From b888af2772a7fdcc3ab001d9e16c8e665186b6e3 Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Mon, 16 Dec 2024 20:19:56 +0000
Subject: [PATCH 1/9] RUM-6286: replacing `joinToString` when it possible,
 refactor a bit

---
 dd-sdk-android-core/api/apiSurface            |  2 +
 .../api/dd-sdk-android-core.api               |  5 ++
 .../datadog/android/core/StringBuilderExt.kt  | 27 ++++++++
 .../internal/data/upload/CurlInterceptor.kt   | 18 ++----
 .../error/internal/DatadogExceptionHandler.kt |  5 +-
 .../android/core/StringBuilderExtKtTest.kt    | 61 ++++++++++++++++++
 .../datadog/android/utils/PerformanceTest.kt  | 64 +++++++++++++++++++
 .../rum/internal/DatadogLateCrashReporter.kt  |  2 +
 .../android/rum/internal/LateCrashReporter.kt |  2 +
 .../rum/internal/anr/AndroidTraceParser.kt    |  7 +-
 .../rum/internal/net/RumRequestFactory.kt     | 20 +++---
 11 files changed, 184 insertions(+), 29 deletions(-)
 create mode 100644 dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/StringBuilderExt.kt
 create mode 100644 dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
 create mode 100644 dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/PerformanceTest.kt

diff --git a/dd-sdk-android-core/api/apiSurface b/dd-sdk-android-core/api/apiSurface
index d5b414c3a4..8d71195036 100644
--- a/dd-sdk-android-core/api/apiSurface
+++ b/dd-sdk-android-core/api/apiSurface
@@ -190,6 +190,8 @@ class com.datadog.android.core.SdkReference
   fun get(): com.datadog.android.api.SdkCore?
 fun <T> allowThreadDiskReads(() -> T): T
 fun <T> allowThreadDiskWrites(() -> T): T
+fun StringBuilder.appendIfNotEmpty(String)
+fun StringBuilder.appendIfNotEmpty(Char)
 enum com.datadog.android.core.configuration.BackPressureMitigation
   - DROP_OLDEST
   - IGNORE_NEWEST
diff --git a/dd-sdk-android-core/api/dd-sdk-android-core.api b/dd-sdk-android-core/api/dd-sdk-android-core.api
index 0e0ac78ac3..c6a9155c45 100644
--- a/dd-sdk-android-core/api/dd-sdk-android-core.api
+++ b/dd-sdk-android-core/api/dd-sdk-android-core.api
@@ -543,6 +543,11 @@ public final class com/datadog/android/core/StrictModeExtKt {
 	public static final fun allowThreadDiskWrites (Lkotlin/jvm/functions/Function0;)Ljava/lang/Object;
 }
 
+public final class com/datadog/android/core/StringBuilderExtKt {
+	public static final fun appendIfNotEmpty (Ljava/lang/StringBuilder;C)Ljava/lang/StringBuilder;
+	public static final fun appendIfNotEmpty (Ljava/lang/StringBuilder;Ljava/lang/String;)Ljava/lang/StringBuilder;
+}
+
 public final class com/datadog/android/core/configuration/BackPressureMitigation : java/lang/Enum {
 	public static final field DROP_OLDEST Lcom/datadog/android/core/configuration/BackPressureMitigation;
 	public static final field IGNORE_NEWEST Lcom/datadog/android/core/configuration/BackPressureMitigation;
diff --git a/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/StringBuilderExt.kt b/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/StringBuilderExt.kt
new file mode 100644
index 0000000000..64e4d76f5e
--- /dev/null
+++ b/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/StringBuilderExt.kt
@@ -0,0 +1,27 @@
+/*
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/).
+ * Copyright 2016-Present Datadog, Inc.
+ */
+
+package com.datadog.android.core
+
+/**
+ * This utility function helps replace joinToString calls with more efficient StringBuilder's methods calls.
+ * In case when content should be separated with some separator it's handy to add it in front of new string only
+ * if buffer already contain some data
+ * @param str - string that should be added into buffer only if it already contains some data
+ */
+fun StringBuilder.appendIfNotEmpty(str: String) = apply {
+    if (isNotEmpty()) append(str)
+}
+
+/**
+ * This utility function helps replace joinToString calls with more efficient StringBuilder's methods calls.
+ * In case when content should be separated with some separator it's handy to add it in front of new string only
+ * if buffer already contain some data
+ * @param char - char that should be added into buffer only if it already contains some data
+ */
+fun StringBuilder.appendIfNotEmpty(char: Char) = apply {
+    if (isNotEmpty()) append(char)
+}
diff --git a/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/internal/data/upload/CurlInterceptor.kt b/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/internal/data/upload/CurlInterceptor.kt
index 09e7d0d9e1..91244a72db 100644
--- a/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/internal/data/upload/CurlInterceptor.kt
+++ b/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/internal/data/upload/CurlInterceptor.kt
@@ -67,25 +67,21 @@ internal class CurlInterceptor(
                 printBody = printBody
             )
 
-        fun toCommand(): String {
-            val parts = mutableListOf<String>()
-            parts.add("curl")
-            parts.add(FORMAT_METHOD.format(Locale.US, method.uppercase(Locale.US)))
-
+        fun toCommand(): String = buildString {
+            append("curl").append(' ')
+            append(FORMAT_METHOD.format(Locale.US, method.uppercase(Locale.US))).append(' ')
             headers.forEach { (key, values) ->
                 values.forEach { value ->
-                    parts.add(FORMAT_HEADER.format(Locale.US, key, value))
+                    append(FORMAT_HEADER.format(Locale.US, key, value)).append(' ')
                 }
             }
 
             if (contentType != null && !headers.containsKey(CONTENT_TYPE)) {
-                parts.add(FORMAT_HEADER.format(Locale.US, CONTENT_TYPE, contentType))
+                append(FORMAT_HEADER.format(Locale.US, CONTENT_TYPE, contentType)).append(' ')
             }
 
-            requestBody?.let { parts.addAll(it.toParts()) }
-            parts.add(FORMAT_URL.format(Locale.US, url))
-
-            return parts.joinToString(" ")
+            requestBody?.toParts()?.forEach { append(it).append(' ') }
+            append(FORMAT_URL.format(Locale.US, url))
         }
 
         private fun RequestBody.toParts(): List<String> {
diff --git a/dd-sdk-android-core/src/main/kotlin/com/datadog/android/error/internal/DatadogExceptionHandler.kt b/dd-sdk-android-core/src/main/kotlin/com/datadog/android/error/internal/DatadogExceptionHandler.kt
index 6996c6c87f..89d28dda4c 100644
--- a/dd-sdk-android-core/src/main/kotlin/com/datadog/android/error/internal/DatadogExceptionHandler.kt
+++ b/dd-sdk-android-core/src/main/kotlin/com/datadog/android/error/internal/DatadogExceptionHandler.kt
@@ -133,12 +133,11 @@ internal class DatadogExceptionHandler(
         ) + safeGetAllStacktraces()
             .filterKeys { it != crashedThread }
             .filterValues { it.isNotEmpty() }
-            .map {
-                val thread = it.key
+            .map { (thread, stackTrace) ->
                 ThreadDump(
                     name = thread.name,
                     state = thread.state.asString(),
-                    stack = it.value.loggableStackTrace(),
+                    stack = stackTrace.loggableStackTrace(),
                     crashed = false
                 )
             }
diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
new file mode 100644
index 0000000000..181b4e1346
--- /dev/null
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
@@ -0,0 +1,61 @@
+package com.datadog.android.core
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+
+class StringBuilderExtKtTest {
+
+    @Test
+    fun `M add char W addIfNotEmpty {buffer is not empty}`() {
+        // Given
+        val initialData = "something inside buffer already"
+        val buffer = StringBuilder(initialData)
+
+        // When
+        buffer.appendIfNotEmpty(' ')
+
+        // Then
+
+        assertThat(buffer.toString()).isEqualTo("$initialData ")
+    }
+
+    @Test
+    fun `M add str W addIfNotEmpty {buffer is not empty}`() {
+        // Given
+        val initialData = "something inside buffer already"
+        val buffer = StringBuilder(initialData)
+
+        // When
+        buffer.appendIfNotEmpty(" ")
+
+        // Then
+
+        assertThat(buffer.toString()).isEqualTo("$initialData ")
+    }
+
+    @Test
+    fun `M not add any char W addIfNotEmpty {buffer is empty}`() {
+        // Given
+        val buffer = StringBuilder()
+
+        // When
+        buffer.appendIfNotEmpty(' ')
+
+        // Then
+
+        assertThat(buffer.toString()).isEqualTo("")
+    }
+
+    @Test
+    fun `M not add any str W addIfNotEmpty {buffer is empty}`() {
+        // Given
+        val buffer = StringBuilder()
+
+        // When
+        buffer.appendIfNotEmpty(" ")
+
+        // Then
+
+        assertThat(buffer.toString()).isEqualTo("")
+    }
+}
diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/PerformanceTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/PerformanceTest.kt
new file mode 100644
index 0000000000..eaf84b4f70
--- /dev/null
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/PerformanceTest.kt
@@ -0,0 +1,64 @@
+/*
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/).
+ * Copyright 2016-Present Datadog, Inc.
+ */
+package com.datadog.android.utils
+
+import com.datadog.android.utils.forge.Configurator
+import fr.xgouchet.elmyr.Forge
+import fr.xgouchet.elmyr.junit5.ForgeConfiguration
+import fr.xgouchet.elmyr.junit5.ForgeExtension
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import org.junit.jupiter.api.extension.Extensions
+import kotlin.system.measureNanoTime
+
+private const val ITEMS_TO_JOINT = 10_000
+private const val REPETITION_COUNT = 10_000
+
+@Extensions(
+    ExtendWith(ForgeExtension::class)
+)
+@ForgeConfiguration(Configurator::class)
+internal class PerformanceTest {
+
+    private fun List<Long>.mean() = sum().toDouble() / size
+
+    @Test
+    fun `M be faster than joinToString W buildString`(forge: Forge) {
+        val itemsForJoin = forge.aList(ITEMS_TO_JOINT) { forge.aString() }
+        val jointToStringResults = mutableListOf<Long>()
+        val builderResults = mutableListOf<Long>()
+
+        var jointToStringResult = ""
+        var builderResult = ""
+
+        for (i in 0..REPETITION_COUNT) {
+            jointToStringResults.add(
+                measureNanoTime {
+                    val jointToStringContainer = mutableListOf<String>()
+                    for (item in itemsForJoin) {
+                        jointToStringContainer.add(item)
+                    }
+                    jointToStringResult = jointToStringContainer.joinToString(separator = " ") { it }
+                }
+            )
+
+            builderResults.add(
+                measureNanoTime {
+                    builderResult = buildString {
+                        itemsForJoin.forEachIndexed { i, item ->
+                            if (i > 0) append(" ")
+                            append(item)
+                        }
+                    }
+                }
+            )
+        }
+
+        assertThat(builderResult).isEqualTo(jointToStringResult) // same result
+        assertThat(builderResults.mean()).isLessThan(jointToStringResults.mean())
+    }
+}
diff --git a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/DatadogLateCrashReporter.kt b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/DatadogLateCrashReporter.kt
index ac1cf8021b..4821c6554b 100644
--- a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/DatadogLateCrashReporter.kt
+++ b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/DatadogLateCrashReporter.kt
@@ -9,6 +9,7 @@ package com.datadog.android.rum.internal
 import android.app.ApplicationExitInfo
 import android.os.Build
 import androidx.annotation.RequiresApi
+import androidx.annotation.WorkerThread
 import com.datadog.android.api.InternalLogger
 import com.datadog.android.api.context.DatadogContext
 import com.datadog.android.api.feature.Feature
@@ -97,6 +98,7 @@ internal class DatadogLateCrashReporter(
         }
     }
 
+    @WorkerThread
     @RequiresApi(Build.VERSION_CODES.R)
     override fun handleAnrCrash(
         anrExitInfo: ApplicationExitInfo,
diff --git a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/LateCrashReporter.kt b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/LateCrashReporter.kt
index 243dc74eba..d767b2139d 100644
--- a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/LateCrashReporter.kt
+++ b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/LateCrashReporter.kt
@@ -9,6 +9,7 @@ package com.datadog.android.rum.internal
 import android.app.ApplicationExitInfo
 import android.os.Build
 import androidx.annotation.RequiresApi
+import androidx.annotation.WorkerThread
 import com.datadog.android.api.storage.DataWriter
 import com.google.gson.JsonObject
 
@@ -16,6 +17,7 @@ internal interface LateCrashReporter {
 
     fun handleNdkCrashEvent(event: Map<*, *>, rumWriter: DataWriter<Any>)
 
+    @WorkerThread
     @RequiresApi(Build.VERSION_CODES.R)
     fun handleAnrCrash(
         anrExitInfo: ApplicationExitInfo,
diff --git a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/anr/AndroidTraceParser.kt b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/anr/AndroidTraceParser.kt
index dba025d225..58f7dcfc22 100644
--- a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/anr/AndroidTraceParser.kt
+++ b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/anr/AndroidTraceParser.kt
@@ -7,6 +7,7 @@
 package com.datadog.android.rum.internal.anr
 
 import com.datadog.android.api.InternalLogger
+import com.datadog.android.core.appendIfNotEmpty
 import com.datadog.android.core.feature.event.ThreadDump
 import java.io.IOException
 import java.io.InputStream
@@ -33,7 +34,7 @@ internal class AndroidTraceParser(
         val threadDumps = mutableListOf<ThreadDump>()
 
         var isInThreadStackBlock = false
-        val currentThreadStack = mutableListOf<String>()
+        val currentThreadStack = StringBuilder()
         var currentThreadName: String? = null
         var currentThreadState: String? = null
 
@@ -45,7 +46,7 @@ internal class AndroidTraceParser(
                     threadDumps += ThreadDump(
                         name = currentThreadName,
                         state = convertThreadState(currentThreadState.orEmpty()),
-                        stack = currentThreadStack.joinToString("\n"),
+                        stack = currentThreadStack.toString(),
                         crashed = currentThreadName == "main"
                     )
                 }
@@ -73,7 +74,7 @@ internal class AndroidTraceParser(
                 // - locked <0x0dd89f49> (a okhttp3.internal.concurrent.TaskRunner)
                 // we want to skip them for now
                 // also we want to skip any non-stack lines in the thread info block
-                currentThreadStack += line
+                currentThreadStack.appendIfNotEmpty('\n').append(line)
             }
         }
 
diff --git a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/net/RumRequestFactory.kt b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/net/RumRequestFactory.kt
index 6277573bc9..2ab2fbd30d 100644
--- a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/net/RumRequestFactory.kt
+++ b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/net/RumRequestFactory.kt
@@ -108,24 +108,20 @@ internal class RumRequestFactory(
         env: String,
         variant: String,
         executionContext: RequestExecutionContext
-    ): String {
-        val elements = mutableListOf(
-            "${RumAttributes.SERVICE_NAME}:$serviceName",
-            "${RumAttributes.APPLICATION_VERSION}:$version",
-            "${RumAttributes.SDK_VERSION}:$sdkVersion",
-            "${RumAttributes.ENV}:$env"
-        )
+    ) = buildString {
+        append("${RumAttributes.SERVICE_NAME}:$serviceName").append(",")
+            .append("${RumAttributes.APPLICATION_VERSION}:$version").append(",")
+            .append("${RumAttributes.SDK_VERSION}:$sdkVersion").append(",")
+            .append("${RumAttributes.ENV}:$env")
 
         if (variant.isNotEmpty()) {
-            elements.add("${RumAttributes.VARIANT}:$variant")
+            append(",").append("${RumAttributes.VARIANT}:$variant")
         }
         if (executionContext.previousResponseCode != null) {
             // we had a previous failure
-            elements.add("${RETRY_COUNT_KEY}:${executionContext.attemptNumber}")
-            elements.add("${LAST_FAILURE_STATUS_KEY}:${executionContext.previousResponseCode}")
+            append(",").append("${RETRY_COUNT_KEY}:${executionContext.attemptNumber}")
+            append(",").append("${LAST_FAILURE_STATUS_KEY}:${executionContext.previousResponseCode}")
         }
-
-        return elements.joinToString(",")
     }
 
     @Suppress("TooGenericExceptionCaught")

From 6e5c73f01368895e3905ead99d581caa7e596d5f Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Tue, 17 Dec 2024 11:03:38 +0000
Subject: [PATCH 2/9] RUM-6286: Adding StringBuilder.clear() to whitelist

---
 detekt_custom.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/detekt_custom.yml b/detekt_custom.yml
index 5ae85b0ace..fbb2885a12 100644
--- a/detekt_custom.yml
+++ b/detekt_custom.yml
@@ -1265,6 +1265,7 @@ datadog:
       - "kotlin.text.StringBuilder()"
       - "kotlin.text.buildString(kotlin.Function1)"
       - "kotlin.text.buildString(kotlin.Int, kotlin.Function1)"
+      - "java.lang.StringBuilder.clear()"
       # endregion
       # region Kotlin Misc
       - "kotlin.IllegalArgumentException(kotlin.String?)"

From 3240dc601362ecf91a65167e3f7aa5156db3c123 Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Tue, 17 Dec 2024 12:09:38 +0000
Subject: [PATCH 3/9] RUM-6286: post-review fixes: using property-base approach
 in string builder tests

---
 .../android/core/StringBuilderExtKtTest.kt    | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
index 181b4e1346..6e0b81b1ea 100644
--- a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
@@ -1,36 +1,39 @@
 package com.datadog.android.core
 
+import fr.xgouchet.elmyr.annotation.StringForgery
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
 
 class StringBuilderExtKtTest {
 
     @Test
-    fun `M add char W addIfNotEmpty {buffer is not empty}`() {
+    fun `M add char W addIfNotEmpty {buffer is not empty}`(
+        @StringForgery(regex = ".+") initialContent: String
+    ) {
         // Given
-        val initialData = "something inside buffer already"
-        val buffer = StringBuilder(initialData)
+        val buffer = StringBuilder(initialContent)
 
         // When
         buffer.appendIfNotEmpty(' ')
 
         // Then
 
-        assertThat(buffer.toString()).isEqualTo("$initialData ")
+        assertThat(buffer.toString()).isEqualTo("$initialContent ")
     }
 
     @Test
-    fun `M add str W addIfNotEmpty {buffer is not empty}`() {
+    fun `M add str W addIfNotEmpty {buffer is not empty}`(
+        @StringForgery(regex = ".+") initialContent: String
+    ) {
         // Given
-        val initialData = "something inside buffer already"
-        val buffer = StringBuilder(initialData)
+        val buffer = StringBuilder(initialContent)
 
         // When
         buffer.appendIfNotEmpty(" ")
 
         // Then
 
-        assertThat(buffer.toString()).isEqualTo("$initialData ")
+        assertThat(buffer.toString()).isEqualTo("$initialContent ")
     }
 
     @Test

From ccb2ae3aae7680b6646440ccf99bad18993e1734 Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Tue, 17 Dec 2024 12:10:02 +0000
Subject: [PATCH 4/9] RUM-6286: post-review fixes: using p95 percentile to
 compare performance

---
 ...tToStringVsStringBuilderPerformanceTest.kt | 111 ++++++++++++++++++
 .../datadog/android/utils/PerformanceTest.kt  |  64 ----------
 2 files changed, 111 insertions(+), 64 deletions(-)
 create mode 100644 dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
 delete mode 100644 dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/PerformanceTest.kt

diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
new file mode 100644
index 0000000000..cad174c375
--- /dev/null
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
@@ -0,0 +1,111 @@
+/*
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/).
+ * Copyright 2016-Present Datadog, Inc.
+ */
+package com.datadog.android.utils
+
+import com.datadog.android.core.appendIfNotEmpty
+import com.datadog.android.utils.forge.Configurator
+import fr.xgouchet.elmyr.Forge
+import fr.xgouchet.elmyr.junit5.ForgeConfiguration
+import fr.xgouchet.elmyr.junit5.ForgeExtension
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import org.junit.jupiter.api.extension.Extensions
+import kotlin.math.pow
+import kotlin.math.round
+import kotlin.math.sqrt
+import kotlin.system.measureNanoTime
+
+private const val ITEMS_TO_JOINT = 10_000
+private const val REPETITION_COUNT = 10_000
+
+@Extensions(
+    ExtendWith(ForgeExtension::class)
+)
+@ForgeConfiguration(value = Configurator::class, seed = 0x50c72968d123L)
+internal class JointToStringVsStringBuilderPerformanceTest {
+
+    @Test
+    fun `M be faster than joinToString W buildString`(forge: Forge) {
+        val itemsForJoin = forge.aList(ITEMS_TO_JOINT) { forge.aString() }
+        val jointToStringExecutionTime = mutableListOf<Long>()
+        val builderResultsExecutionTime = mutableListOf<Long>()
+
+        var jointToStringResult: String
+        var builderResult: String
+
+        for (i in 0..REPETITION_COUNT) {
+            jointToStringExecutionTime.add(
+                measureNanoTime {
+                    val jointToStringContainer = mutableListOf<String>()
+                    for (item in itemsForJoin) {
+                        jointToStringContainer.add(item)
+                    }
+                    jointToStringResult = jointToStringContainer.joinToString(separator = " ") { it }
+                }
+            )
+
+            builderResultsExecutionTime.add(
+                measureNanoTime {
+                    builderResult = buildString {
+                        itemsForJoin.forEach { item -> appendIfNotEmpty(' ').append(item) }
+                    }
+                }
+            )
+
+            assertThat(builderResult).isEqualTo(jointToStringResult) // same result
+        }
+
+        val statisticsReport = (
+            "buildString:\n" +
+                " mean = ${builderResultsExecutionTime.mean}\n" +
+                " std = ${builderResultsExecutionTime.std}\n" +
+                " cv = ${"%.2f".format(builderResultsExecutionTime.cv)}%\n" +
+                " p50 = ${builderResultsExecutionTime.percentile(50)}\n" +
+                " p90 = ${builderResultsExecutionTime.percentile(90)}\n" +
+                " p95 = ${builderResultsExecutionTime.percentile(95)}\n" +
+                " p99 = ${builderResultsExecutionTime.percentile(99)}\n" +
+                "\n" +
+                "joinToString:\n" +
+                " mean = ${jointToStringExecutionTime.mean}\n" +
+                " std = ${jointToStringExecutionTime.std}\n" +
+                " cv = ${"%.2f".format(jointToStringExecutionTime.cv)}%\n" +
+                " p50 = ${jointToStringExecutionTime.percentile(50)},\n" +
+                " p90 = ${jointToStringExecutionTime.percentile(90)},\n" +
+                " p95 = ${jointToStringExecutionTime.percentile(95)},\n" +
+                " p99 = ${jointToStringExecutionTime.percentile(99)}\n"
+            )
+
+        println(statisticsReport)
+
+        assertThat(
+            builderResultsExecutionTime.percentile(95)
+        ).isLessThan(
+            jointToStringExecutionTime.percentile(95)
+        )
+    }
+
+    companion object {
+        private val List<Long>.mean
+            get() = (sum().toDouble() / size)
+
+        private val List<Long>.std: Double
+            get() {
+                val m = mean
+                return sqrt(
+                    sumOf { (it - m).pow(2.0) } / size
+                )
+            }
+
+        private val List<Long>.cv: Double
+            get() = std / mean * 100.0
+
+        private fun List<Long>.percentile(k: Int): Long {
+            val p = (k / 100.0) * (size + 1)
+            return sorted()[round(p).toInt()]
+        }
+    }
+}
diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/PerformanceTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/PerformanceTest.kt
deleted file mode 100644
index eaf84b4f70..0000000000
--- a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/PerformanceTest.kt
+++ /dev/null
@@ -1,64 +0,0 @@
-/*
- * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
- * This product includes software developed at Datadog (https://www.datadoghq.com/).
- * Copyright 2016-Present Datadog, Inc.
- */
-package com.datadog.android.utils
-
-import com.datadog.android.utils.forge.Configurator
-import fr.xgouchet.elmyr.Forge
-import fr.xgouchet.elmyr.junit5.ForgeConfiguration
-import fr.xgouchet.elmyr.junit5.ForgeExtension
-import org.assertj.core.api.Assertions.assertThat
-import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.extension.ExtendWith
-import org.junit.jupiter.api.extension.Extensions
-import kotlin.system.measureNanoTime
-
-private const val ITEMS_TO_JOINT = 10_000
-private const val REPETITION_COUNT = 10_000
-
-@Extensions(
-    ExtendWith(ForgeExtension::class)
-)
-@ForgeConfiguration(Configurator::class)
-internal class PerformanceTest {
-
-    private fun List<Long>.mean() = sum().toDouble() / size
-
-    @Test
-    fun `M be faster than joinToString W buildString`(forge: Forge) {
-        val itemsForJoin = forge.aList(ITEMS_TO_JOINT) { forge.aString() }
-        val jointToStringResults = mutableListOf<Long>()
-        val builderResults = mutableListOf<Long>()
-
-        var jointToStringResult = ""
-        var builderResult = ""
-
-        for (i in 0..REPETITION_COUNT) {
-            jointToStringResults.add(
-                measureNanoTime {
-                    val jointToStringContainer = mutableListOf<String>()
-                    for (item in itemsForJoin) {
-                        jointToStringContainer.add(item)
-                    }
-                    jointToStringResult = jointToStringContainer.joinToString(separator = " ") { it }
-                }
-            )
-
-            builderResults.add(
-                measureNanoTime {
-                    builderResult = buildString {
-                        itemsForJoin.forEachIndexed { i, item ->
-                            if (i > 0) append(" ")
-                            append(item)
-                        }
-                    }
-                }
-            )
-        }
-
-        assertThat(builderResult).isEqualTo(jointToStringResult) // same result
-        assertThat(builderResults.mean()).isLessThan(jointToStringResults.mean())
-    }
-}

From f56fefbf6c778d0fb57588b52fb96eb43eb97d9b Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Tue, 17 Dec 2024 12:19:52 +0000
Subject: [PATCH 5/9] RUM-6286: post-review fixes: using p95 percentile to
 compare performance

---
 ...tToStringVsStringBuilderPerformanceTest.kt | 22 +++++++++----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
index cad174c375..481a3bcd77 100644
--- a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
@@ -32,12 +32,12 @@ internal class JointToStringVsStringBuilderPerformanceTest {
     fun `M be faster than joinToString W buildString`(forge: Forge) {
         val itemsForJoin = forge.aList(ITEMS_TO_JOINT) { forge.aString() }
         val jointToStringExecutionTime = mutableListOf<Long>()
-        val builderResultsExecutionTime = mutableListOf<Long>()
+        val buildStringExecutionTime = mutableListOf<Long>()
 
         var jointToStringResult: String
         var builderResult: String
 
-        for (i in 0..REPETITION_COUNT) {
+        repeat(REPETITION_COUNT) {
             jointToStringExecutionTime.add(
                 measureNanoTime {
                     val jointToStringContainer = mutableListOf<String>()
@@ -48,7 +48,7 @@ internal class JointToStringVsStringBuilderPerformanceTest {
                 }
             )
 
-            builderResultsExecutionTime.add(
+            buildStringExecutionTime.add(
                 measureNanoTime {
                     builderResult = buildString {
                         itemsForJoin.forEach { item -> appendIfNotEmpty(' ').append(item) }
@@ -61,13 +61,13 @@ internal class JointToStringVsStringBuilderPerformanceTest {
 
         val statisticsReport = (
             "buildString:\n" +
-                " mean = ${builderResultsExecutionTime.mean}\n" +
-                " std = ${builderResultsExecutionTime.std}\n" +
-                " cv = ${"%.2f".format(builderResultsExecutionTime.cv)}%\n" +
-                " p50 = ${builderResultsExecutionTime.percentile(50)}\n" +
-                " p90 = ${builderResultsExecutionTime.percentile(90)}\n" +
-                " p95 = ${builderResultsExecutionTime.percentile(95)}\n" +
-                " p99 = ${builderResultsExecutionTime.percentile(99)}\n" +
+                " mean = ${buildStringExecutionTime.mean}\n" +
+                " std = ${buildStringExecutionTime.std}\n" +
+                " cv = ${"%.2f".format(buildStringExecutionTime.cv)}%\n" +
+                " p50 = ${buildStringExecutionTime.percentile(50)}\n" +
+                " p90 = ${buildStringExecutionTime.percentile(90)}\n" +
+                " p95 = ${buildStringExecutionTime.percentile(95)}\n" +
+                " p99 = ${buildStringExecutionTime.percentile(99)}\n" +
                 "\n" +
                 "joinToString:\n" +
                 " mean = ${jointToStringExecutionTime.mean}\n" +
@@ -82,7 +82,7 @@ internal class JointToStringVsStringBuilderPerformanceTest {
         println(statisticsReport)
 
         assertThat(
-            builderResultsExecutionTime.percentile(95)
+            buildStringExecutionTime.percentile(95)
         ).isLessThan(
             jointToStringExecutionTime.percentile(95)
         )

From b7a8a442f1eb92f22961dce00190254dea5a0f51 Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Tue, 17 Dec 2024 13:38:26 +0000
Subject: [PATCH 6/9] RUM-6286: reduce flakiness, fix configuration

---
 .../com/datadog/android/core/StringBuilderExtKtTest.kt    | 8 +++++++-
 .../utils/JointToStringVsStringBuilderPerformanceTest.kt  | 4 ++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
index 6e0b81b1ea..f0cb5979cd 100644
--- a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
@@ -1,10 +1,16 @@
 package com.datadog.android.core
 
 import fr.xgouchet.elmyr.annotation.StringForgery
+import fr.xgouchet.elmyr.junit5.ForgeExtension
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import org.junit.jupiter.api.extension.Extensions
 
-class StringBuilderExtKtTest {
+@Extensions(
+    ExtendWith(ForgeExtension::class)
+)
+internal class StringBuilderExtKtTest {
 
     @Test
     fun `M add char W addIfNotEmpty {buffer is not empty}`(
diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
index 481a3bcd77..cf1e1303a1 100644
--- a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
@@ -82,9 +82,9 @@ internal class JointToStringVsStringBuilderPerformanceTest {
         println(statisticsReport)
 
         assertThat(
-            buildStringExecutionTime.percentile(95)
+            buildStringExecutionTime.percentile(90)
         ).isLessThan(
-            jointToStringExecutionTime.percentile(95)
+            jointToStringExecutionTime.percentile(90)
         )
     }
 

From d6a6b62b34ed9e29320e0b16bf189873255d8bcc Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Wed, 18 Dec 2024 10:20:43 +0000
Subject: [PATCH 7/9] RUM-6286: post-review fixes - moving StringBuilderExt
 into internal module

---
 dd-sdk-android-core/api/apiSurface            |  2 --
 .../api/dd-sdk-android-core.api               |  5 ---
 .../datadog/android/core/StringBuilderExt.kt  | 27 ---------------
 ...tToStringVsStringBuilderPerformanceTest.kt | 34 +++++++++----------
 dd-sdk-android-internal/api/apiSurface        |  2 ++
 .../api/dd-sdk-android-internal.api           |  5 +++
 .../internal/utils/StringBuilderExt.kt        | 27 +++++++++++++++
 .../internal/utils}/StringBuilderExtKtTest.kt | 12 ++++---
 detekt_custom.yml                             |  2 +-
 .../rum/internal/anr/AndroidTraceParser.kt    |  2 +-
 10 files changed, 61 insertions(+), 57 deletions(-)
 delete mode 100644 dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/StringBuilderExt.kt
 create mode 100644 dd-sdk-android-internal/src/main/java/com/datadog/android/internal/utils/StringBuilderExt.kt
 rename {dd-sdk-android-core/src/test/kotlin/com/datadog/android/core => dd-sdk-android-internal/src/test/java/com/datadog/internal/utils}/StringBuilderExtKtTest.kt (82%)

diff --git a/dd-sdk-android-core/api/apiSurface b/dd-sdk-android-core/api/apiSurface
index 8d71195036..d5b414c3a4 100644
--- a/dd-sdk-android-core/api/apiSurface
+++ b/dd-sdk-android-core/api/apiSurface
@@ -190,8 +190,6 @@ class com.datadog.android.core.SdkReference
   fun get(): com.datadog.android.api.SdkCore?
 fun <T> allowThreadDiskReads(() -> T): T
 fun <T> allowThreadDiskWrites(() -> T): T
-fun StringBuilder.appendIfNotEmpty(String)
-fun StringBuilder.appendIfNotEmpty(Char)
 enum com.datadog.android.core.configuration.BackPressureMitigation
   - DROP_OLDEST
   - IGNORE_NEWEST
diff --git a/dd-sdk-android-core/api/dd-sdk-android-core.api b/dd-sdk-android-core/api/dd-sdk-android-core.api
index c6a9155c45..0e0ac78ac3 100644
--- a/dd-sdk-android-core/api/dd-sdk-android-core.api
+++ b/dd-sdk-android-core/api/dd-sdk-android-core.api
@@ -543,11 +543,6 @@ public final class com/datadog/android/core/StrictModeExtKt {
 	public static final fun allowThreadDiskWrites (Lkotlin/jvm/functions/Function0;)Ljava/lang/Object;
 }
 
-public final class com/datadog/android/core/StringBuilderExtKt {
-	public static final fun appendIfNotEmpty (Ljava/lang/StringBuilder;C)Ljava/lang/StringBuilder;
-	public static final fun appendIfNotEmpty (Ljava/lang/StringBuilder;Ljava/lang/String;)Ljava/lang/StringBuilder;
-}
-
 public final class com/datadog/android/core/configuration/BackPressureMitigation : java/lang/Enum {
 	public static final field DROP_OLDEST Lcom/datadog/android/core/configuration/BackPressureMitigation;
 	public static final field IGNORE_NEWEST Lcom/datadog/android/core/configuration/BackPressureMitigation;
diff --git a/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/StringBuilderExt.kt b/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/StringBuilderExt.kt
deleted file mode 100644
index 64e4d76f5e..0000000000
--- a/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/StringBuilderExt.kt
+++ /dev/null
@@ -1,27 +0,0 @@
-/*
- * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
- * This product includes software developed at Datadog (https://www.datadoghq.com/).
- * Copyright 2016-Present Datadog, Inc.
- */
-
-package com.datadog.android.core
-
-/**
- * This utility function helps replace joinToString calls with more efficient StringBuilder's methods calls.
- * In case when content should be separated with some separator it's handy to add it in front of new string only
- * if buffer already contain some data
- * @param str - string that should be added into buffer only if it already contains some data
- */
-fun StringBuilder.appendIfNotEmpty(str: String) = apply {
-    if (isNotEmpty()) append(str)
-}
-
-/**
- * This utility function helps replace joinToString calls with more efficient StringBuilder's methods calls.
- * In case when content should be separated with some separator it's handy to add it in front of new string only
- * if buffer already contain some data
- * @param char - char that should be added into buffer only if it already contains some data
- */
-fun StringBuilder.appendIfNotEmpty(char: Char) = apply {
-    if (isNotEmpty()) append(char)
-}
diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
index cf1e1303a1..ea6583a03b 100644
--- a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
@@ -5,7 +5,7 @@
  */
 package com.datadog.android.utils
 
-import com.datadog.android.core.appendIfNotEmpty
+import com.datadog.android.internal.utils.appendIfNotEmpty
 import com.datadog.android.utils.forge.Configurator
 import fr.xgouchet.elmyr.Forge
 import fr.xgouchet.elmyr.junit5.ForgeConfiguration
@@ -19,9 +19,6 @@ import kotlin.math.round
 import kotlin.math.sqrt
 import kotlin.system.measureNanoTime
 
-private const val ITEMS_TO_JOINT = 10_000
-private const val REPETITION_COUNT = 10_000
-
 @Extensions(
     ExtendWith(ForgeExtension::class)
 )
@@ -30,15 +27,15 @@ internal class JointToStringVsStringBuilderPerformanceTest {
 
     @Test
     fun `M be faster than joinToString W buildString`(forge: Forge) {
-        val itemsForJoin = forge.aList(ITEMS_TO_JOINT) { forge.aString() }
-        val jointToStringExecutionTime = mutableListOf<Long>()
+        val itemsForJoin = forge.aList(ITEMS_TO_JOIN) { forge.aString() }
+        val joinToStringExecutionTime = mutableListOf<Long>()
         val buildStringExecutionTime = mutableListOf<Long>()
 
         var jointToStringResult: String
         var builderResult: String
 
         repeat(REPETITION_COUNT) {
-            jointToStringExecutionTime.add(
+            joinToStringExecutionTime.add(
                 measureNanoTime {
                     val jointToStringContainer = mutableListOf<String>()
                     for (item in itemsForJoin) {
@@ -70,25 +67,28 @@ internal class JointToStringVsStringBuilderPerformanceTest {
                 " p99 = ${buildStringExecutionTime.percentile(99)}\n" +
                 "\n" +
                 "joinToString:\n" +
-                " mean = ${jointToStringExecutionTime.mean}\n" +
-                " std = ${jointToStringExecutionTime.std}\n" +
-                " cv = ${"%.2f".format(jointToStringExecutionTime.cv)}%\n" +
-                " p50 = ${jointToStringExecutionTime.percentile(50)},\n" +
-                " p90 = ${jointToStringExecutionTime.percentile(90)},\n" +
-                " p95 = ${jointToStringExecutionTime.percentile(95)},\n" +
-                " p99 = ${jointToStringExecutionTime.percentile(99)}\n"
+                " mean = ${joinToStringExecutionTime.mean}\n" +
+                " std = ${joinToStringExecutionTime.std}\n" +
+                " cv = ${"%.2f".format(joinToStringExecutionTime.cv)}%\n" +
+                " p50 = ${joinToStringExecutionTime.percentile(50)},\n" +
+                " p90 = ${joinToStringExecutionTime.percentile(90)},\n" +
+                " p95 = ${joinToStringExecutionTime.percentile(95)},\n" +
+                " p99 = ${joinToStringExecutionTime.percentile(99)}\n"
             )
 
-        println(statisticsReport)
-
         assertThat(
             buildStringExecutionTime.percentile(90)
+        ).withFailMessage(
+            statisticsReport
         ).isLessThan(
-            jointToStringExecutionTime.percentile(90)
+            joinToStringExecutionTime.percentile(90)
         )
     }
 
     companion object {
+        private const val ITEMS_TO_JOIN = 10_000
+        private const val REPETITION_COUNT = 10_000
+
         private val List<Long>.mean
             get() = (sum().toDouble() / size)
 
diff --git a/dd-sdk-android-internal/api/apiSurface b/dd-sdk-android-internal/api/apiSurface
index 8f42e63ef2..8a1d378cd6 100644
--- a/dd-sdk-android-internal/api/apiSurface
+++ b/dd-sdk-android-internal/api/apiSurface
@@ -38,6 +38,8 @@ object com.datadog.android.internal.utils.ImageViewUtils
   fun resolveContentRectWithScaling(android.widget.ImageView, android.graphics.drawable.Drawable, android.widget.ImageView.ScaleType? = null): android.graphics.Rect
 fun Int.densityNormalized(Float): Int
 fun Long.densityNormalized(Float): Long
+fun StringBuilder.appendIfNotEmpty(String)
+fun StringBuilder.appendIfNotEmpty(Char)
 fun Throwable.loggableStackTrace(): String
 annotation com.datadog.tools.annotation.NoOpImplementation
   constructor(Boolean = false)
diff --git a/dd-sdk-android-internal/api/dd-sdk-android-internal.api b/dd-sdk-android-internal/api/dd-sdk-android-internal.api
index 1b50c65949..a8a3271696 100644
--- a/dd-sdk-android-internal/api/dd-sdk-android-internal.api
+++ b/dd-sdk-android-internal/api/dd-sdk-android-internal.api
@@ -130,6 +130,11 @@ public final class com/datadog/android/internal/utils/LongExtKt {
 	public static final fun densityNormalized (JF)J
 }
 
+public final class com/datadog/android/internal/utils/StringBuilderExtKt {
+	public static final fun appendIfNotEmpty (Ljava/lang/StringBuilder;C)Ljava/lang/StringBuilder;
+	public static final fun appendIfNotEmpty (Ljava/lang/StringBuilder;Ljava/lang/String;)Ljava/lang/StringBuilder;
+}
+
 public final class com/datadog/android/internal/utils/ThrowableExtKt {
 	public static final fun loggableStackTrace (Ljava/lang/Throwable;)Ljava/lang/String;
 }
diff --git a/dd-sdk-android-internal/src/main/java/com/datadog/android/internal/utils/StringBuilderExt.kt b/dd-sdk-android-internal/src/main/java/com/datadog/android/internal/utils/StringBuilderExt.kt
new file mode 100644
index 0000000000..1c57cbe6b9
--- /dev/null
+++ b/dd-sdk-android-internal/src/main/java/com/datadog/android/internal/utils/StringBuilderExt.kt
@@ -0,0 +1,27 @@
+/*
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/).
+ * Copyright 2016-Present Datadog, Inc.
+ */
+
+package com.datadog.android.internal.utils
+
+/**
+ * This utility function helps to replace [joinToString] calls with more efficient [StringBuilder] methods calls.
+ * In case when content should be separated with some separator, it's handy to add it in front of a new string only
+ * if buffer already contains some data.
+ * @param str string that should be added to the buffer only if it already contains some data.
+ */
+fun StringBuilder.appendIfNotEmpty(str: String) = apply {
+    if (isNotEmpty()) append(str)
+}
+
+/**
+ * This utility function helps to replace [joinToString] calls with more efficient [StringBuilder] methods calls.
+ * In case when content should be separated with some separator, it's handy to add it in front of a new string only
+ * if buffer already contains some data.
+ * @param char char that should be added to the buffer only if it already contains some data.
+ */
+fun StringBuilder.appendIfNotEmpty(char: Char) = apply {
+    if (isNotEmpty()) append(char)
+}
diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt b/dd-sdk-android-internal/src/test/java/com/datadog/internal/utils/StringBuilderExtKtTest.kt
similarity index 82%
rename from dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
rename to dd-sdk-android-internal/src/test/java/com/datadog/internal/utils/StringBuilderExtKtTest.kt
index f0cb5979cd..8817047753 100644
--- a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/core/StringBuilderExtKtTest.kt
+++ b/dd-sdk-android-internal/src/test/java/com/datadog/internal/utils/StringBuilderExtKtTest.kt
@@ -1,5 +1,12 @@
-package com.datadog.android.core
+/*
+ * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
+ * This product includes software developed at Datadog (https://www.datadoghq.com/).
+ * Copyright 2016-Present Datadog, Inc.
+ */
 
+package com.datadog.internal.utils
+
+import com.datadog.android.internal.utils.appendIfNotEmpty
 import fr.xgouchet.elmyr.annotation.StringForgery
 import fr.xgouchet.elmyr.junit5.ForgeExtension
 import org.assertj.core.api.Assertions.assertThat
@@ -38,7 +45,6 @@ internal class StringBuilderExtKtTest {
         buffer.appendIfNotEmpty(" ")
 
         // Then
-
         assertThat(buffer.toString()).isEqualTo("$initialContent ")
     }
 
@@ -51,7 +57,6 @@ internal class StringBuilderExtKtTest {
         buffer.appendIfNotEmpty(' ')
 
         // Then
-
         assertThat(buffer.toString()).isEqualTo("")
     }
 
@@ -64,7 +69,6 @@ internal class StringBuilderExtKtTest {
         buffer.appendIfNotEmpty(" ")
 
         // Then
-
         assertThat(buffer.toString()).isEqualTo("")
     }
 }
diff --git a/detekt_custom.yml b/detekt_custom.yml
index fbb2885a12..988918490f 100644
--- a/detekt_custom.yml
+++ b/detekt_custom.yml
@@ -780,6 +780,7 @@ datadog:
       - "java.lang.StringBuilder.append(kotlin.Char)"
       - "java.lang.StringBuilder.append(kotlin.CharArray?)"
       - "java.lang.StringBuilder.append(kotlin.String?)"
+      - "java.lang.StringBuilder.clear()"
       - "java.lang.StringBuilder.constructor()"
       - "java.math.BigInteger.toHexString()"
       - "java.math.BigInteger.toLong()"
@@ -1265,7 +1266,6 @@ datadog:
       - "kotlin.text.StringBuilder()"
       - "kotlin.text.buildString(kotlin.Function1)"
       - "kotlin.text.buildString(kotlin.Int, kotlin.Function1)"
-      - "java.lang.StringBuilder.clear()"
       # endregion
       # region Kotlin Misc
       - "kotlin.IllegalArgumentException(kotlin.String?)"
diff --git a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/anr/AndroidTraceParser.kt b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/anr/AndroidTraceParser.kt
index 58f7dcfc22..ccb599b5e5 100644
--- a/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/anr/AndroidTraceParser.kt
+++ b/features/dd-sdk-android-rum/src/main/kotlin/com/datadog/android/rum/internal/anr/AndroidTraceParser.kt
@@ -7,8 +7,8 @@
 package com.datadog.android.rum.internal.anr
 
 import com.datadog.android.api.InternalLogger
-import com.datadog.android.core.appendIfNotEmpty
 import com.datadog.android.core.feature.event.ThreadDump
+import com.datadog.android.internal.utils.appendIfNotEmpty
 import java.io.IOException
 import java.io.InputStream
 import java.util.Locale

From 0ed3809fd7927675f88bb49eaba08a34c3049d7e Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Wed, 18 Dec 2024 13:18:14 +0000
Subject: [PATCH 8/9] RUM-6286: post-review fixes - removing seed

---
 .../utils/JointToStringVsStringBuilderPerformanceTest.kt       | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
index ea6583a03b..6f3b8acd40 100644
--- a/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
+++ b/dd-sdk-android-core/src/test/kotlin/com/datadog/android/utils/JointToStringVsStringBuilderPerformanceTest.kt
@@ -6,9 +6,7 @@
 package com.datadog.android.utils
 
 import com.datadog.android.internal.utils.appendIfNotEmpty
-import com.datadog.android.utils.forge.Configurator
 import fr.xgouchet.elmyr.Forge
-import fr.xgouchet.elmyr.junit5.ForgeConfiguration
 import fr.xgouchet.elmyr.junit5.ForgeExtension
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
@@ -22,7 +20,6 @@ import kotlin.system.measureNanoTime
 @Extensions(
     ExtendWith(ForgeExtension::class)
 )
-@ForgeConfiguration(value = Configurator::class, seed = 0x50c72968d123L)
 internal class JointToStringVsStringBuilderPerformanceTest {
 
     @Test

From b2a6eaef92804964f5b304839642a32ebacb72d4 Mon Sep 17 00:00:00 2001
From: Timur Valeev <timur.valeev@datadoghq.com>
Date: Wed, 18 Dec 2024 14:47:05 +0000
Subject: [PATCH 9/9] RUM-6286: post-review fixes - align test names with
 methods

---
 .../com/datadog/internal/utils/StringBuilderExtKtTest.kt | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/dd-sdk-android-internal/src/test/java/com/datadog/internal/utils/StringBuilderExtKtTest.kt b/dd-sdk-android-internal/src/test/java/com/datadog/internal/utils/StringBuilderExtKtTest.kt
index 8817047753..2350c6c887 100644
--- a/dd-sdk-android-internal/src/test/java/com/datadog/internal/utils/StringBuilderExtKtTest.kt
+++ b/dd-sdk-android-internal/src/test/java/com/datadog/internal/utils/StringBuilderExtKtTest.kt
@@ -20,7 +20,7 @@ import org.junit.jupiter.api.extension.Extensions
 internal class StringBuilderExtKtTest {
 
     @Test
-    fun `M add char W addIfNotEmpty {buffer is not empty}`(
+    fun `M add char W appendIfNotEmpty {buffer is not empty}`(
         @StringForgery(regex = ".+") initialContent: String
     ) {
         // Given
@@ -30,12 +30,11 @@ internal class StringBuilderExtKtTest {
         buffer.appendIfNotEmpty(' ')
 
         // Then
-
         assertThat(buffer.toString()).isEqualTo("$initialContent ")
     }
 
     @Test
-    fun `M add str W addIfNotEmpty {buffer is not empty}`(
+    fun `M add str W appendIfNotEmpty {buffer is not empty}`(
         @StringForgery(regex = ".+") initialContent: String
     ) {
         // Given
@@ -49,7 +48,7 @@ internal class StringBuilderExtKtTest {
     }
 
     @Test
-    fun `M not add any char W addIfNotEmpty {buffer is empty}`() {
+    fun `M not add any char W appendIfNotEmpty {buffer is empty}`() {
         // Given
         val buffer = StringBuilder()
 
@@ -61,7 +60,7 @@ internal class StringBuilderExtKtTest {
     }
 
     @Test
-    fun `M not add any str W addIfNotEmpty {buffer is empty}`() {
+    fun `M not add any str W appendIfNotEmpty {buffer is empty}`() {
         // Given
         val buffer = StringBuilder()