/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 java.nio.charset;
import java.io.UTFDataFormatException;
import java.nio.ByteOrder;
import libcore.io.Memory;
import libcore.io.SizeOf;
/**
* @hide internal use only
*/
public class ModifiedUtf8 {
/**
* Decodes a byte array containing <i>modified UTF-8</i> bytes into a string.
*
* <p>Note that although this method decodes the (supposedly impossible) zero byte to U+0000,
* that's what the RI does too.
*/
public static String decode(byte[] in, char[] out, int offset, int utfSize) throws UTFDataFormatException {
int count = 0, s = 0, a;
while (count < utfSize) {
if ((out[s] = (char) in[offset + count++]) < '\u0080') {
s++;
} else if (((a = out[s]) & 0xe0) == 0xc0) {
if (count >= utfSize) {
throw new UTFDataFormatException("bad second byte at " + count);
}
int b = in[offset + count++];
if ((b & 0xC0) != 0x80) {
throw new UTFDataFormatException("bad second byte at " + (count - 1));
}
out[s++] = (char) (((a & 0x1F) << 6) | (b & 0x3F));
} else if ((a & 0xf0) == 0xe0) {
if (count + 1 >= utfSize) {
throw new UTFDataFormatException("bad third byte at " + (count + 1));
}
int b = in[offset + count++];
int c = in[offset + count++];
if (((b & 0xC0) != 0x80) || ((c & 0xC0) != 0x80)) {
throw new UTFDataFormatException("bad second or third byte at " + (count - 2));
}
out[s++] = (char) (((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F));
} else {
throw new UTFDataFormatException("bad byte at " + (count - 1));
}
}
return new String(out, 0, s);
}
/**
* Returns the number of bytes the modified UTF-8 representation of 's' would take. Note
* that this is just the space for the bytes representing the characters, not the length
* which precedes those bytes, because different callers represent the length differently,
* as two, four, or even eight bytes. If {@code shortLength} is true, we'll throw an
* exception if the string is too long for its length to be represented by a short.
*/
public static long countBytes(String s, boolean shortLength) throws UTFDataFormatException {
long result = 0;
final int length = s.length();
for (int i = 0; i < length; ++i) {
char ch = s.charAt(i);
if (ch != 0 && ch <= 127) { // U+0000 uses two bytes.
++result;
} else if (ch <= 2047) {
result += 2;
} else {
result += 3;
}
if (shortLength && result > 65535) {
throw new UTFDataFormatException("String more than 65535 UTF bytes long");
}
}
return result;
}
/**
* Encodes the <i>modified UTF-8</i> bytes corresponding to string {@code s} into the
* byte array {@code dst}, starting at the given {@code offset}.
*/
public static void encode(byte[] dst, int offset, String s) {
final int length = s.length();
for (int i = 0; i < length; i++) {
char ch = s.charAt(i);
if (ch != 0 && ch <= 127) { // U+0000 uses two bytes.
dst[offset++] = (byte) ch;
} else if (ch <= 2047) {
dst[offset++] = (byte) (0xc0 | (0x1f & (ch >> 6)));
dst[offset++] = (byte) (0x80 | (0x3f & ch));
} else {
dst[offset++] = (byte) (0xe0 | (0x0f & (ch >> 12)));
dst[offset++] = (byte) (0x80 | (0x3f & (ch >> 6)));
dst[offset++] = (byte) (0x80 | (0x3f & ch));
}
}
}
/**
* Returns an array containing the <i>modified UTF-8</i> form of {@code s}, using a
* big-endian 16-bit length. Throws UTFDataFormatException if {@code s} is too long
* for a two-byte length.
*/
public static byte[] encode(String s) throws UTFDataFormatException {
int utfCount = (int) ModifiedUtf8.countBytes(s, true);
byte[] result = new byte[SizeOf.SHORT + utfCount];
Memory.pokeShort(result, 0, (short) utfCount, ByteOrder.BIG_ENDIAN);
ModifiedUtf8.encode(result, SizeOf.SHORT, s);
return result;
}
private ModifiedUtf8() {
}
}