Move longToPaddedHex function out of Tracers

tracing/src/main/java/com/palantir/remoting3/tracing/Tracers.java

@@ -24,8 +24,6 @@
 public final class Tracers {
     /** The key under which trace ids are inserted into SLF4J {@link org.slf4j.MDC MDCs}. */
     public static final String TRACE_ID_KEY = "traceId";
-    private static final char[] HEX_DIGITS =
-            {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
 
     private Tracers() {}
 
@@ -34,32 +32,6 @@ public static String randomId() {
         return com.palantir.tracing.Tracers.randomId();
     }
 
-    /**
-     * Convert a long to a big-endian hex string. Hand-coded implementation is more efficient than
-     * Strings.pad(Long.toHexString) because that code has to deal with mixed length longs, and then mixed length
-     * amounts of padding - we want to minimise the overhead of tracing.
-     */
-    static String longToPaddedHex(long number) {
-        char[] data = new char[16];
-        data[0] = HEX_DIGITS[(int) ((number >> 60) & 0xF)];
-        data[1] = HEX_DIGITS[(int) ((number >> 56) & 0xF)];
-        data[2] = HEX_DIGITS[(int) ((number >> 52) & 0xF)];
-        data[3] = HEX_DIGITS[(int) ((number >> 48) & 0xF)];
-        data[4] = HEX_DIGITS[(int) ((number >> 44) & 0xF)];
-        data[5] = HEX_DIGITS[(int) ((number >> 40) & 0xF)];
-        data[6] = HEX_DIGITS[(int) ((number >> 36) & 0xF)];
-        data[7] = HEX_DIGITS[(int) ((number >> 32) & 0xF)];
-        data[8] = HEX_DIGITS[(int) ((number >> 28) & 0xF)];
-        data[9] = HEX_DIGITS[(int) ((number >> 24) & 0xF)];
-        data[10] = HEX_DIGITS[(int) ((number >> 20) & 0xF)];
-        data[11] = HEX_DIGITS[(int) ((number >> 16) & 0xF)];
-        data[12] = HEX_DIGITS[(int) ((number >> 12) & 0xF)];
-        data[13] = HEX_DIGITS[(int) ((number >> 8) & 0xF)];
-        data[14] = HEX_DIGITS[(int) ((number >> 4) & 0xF)];
-        data[15] = HEX_DIGITS[(int) ((number >> 0) & 0xF)];
-        return new String(data);
-    }
-
     /**
      * Wraps the provided executor service such that any submitted {@link Callable} (or {@link Runnable}) is {@link
      * #wrap wrapped} in order to be trace-aware.

tracing/src/main/java/com/palantir/remoting3/tracing/Utilities.java

@@ -0,0 +1,50 @@
+/*
+ * (c) Copyright 2018 Palantir Technologies Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.palantir.remoting3.tracing;
+
+public final class Utilities {
+    private static final char[] HEX_DIGITS =
+            {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
+    private Utilities() {}
+
+    /**
+     * Convert a long to a big-endian hex string. Hand-coded implementation is more efficient than
+     * Strings.pad(Long.toHexString) because that code has to deal with mixed length longs, and then mixed length
+     * amounts of padding - we want to minimise the overhead of tracing.
+     */
+    static String longToPaddedHex(long number) {
+        char[] data = new char[16];
+        data[0] = HEX_DIGITS[(int) ((number >> 60) & 0xF)];
+        data[1] = HEX_DIGITS[(int) ((number >> 56) & 0xF)];
+        data[2] = HEX_DIGITS[(int) ((number >> 52) & 0xF)];
+        data[3] = HEX_DIGITS[(int) ((number >> 48) & 0xF)];
+        data[4] = HEX_DIGITS[(int) ((number >> 44) & 0xF)];
+        data[5] = HEX_DIGITS[(int) ((number >> 40) & 0xF)];
+        data[6] = HEX_DIGITS[(int) ((number >> 36) & 0xF)];
+        data[7] = HEX_DIGITS[(int) ((number >> 32) & 0xF)];
+        data[8] = HEX_DIGITS[(int) ((number >> 28) & 0xF)];
+        data[9] = HEX_DIGITS[(int) ((number >> 24) & 0xF)];
+        data[10] = HEX_DIGITS[(int) ((number >> 20) & 0xF)];
+        data[11] = HEX_DIGITS[(int) ((number >> 16) & 0xF)];
+        data[12] = HEX_DIGITS[(int) ((number >> 12) & 0xF)];
+        data[13] = HEX_DIGITS[(int) ((number >> 8) & 0xF)];
+        data[14] = HEX_DIGITS[(int) ((number >> 4) & 0xF)];
+        data[15] = HEX_DIGITS[(int) ((number >> 0) & 0xF)];
+        return new String(data);
+    }
+}

tracing/src/test/java/com/palantir/remoting3/tracing/TracersTest.java

@@ -308,10 +308,10 @@ public void testWrapRunnableWithAlternateTraceId_traceStateRestoredWhenThrows()
     @Test
     public void testTraceIdGeneration() throws Exception {
         assertThat(Tracers.randomId()).hasSize(16); // fails with p=1/16 if generated string is not padded
-        assertThat(Tracers.longToPaddedHex(0)).isEqualTo("0000000000000000");
-        assertThat(Tracers.longToPaddedHex(42)).isEqualTo("000000000000002a");
-        assertThat(Tracers.longToPaddedHex(-42)).isEqualTo("ffffffffffffffd6");
-        assertThat(Tracers.longToPaddedHex(123456789L)).isEqualTo("00000000075bcd15");
+        assertThat(Utilities.longToPaddedHex(0)).isEqualTo("0000000000000000");
+        assertThat(Utilities.longToPaddedHex(42)).isEqualTo("000000000000002a");
+        assertThat(Utilities.longToPaddedHex(-42)).isEqualTo("ffffffffffffffd6");
+        assertThat(Utilities.longToPaddedHex(123456789L)).isEqualTo("00000000075bcd15");
     }
 
     private static Callable<Void> newTraceExpectingCallable() {