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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.config.text;
import java.nio.charset.Charset;
import java.io.ByteArrayOutputStream;
import java.nio.charset.StandardCharsets;
/**
* Escapes strings into and out of a format where they only contain printable characters.
*
* Need to duplicate escape / unescape of strings as we have in C++ for java version of system states.
*
* @author Haakon Humberset
*/
public class StringUtilities {
private static final Charset UTF8 = StandardCharsets.UTF_8;
private static byte toHex(int val) { return (byte) (val < 10 ? '0' + val : 'a' + (val - 10)); }
private static class ReplacementCharacters {
public final byte[] needEscape = new byte[256];
public final byte[] replacement1 = new byte[256];
public final byte[] replacement2 = new byte[256];
public ReplacementCharacters() {
for (int i=0; i<256; ++i) {
if (i >= 32 && i <= 126) {
needEscape[i] = 0;
} else if (i > 127) {
needEscape[i] = 0;
} else {
needEscape[i] = 3;
replacement1[i] = toHex((i >> 4) & 0xF);
replacement2[i] = toHex(i & 0xF);
}
}
makeSimpleEscape('"', '"');
makeSimpleEscape('\\', '\\');
makeSimpleEscape('\t', 't');
makeSimpleEscape('\n', 'n');
makeSimpleEscape('\r', 'r');
makeSimpleEscape('\f', 'f');
}
private void makeSimpleEscape(char source, char dest) {
needEscape[source] = 1;
replacement1[source] = '\\';
replacement2[source] = (byte) dest;
}
}
private final static ReplacementCharacters replacementCharacters = new ReplacementCharacters();
public static String escape(String source) { return escape(source, '\0'); }
/**
* Escapes strings into a format with only printable ASCII characters.
*
* @param source the string to escape
* @param delimiter escape this character too, even if it is printable
* @return the escaped string
*/
public static String escape(String source, char delimiter) {
byte[] bytes = source.getBytes(UTF8);
ByteArrayOutputStream result = new ByteArrayOutputStream();
for (byte b : bytes) {
int val = b;
if (val < 0) val += 256;
if (b == delimiter) {
result.write('\\');
result.write('x');
result.write(toHex((val >> 4) & 0xF));
result.write(toHex(val & 0xF));
} else if (replacementCharacters.needEscape[val] == 0) {
result.write(b);
} else {
if (replacementCharacters.needEscape[val] == 3) {
result.write('\\');
result.write('x');
}
result.write(replacementCharacters.replacement1[val]);
result.write(replacementCharacters.replacement2[val]);
}
}
return result.toString(UTF8);
}
}
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