java.io.OutputStreamWriter Maven / Gradle / Ivy
/*
* 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.io;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;
import java.util.Arrays;
/**
* A class for turning a character stream into a byte stream. Data written to
* the target input stream is converted into bytes by either a default or a
* provided character converter. The default encoding is taken from the
* "file.encoding" system property. {@code OutputStreamWriter} contains a buffer
* of bytes to be written to target stream and converts these into characters as
* needed. The buffer size is 8K.
*
* @see InputStreamReader
*/
public class OutputStreamWriter extends Writer {
private final OutputStream out;
private CharsetEncoder encoder;
private ByteBuffer bytes = ByteBuffer.allocate(8192);
/**
* Constructs a new OutputStreamWriter using {@code out} as the target
* stream to write converted characters to. The default character encoding
* is used.
*
* @param out
* the non-null target stream to write converted bytes to.
*/
public OutputStreamWriter(OutputStream out) {
this(out, Charset.defaultCharset());
}
/**
* Constructs a new OutputStreamWriter using {@code out} as the target
* stream to write converted characters to and {@code charsetName} as the character
* encoding. If the encoding cannot be found, an
* UnsupportedEncodingException error is thrown.
*
* @param out
* the target stream to write converted bytes to.
* @param charsetName
* the string describing the desired character encoding.
* @throws NullPointerException
* if {@code charsetName} is {@code null}.
* @throws UnsupportedEncodingException
* if the encoding specified by {@code charsetName} cannot be found.
*/
public OutputStreamWriter(OutputStream out, final String charsetName)
throws UnsupportedEncodingException {
super(out);
if (charsetName == null) {
throw new NullPointerException("charsetName == null");
}
this.out = out;
try {
encoder = Charset.forName(charsetName).newEncoder();
} catch (Exception e) {
throw new UnsupportedEncodingException(charsetName);
}
encoder.onMalformedInput(CodingErrorAction.REPLACE);
encoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
}
/**
* Constructs a new OutputStreamWriter using {@code out} as the target
* stream to write converted characters to and {@code cs} as the character
* encoding.
*
* @param out
* the target stream to write converted bytes to.
* @param cs
* the {@code Charset} that specifies the character encoding.
*/
public OutputStreamWriter(OutputStream out, Charset cs) {
super(out);
this.out = out;
encoder = cs.newEncoder();
encoder.onMalformedInput(CodingErrorAction.REPLACE);
encoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
}
/**
* Constructs a new OutputStreamWriter using {@code out} as the target
* stream to write converted characters to and {@code charsetEncoder} as the character
* encoder.
*
* @param out
* the target stream to write converted bytes to.
* @param charsetEncoder
* the character encoder used for character conversion.
*/
public OutputStreamWriter(OutputStream out, CharsetEncoder charsetEncoder) {
super(out);
charsetEncoder.charset();
this.out = out;
encoder = charsetEncoder;
}
/**
* Closes this writer. This implementation flushes the buffer as well as the
* target stream. The target stream is then closed and the resources for the
* buffer and converter are released.
*
* Only the first invocation of this method has any effect. Subsequent calls
* do nothing.
*
* @throws IOException
* if an error occurs while closing this writer.
*/
@Override
public void close() throws IOException {
synchronized (lock) {
if (encoder != null) {
drainEncoder();
flushBytes(false);
out.close();
encoder = null;
bytes = null;
}
}
}
/**
* Flushes this writer. This implementation ensures that all buffered bytes
* are written to the target stream. After writing the bytes, the target
* stream is flushed as well.
*
* @throws IOException
* if an error occurs while flushing this writer.
*/
@Override
public void flush() throws IOException {
flushBytes(true);
}
private void flushBytes(boolean flushUnderlyingStream) throws IOException {
synchronized (lock) {
checkStatus();
int position = bytes.position();
if (position > 0) {
bytes.flip();
out.write(bytes.array(), bytes.arrayOffset(), position);
bytes.clear();
}
if (flushUnderlyingStream) {
out.flush();
}
}
}
private void convert(CharBuffer chars) throws IOException {
while (true) {
CoderResult result = encoder.encode(chars, bytes, false);
if (result.isOverflow()) {
// Make room and try again.
flushBytes(false);
continue;
} else if (result.isError()) {
result.throwException();
}
break;
}
}
private void drainEncoder() throws IOException {
// Strictly speaking, I think it's part of the CharsetEncoder contract that you call
// encode with endOfInput true before flushing. Our ICU-based implementations don't
// actually need this, and you'd hope that any reasonable implementation wouldn't either.
// CharsetEncoder.encode doesn't actually pass the boolean through to encodeLoop anyway!
CharBuffer chars = CharBuffer.allocate(0);
while (true) {
CoderResult result = encoder.encode(chars, bytes, true);
if (result.isError()) {
result.throwException();
} else if (result.isOverflow()) {
flushBytes(false);
continue;
}
break;
}
// Some encoders (such as ISO-2022-JP) have stuff to write out after all the
// characters (such as shifting back into a default state). In our implementation,
// this is actually the first time ICU is told that we've run out of input.
CoderResult result = encoder.flush(bytes);
while (!result.isUnderflow()) {
if (result.isOverflow()) {
flushBytes(false);
result = encoder.flush(bytes);
} else {
result.throwException();
}
}
}
private void checkStatus() throws IOException {
if (encoder == null) {
throw new IOException("OutputStreamWriter is closed");
}
}
/**
* Returns the canonical name of the encoding used by this writer to convert characters to
* bytes, or null if this writer has been closed. Most callers should probably keep
* track of the String or Charset they passed in; this method may not return the same
* name.
*/
public String getEncoding() {
if (encoder == null) {
return null;
}
return encoder.charset().name();
}
/**
* Writes {@code count} characters starting at {@code offset} in {@code buf}
* to this writer. The characters are immediately converted to bytes by the
* character converter and stored in a local buffer. If the buffer gets full
* as a result of the conversion, this writer is flushed.
*
* @param buffer
* the array containing characters to write.
* @param offset
* the index of the first character in {@code buf} to write.
* @param count
* the maximum number of characters to write.
* @throws IndexOutOfBoundsException
* if {@code offset < 0} or {@code count < 0}, or if
* {@code offset + count} is greater than the size of
* {@code buf}.
* @throws IOException
* if this writer has already been closed or another I/O error
* occurs.
*/
@Override
public void write(char[] buffer, int offset, int count) throws IOException {
synchronized (lock) {
checkStatus();
Arrays.checkOffsetAndCount(buffer.length, offset, count);
CharBuffer chars = CharBuffer.wrap(buffer, offset, count);
convert(chars);
}
}
/**
* Writes the character {@code oneChar} to this writer. The lowest two bytes
* of the integer {@code oneChar} are immediately converted to bytes by the
* character converter and stored in a local buffer. If the buffer gets full
* by converting this character, this writer is flushed.
*
* @param oneChar
* the character to write.
* @throws IOException
* if this writer is closed or another I/O error occurs.
*/
@Override
public void write(int oneChar) throws IOException {
synchronized (lock) {
checkStatus();
CharBuffer chars = CharBuffer.wrap(new char[] { (char) oneChar });
convert(chars);
}
}
/**
* Writes {@code count} characters starting at {@code offset} in {@code str}
* to this writer. The characters are immediately converted to bytes by the
* character converter and stored in a local buffer. If the buffer gets full
* as a result of the conversion, this writer is flushed.
*
* @param str
* the string containing characters to write.
* @param offset
* the start position in {@code str} for retrieving characters.
* @param count
* the maximum number of characters to write.
* @throws IOException
* if this writer has already been closed or another I/O error
* occurs.
* @throws IndexOutOfBoundsException
* if {@code offset < 0} or {@code count < 0}, or if
* {@code offset + count} is bigger than the length of
* {@code str}.
*/
@Override
public void write(String str, int offset, int count) throws IOException {
synchronized (lock) {
if (count < 0) {
throw new StringIndexOutOfBoundsException(str, offset, count);
}
if (str == null) {
throw new NullPointerException("str == null");
}
if ((offset | count) < 0 || offset > str.length() - count) {
throw new StringIndexOutOfBoundsException(str, offset, count);
}
checkStatus();
CharBuffer chars = CharBuffer.wrap(str, offset, count + offset);
convert(chars);
}
}
@Override boolean checkError() {
return out.checkError();
}
}