From a18c8f83e3adbfd70b6b229c2afdb3f05e3586a6 Mon Sep 17 00:00:00 2001
From: Victor Chang <vichang@google.com>
Date: Fri, 12 May 2023 16:01:56 +0100
Subject: [PATCH] ICU-22390 Speed-up ICU4J Transliterator.<clinit>

It reduces the method runtime by approx. 60%.
---
 .../ibm/icu/impl/ICUResourceBundleReader.java | 12 ++++++------
 .../com/ibm/icu/text/AnyTransliterator.java   | 19 ++++++++++---------
 .../ibm/icu/text/TransliteratorRegistry.java  | 10 +++++-----
 3 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/icu4j/main/classes/core/src/com/ibm/icu/impl/ICUResourceBundleReader.java b/icu4j/main/classes/core/src/com/ibm/icu/impl/ICUResourceBundleReader.java
index 746b1d9c1ac..7800f904c59 100644
--- a/icu4j/main/classes/core/src/com/ibm/icu/impl/ICUResourceBundleReader.java
+++ b/icu4j/main/classes/core/src/com/ibm/icu/impl/ICUResourceBundleReader.java
@@ -14,6 +14,7 @@ import java.lang.ref.SoftReference;
 import java.nio.ByteBuffer;
 import java.nio.CharBuffer;
 import java.nio.IntBuffer;
+import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 
 import com.ibm.icu.util.ICUException;
@@ -444,13 +445,12 @@ public final class ICUResourceBundleReader {
     }
 
     private static String makeKeyStringFromBytes(byte[] keyBytes, int keyOffset) {
-        StringBuilder sb = new StringBuilder();
-        byte b;
-        while((b = keyBytes[keyOffset]) != 0) {
-            ++keyOffset;
-            sb.append((char)b);
+        int end = keyOffset;
+        while(keyBytes[end] != 0) {
+            ++end;
         }
-        return sb.toString();
+        int len = end - keyOffset;
+        return new String(keyBytes, keyOffset, len, StandardCharsets.ISO_8859_1);
     }
     private String getKey16String(int keyOffset) {
         if(keyOffset < localKeyLimit) {
diff --git a/icu4j/main/classes/translit/src/com/ibm/icu/text/AnyTransliterator.java b/icu4j/main/classes/translit/src/com/ibm/icu/text/AnyTransliterator.java
index d7fbcb3b3f9..b051a6798e7 100644
--- a/icu4j/main/classes/translit/src/com/ibm/icu/text/AnyTransliterator.java
+++ b/icu4j/main/classes/translit/src/com/ibm/icu/text/AnyTransliterator.java
@@ -52,6 +52,12 @@ class AnyTransliterator extends Transliterator {
     static final String NULL_ID = "Null";
     static final String LATIN_PIVOT = "-Latin;Latin-";
 
+    /**
+     * Special code for handling width characters
+     */
+    private static final Transliterator WIDTH_FIX =
+            Transliterator.getInstance("[[:dt=Nar:][:dt=Wide:]] nfkd");
+
     /**
      * Cache mapping UScriptCode values to Transliterator*.
      */
@@ -67,11 +73,6 @@ class AnyTransliterator extends Transliterator {
      */
     private int targetScript;
 
-    /**
-     * Special code for handling width characters
-     */
-    private Transliterator widthFix = Transliterator.getInstance("[[:dt=Nar:][:dt=Wide:]] nfkd");
-
     /**
      * Implements {@link Transliterator#handleTransliterate}.
      */
@@ -176,7 +177,7 @@ class AnyTransliterator extends Transliterator {
             if (isWide(targetScript)) {
                 return null;
             } else {
-                return widthFix;
+                return WIDTH_FIX;
             }
         }
 
@@ -201,7 +202,7 @@ class AnyTransliterator extends Transliterator {
             if (t != null) {
                 if (!isWide(targetScript)) {
                     List<Transliterator> v = new ArrayList<Transliterator>();
-                    v.add(widthFix);
+                    v.add(WIDTH_FIX);
                     v.add(t);
                     t = new CompoundTransliterator(v);
                 }
@@ -210,7 +211,7 @@ class AnyTransliterator extends Transliterator {
                     t = prevCachedT;
                 }
             } else if (!isWide(targetScript)) {
-                return widthFix;
+                return WIDTH_FIX;
             }
         }
 
@@ -408,7 +409,7 @@ class AnyTransliterator extends Transliterator {
         if (filter != null && filter instanceof UnicodeSet) {
             filter = new UnicodeSet((UnicodeSet)filter);
         }
-        return new AnyTransliterator(getID(), filter, target, targetScript, widthFix, cache);
+        return new AnyTransliterator(getID(), filter, target, targetScript, WIDTH_FIX, cache);
     }
 
     /* (non-Javadoc)
diff --git a/icu4j/main/classes/translit/src/com/ibm/icu/text/TransliteratorRegistry.java b/icu4j/main/classes/translit/src/com/ibm/icu/text/TransliteratorRegistry.java
index b39d8353c97..be6bda49630 100644
--- a/icu4j/main/classes/translit/src/com/ibm/icu/text/TransliteratorRegistry.java
+++ b/icu4j/main/classes/translit/src/com/ibm/icu/text/TransliteratorRegistry.java
@@ -16,11 +16,13 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashMap;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.MissingResourceException;
 import java.util.ResourceBundle;
+import java.util.Set;
 
 import com.ibm.icu.impl.ICUData;
 import com.ibm.icu.impl.ICUResourceBundle;
@@ -69,7 +71,7 @@ class TransliteratorRegistry {
     /**
      * Vector of public full IDs (CaseInsensitiveString objects).
      */
-    private List<CaseInsensitiveString> availableIDs;
+    private final Set<CaseInsensitiveString> availableIDs;
 
     //----------------------------------------------------------------------
     // class Spec
@@ -293,7 +295,7 @@ class TransliteratorRegistry {
     public TransliteratorRegistry() {
         registry = Collections.synchronizedMap(new HashMap<CaseInsensitiveString, Object[]>());
         specDAG = Collections.synchronizedMap(new HashMap<CaseInsensitiveString, Map<CaseInsensitiveString, List<CaseInsensitiveString>>>());
-        availableIDs = new ArrayList<CaseInsensitiveString>();
+        availableIDs = new LinkedHashSet<>();
     }
 
     /**
@@ -520,9 +522,7 @@ class TransliteratorRegistry {
         registry.put(ciID, arrayOfObj);
         if (visible) {
             registerSTV(source, target, variant);
-            if (!availableIDs.contains(ciID)) {
-                availableIDs.add(ciID);
-            }
+            availableIDs.add(ciID);
         } else {
             removeSTV(source, target, variant);
             availableIDs.remove(ciID);