protocol/aprs: refactored

protocol/aprs/base91.go

@@ -2,12 +2,14 @@ package aprs
 
 import (
 	"fmt"
+	"slices"
 )
 
 func base91Decode(s string) (n int, err error) {
 	for i, l := 0, len(s); i < l; i++ {
 		c := s[i]
 		if c < 33 || c > 122 {
+			//			panic(fmt.Sprintf("aprs: invalid base-91 encoding char %q (%d)", c, c))
 			return 0, fmt.Errorf("aprs: invalid base-91 encoding char %q (%d)", c, c)
 		}
 
@@ -17,14 +19,13 @@ func base91Decode(s string) (n int, err error) {
 	return
 }
 
-/*
-func base91Encode(n int) string {
-	var s []string
-	for n > 0 {
-		c := n % 91
+func base91Encode(b []byte, n int) {
+	i := 0
+	for n > 1 {
+		x := n % 91
 		n /= 91
-		s = append([]string{string(byte(c) + 33)}, s...)
+		b[i] = byte(x) + 33
+		i++
 	}
-	return strings.Join(s, "")
+	slices.Reverse(b[:i])
 }
-*/