icu4c DateIntervalFormat objects are expensive enough that we need to cache them.

It takes ~1ms to create a DateIntervalFormat on a z620, and around 8ms on a
current mobile device (Nexus 4). Add a small cache of recently-used formatters,
using a big lock rather than per-thread caches since this typically only
happens on the UI thread anyway, and because all the other frameworks date/time
formatting is behind a single lock too.

Bug: 10696944
Change-Id: I8ccbe0b31b722a95a08fbc5a119173b7a0f44807

benchmarks/src/benchmarks/regression/DateIntervalFormatBenchmark.java

+/*
+ * Copyright (C) 2013 Google Inc.
+ *
+ * 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 benchmarks.regression;
+
+import com.google.caliper.SimpleBenchmark;
+
+import java.util.Locale;
+import java.util.TimeZone;
+
+import static libcore.icu.DateIntervalFormat.*;
+
+public class DateIntervalFormatBenchmark extends SimpleBenchmark {
+  public void timeDateIntervalFormat_formatDateRange_DATE(int reps) throws Exception {
+    Locale l = Locale.US;
+    TimeZone utc = TimeZone.getTimeZone("UTC");
+    int flags = FORMAT_SHOW_DATE | FORMAT_SHOW_WEEKDAY;
+
+    for (int rep = 0; rep < reps; ++rep) {
+      formatDateRange(l, utc, 0L, 0L, flags);
+    }
+  }
+
+  public void timeDateIntervalFormat_formatDateRange_TIME(int reps) throws Exception {
+    Locale l = Locale.US;
+    TimeZone utc = TimeZone.getTimeZone("UTC");
+    int flags = FORMAT_SHOW_TIME | FORMAT_24HOUR;
+
+    for (int rep = 0; rep < reps; ++rep) {
+      formatDateRange(l, utc, 0L, 0L, flags);
+    }
+  }
+
+  public void timeDateIntervalFormat_formatDateRange_DATE_TIME(int reps) throws Exception {
+    Locale l = Locale.US;
+    TimeZone utc = TimeZone.getTimeZone("UTC");
+    int flags = FORMAT_SHOW_DATE | FORMAT_SHOW_WEEKDAY | FORMAT_SHOW_TIME | FORMAT_24HOUR;
+
+    for (int rep = 0; rep < reps; ++rep) {
+      formatDateRange(l, utc, 0L, 0L, flags);
+    }
+  }
+}

luni/src/main/java/libcore/icu/DateIntervalFormat.java

@@ -19,6 +19,7 @@ package libcore.icu;
 import java.util.Calendar;
 import java.util.Locale;
 import java.util.TimeZone;
+import libcore.util.BasicLruCache;
 
 /**
  * Exposes icu4c's DateIntervalFormat.
@@ -46,7 +47,18 @@ public final class DateIntervalFormat {
   private static final int DAY_IN_MS = 24 * 60 * 60 * 1000;
   private static final int EPOCH_JULIAN_DAY = 2440588;
 
-  // TODO: check whether icu4c's DateIntervalFormat is expensive enough to warrant a native peer.
+  private static final FormatterCache CACHED_FORMATTERS = new FormatterCache();
+
+  static class FormatterCache extends BasicLruCache<String, Long> {
+    FormatterCache() {
+      super(8);
+    }
+
+    protected void entryEvicted(String key, Long value) {
+      destroyDateIntervalFormat(value);
+    }
+  };
+
   private DateIntervalFormat() {
   }
 
@@ -86,7 +98,20 @@ public final class DateIntervalFormat {
     }
 
     String skeleton = toSkeleton(startCalendar, endCalendar, flags);
-    return formatDateInterval(skeleton, locale.toString(), tz.getID(), startMs, endMs);
+    synchronized (CACHED_FORMATTERS) {
+      return formatDateInterval(getFormatter(skeleton, locale.toString(), tz.getID()), startMs, endMs);
+    }
+  }
+
+  private static long getFormatter(String skeleton, String localeName, String tzName) {
+    String key = skeleton + "\t" + localeName + "\t" + tzName;
+    Long formatter = CACHED_FORMATTERS.get(key);
+    if (formatter != null) {
+      return formatter;
+    }
+    long address = createDateIntervalFormat(skeleton, localeName, tzName);
+    CACHED_FORMATTERS.put(key, address);
+    return address;
   }
 
   private static String toSkeleton(Calendar startCalendar, Calendar endCalendar, int flags) {
@@ -204,5 +229,7 @@ public final class DateIntervalFormat {
     return (int) (utcMs / DAY_IN_MS) + EPOCH_JULIAN_DAY;
   }
 
-  private static native String formatDateInterval(String skeleton, String localeName, String timeZoneName, long fromDate, long toDate);
+  private static native long createDateIntervalFormat(String skeleton, String localeName, String tzName);
+  private static native void destroyDateIntervalFormat(long address);
+  private static native String formatDateInterval(long address, long fromDate, long toDate);
 }

luni/src/main/native/libcore_icu_DateIntervalFormat.cpp

@@ -23,41 +23,52 @@
 #include "cutils/log.h"
 #include "unicode/dtitvfmt.h"
 
-static jstring DateIntervalFormat_formatDateInterval(JNIEnv* env, jclass, jstring javaSkeleton, jstring javaLocaleName, jstring javaTzName, jlong fromDate, jlong toDate) {
+static jlong DateIntervalFormat_createDateIntervalFormat(JNIEnv* env, jclass, jstring javaSkeleton, jstring javaLocaleName, jstring javaTzName) {
   Locale locale = getLocale(env, javaLocaleName);
 
   ScopedJavaUnicodeString skeletonHolder(env, javaSkeleton);
   if (!skeletonHolder.valid()) {
-    return NULL;
-  }
-
-  ScopedJavaUnicodeString tzNameHolder(env, javaTzName);
-  if (!tzNameHolder.valid()) {
-    return NULL;
+    return 0;
   }
 
   UErrorCode status = U_ZERO_ERROR;
-  UniquePtr<DateIntervalFormat> formatter(DateIntervalFormat::createInstance(skeletonHolder.unicodeString(), locale, status));
+  DateIntervalFormat* formatter(DateIntervalFormat::createInstance(skeletonHolder.unicodeString(), locale, status));
   if (maybeThrowIcuException(env, "DateIntervalFormat::createInstance", status)) {
-    return NULL;
+    return 0;
   }
 
+  ScopedJavaUnicodeString tzNameHolder(env, javaTzName);
+  if (!tzNameHolder.valid()) {
+    return 0;
+  }
   formatter->adoptTimeZone(TimeZone::createTimeZone(tzNameHolder.unicodeString()));
 
+  return reinterpret_cast<uintptr_t>(formatter);
+}
+
+static void DateIntervalFormat_destroyDateIntervalFormat(JNIEnv*, jclass, jlong address) {
+  delete reinterpret_cast<DateIntervalFormat*>(address);
+}
+
+static jstring DateIntervalFormat_formatDateInterval(JNIEnv* env, jclass, jlong address, jlong fromDate, jlong toDate) {
+  DateIntervalFormat* formatter(reinterpret_cast<DateIntervalFormat*>(address));
   DateInterval date_interval(fromDate, toDate);
 
-  UnicodeString result;
+  UnicodeString s;
   FieldPosition pos = 0;
-  formatter->format(&date_interval, result, pos, status);
+  UErrorCode status = U_ZERO_ERROR;
+  formatter->format(&date_interval, s, pos, status);
   if (maybeThrowIcuException(env, "DateIntervalFormat::format", status)) {
-      return NULL;
+    return NULL;
   }
 
-  return env->NewString(result.getBuffer(), result.length());
+  return env->NewString(s.getBuffer(), s.length());
 }
 
 static JNINativeMethod gMethods[] = {
-  NATIVE_METHOD(DateIntervalFormat, formatDateInterval, "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;JJ)Ljava/lang/String;"),
+  NATIVE_METHOD(DateIntervalFormat, createDateIntervalFormat, "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)J"),
+  NATIVE_METHOD(DateIntervalFormat, destroyDateIntervalFormat, "(J)V"),
+  NATIVE_METHOD(DateIntervalFormat, formatDateInterval, "(JJJ)Ljava/lang/String;"),
 };
 void register_libcore_icu_DateIntervalFormat(JNIEnv* env) {
   jniRegisterNativeMethods(env, "libcore/icu/DateIntervalFormat", gMethods, NELEM(gMethods));