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: 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 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);
}
// ----------------------------------------------------------------
// byte[] -> Writer
// ----------------------------------------------------------------
/**
* 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);
}
// ----------------------------------------------------------------
// Core copy methods
// ----------------------------------------------------------------
/**
* 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;
}
// ----------------------------------------------------------------
// Reader -> Writer
// ----------------------------------------------------------------
/**
* 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;
}
// ----------------------------------------------------------------
// InputStream -> Writer
// ----------------------------------------------------------------
/**
* 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);
}
// ----------------------------------------------------------------
// Reader -> OutputStream
// ----------------------------------------------------------------
/**
* 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();
}
// ----------------------------------------------------------------
// String -> OutputStream
// ----------------------------------------------------------------
/**
* 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();
}
// ----------------------------------------------------------------
// String -> Writer
// ----------------------------------------------------------------
/**
* 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);
}
}