[GitHub] [jena] afs commented on a diff in pull request #1818: Misc

["afs (via GitHub)" <gi...@apache.org>]

afs commented on code in PR #1818:
URL: https://github.com/apache/jena/pull/1818#discussion_r1152443056


##########
jena-arq/src/main/java/org/apache/jena/riot/out/NodeFmtLib.java:
##########
@@ -195,19 +198,24 @@ private static String displayStrNodes(Node...nodes) {
     // ---- Blank node labels.
 
     // Strict N-triples only allows [A-Za-z][A-Za-z0-9]
-    static char encodeMarkerChar = 'X';
+    private static final char encodeMarkerChar = 'X';
 
     // These two form a pair to convert bNode labels to a safe (i.e. legal N-triples form) and back again.
 
-    // Encoding is:
-    // 1 - Add a Letter
-    // 2 - Hexify, as Xnn, anything outside ASCII A-Za-z0-9
-    // 3 - X is encoded as XX
+    /**
+     *  Encoding is:
+     *  <ul>
+     *  <li> Add a start letter
+     *  <li> Hexify, as Xnn, anything outside ASCII A-Za-z0-9
+     *  <li> X is encoded as XX
+     */
 
-    private static char LabelLeadingLetter = 'B';
+    private static final char LabelLeadingLetter = 'B';
 
     public static String encodeBNodeLabel(String label) {
-        StringBuilder buff = new StringBuilder();
+        // A UUID string is 36 characters including 4 dashes.
+        // Together with the leading 'B', a total of 45 characters + any additional encoding needed.
+        StringBuilder buff = new StringBuilder(48);

Review Comment:
   The import thing is to avoid reallocation in the StringBuilder in common usage (UUID strings).
   
   Dashes get X-encoded so the overall is 45 -- a dash is "X2D".
   
   `878b5787-2c84-4624-a237-ad6fc35ec260`
   becomes 
   `B878b5787X2D2c84X2D4624X2Da237X2Dad6fc35ec260` which is 45.
   
   So the buffer must be >=45 for UUIDs.
   
   48 is a multiple of 8 (possible cache effect) and more than 45.
   
   The label isn't required to be a UUID.
   
   😄 
   



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