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The Apache Commons IO library contains utility classes, stream implementations, file filters, file comparators, endian transformation classes, and much more.

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/*
 * 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 org.apache.commons.io.input;

import static org.apache.commons.io.IOUtils.EOF;

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.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;

/**
 * {@link InputStream} implementation that reads a character stream from a {@link Reader}
 * and transforms it to a byte stream using a specified charset encoding. The stream
 * is transformed using a {@link CharsetEncoder} object, guaranteeing that all charset
 * encodings supported by the JRE are handled correctly. In particular for charsets such as
 * UTF-16, the implementation ensures that one and only one byte order marker
 * is produced.
 * 

* Since in general it is not possible to predict the number of characters to be read from the * {@link Reader} to satisfy a read request on the {@link ReaderInputStream}, all reads from * the {@link Reader} are buffered. There is therefore no well defined correlation * between the current position of the {@link Reader} and that of the {@link ReaderInputStream}. * This also implies that in general there is no need to wrap the underlying {@link Reader} * in a {@link java.io.BufferedReader}. *

* {@link ReaderInputStream} implements the inverse transformation of {@link java.io.InputStreamReader}; * in the following example, reading from {@code in2} would return the same byte * sequence as reading from {@code in} (provided that the initial byte sequence is legal * with respect to the charset encoding): *

 * InputStream in = ...
 * Charset cs = ...
 * InputStreamReader reader = new InputStreamReader(in, cs);
 * ReaderInputStream in2 = new ReaderInputStream(reader, cs);
* {@link ReaderInputStream} implements the same transformation as {@link java.io.OutputStreamWriter}, * except that the control flow is reversed: both classes transform a character stream * into a byte stream, but {@link java.io.OutputStreamWriter} pushes data to the underlying stream, * while {@link ReaderInputStream} pulls it from the underlying stream. *

* Note that while there are use cases where there is no alternative to using * this class, very often the need to use this class is an indication of a flaw * in the design of the code. This class is typically used in situations where an existing * API only accepts an {@link InputStream}, but where the most natural way to produce the data * is as a character stream, i.e. by providing a {@link Reader} instance. An example of a situation * where this problem may appear is when implementing the {@code javax.activation.DataSource} * interface from the Java Activation Framework. *

* Given the fact that the {@link Reader} class doesn't provide any way to predict whether the next * read operation will block or not, it is not possible to provide a meaningful * implementation of the {@link InputStream#available()} method. A call to this method * will always return 0. Also, this class doesn't support {@link InputStream#mark(int)}. *

* Instances of {@link ReaderInputStream} are not thread safe. * * @see org.apache.commons.io.output.WriterOutputStream * * @since 2.0 */ public class ReaderInputStream extends InputStream { private static final int DEFAULT_BUFFER_SIZE = 1024; private final Reader reader; private final CharsetEncoder encoder; /** * CharBuffer used as input for the decoder. It should be reasonably * large as we read data from the underlying Reader into this buffer. */ private final CharBuffer encoderIn; /** * ByteBuffer used as output for the decoder. This buffer can be small * as it is only used to transfer data from the decoder to the * buffer provided by the caller. */ private final ByteBuffer encoderOut; private CoderResult lastCoderResult; private boolean endOfInput; /** * Construct a new {@link ReaderInputStream}. * * @param reader the target {@link Reader} * @param encoder the charset encoder * @since 2.1 */ public ReaderInputStream(final Reader reader, final CharsetEncoder encoder) { this(reader, encoder, DEFAULT_BUFFER_SIZE); } /** * Construct a new {@link ReaderInputStream}. * * @param reader the target {@link Reader} * @param encoder the charset encoder * @param bufferSize the size of the input buffer in number of characters * @since 2.1 */ public ReaderInputStream(final Reader reader, final CharsetEncoder encoder, final int bufferSize) { this.reader = reader; this.encoder = encoder; this.encoderIn = CharBuffer.allocate(bufferSize); this.encoderIn.flip(); this.encoderOut = ByteBuffer.allocate(128); this.encoderOut.flip(); } /** * Construct a new {@link ReaderInputStream}. * * @param reader the target {@link Reader} * @param charset the charset encoding * @param bufferSize the size of the input buffer in number of characters */ public ReaderInputStream(final Reader reader, final Charset charset, final int bufferSize) { this(reader, charset.newEncoder() .onMalformedInput(CodingErrorAction.REPLACE) .onUnmappableCharacter(CodingErrorAction.REPLACE), bufferSize); } /** * Construct a new {@link ReaderInputStream} with a default input buffer size of * 1024 characters. * * @param reader the target {@link Reader} * @param charset the charset encoding */ public ReaderInputStream(final Reader reader, final Charset charset) { this(reader, charset, DEFAULT_BUFFER_SIZE); } /** * Construct a new {@link ReaderInputStream}. * * @param reader the target {@link Reader} * @param charsetName the name of the charset encoding * @param bufferSize the size of the input buffer in number of characters */ public ReaderInputStream(final Reader reader, final String charsetName, final int bufferSize) { this(reader, Charset.forName(charsetName), bufferSize); } /** * Construct a new {@link ReaderInputStream} with a default input buffer size of * 1024 characters. * * @param reader the target {@link Reader} * @param charsetName the name of the charset encoding */ public ReaderInputStream(final Reader reader, final String charsetName) { this(reader, charsetName, DEFAULT_BUFFER_SIZE); } /** * Construct a new {@link ReaderInputStream} that uses the default character encoding * with a default input buffer size of 1024 characters. * * @param reader the target {@link Reader} * @deprecated 2.5 use {@link #ReaderInputStream(Reader, Charset)} instead */ @Deprecated public ReaderInputStream(final Reader reader) { this(reader, Charset.defaultCharset()); } /** * Fills the internal char buffer from the reader. * * @throws IOException * If an I/O error occurs */ private void fillBuffer() throws IOException { if (!endOfInput && (lastCoderResult == null || lastCoderResult.isUnderflow())) { encoderIn.compact(); final int position = encoderIn.position(); // We don't use Reader#read(CharBuffer) here because it is more efficient // to write directly to the underlying char array (the default implementation // copies data to a temporary char array). final int c = reader.read(encoderIn.array(), position, encoderIn.remaining()); if (c == EOF) { endOfInput = true; } else { encoderIn.position(position+c); } encoderIn.flip(); } encoderOut.compact(); lastCoderResult = encoder.encode(encoderIn, encoderOut, endOfInput); encoderOut.flip(); } /** * Read the specified number of bytes into an array. * * @param b the byte array to read into * @param off the offset to start reading bytes into * @param len the number of bytes to read * @return the number of bytes read or -1 * if the end of the stream has been reached * @throws IOException if an I/O error occurs */ @Override public int read(final byte[] b, int off, int len) throws IOException { if (b == null) { throw new NullPointerException("Byte array must not be null"); } if (len < 0 || off < 0 || (off + len) > b.length) { throw new IndexOutOfBoundsException("Array Size=" + b.length + ", offset=" + off + ", length=" + len); } int read = 0; if (len == 0) { return 0; // Always return 0 if len == 0 } while (len > 0) { if (encoderOut.hasRemaining()) { final int c = Math.min(encoderOut.remaining(), len); encoderOut.get(b, off, c); off += c; len -= c; read += c; } else { fillBuffer(); if (endOfInput && !encoderOut.hasRemaining()) { break; } } } return read == 0 && endOfInput ? EOF : read; } /** * Read the specified number of bytes into an array. * * @param b the byte array to read into * @return the number of bytes read or -1 * if the end of the stream has been reached * @throws IOException if an I/O error occurs */ @Override public int read(final byte[] b) throws IOException { return read(b, 0, b.length); } /** * Read a single byte. * * @return either the byte read or -1 if the end of the stream * has been reached * @throws IOException if an I/O error occurs */ @Override public int read() throws IOException { for (;;) { if (encoderOut.hasRemaining()) { return encoderOut.get() & 0xFF; } fillBuffer(); if (endOfInput && !encoderOut.hasRemaining()) { return EOF; } } } /** * Close the stream. This method will cause the underlying {@link Reader} * to be closed. * @throws IOException if an I/O error occurs */ @Override public void close() throws IOException { reader.close(); } }





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