Prevent unnecessary allocations in the StringUtil#escapeCsv
Motivation: A `StringUtil#escapeCsv` creates new `StringBuilder` on each value even if the same string is returned in the end. Modifications: Create new `StringBuilder` only if it really needed. Otherwise, return the original string (or just trimmed substring). Result: Less GC load. Up to 4x faster work for not changed strings.
This commit is contained in:
Nikolay Fedorovskikh
Scott Mitchell
parent
94c0ef3c96
commit
aa38b6a769
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@ -228,7 +228,7 @@ public final class StringUtil {
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* with anonymous classes.
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*/
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public static String simpleClassName(Class<?> clazz) {
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String className = ObjectUtil.checkNotNull(clazz, "clazz").getName();
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String className = checkNotNull(clazz, "clazz").getName();
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final int lastDotIdx = className.lastIndexOf(PACKAGE_SEPARATOR_CHAR);
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if (lastDotIdx > -1) {
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return className.substring(lastDotIdx + 1);
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@ -260,67 +260,80 @@ public final class StringUtil {
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*/
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public static CharSequence escapeCsv(CharSequence value, boolean trimWhiteSpace) {
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int length = checkNotNull(value, "value").length();
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if (length == 0) {
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return value;
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}
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int start = 0;
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int last = length - 1;
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boolean trimmed = false;
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int start;
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int last;
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if (trimWhiteSpace) {
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start = indexOfFirstNonOwsChar(value, length);
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if (start == length) {
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return EMPTY_STRING;
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}
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last = indexOfLastNonOwsChar(value, start, length);
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trimmed = start > 0 || last < length - 1;
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if (trimmed) {
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length = last - start + 1;
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} else {
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start = 0;
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last = length - 1;
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}
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if (start > last) {
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return EMPTY_STRING;
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}
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int firstUnescapedSpecial = -1;
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boolean quoted = false;
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if (isDoubleQuote(value.charAt(start))) {
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quoted = isDoubleQuote(value.charAt(last)) && last > start;
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if (quoted) {
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start++;
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last--;
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} else {
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firstUnescapedSpecial = start;
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}
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}
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StringBuilder result = new StringBuilder(length + CSV_NUMBER_ESCAPE_CHARACTERS);
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boolean quoted = isDoubleQuote(value.charAt(start)) && isDoubleQuote(value.charAt(last)) && length != 1;
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boolean foundSpecialCharacter = false;
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boolean escapedDoubleQuote = false;
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for (int i = start; i <= last; i++) {
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char current = value.charAt(i);
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switch (current) {
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case DOUBLE_QUOTE:
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if (i == start || i == last) {
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if (!quoted) {
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result.append(DOUBLE_QUOTE);
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} else {
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continue;
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}
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} else {
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boolean isNextCharDoubleQuote = isDoubleQuote(value.charAt(i + 1));
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if (!isDoubleQuote(value.charAt(i - 1)) &&
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(!isNextCharDoubleQuote || i + 1 == last)) {
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result.append(DOUBLE_QUOTE);
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escapedDoubleQuote = true;
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if (firstUnescapedSpecial < 0) {
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if (quoted) {
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for (int i = start; i <= last; i++) {
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if (isDoubleQuote(value.charAt(i))) {
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if (i == last || !isDoubleQuote(value.charAt(i + 1))) {
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firstUnescapedSpecial = i;
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break;
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}
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i++;
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}
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}
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} else {
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for (int i = start; i <= last; i++) {
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char c = value.charAt(i);
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if (c == LINE_FEED || c == CARRIAGE_RETURN || c == COMMA) {
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firstUnescapedSpecial = i;
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break;
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}
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case LINE_FEED:
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case CARRIAGE_RETURN:
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case COMMA:
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foundSpecialCharacter = true;
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if (isDoubleQuote(c)) {
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if (i == last || !isDoubleQuote(value.charAt(i + 1))) {
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firstUnescapedSpecial = i;
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break;
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}
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i++;
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}
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}
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}
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if (firstUnescapedSpecial < 0) {
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// Special characters is not found or all of them already escaped.
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// In the most cases returns a same string. New string will be instantiated (via StringBuilder)
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// only if it really needed. It's important to prevent GC extra load.
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return quoted? value.subSequence(start - 1, last + 2) : value.subSequence(start, last + 1);
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}
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result.append(current);
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}
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if (escapedDoubleQuote || foundSpecialCharacter && !quoted) {
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return quote(result);
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StringBuilder result = new StringBuilder(last - start + 1 + CSV_NUMBER_ESCAPE_CHARACTERS);
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result.append(DOUBLE_QUOTE).append(value, start, firstUnescapedSpecial);
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for (int i = firstUnescapedSpecial; i <= last; i++) {
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char c = value.charAt(i);
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if (isDoubleQuote(c)) {
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result.append(DOUBLE_QUOTE);
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if (i < last && isDoubleQuote(value.charAt(i + 1))) {
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i++;
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}
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}
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result.append(c);
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}
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if (trimmed) {
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return quoted ? quote(result) : result;
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}
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return value;
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}
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private static StringBuilder quote(StringBuilder builder) {
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return builder.insert(0, DOUBLE_QUOTE).append(DOUBLE_QUOTE);
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return result.append(DOUBLE_QUOTE);
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}
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/**
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@ -377,6 +377,18 @@ public class StringUtilTest {
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escapeCsvWithTrimming("\ttest,ing ", "\"test,ing\"");
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}
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@Test
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public void escapeCsvGarbageFree() {
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// 'StringUtil#escapeCsv()' should return same string object if string didn't changing.
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assertSame("1", StringUtil.escapeCsv("1", true));
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assertSame(" 123 ", StringUtil.escapeCsv(" 123 ", false));
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assertSame("\" 123 \"", StringUtil.escapeCsv("\" 123 \"", true));
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assertSame("\"\"", StringUtil.escapeCsv("\"\"", true));
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assertSame("123 \"\"", StringUtil.escapeCsv("123 \"\"", true));
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assertSame("123\"\"321", StringUtil.escapeCsv("123\"\"321", true));
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assertSame("\"123\"\"321\"", StringUtil.escapeCsv("\"123\"\"321\"", true));
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}
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@Test
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public void testUnescapeCsv() {
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assertEquals("", unescapeCsv(""));
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@ -0,0 +1,160 @@
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/*
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* Copyright 2017 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.microbench.internal;
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import io.netty.microbench.util.AbstractMicrobenchmark;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.Measurement;
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import org.openjdk.jmh.annotations.OutputTimeUnit;
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import org.openjdk.jmh.annotations.Param;
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import org.openjdk.jmh.annotations.Threads;
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import org.openjdk.jmh.annotations.Warmup;
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import org.openjdk.jmh.runner.options.ChainedOptionsBuilder;
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import java.util.concurrent.TimeUnit;
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import static io.netty.util.internal.ObjectUtil.*;
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import static io.netty.util.internal.StringUtil.*;
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@Threads(1)
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@Warmup(iterations = 3)
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@Measurement(iterations = 3)
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@OutputTimeUnit(TimeUnit.MICROSECONDS)
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public class EscapeCsvBenchmark extends AbstractMicrobenchmark {
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private static final String value1024;
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private static final String value1024commaAtEnd;
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static {
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StringBuilder s1024 = new StringBuilder(1024);
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while (s1024.length() < 1024) {
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s1024.append('A' + s1024.length() % 10);
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}
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value1024 = s1024.toString();
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value1024commaAtEnd = value1024 + ',';
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}
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@Param("netty")
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private String value;
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@Override
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protected ChainedOptionsBuilder newOptionsBuilder() throws Exception {
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return super.newOptionsBuilder()
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.param("value", "netty")
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.param("value", "\"123\"", "need\"escape", "need,quotes", " trim-me ", "short-comma-ended,")
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.param("value", value1024)
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.param("value", value1024commaAtEnd);
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}
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private static CharSequence escapeCsvOld(CharSequence value, boolean trimWhiteSpace) {
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int length = checkNotNull(value, "value").length();
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if (length == 0) {
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return value;
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}
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int start = 0;
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int last = length - 1;
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boolean trimmed = false;
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if (trimWhiteSpace) {
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start = indexOfFirstNonOwsChar(value, length);
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if (start == length) {
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return EMPTY_STRING;
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}
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last = indexOfLastNonOwsChar(value, start, length);
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trimmed = start > 0 || last < length - 1;
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if (trimmed) {
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length = last - start + 1;
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}
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}
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StringBuilder result = new StringBuilder(length + 7);
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boolean quoted = isDoubleQuote(value.charAt(start)) && isDoubleQuote(value.charAt(last)) && length != 1;
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boolean foundSpecialCharacter = false;
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boolean escapedDoubleQuote = false;
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for (int i = start; i <= last; i++) {
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char current = value.charAt(i);
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switch (current) {
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case DOUBLE_QUOTE:
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if (i == start || i == last) {
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if (!quoted) {
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result.append(DOUBLE_QUOTE);
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} else {
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continue;
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}
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} else {
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boolean isNextCharDoubleQuote = isDoubleQuote(value.charAt(i + 1));
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if (!isDoubleQuote(value.charAt(i - 1)) &&
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(!isNextCharDoubleQuote || i + 1 == last)) {
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result.append(DOUBLE_QUOTE);
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escapedDoubleQuote = true;
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}
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break;
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}
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case LINE_FEED:
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case CARRIAGE_RETURN:
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case COMMA:
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foundSpecialCharacter = true;
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}
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result.append(current);
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}
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if (escapedDoubleQuote || foundSpecialCharacter && !quoted) {
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return quote(result);
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}
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if (trimmed) {
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return quoted? quote(result) : result;
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}
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return value;
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}
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private static StringBuilder quote(StringBuilder builder) {
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return builder.insert(0, DOUBLE_QUOTE).append(DOUBLE_QUOTE);
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}
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private static boolean isDoubleQuote(char c) {
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return c == DOUBLE_QUOTE;
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}
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private static int indexOfFirstNonOwsChar(CharSequence value, int length) {
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int i = 0;
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while (i < length && isOws(value.charAt(i))) {
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i++;
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}
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return i;
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}
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private static int indexOfLastNonOwsChar(CharSequence value, int start, int length) {
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int i = length - 1;
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while (i > start && isOws(value.charAt(i))) {
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i--;
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}
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return i;
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}
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private static boolean isOws(char c) {
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return c == SPACE || c == TAB;
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}
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@Benchmark
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public CharSequence escapeCsvOld() {
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return escapeCsvOld(value, true);
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}
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@Benchmark
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public CharSequence escapeCsvNew() {
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return escapeCsv(value, true);
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}
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}
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