := m[*keys[i]]; ok {
     39 			delete(m, *keys[i])
     40 			rrs[j] = r
     41 			j++
     42 		}
     43 
     44 		if len(m) == 0 {
     45 			break
     46 		}
     47 	}
     48 
     49 	return rrs[:j]
     50 }
     51 
     52 // normalizedString returns a normalized string from r. The TTL
     53 // is removed and the domain name is lowercased. We go from this:
     54 // DomainName<TAB>TTL<TAB>CLASS<TAB>TYPE<TAB>RDATA to:
     55 // lowercasename<TAB>CLASS<TAB>TYPE...
     56 func normalizedString(r RR) string {
     57 	// A string Go DNS makes has: domainname<TAB>TTL<TAB>...
     58 	b := []byte(r.String())
     59 
     60 	// find the first non-escaped tab, then another, so we capture where the TTL lives.
     61 	esc := false
     62 	ttlStart, ttlEnd := 0, 0
     63 	for i := 0; i < len(b) && ttlEnd == 0; i++ {
     64 		switch {
     65 		case b[i] == '\\':
     66 			esc = !esc
     67 		case b[i] == '\t' && !esc:
     68 			if ttlStart == 0 {
     69 				ttlStart = i
     70 				continue
     71 			}
     72 			if ttlEnd == 0 {
     73 				ttlEnd = i
     74 			}
     75 		case b[i] >= 'A' && b[i] <= 'Z' && !esc:
     76 			b[i] += 32
     77 		default:
     78 			esc = false
     79 		}
     80 	}
     81 
     82 	// remove TTL.
     83 	copy(b[ttlStart:], b[ttlEnd:])
     84 	cut := ttlEnd - ttlStart
     85 	return string(b[:len(b)-cut])
     86 }