org.directwebremoting.util.CopyUtils Maven / Gradle / Ivy
/*
* 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.
*/
package org.directwebremoting.util;
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 (InputStream, Reader, String and
* byte[]) and destinations (OutputStream, Writer,
* String and byte[]).
*
*
* Unless otherwise noted, these copy methods do not 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' close() 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 this
* UnixReview article.
*
* For byte-to-char methods, a copy 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.
*
* We don't provide special variants for the copy 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.
*
* The copy methods use an internal buffer when copying. It is therefore advisable
* not to deliberately wrap the stream arguments to the copy methods in
* Buffered* streams. For example, don't do the
* following:
*
* copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );
*
* The rationale is as follows:
*
* 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 read requests can inexpensively get
* their data (until the buffer runs out).
* However, the copy 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).
*
* Behold, intrepid explorers; a map of this class:
*
* 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)
*
*
* 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.
*
* Origin of code: Apache Avalon (Excalibur)
*
* @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 byte[] to an OutputStream.
* @param input the byte array to read from
* @param output the OutputStream 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 byte[] to chars on a
* Writer.
* The platform's default encoding is used for the byte-to-char conversion.
* @param input the byte array to read from
* @param output the Writer 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 byte[] to chars on a
* Writer, using the specified encoding.
* @param input the byte array to read from
* @param output the Writer to write to
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry 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 InputStream to an OutputStream.
* @param input the InputStream to read from
* @param output the OutputStream 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 Reader to a Writer.
* @param input the Reader to read from
* @param output the Writer 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 InputStream to chars on a
* Writer.
* The platform's default encoding is used for the byte-to-char conversion.
* @param input the InputStream to read from
* @param output the Writer 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 InputStream to chars on a
* Writer, using the specified encoding.
* @param input the InputStream to read from
* @param output the Writer to write to
* @param encoding The name of a supported character encoding. See the
* IANA
* Charset Registry 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 Reader to bytes on an
* OutputStream, and flush the OutputStream.
* @param input the Reader to read from
* @param output the OutputStream 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 String to bytes on an OutputStream, and
* flush the OutputStream.
* @param input the String to read from
* @param output the OutputStream 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 String to a Writer.
* @param input the String to read from
* @param output the Writer 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;
}