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ProGuardCORE is a free library to read, analyze, modify, and write Java class files.
/*
* ProGuardCORE -- library to process Java bytecode.
*
* Copyright (c) 2002-2020 Guardsquare NV
*
* 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 proguard.util;
/**
* This class contains utility methods for strings.
*/
public class StringUtil
{
private static final char TWO_BYTE_LIMIT = 0x80;
private static final int TWO_BYTE_CONSTANT1 = 0xc0;
private static final int TWO_BYTE_CONSTANT2 = 0x80;
private static final int TWO_BYTE_SHIFT1 = 6;
private static final int TWO_BYTE_MASK1 = 0x1f;
private static final int TWO_BYTE_MASK2 = 0x3f;
private static final char THREE_BYTE_LIMIT = 0x800;
private static final int THREE_BYTE_CONSTANT1 = 0xe0;
private static final int THREE_BYTE_CONSTANT2 = 0x80;
private static final int THREE_BYTE_CONSTANT3 = 0x80;
private static final int THREE_BYTE_SHIFT1 = 12;
private static final int THREE_BYTE_SHIFT2 = 6;
private static final int THREE_BYTE_MASK1 = 0x0f;
private static final int THREE_BYTE_MASK2 = 0x3f;
private static final int THREE_BYTE_MASK3 = 0x3f;
/**
* Returns the length of the modified UTF-8 byte array representation of the given string.
*/
public static int getModifiedUtf8Length(String string)
{
int byteLength = 0;
int stringLength = string.length();
for (int stringIndex = 0; stringIndex < stringLength; stringIndex++)
{
char c = string.charAt(stringIndex);
// The character is represented by one, two, or three bytes.
byteLength += c == 0 ? 2 :
c < TWO_BYTE_LIMIT ? 1 :
c < THREE_BYTE_LIMIT ? 2 :
3;
}
return byteLength;
}
/**
* Returns the modified UTF-8 byte array representation of the given string.
*
* Note: surrogate pairs are encoded separately as three byte values as requested
* by the modified UTF-8 specification. This method is suited for encoding strings
* stored in class files, dex files or native libraries.
*
* @link https://www.oracle.com/technetwork/articles/java/supplementary-142654.html
* @link https://source.android.com/devices/tech/dalvik/dex-format#mutf-8
*/
public static byte[] getModifiedUtf8Bytes(String string)
{
// We're computing the byte array ourselves, because the implementation
// of String.getBytes("UTF-8") has a bug, at least up to JRE 1.4.2.
// Also note the special treatment of the 0 character.
int byteLength = getModifiedUtf8Length(string);
int stringLength = string.length();
// Allocate the byte array with the computed length.
byte[] bytes = new byte[byteLength];
// Fill out the array.
int byteIndex = 0;
for (int stringIndex = 0; stringIndex < stringLength; stringIndex++)
{
char c = string.charAt(stringIndex);
if (c == 0)
{
// The 0 character gets a two-byte representation in classes.
bytes[byteIndex++] = (byte)TWO_BYTE_CONSTANT1;
bytes[byteIndex++] = (byte)TWO_BYTE_CONSTANT2;
}
else if (c < TWO_BYTE_LIMIT)
{
// The character is represented by a single byte.
bytes[byteIndex++] = (byte)c;
}
else if (c < THREE_BYTE_LIMIT)
{
// The character is represented by two bytes.
bytes[byteIndex++] = (byte)(TWO_BYTE_CONSTANT1 | ((c >>> TWO_BYTE_SHIFT1) & TWO_BYTE_MASK1));
bytes[byteIndex++] = (byte)(TWO_BYTE_CONSTANT2 | ( c & TWO_BYTE_MASK2));
}
else
{
// The character is represented by three bytes.
bytes[byteIndex++] = (byte)(THREE_BYTE_CONSTANT1 | ((c >>> THREE_BYTE_SHIFT1) & THREE_BYTE_MASK1));
bytes[byteIndex++] = (byte)(THREE_BYTE_CONSTANT2 | ((c >>> THREE_BYTE_SHIFT2) & THREE_BYTE_MASK2));
bytes[byteIndex++] = (byte)(THREE_BYTE_CONSTANT3 | ( c & THREE_BYTE_MASK3));
}
}
return bytes;
}
/**
* Returns the String representation of the given modified UTF-8 byte array.
*/
public static String getString(byte[] modifiedUtf8Bytes)
{
return getString(modifiedUtf8Bytes, 0, modifiedUtf8Bytes.length);
}
/**
* Returns the String representation of the given modified UTF-8 byte array.
*/
public static String getString(byte[] modifiedUtf8Bytes,
int startIndex,
int endIndex)
{
// We're computing the string ourselves, because the implementation
// of "new String(bytes)" doesn't honor the special treatment of
// the 0 character in JRE 1.6_u11 and higher.
StringBuilder builder = new StringBuilder(endIndex - startIndex);
// Fill out the array.
int byteIndex = startIndex;
while (byteIndex < endIndex)
{
int b = modifiedUtf8Bytes[byteIndex++] & 0xff;
// Depending on the flag bits in the first byte, the character
// is represented by a single byte, by two bytes, or by three
// bytes. We're not checking the redundant flag bits in the
// second byte and the third byte.
try
{
char c =
(char)(b < TWO_BYTE_CONSTANT1 ? b :
b < THREE_BYTE_CONSTANT1 ? ((b & TWO_BYTE_MASK1) << TWO_BYTE_SHIFT1) |
((modifiedUtf8Bytes[byteIndex++] & TWO_BYTE_MASK2) ) :
((b & THREE_BYTE_MASK1) << THREE_BYTE_SHIFT1) |
((modifiedUtf8Bytes[byteIndex++] & THREE_BYTE_MASK2) << THREE_BYTE_SHIFT2) |
((modifiedUtf8Bytes[byteIndex++] & THREE_BYTE_MASK3) ));
builder.append(c);
}
catch (ArrayIndexOutOfBoundsException e)
{
throw new IllegalArgumentException("Missing UTF-8 bytes after byte [0x"+Integer.toHexString(b)+"] in string ["+builder.toString()+"]");
}
}
return builder.toString();
}
/**
* Joins the given strings using the provided separator.
*
* @param separator The separator to use.
* @param strings The strings to join.
* @return The input strings, concatenated together using the separator
*/
public static String join(String separator, String... strings)
{
StringBuilder sb = new StringBuilder();
for (int i = 0; i < strings.length; i++)
{
sb.append(strings[i]);
if (i + 1 < strings.length)
{
sb.append(separator);
}
}
return sb.toString();
}
/**
* Returns the hexadecimal representation of the given byte array.
*/
public static String toHexString(byte[] bytes)
{
return toHexString(bytes, null, true);
}
/**
* Returns the hexadecimal representation of the given byte array.
*/
public static String toHexString(byte[] bytes,
String separator,
boolean upperCase)
{
if (bytes == null)
{
return null;
}
StringBuilder builder = new StringBuilder(2 * bytes.length +
(separator == null ? 0 : separator.length() * (bytes.length-1)));
for (int index = 0; index < bytes.length; index++)
{
byte b = bytes[index];
// Append the two nibbles of the byte.
builder.append(hexNibble(b >> 4, upperCase))
.append(hexNibble(b, upperCase));
// Append the separator, if any.
if (separator != null && index < bytes.length - 1)
{
builder.append(separator);
}
}
return builder.toString();
}
/**
* Returns the hexadecimal representation of the given nibble.
*/
private static char hexNibble(int nibble, boolean upperCase)
{
nibble &= 0xf;
return (char)(nibble < 10 ?
'0' + nibble :
(upperCase ? 'A' : 'a') + nibble - 10);
}
/**
* Escapes control characters (\n, \r, \b, \t, \f).
*/
public static String escapeControlCharacters(String input)
{
String result = input;
result = result.replaceAll("\n", "\\\\n");
result = result.replaceAll("\r", "\\\\r");
result = result.replaceAll("\t", "\\\\t");
result = result.replaceAll("\f", "\\\\f");
result = result.replaceAll("\b", "\\\\b");
return result;
}
}
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