From ff85102a46da8c63b511bb7b8b2b88a52b57028a Mon Sep 17 00:00:00 2001
From: Nikita Salnikov-Tarnovski <gnikem@gmail.com>
Date: Thu, 3 Jun 2021 02:57:16 +0300
Subject: [PATCH] Remove unnecessary string allocation on hot path (#3272)

---
 .../api/trace/SpanIdBenchmark.java            | 33 +++++++++++++++++++
 .../api/internal/OtelEncodingUtils.java       |  4 +--
 .../io/opentelemetry/api/internal/Utils.java  | 14 ++++++++
 3 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 api/all/src/jmh/java/io/opentelemetry/api/trace/SpanIdBenchmark.java

diff --git a/api/all/src/jmh/java/io/opentelemetry/api/trace/SpanIdBenchmark.java b/api/all/src/jmh/java/io/opentelemetry/api/trace/SpanIdBenchmark.java
new file mode 100644
index 0000000000..975cb0c157
--- /dev/null
+++ b/api/all/src/jmh/java/io/opentelemetry/api/trace/SpanIdBenchmark.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.trace;
+
+import java.util.concurrent.TimeUnit;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Threads;
+import org.openjdk.jmh.annotations.Warmup;
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.AverageTime)
+@Warmup(iterations = 5, time = 1)
+@Measurement(iterations = 15, time = 1)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Fork(1)
+@Threads(1)
+public class SpanIdBenchmark {
+
+  @Benchmark
+  public byte[] getSpanIdBytes() {
+    return SpanContext.getInvalid().getSpanIdBytes();
+  }
+}
diff --git a/api/all/src/main/java/io/opentelemetry/api/internal/OtelEncodingUtils.java b/api/all/src/main/java/io/opentelemetry/api/internal/OtelEncodingUtils.java
index 914fe76245..e4203d5228 100644
--- a/api/all/src/main/java/io/opentelemetry/api/internal/OtelEncodingUtils.java
+++ b/api/all/src/main/java/io/opentelemetry/api/internal/OtelEncodingUtils.java
@@ -111,9 +111,9 @@ public final class OtelEncodingUtils {
    */
   public static byte byteFromBase16(char first, char second) {
     Utils.checkArgument(
-        first < ASCII_CHARACTERS && DECODING[first] != -1, "invalid character " + first);
+        first < ASCII_CHARACTERS && DECODING[first] != -1, () -> "invalid character " + first);
     Utils.checkArgument(
-        second < ASCII_CHARACTERS && DECODING[second] != -1, "invalid character " + second);
+        second < ASCII_CHARACTERS && DECODING[second] != -1, () -> "invalid character " + second);
     int decoded = DECODING[first] << 4 | DECODING[second];
     return (byte) decoded;
   }
diff --git a/api/all/src/main/java/io/opentelemetry/api/internal/Utils.java b/api/all/src/main/java/io/opentelemetry/api/internal/Utils.java
index 2f6603e0da..5fda975b43 100644
--- a/api/all/src/main/java/io/opentelemetry/api/internal/Utils.java
+++ b/api/all/src/main/java/io/opentelemetry/api/internal/Utils.java
@@ -5,6 +5,7 @@
 
 package io.opentelemetry.api.internal;
 
+import java.util.function.Supplier;
 import javax.annotation.concurrent.Immutable;
 
 /** General internal utility methods. */
@@ -25,4 +26,17 @@ public final class Utils {
       throw new IllegalArgumentException(errorMessage);
     }
   }
+
+  /**
+   * Throws an {@link IllegalArgumentException} if the argument is false. This method is similar to
+   * {@code Preconditions.checkArgument(boolean, Object)} from Guava.
+   *
+   * @param isValid whether the argument check passed.
+   * @param errorMessage the supplier of the message to use for the exception.
+   */
+  public static void checkArgument(boolean isValid, Supplier<String> errorMessage) {
+    if (!isValid) {
+      throw new IllegalArgumentException(errorMessage.get());
+    }
+  }
 }