/*
* Copyright (C) 2009 Archie L. Cobbs. All rights reserved.
*
* $Id: UTF8.java 2 2009-12-17 02:39:56Z archie.cobbs $
*/
package org.dellroad.lzma.client;
/**
* Encodes and decodes strings to/from binary using "modified UTF-8 encoding".
* This is the same encoding as is used by Java class files.
*/
public final class UTF8 {
private UTF8() {
}
/**
* Encode the given string.
*/
public static byte[] encode(String s) {
final char[] chars = s.toCharArray();
int elen;
// Compute encoded length
elen = 0;
for (int i = 0; i < s.length(); i++) {
int ch = chars[i];
if (ch >= 0x0001 && ch <= 0x007f)
elen++;
else if (ch == 0x0000 || (ch >= 0x0080 && ch <= 0x07ff))
elen += 2;
else
elen += 3;
}
// Do the actual encoding
byte[] data = new byte[elen];
elen = 0;
for (int i = 0; i < s.length(); i++) {
int ch = chars[i];
if (ch >= 0x0001 && ch <= 0x007f)
data[elen++] = (byte)ch;
else if (ch == 0x0000
|| (ch >= 0x0080 && ch <= 0x07ff)) {
data[elen++]
= (byte)(0xc0 | ((ch >> 6) & 0x1f));
data[elen++] = (byte)(0x80 | (ch & 0x3f));
} else {
data[elen++]
= (byte)(0xe0 | ((ch >> 12) & 0x0f));
data[elen++]
= (byte)(0x80 | ((ch >> 6) & 0x3f));
data[elen++] = (byte)(0x80 | (ch & 0x3f));
}
}
return data;
}
/**
* Decode the given UTF-8 data.
*
* @throws IllegalArgumentException if the UTF-8 input is invalid
*/
public static String decode(byte[] utf) {
StringBuilder buf = new StringBuilder(utf.length);
for (int i = 0; i < utf.length; i++) {
int x = utf[i] & 0xff;
if ((x & 0x80) == 0) {
if (x == 0)
throw new IllegalArgumentException("invalid UTF-8");
buf.append((char)x);
} else if ((x & 0xe0) == 0xc0) {
if (i + 1 >= utf.length)
throw new IllegalArgumentException("invalid UTF-8");
int y = utf[++i] & 0xff;
if ((y & 0xc0) != 0x80)
throw new IllegalArgumentException("invalid UTF-8");
buf.append((char)((x & 0x1f) << 6) | (y & 0x3f));
} else if ((x & 0xf0) == 0xe0) {
if (i + 2 >= utf.length)
throw new IllegalArgumentException("invalid UTF-8");
int y = utf[++i] & 0xff;
if ((y & 0xc0) != 0x80)
throw new IllegalArgumentException("invalid UTF-8");
int z = utf[++i] & 0xff;
if ((z & 0xc0) != 0x80)
throw new IllegalArgumentException("invalid UTF-8");
buf.append((char)(((x & 0x0f) << 12) | ((y & 0x3f) << 6) | (z & 0x3f)));
} else
throw new IllegalArgumentException("invalid UTF-8");
}
return buf.toString();
}
}