/*
* 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 com.facebook.presto.jdbc.internal.airlift.slice;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;
import java.util.IdentityHashMap;
import java.util.Map;
import static com.facebook.presto.jdbc.internal.airlift.slice.Preconditions.checkNotNull;
final class StringDecoder
{
private static final ThreadLocal<Map<Charset, CharsetDecoder>> decoders = new ThreadLocal<Map<Charset, CharsetDecoder>>()
{
@Override
protected Map<Charset, CharsetDecoder> initialValue()
{
return new IdentityHashMap<>();
}
};
private StringDecoder() {}
@SuppressWarnings("ObjectToString")
public static String decodeString(ByteBuffer src, Charset charset)
{
CharsetDecoder decoder = getDecoder(charset);
CharBuffer dst = CharBuffer.allocate((int) ((double) src.remaining() * decoder.maxCharsPerByte()));
try {
CoderResult cr = decoder.decode(src, dst, true);
if (!cr.isUnderflow()) {
cr.throwException();
}
cr = decoder.flush(dst);
if (!cr.isUnderflow()) {
cr.throwException();
}
}
catch (CharacterCodingException x) {
throw new IllegalStateException(x);
}
return dst.flip().toString();
}
/**
* Returns a cached thread-local {@link java.nio.charset.CharsetDecoder} for the specified <tt>charset</tt>.
*/
private static CharsetDecoder getDecoder(Charset charset)
{
checkNotNull(charset, "charset is null");
Map<Charset, CharsetDecoder> map = decoders.get();
CharsetDecoder d = map.get(charset);
if (d != null) {
d.reset();
d.onMalformedInput(CodingErrorAction.REPLACE);
d.onUnmappableCharacter(CodingErrorAction.REPLACE);
return d;
}
d = charset.newDecoder();
d.onMalformedInput(CodingErrorAction.REPLACE);
d.onUnmappableCharacter(CodingErrorAction.REPLACE);
map.put(charset, d);
return d;
}
}