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8046201: Avoid repeated flattening of nested ConsStrings

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Reviewed-by: lagergren, attila
This commit is contained in:
Hannes Wallnöfer 2014-06-23 18:32:11 +02:00
parent 90b667d865
commit 3ad3dd1d89
2 changed files with 166 additions and 12 deletions
nashorn
src/jdk/nashorn/internal/runtime
ConsString.java
test/src/jdk/nashorn/internal/runtime
ConsStringTest.java

43
nashorn/src/jdk/nashorn/internal/runtime/ConsString.java

@ -36,8 +36,12 @@ import java.util.Deque;
public final class ConsString implements CharSequence {
private CharSequence left, right;
final private int length;
private boolean flat = false;
private final int length;
private volatile int state = STATE_NEW;
private final static int STATE_NEW = 0;
private final static int STATE_THRESHOLD = 2;
private final static int STATE_FLATTENED = -1;
/**
* Constructor
@ -57,7 +61,7 @@ public final class ConsString implements CharSequence {
@Override
public String toString() {
return (String) flattened();
return (String) flattened(true);
}
@Override
@ -67,22 +71,31 @@ public final class ConsString implements CharSequence {
@Override
public char charAt(final int index) {
return flattened().charAt(index);
return flattened(true).charAt(index);
}
@Override
public CharSequence subSequence(final int start, final int end) {
return flattened().subSequence(start, end);
return flattened(true).subSequence(start, end);
}
private CharSequence flattened() {
if (!flat) {
flatten();
/**
* Returns the components of this ConsString as a {@code CharSequence} array with two elements.
* The elements will be either {@code Strings} or other {@code ConsStrings}.
* @return CharSequence array of length 2
*/
public synchronized CharSequence[] getComponents() {
return new CharSequence[] { left, right };
}
private CharSequence flattened(boolean flattenNested) {
if (state != STATE_FLATTENED) {
flatten(flattenNested);
}
return left;
}
private void flatten() {
private synchronized void flatten(boolean flattenNested) {
// We use iterative traversal as recursion may exceed the stack size limit.
final char[] chars = new char[length];
int pos = length;
@ -97,8 +110,14 @@ public final class ConsString implements CharSequence {
do {
if (cs instanceof ConsString) {
final ConsString cons = (ConsString) cs;
stack.addFirst(cons.left);
cs = cons.right;
// Count the times a cons-string is traversed as part of other cons-strings being flattened.
// If it crosses a threshold we flatten the nested cons-string internally.
if (cons.state == STATE_FLATTENED || (flattenNested && ++cons.state >= STATE_THRESHOLD)) {
cs = cons.flattened(false);
} else {
stack.addFirst(cons.left);
cs = cons.right;
}
} else {
final String str = (String) cs;
pos -= str.length();
@ -109,7 +128,7 @@ public final class ConsString implements CharSequence {
left = new String(chars);
right = "";
flat = true;
state = STATE_FLATTENED;
}
}

135
nashorn/test/src/jdk/nashorn/internal/runtime/ConsStringTest.java Normal file

@ -0,0 +1,135 @@
/*
* Copyright (c) 2010, 2014, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package jdk.nashorn.internal.runtime;
import static org.testng.Assert.assertEquals;
import static org.testng.Assert.assertFalse;
import static org.testng.Assert.assertTrue;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.ScriptRuntime;
import org.testng.annotations.Test;
/**
* Tests for JSType methods.
*
* @test
* @run testng jdk.nashorn.internal.runtime.ConsStringTest
*/
public class ConsStringTest {
/**
* Test toString conversion
*/
@Test
public void testConsStringToString() {
final ConsString cs1 = new ConsString("b", "c");
final ConsString cs2 = new ConsString("d", "e");
final ConsString cs3 = new ConsString(cs1, cs2);
final ConsString cs4 = new ConsString(cs3, "f");
final ConsString cs5 = new ConsString("a", cs4);
assertEquals(cs5.toString(), "abcdef");
assertEquals(cs4.toString(), "bcdef");
assertEquals(cs3.toString(), "bcde");
assertEquals(cs2.toString(), "de");
assertEquals(cs1.toString(), "bc");
// ConsStrings should be flattened now
assertEquals(cs1.getComponents()[0], "bc");
assertEquals(cs1.getComponents()[1], "");
assertEquals(cs2.getComponents()[0], "de");
assertEquals(cs2.getComponents()[1], "");
assertEquals(cs3.getComponents()[0], "bcde");
assertEquals(cs3.getComponents()[1], "");
assertEquals(cs4.getComponents()[0], "bcdef");
assertEquals(cs4.getComponents()[1], "");
assertEquals(cs5.getComponents()[0], "abcdef");
assertEquals(cs5.getComponents()[1], "");
}
/**
* Test charAt
*/
@Test
public void testConsStringCharAt() {
final ConsString cs1 = new ConsString("b", "c");
final ConsString cs2 = new ConsString("d", "e");
final ConsString cs3 = new ConsString(cs1, cs2);
final ConsString cs4 = new ConsString(cs3, "f");
final ConsString cs5 = new ConsString("a", cs4);
assertEquals(cs1.charAt(1), 'c');
assertEquals(cs2.charAt(0), 'd');
assertEquals(cs3.charAt(3), 'e');
assertEquals(cs4.charAt(1), 'c');
assertEquals(cs5.charAt(2), 'c');
// ConsStrings should be flattened now
assertEquals(cs1.getComponents()[0], "bc");
assertEquals(cs1.getComponents()[1], "");
assertEquals(cs2.getComponents()[0], "de");
assertEquals(cs2.getComponents()[1], "");
assertEquals(cs3.getComponents()[0], "bcde");
assertEquals(cs3.getComponents()[1], "");
assertEquals(cs4.getComponents()[0], "bcdef");
assertEquals(cs4.getComponents()[1], "");
assertEquals(cs5.getComponents()[0], "abcdef");
assertEquals(cs5.getComponents()[1], "");
}
/**
* Test flattening of top-level and internal ConsStrings
*/
@Test
public void testConsStringFlattening() {
final ConsString cs1 = new ConsString("b", "c");
final ConsString cs2 = new ConsString("d", "e");
final ConsString cs3 = new ConsString(cs1, cs2);
final ConsString cs4 = new ConsString(cs3, "f");
final ConsString cs5 = new ConsString("a", cs4);
// top-level ConsString should not yet be flattened
assert(cs5.getComponents()[0] == "a");
assert(cs5.getComponents()[1] == cs4);
assertEquals(cs5.toString(), "abcdef");
// top-level ConsString should be flattened
assertEquals(cs5.getComponents()[0], "abcdef");
assertEquals(cs5.getComponents()[1], "");
// internal ConsString should not yet be flattened after first traversal
assertEquals(cs4.getComponents()[0], cs3);
assertEquals(cs4.getComponents()[1], "f");
final ConsString cs6 = new ConsString("a", cs4);
// top-level ConsString should not yet be flattened
assertEquals(cs6.getComponents()[0], "a");
assertEquals(cs6.getComponents()[1], cs4);
assertEquals(cs6.toString(), "abcdef");
// top-level ConsString should be flattened
assertEquals(cs6.getComponents()[0], "abcdef");
assertEquals(cs6.getComponents()[1], "");
// internal ConsString should have been flattened after second traversal
assertEquals(cs4.getComponents()[0], "bcdef");
assertEquals(cs4.getComponents()[1], "");
}
}