Permit zone file strings upto AND including 255 characters in length. (#284)

This PR fixes a bug in the inplace zone parser that rejects character string of length 255.

src/zonefile/inplace.rs

@@ -913,7 +913,7 @@ impl<'a> EntryScanner<'a> {
             // or an escape sequence.
             while self.zonefile.buf.next_ascii_symbol()?.is_some() {
                 *write += 1;
-                if *write >= latest {
+                if *write > latest {
                     return Err(EntryError::bad_charstr());
                 }
             }
@@ -930,7 +930,7 @@ impl<'a> EntryScanner<'a> {
                 Some(sym) => {
                     self.zonefile.buf.buf[*write] = sym.into_octet()?;
                     *write += 1;
-                    if *write >= latest {
+                    if *write > latest {
                         return Err(EntryError::bad_charstr());
                     }
                 }
@@ -1638,4 +1638,17 @@ mod test {
             "../../test-data/zonefiles/unknown.yaml"
         ));
     }
+
+    #[test]
+    fn test_chrstr_decoding() {
+        TestCase::test(include_str!("../../test-data/zonefiles/strlen.yaml"));
+    }
+
+    #[test]
+    #[should_panic(expected = "character string with more than 255 octets")]
+    fn test_chrstr_overlfow_decoding() {
+        TestCase::test(include_str!(
+            "../../test-data/zonefiles/stroverflow.yaml"
+        ));
+    }
 }

test-data/zonefiles/strlen.yaml

@@ -0,0 +1,15 @@
+origin: example.com.
+zonefile: |
+  254.short 3600 IN TXT	"12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234"
+  255.max   3600 IN TXT	"123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345"
+result:
+  - owner: 254.short.example.com.
+    class: IN
+    ttl: 3600
+    data: !Txt
+      - 12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234
+  - owner: 255.max.example.com.
+    class: IN
+    ttl: 3600
+    data: !Txt
+      - 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345

test-data/zonefiles/stroverflow.yaml

@@ -0,0 +1,9 @@
+origin: example.com.
+zonefile: |
+  256.long 3600 IN TXT "1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456"
+result:
+  - owner: 256.long.example.com.
+    class: IN
+    ttl: 3600
+    data: !Txt
+      - 1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456