Merge "Copy StringPool to framework" am: ffe7986d71 am: 91a9308a30
Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1684883
Change-Id: I980dc82d702bc8ccd90ee1ec5ef7e125ab670931
diff --git a/core/java/android/util/JsonReader.java b/core/java/android/util/JsonReader.java
index 50f63f8..c75e238 100644
--- a/core/java/android/util/JsonReader.java
+++ b/core/java/android/util/JsonReader.java
@@ -16,7 +16,7 @@
package android.util;
-import libcore.internal.StringPool;
+import com.android.internal.util.StringPool;
import java.io.Closeable;
import java.io.EOFException;
diff --git a/core/java/com/android/internal/util/StringPool.java b/core/java/com/android/internal/util/StringPool.java
new file mode 100644
index 0000000..c5180a3
--- /dev/null
+++ b/core/java/com/android/internal/util/StringPool.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * 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.android.internal.util;
+
+/**
+ * A pool of string instances. Unlike the {@link String#intern() VM's
+ * interned strings}, this pool provides no guarantee of reference equality.
+ * It is intended only to save allocations. This class is not thread safe.
+ *
+ * @hide
+ */
+public final class StringPool {
+
+ private final String[] mPool = new String[512];
+
+ /**
+ * Constructs string pool.
+ */
+ public StringPool() {
+ }
+
+ private static boolean contentEquals(String s, char[] chars, int start, int length) {
+ if (s.length() != length) {
+ return false;
+ }
+ for (int i = 0; i < length; i++) {
+ if (chars[start + i] != s.charAt(i)) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ /**
+ * Returns a string equal to {@code new String(array, start, length)}.
+ *
+ * @param array buffer containing string chars
+ * @param start offset in {@code array} where string starts
+ * @param length length of string
+ * @return string equal to {@code new String(array, start, length)}
+ */
+ public String get(char[] array, int start, int length) {
+ // Compute an arbitrary hash of the content
+ int hashCode = 0;
+ for (int i = start; i < start + length; i++) {
+ hashCode = (hashCode * 31) + array[i];
+ }
+
+ // Pick a bucket using Doug Lea's supplemental secondaryHash function (from HashMap)
+ hashCode ^= (hashCode >>> 20) ^ (hashCode >>> 12);
+ hashCode ^= (hashCode >>> 7) ^ (hashCode >>> 4);
+ int index = hashCode & (mPool.length - 1);
+
+ String pooled = mPool[index];
+ if (pooled != null && contentEquals(pooled, array, start, length)) {
+ return pooled;
+ }
+
+ String result = new String(array, start, length);
+ mPool[index] = result;
+ return result;
+ }
+}
diff --git a/core/tests/utiltests/src/com/android/internal/util/StringPoolTest.java b/core/tests/utiltests/src/com/android/internal/util/StringPoolTest.java
new file mode 100644
index 0000000..f67fd51
--- /dev/null
+++ b/core/tests/utiltests/src/com/android/internal/util/StringPoolTest.java
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * 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.android.internal.util;
+
+import android.test.AndroidTestCase;
+import android.test.suitebuilder.annotation.SmallTest;
+
+@SmallTest
+public final class StringPoolTest extends AndroidTestCase {
+
+ public void testStringPool() {
+ StringPool stringPool = new StringPool();
+ String bcd = stringPool.get(new char[] { 'a', 'b', 'c', 'd', 'e' }, 1, 3);
+ assertEquals("bcd", bcd);
+ assertSame(bcd, stringPool.get(new char[] { 'a', 'b', 'c', 'd', 'e' }, 1, 3));
+ }
+
+ public void testHashCollision() {
+ StringPool stringPool = new StringPool();
+ char[] a = { (char) 1, (char) 0 };
+ char[] b = { (char) 0, (char) 31 };
+ assertEquals(new String(a).hashCode(), new String(b).hashCode());
+
+ String aString = stringPool.get(a, 0, 2);
+ assertEquals(new String(a), aString);
+ String bString = stringPool.get(b, 0, 2);
+ assertEquals(new String(b), bString);
+ assertSame(bString, stringPool.get(b, 0, 2));
+ assertNotSame(aString, stringPool.get(a, 0, 2));
+ }
+}