[GitHub] [incubator-zipkin] anuraaga commented on a change in pull request #2587: Reduces array copying when converting uint64 to hex strings

[GitBox <gi...@apache.org>]

anuraaga commented on a change in pull request #2587: Reduces array copying when converting uint64 to hex strings
URL: https://github.com/apache/incubator-zipkin/pull/2587#discussion_r283126284
 
 

 ##########
 File path: zipkin/src/main/java/zipkin2/Span.java
 ##########
 @@ -415,14 +416,14 @@ public Builder traceId(String traceId) {
      */
     public Builder traceId(long high, long low) {
       if (high == 0L && low == 0L) throw new IllegalArgumentException("empty trace ID");
-      char[] result = new char[high != 0L ? 32 : 16];
+      char[] data = Platform.get().idBuffer();
       int pos = 0;
       if (high != 0L) {
-        writeHexLong(result, pos, high);
+        writeHexLong(data, pos, high);
         pos += 16;
       }
-      writeHexLong(result, pos, low);
-      this.traceId = new String(result);
+      writeHexLong(data, pos, low);
+      this.traceId = new String(data, 0, high != 0L ? 32 : 16);
 
 Review comment:
   Think it might be worth the readability of extracting a `length` variable.

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