/*
* 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.CharsetDecoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;
import java.nio.charset.MalformedInputException;
import java.nio.charset.UnmappableCharacterException;
import java.util.Arrays;
/**
* A class for turning a byte stream into a character stream. Data read from the
* source input stream is converted into characters by either a default or a
* provided character converter. The default encoding is taken from the
* "file.encoding" system property. {@code InputStreamReader} contains a buffer
* of bytes read from the source stream and converts these into characters as
* needed. The buffer size is 8K.
*
* @see OutputStreamWriter
*/
public class InputStreamReader extends Reader {
private InputStream in;
private boolean endOfInput = false;
private CharsetDecoder decoder;
private final ByteBuffer bytes = ByteBuffer.allocate(8192);
/**
* Constructs a new {@code InputStreamReader} on the {@link InputStream}
* {@code in}. This constructor sets the character converter to the encoding
* specified in the "file.encoding" property and falls back to ISO 8859_1
* (ISO-Latin-1) if the property doesn't exist.
*
* @param in
* the input stream from which to read characters.
*/
public InputStreamReader(InputStream in) {
this(in, Charset.defaultCharset());
}
/**
* Constructs a new InputStreamReader on the InputStream {@code in}. The
* character converter that is used to decode bytes into characters is
* identified by name by {@code charsetName}. If the encoding cannot be found, an
* UnsupportedEncodingException error is thrown.
*
* @param in
* the InputStream from which to read characters.
* @param charsetName
* identifies the character converter to use.
* @throws NullPointerException
* if {@code charsetName} is {@code null}.
* @throws UnsupportedEncodingException
* if the encoding specified by {@code charsetName} cannot be found.
*/
public InputStreamReader(InputStream in, final String charsetName)
throws UnsupportedEncodingException {
super(in);
if (charsetName == null) {
throw new NullPointerException("charsetName == null");
}
this.in = in;
try {
decoder = Charset.forName(charsetName).newDecoder().onMalformedInput(
CodingErrorAction.REPLACE).onUnmappableCharacter(
CodingErrorAction.REPLACE);
} catch (IllegalArgumentException e) {
throw (UnsupportedEncodingException)
new UnsupportedEncodingException(charsetName).initCause(e);
}
bytes.limit(0);
}
/**
* Constructs a new InputStreamReader on the InputStream {@code in} and
* CharsetDecoder {@code dec}.
*
* @param in
* the source InputStream from which to read characters.
* @param dec
* the CharsetDecoder used by the character conversion.
*/
public InputStreamReader(InputStream in, CharsetDecoder dec) {
super(in);
dec.averageCharsPerByte();
this.in = in;
decoder = dec;
bytes.limit(0);
}
/**
* Constructs a new InputStreamReader on the InputStream {@code in} and
* Charset {@code charset}.
*
* @param in
* the source InputStream from which to read characters.
* @param charset
* the Charset that defines the character converter
*/
public InputStreamReader(InputStream in, Charset charset) {
super(in);
this.in = in;
decoder = charset.newDecoder().onMalformedInput(
CodingErrorAction.REPLACE).onUnmappableCharacter(
CodingErrorAction.REPLACE);
bytes.limit(0);
}
/**
* Closes this reader. This implementation closes the source InputStream and
* releases all local storage.
*
* @throws IOException
* if an error occurs attempting to close this reader.
*/
@Override
public void close() throws IOException {
synchronized (lock) {
if (decoder != null) {
decoder.reset();
}
decoder = null;
if (in != null) {
in.close();
in = null;
}
}
}
/**
* Returns the historical 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 (!isOpen()) {
return null;
}
return HistoricalCharsetNames.get(decoder.charset());
}
/**
* Reads a single character from this reader and returns it as an integer
* with the two higher-order bytes set to 0. Returns -1 if the end of the
* reader has been reached. The byte value is either obtained from
* converting bytes in this reader's buffer or by first filling the buffer
* from the source InputStream and then reading from the buffer.
*
* @return the character read or -1 if the end of the reader has been
* reached.
* @throws IOException
* if this reader is closed or some other I/O error occurs.
*/
@Override
public int read() throws IOException {
synchronized (lock) {
if (!isOpen()) {
throw new IOException("InputStreamReader is closed");
}
char[] buf = new char[1];
return read(buf, 0, 1) != -1 ? buf[0] : -1;
}
}
/**
* Reads at most {@code length} characters from this reader and stores them
* at position {@code offset} in the character array {@code buf}. Returns
* the number of characters actually read or -1 if the end of the reader has
* been reached. The bytes are either obtained from converting bytes in this
* reader's buffer or by first filling the buffer from the source
* InputStream and then reading from the buffer.
*
* @param buffer
* the array to store the characters read.
* @param offset
* the initial position in {@code buf} to store the characters
* read from this reader.
* @param length
* the maximum number of characters to read.
* @return the number of characters read or -1 if the end of the reader has
* been reached.
* @throws IndexOutOfBoundsException
* if {@code offset < 0} or {@code length < 0}, or if
* {@code offset + length} is greater than the length of
* {@code buf}.
* @throws IOException
* if this reader is closed or some other I/O error occurs.
*/
@Override
public int read(char[] buffer, int offset, int length) throws IOException {
synchronized (lock) {
if (!isOpen()) {
throw new IOException("InputStreamReader is closed");
}
Arrays.checkOffsetAndCount(buffer.length, offset, length);
if (length == 0) {
return 0;
}
CharBuffer out = CharBuffer.wrap(buffer, offset, length);
CoderResult result = CoderResult.UNDERFLOW;
// bytes.remaining() indicates number of bytes in buffer
// when 1-st time entered, it'll be equal to zero
boolean needInput = !bytes.hasRemaining();
while (out.hasRemaining()) {
// fill the buffer if needed
if (needInput) {
try {
if (in.available() == 0 && out.position() > offset) {
// we could return the result without blocking read
break;
}
} catch (IOException e) {
// available didn't work so just try the read
}
int desiredByteCount = bytes.capacity() - bytes.limit();
int off = bytes.arrayOffset() + bytes.limit();
int actualByteCount = in.read(bytes.array(), off, desiredByteCount);
if (actualByteCount == -1) {
endOfInput = true;
break;
} else if (actualByteCount == 0) {
break;
}
bytes.limit(bytes.limit() + actualByteCount);
needInput = false;
}
// decode bytes
result = decoder.decode(bytes, out, false);
if (result.isUnderflow()) {
// compact the buffer if no space left
if (bytes.limit() == bytes.capacity()) {
bytes.compact();
bytes.limit(bytes.position());
bytes.position(0);
}
needInput = true;
} else {
break;
}
}
if (result == CoderResult.UNDERFLOW && endOfInput) {
result = decoder.decode(bytes, out, true);
decoder.flush(out);
decoder.reset();
}
if (result.isMalformed() || result.isUnmappable()) {
result.throwException();
}
return out.position() - offset == 0 ? -1 : out.position() - offset;
}
}
private boolean isOpen() {
return in != null;
}
/**
* Indicates whether this reader is ready to be read without blocking. If
* the result is {@code true}, the next {@code read()} will not block. If
* the result is {@code false} then this reader may or may not block when
* {@code read()} is called. This implementation returns {@code true} if
* there are bytes available in the buffer or the source stream has bytes
* available.
*
* @return {@code true} if the receiver will not block when {@code read()}
* is called, {@code false} if unknown or blocking will occur.
* @throws IOException
* if this reader is closed or some other I/O error occurs.
*/
@Override
public boolean ready() throws IOException {
synchronized (lock) {
if (in == null) {
throw new IOException("InputStreamReader is closed");
}
try {
return bytes.hasRemaining() || in.available() > 0;
} catch (IOException e) {
return false;
}
}
}
}