Buffered copying
/*
* 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.
*/
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;
/**
* 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>
* 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>
* 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
* 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>
* 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:
* <pre>
* copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );
* </pre>
* The rationale is as follows:
* <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>
* 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>
* Behold, intrepid explorers; a map of this class:
* <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>
* Origin of code: Excalibur.
*
* @author Peter Donald
* @author Jeff Turner
* @author Matthew Hawthorne
* @version $Id: CopyUtils.java 437680 2006-08-28 11:57:00Z scolebourne $
*/
public class CopyUtils {
/**
* The default size of the buffer.
*/
private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;
/**
* Instances should NOT be constructed in standard programming.
*/
public CopyUtils() { }
// ----------------------------------------------------------------
// byte[] -> OutputStream
// ----------------------------------------------------------------
/**
* 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);
}
// ----------------------------------------------------------------
// byte[] -> Writer
// ----------------------------------------------------------------
/**
* 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);
}
// ----------------------------------------------------------------
// Core copy methods
// ----------------------------------------------------------------
/**
* 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;
}
// ----------------------------------------------------------------
// Reader -> Writer
// ----------------------------------------------------------------
/**
* 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;
}
// ----------------------------------------------------------------
// InputStream -> Writer
// ----------------------------------------------------------------
/**
* 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);
}
// ----------------------------------------------------------------
// Reader -> OutputStream
// ----------------------------------------------------------------
/**
* 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();
}
// ----------------------------------------------------------------
// String -> OutputStream
// ----------------------------------------------------------------
/**
* 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();
}
// ----------------------------------------------------------------
// String -> Writer
// ----------------------------------------------------------------
/**
* 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);
}
}
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