Buffered copying between source(InputStream, Reader, String and byte[]) and destinations (OutputStream, Writer, String and byte[]).
/*
* Copyright 2001-2004 The Apache Software Foundation.
*
* 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.
*/
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.Writer;
/**
* <p>
* This class provides static utility methods for buffered
* copying between sources (<code>InputStream</code>, <code>Reader</code>, <code>String</code> and
* <code>byte[]</code>) and destinations (<code>OutputStream</code>, <code>Writer</code>,
* <code>String</code> and <code>byte[]</code>).
* </p>
*
* <p>Unless otherwise noted, these <code>copy</code> methods do <em>not</em> flush or close the
* streams. Often doing so would require making non-portable assumptions about the streams' origin
* and further use. This means that both streams' <code>close()</code> methods must be called after
* copying. if one omits this step, then the stream resources (sockets, file descriptors) are
* released when the associated Stream is garbage-collected. It is not a good idea to rely on this
* mechanism. For a good overview of the distinction between "memory management" and "resource
* management", see <a href="http://www.unixreview.com/articles/1998/9804/9804ja/ja.htm">this
* UnixReview article</a>.</p>
*
* <p>For byte-to-char methods, a <code>copy</code> variant allows the encoding
* to be selected (otherwise the platform default is used). We would like to
* encourage you to always specify the encoding because relying on the platform
* default can lead to unexpected results.</p>
*
* <p>We don't provide special variants for the <code>copy</code> methods that
* let you specify the buffer size because in modern VMs the impact on speed
* seems to be minimal. We're using a default buffer size of 4 KB.</p>
*
* <p>The <code>copy</code> methods use an internal buffer when copying. It is therefore advisable
* <em>not</em> to deliberately wrap the stream arguments to the <code>copy</code> methods in
* <code>Buffered*</code> streams. For example, don't do the
* following:</p>
*
* <code>copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );</code>
*
* <p>The rationale is as follows:</p>
*
* <p>Imagine that an InputStream's read() is a very expensive operation, which would usually suggest
* wrapping in a BufferedInputStream. The BufferedInputStream works by issuing infrequent
* {@link java.io.InputStream#read(byte[] b, int off, int len)} requests on the underlying InputStream, to
* fill an internal buffer, from which further <code>read</code> requests can inexpensively get
* their data (until the buffer runs out).</p>
* <p>However, the <code>copy</code> methods do the same thing, keeping an internal buffer,
* populated by {@link InputStream#read(byte[] b, int off, int len)} requests. Having two buffers
* (or three if the destination stream is also buffered) is pointless, and the unnecessary buffer
* management hurts performance slightly (about 3%, according to some simple experiments).</p>
*
* <p>Behold, intrepid explorers; a map of this class:</p>
* <pre>
* Method Input Output Dependency
* ------ ----- ------ -------
* 1 copy InputStream OutputStream (primitive)
* 2 copy Reader Writer (primitive)
*
* 3 copy InputStream Writer 2
*
* 4 copy Reader OutputStream 2
*
* 5 copy String OutputStream 2
* 6 copy String Writer (trivial)
*
* 7 copy byte[] Writer 3
* 8 copy byte[] OutputStream (trivial)
* </pre>
*
* <p>Note that only the first two methods shuffle bytes; the rest use these
* two, or (if possible) copy using native Java copy methods. As there are
* method variants to specify the encoding, each row may
* correspond to up to 2 methods.</p>
*
* <p>Origin of code: Apache Avalon (Excalibur)</p>
*
* @author Peter Donald
* @author Jeff Turner
* @author Matthew Hawthorne
*/
public class CopyUtils
{
/**
* Instances should NOT be constructed in standard programming.
*/
private CopyUtils()
{
}
/**
* Copy bytes from a <code>byte[]</code> to an <code>OutputStream</code>.
* @param input the byte array to read from
* @param output the <code>OutputStream</code> to write to
* @throws IOException In case of an I/O problem
*/
public static void copy(byte[] input, OutputStream output) throws IOException
{
output.write(input);
}
/**
* Copy and convert bytes from a <code>byte[]</code> to chars on a
* <code>Writer</code>.
* The platform's default encoding is used for the byte-to-char conversion.
* @param input the byte array to read from
* @param output the <code>Writer</code> to write to
* @throws IOException In case of an I/O problem
*/
public static void copy(byte[] input, Writer output) throws IOException
{
ByteArrayInputStream in = new ByteArrayInputStream(input);
copy(in, output);
}
/**
* Copy and convert bytes from a <code>byte[]</code> to chars on a
* <code>Writer</code>, using the specified encoding.
* @param input the byte array to read from
* @param output the <code>Writer</code> to write to
* @param encoding The name of a supported character encoding. See the
* <a href="http://www.iana.org/assignments/character-sets">IANA
* Charset Registry</a> for a list of valid encoding types.
* @throws IOException In case of an I/O problem
*/
public static void copy(byte[] input, Writer output, String encoding) throws IOException
{
ByteArrayInputStream in = new ByteArrayInputStream(input);
copy(in, output, encoding);
}
/**
* Copy bytes from an <code>InputStream</code> to an <code>OutputStream</code>.
* @param input the <code>InputStream</code> to read from
* @param output the <code>OutputStream</code> to write to
* @return the number of bytes copied
* @throws IOException In case of an I/O problem
*/
public static int copy(InputStream input, OutputStream output) throws IOException
{
byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
int count = 0;
int n = 0;
while (-1 != (n = input.read(buffer)))
{
output.write(buffer, 0, n);
count += n;
}
return count;
}
/**
* Copy chars from a <code>Reader</code> to a <code>Writer</code>.
* @param input the <code>Reader</code> to read from
* @param output the <code>Writer</code> to write to
* @return the number of characters copied
* @throws IOException In case of an I/O problem
*/
public static int copy(Reader input, Writer output) throws IOException
{
char[] buffer = new char[DEFAULT_BUFFER_SIZE];
int count = 0;
int n = 0;
while (-1 != (n = input.read(buffer)))
{
output.write(buffer, 0, n);
count += n;
}
return count;
}
/**
* Copy and convert bytes from an <code>InputStream</code> to chars on a
* <code>Writer</code>.
* The platform's default encoding is used for the byte-to-char conversion.
* @param input the <code>InputStream</code> to read from
* @param output the <code>Writer</code> to write to
* @throws IOException In case of an I/O problem
*/
public static void copy(InputStream input, Writer output) throws IOException
{
InputStreamReader in = new InputStreamReader(input);
copy(in, output);
}
/**
* Copy and convert bytes from an <code>InputStream</code> to chars on a
* <code>Writer</code>, using the specified encoding.
* @param input the <code>InputStream</code> to read from
* @param output the <code>Writer</code> to write to
* @param encoding The name of a supported character encoding. See the
* <a href="http://www.iana.org/assignments/character-sets">IANA
* Charset Registry</a> for a list of valid encoding types.
* @throws IOException In case of an I/O problem
*/
public static void copy(InputStream input, Writer output, String encoding) throws IOException
{
InputStreamReader in = new InputStreamReader(input, encoding);
copy(in, output);
}
/**
* Serialize chars from a <code>Reader</code> to bytes on an
* <code>OutputStream</code>, and flush the <code>OutputStream</code>.
* @param input the <code>Reader</code> to read from
* @param output the <code>OutputStream</code> to write to
* @throws IOException In case of an I/O problem
*/
public static void copy(Reader input, OutputStream output) throws IOException
{
OutputStreamWriter out = new OutputStreamWriter(output);
copy(input, out);
// XXX Unless anyone is planning on rewriting OutputStreamWriter, we have to flush here.
out.flush();
}
/**
* Serialize chars from a <code>String</code> to bytes on an <code>OutputStream</code>, and
* flush the <code>OutputStream</code>.
* @param input the <code>String</code> to read from
* @param output the <code>OutputStream</code> to write to
* @throws IOException In case of an I/O problem
*/
public static void copy(String input, OutputStream output) throws IOException
{
StringReader in = new StringReader(input);
OutputStreamWriter out = new OutputStreamWriter(output);
copy(in, out);
// XXX Unless anyone is planning on rewriting OutputStreamWriter, we have to flush here.
out.flush();
}
/**
* Copy chars from a <code>String</code> to a <code>Writer</code>.
* @param input the <code>String</code> to read from
* @param output the <code>Writer</code> to write to
* @throws IOException In case of an I/O problem
*/
public static void copy(String input, Writer output) throws IOException
{
output.write(input);
}
/**
* The name says it all.
*/
private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;
}
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