[GitHub] [incubator-zipkin] adriancole commented on a change in pull request #2582: Reuse char[] buffer when decoding hex fields.

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

adriancole commented on a change in pull request #2582: Reuse char[] buffer when decoding hex fields.
URL: https://github.com/apache/incubator-zipkin/pull/2582#discussion_r283085221
 
 

 ##########
 File path: zipkin/src/main/java/zipkin2/internal/Proto3Fields.java
 ##########
 @@ -164,6 +164,13 @@ final int readLengthPrefix(Buffer b) {
     static final char[] HEX_DIGITS =
       {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
 
+    // Reuse the buffer for decoding into hex since it's immediately copied into a String.
+    static final ThreadLocal<char[]> THIRTY_TWO_CHARS = new ThreadLocal<char[]>() {
 
 Review comment:
   Sorry for not remembering the specific nuance, but I recall us doing something like this vs using an anonymous subclass in brave. If same to you, mind following that vs us hunting down the conversations around it?
   
   ```java
     static final ThreadLocal<char[]> CHAR_BUFFER = new ThreadLocal<>();
   
     static char[] getCharBuffer() {
       char[] charBuffer = CHAR_BUFFER.get();
       if (charBuffer == null) {
         charBuffer = new char[FORMAT_MAX_LENGTH];
         CHAR_BUFFER.set(charBuffer);
       }
       return charBuffer;
     }
   ```

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