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8246338: Reduce overhead of normalizing file paths
Reviewed-by: alanb
  • Loading branch information
cl4es committed Jun 2, 2020
1 parent ddbc7ed commit 0366f6bf452e420c5aaf851a265a2faf295b9214
Showing with 86 additions and 17 deletions.
  1. +17 −17 src/java.base/unix/classes/java/io/UnixFileSystem.java
  2. +69 −0 test/micro/org/openjdk/bench/java/io/FileOpen.java
@@ -1,5 +1,5 @@
/*
* Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1998, 2020, 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
@@ -64,14 +64,17 @@ public char getPathSeparator() {
/* A normal Unix pathname contains no duplicate slashes and does not end
with a slash. It may be the empty string. */

/* Normalize the given pathname, whose length is len, starting at the given
offset; everything before this offset is already normal. */
private String normalize(String pathname, int len, int off) {
if (len == 0) return pathname;
int n = len;
/**
* Normalize the given pathname, starting at the given
* offset; everything before off is already normal, and there's at least
* one duplicate or trailing slash to be removed
*/
private String normalize(String pathname, int off) {
int n = pathname.length();
while ((n > 0) && (pathname.charAt(n - 1) == '/')) n--;
if (n == 0) return "/";
StringBuilder sb = new StringBuilder(pathname.length());

StringBuilder sb = new StringBuilder(n);
if (off > 0) sb.append(pathname, 0, off);
char prevChar = 0;
for (int i = off; i < n; i++) {
@@ -88,22 +91,19 @@ private String normalize(String pathname, int len, int off) {
This way we iterate through the whole pathname string only once. */
@Override
public String normalize(String pathname) {
int n = pathname.length();
char prevChar = 0;
for (int i = 0; i < n; i++) {
char c = pathname.charAt(i);
if ((prevChar == '/') && (c == '/'))
return normalize(pathname, n, i - 1);
prevChar = c;
int doubleSlash = pathname.indexOf("//");
if (doubleSlash >= 0) {
return normalize(pathname, doubleSlash);
}
if (pathname.endsWith("/")) {
return normalize(pathname, pathname.length() - 1);
}
if (prevChar == '/') return normalize(pathname, n, n - 1);
return pathname;
}

@Override
public int prefixLength(String pathname) {
if (pathname.isEmpty()) return 0;
return (pathname.charAt(0) == '/') ? 1 : 0;
return pathname.startsWith("/") ? 1 : 0;
}

@Override
@@ -0,0 +1,69 @@
/*
* Copyright (c) 2020, 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.
*
* 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 org.openjdk.bench.java.io;

import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;

import java.io.File;
import java.util.concurrent.TimeUnit;

/**
* Tests the overheads of I/O API.
*/
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
@State(Scope.Thread)
@Warmup(time=2, iterations=5)
@Measurement(time=3, iterations=5)
@Fork(value=2, jvmArgs="-Xmx1g")
public class FileOpen {

public String normalFile = "/test/dir/file/name.txt";
public String root = "/";
public String trailingSlash = "/test/dir/file//name.txt";
public String notNormalizedFile = "/test/dir/file//name.txt";

@Benchmark
public void mix(Blackhole bh) {
bh.consume(new File(normalFile));
bh.consume(new File(root));
bh.consume(new File(trailingSlash));
bh.consume(new File(notNormalizedFile));
}

@Benchmark
public File normalized() {
return new File(normalFile);
}

@Benchmark
public File trailingSlash() {
return new File(trailingSlash);
}

@Benchmark
public File notNormalized() {
return new File(notNormalizedFile);
}
}

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