/* gnu.classpath.tools.NotifyingInputStreamReader
Copyright (C) 2004 Free Software Foundation, Inc.
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
package gnu.classpath.tools;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
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.IllegalCharsetNameException;
import java.nio.charset.UnsupportedCharsetException;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
/**
* Similar to {@link java.io.InputStreamReader}, but can give
* notification when malformed input is encountered.
*
* <p> Users of this class can register interest in the event of
* malformed input by calling {@link
* #addMalformedInputListener}. Each time a run of malformed input
* data is encountered, all listener objects are notified. For
* instance, this allows the calling code to inform the user about
* problems in the input stream. </p>
*
* <p> <strong>Background:</strong> The default
* <code>InputStreamReader</code> implementation will ignore
* malformed input, silently replacing it with the default
* replacement string (usually the question mark). Alternatively, you
* can configure a <code>CharsetDecoder</code> for the default
* <char>InputStreamReader</code> implementation, instructing it to
* ignore malformed input without replacing it; to replace it with a
* different string; or to throw an exception when malformed input is
* encountered. However, you cannot configure an
* <code>InputStreamReader</code> to gracefully handle malformed data
* but notify the client code about such
* problems. <code>NotifyingInputStreamReader</code> fills this
* gap. </p>
*
* @author Julian Scheid
*/
public class NotifyingInputStreamReader
extends Reader
{
/**
* The default size (in bytes) for byteBuf, i.e. the size of data
* chunks read from the underlying input stream.
*/
private static final int DEFAULT_INPUT_BUFFER_SIZE = 64;
/**
* The default size (in chars) for charBuf. This should be large
* enough to hold a decoded chunk of input data for the Charset
* with the minimum number of bytes per character. Since the
* minimum number of bytes per character for usual Charsets is
* one, this number should be identical to
* DEFAULT_INPUT_BUFFER_SIZE.
*/
private static final int DEFAULT_OUTPUT_BUFFER_SIZE = 64;
/**
* The underlying InputStream.
*/
private InputStream in;
/**
* The CharsetDecoder used to decode the underlying stream.
*/
private CharsetDecoder decoder;
/**
* Holds bytes already read from the underlying stream, but not
* yet decoded.
*/
private ByteBuffer byteBuffer;
/**
* Holds characters already decoded, but not yet fetched via
* read().
*/
private CharBuffer charBuffer;
/**
* This is the primitive byte array wrapped in byteBuffer for
* passing to to InputStream.read().
*/
private byte[] readBuffer;
/**
* Keeps track of the current line number (1-based).
*/
private int lineNumber = 1;
/**
* Keeps track of the current column number (0-based).
*/
private int columnNumber = 0;
/**
* Becomes true as soon as EOF has been reached in the underlying
* InputStream. At this point, byteBuffer contains the last chunk
* of data from the underlying InputStream.
*/
private boolean allInputConsumed = false;
/**
* Becomes true as soon as the decoder has been supplied with the
* last chunk of data from the InputStream after EOF has been
* reached. At this point, the last chunk of data has been drained
* from the byteBuffer.
*/
private boolean decodingFinished = false;
/**
* Becomes true as soon as the decoder has been flushed. At this
* point, the last chunk of character data has been written to the
* charBuffer.
*/
private boolean flushed = false;
/**
* Stores all registered MalformedInputListeners.
*/
private Set listeners = new LinkedHashSet();
/**
* Initializes a new instance for reading from the given
* InputStream using the default encoding. The default encoding is
* currently determined by looking at the system property
* <code>file.encoding</code>. If this property isn't set,
* <code>ISO-8859-1</code> is used as a fallback.
*
* <p>This method should use {@link Charset.defaultCharset()}
* instead, but this isn't implemented in Classpath at the
* moment.</p>
*
* @param in the <code>InputStream</code> to read from.
*/
public NotifyingInputStreamReader(InputStream in)
{
this(in, System.getProperty("file.encoding", "ISO-8859-1"));
}
/**
* Initializes a new instance for reading from the given
* InputStream using the specified charset.
*
* @param in the <code>InputStream</code> to read from.
* @param charsetName the canonical name or an alias of a
* <code>Charset</code>.
*
* @throws IllegalCharsetNameException if there is no
* <code>Charset</code> with the given canonical name or alias.
*
* @throws UnsupportedCharsetException if there is no support for
* the specified <code>Charset</code> in the runtime environment.
*/
public NotifyingInputStreamReader(InputStream in, String charsetName)
throws IllegalCharsetNameException, UnsupportedCharsetException
{
this(in, Charset.forName(charsetName));
}
/**
* Initializes a new instance for reading from the given
* InputStream using the specified charset.
*
* @param in the <code>InputStream</code> to read from.
* @param charset the <code>Charset</code> to use for decoding
* characters.
*/
public NotifyingInputStreamReader(InputStream in, Charset charset)
{
this(in, charset.newDecoder());
}
/**
* Initializes a new instance for reading from the given
* InputStream using the specified charset decoder.
*
* <strong>Note:</strong> the
* <code>NotifyingInputStreamReader</code> will not exhibit the
* advertised behaviour if you changed the action to take on
* malformed input in the specified
* <code>CharsetDecoder</code>. In other words, you should not
* call {@link CharsetDecoder.onMalformedInput(CodingErrorAction)}
* on the specified decoder before or while this reader is being
* used unless you know what you're doing.
*
* @param in the <code>InputStream</code> to read from.
* @param charset the <code>CharsetDecoder</code> to use for
* decoding characters.
*/
public NotifyingInputStreamReader(InputStream in, CharsetDecoder decoder)
{
this.in = in;
this.decoder = decoder;
this.charBuffer = CharBuffer.wrap(new char[DEFAULT_INPUT_BUFFER_SIZE]);
this.charBuffer.position(charBuffer.limit());
this.readBuffer = new byte[DEFAULT_OUTPUT_BUFFER_SIZE];
this.byteBuffer = ByteBuffer.wrap(readBuffer);
this.byteBuffer.position(byteBuffer.limit());
}
public void close()
throws IOException
{
in.close();
}
/**
* Fill charBuffer with new character data. This method returns if
* either the charBuffer has been filled completely with decoded
* character data, or if EOF is reached in the underlying
* InputStream. When this method returns, charBuffer is flipped
* and ready to be read from.
*/
private void fillCharBuf()
throws IOException
{
charBuffer.clear();
outer:
while (!flushed) {
CoderResult coderResult;
int charBufferPositionBefore = charBuffer.position();
if (!decodingFinished) {
coderResult = decoder.decode(byteBuffer, charBuffer, allInputConsumed);
if (allInputConsumed) {
decodingFinished = true;
}
}
else {
coderResult = decoder.flush(charBuffer);
flushed = coderResult.isUnderflow();
}
int charBufferPositionAfter = charBuffer.position();
for (int i=charBufferPositionBefore; i<charBufferPositionAfter; ++i) {
if (10 == charBuffer.get(i)) {
++ lineNumber;
columnNumber = 0;
}
else {
++ columnNumber;
}
}
if (coderResult.isOverflow()) {
break;
}
else if (coderResult.isUnderflow()) {
if (!allInputConsumed) {
int nRemainingBytes = 0;
if (byteBuffer.position() > 0) {
nRemainingBytes = Math.max(0, byteBuffer.limit() - byteBuffer.position());
}
if (nRemainingBytes > 0) {
byteBuffer.get(readBuffer, 0, nRemainingBytes);
}
byteBuffer.rewind();
int nread = in.read(readBuffer, nRemainingBytes,
readBuffer.length - nRemainingBytes);
if (nread < 0) {
allInputConsumed = true;
}
byteBuffer.limit(nRemainingBytes + Math.max(0, nread));
}
else {
break;
}
}
else if (coderResult.isMalformed()) {
fireMalformedInputEncountered(coderResult.length());
String replacement = decoder.replacement();
for (int i=0; i<coderResult.length(); ++i) {
if (charBuffer.remaining() > replacement.length()) {
charBuffer.put(replacement);
byteBuffer.position(byteBuffer.position() + 1);
columnNumber ++;
}
else {
break outer;
}
}
}
else if (coderResult.isUnmappable()) {
// This should not happen, since unmappable input bytes
// trigger a "malformed" event instead.
coderResult.throwException();
}
else {
// This should only happen if run in a future environment
// where additional events apart from underflow, overflow,
// malformed and unmappable can be generated.
coderResult.throwException();
}
}
charBuffer.flip();
}
/**
* Fire a MalformedInputEvent, notifying all registered listeners.
*/
private void fireMalformedInputEncountered(int length)
{
MalformedInputEvent event
= new MalformedInputEvent(this, lineNumber, columnNumber, length);
Iterator it = listeners.iterator();
while (it.hasNext()) {
MalformedInputListener listener
= (MalformedInputListener)it.next();
listener.malformedInputEncountered(event);
}
}
public int read(char[] cbuf, int offset, int length)
throws IOException
{
if (flushed) {
return -1;
}
else {
int nread = 0;
while (nread < length && !flushed) {
while (charBuffer.hasRemaining() && nread < length) {
int copyLen = Math.min(length - nread,
charBuffer.remaining());
charBuffer.get(cbuf, offset + nread, copyLen);
nread += copyLen;
}
if (nread < length) {
fillCharBuf();
}
}
return nread;
}
}
public int read()
throws IOException
{
while (!flushed) {
if (charBuffer.hasRemaining()) {
return charBuffer.get();
}
else {
fillCharBuf();
}
}
return -1;
}
/**
* Returns whether this reader is ready. The reader is ready if
* there is data in the internal buffer, or if additional data can
* be read from the underlying InputStream.
*/
public boolean ready()
{
return charBuffer.hasRemaining() || !flushed;
}
/**
* Register a <code>MalformedInputListener</code> which should be
* notified when malformed input is encountered.
*/
public void addMalformedInputListener(MalformedInputListener listener)
{
this.listeners.add(listener);
}
/**
* Unregister a previously registered
* <code>MalformedInputListener</code> if it should no longer be
* notified when malformed input is encountered.
*/
public void removeMalformedInputListener(MalformedInputListener listener)
{
this.listeners.remove(listener);
}
}