ChannelCopypublic class ChannelCopy extends Object | Test copying between channels.
Created and tested: Dec 31, 2001
Revised for NIO book, April 2002 |
| Methods Summary |
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| private static void | channelCopy1(java.nio.channels.ReadableByteChannel src, java.nio.channels.WritableByteChannel dest)Channel copy method 1. This method copies data from the src
channel and writes it to the dest channel until EOF on src.
This implementation makes use of compact() on the temp buffer
to pack down the data if the buffer wasn't fully drained. This
may result in data copying, but minimizes system calls. It also
requires a cleanup loop to make sure all the data gets sent.
ByteBuffer buffer = ByteBuffer.allocateDirect (16 * 1024);
while (src.read (buffer) != -1) {
// prepare the buffer to be drained
buffer.flip();
// write to the channel, may block
dest.write (buffer);
// If partial transfer, shift remainder down
// If buffer is empty, same as doing clear()
buffer.compact();
}
// EOF will leave buffer in fill state
buffer.flip();
// make sure the buffer is fully drained.
while (buffer.hasRemaining()) {
dest.write (buffer);
}
| | private static void | channelCopy2(java.nio.channels.ReadableByteChannel src, java.nio.channels.WritableByteChannel dest)Channel copy method 2. This method performs the same copy, but
assures the temp buffer is empty before reading more data. This
never requires data copying but may result in more systems calls.
No post-loop cleanup is needed because the buffer will be empty
when the loop is exited.
ByteBuffer buffer = ByteBuffer.allocateDirect (16 * 1024);
while (src.read (buffer) != -1) {
// prepare the buffer to be drained
buffer.flip();
// make sure the buffer was fully drained.
while (buffer.hasRemaining()) {
dest.write (buffer);
}
// make the buffer empty, ready for filling
buffer.clear();
}
| | public static void | main(java.lang.String[] argv)This code copies data from stdin to stdout. Like the 'cat'
command, but without any useful options.
ReadableByteChannel source = Channels.newChannel (System.in);
WritableByteChannel dest = Channels.newChannel (System.out);
channelCopy1 (source, dest);
// alternatively, call channelCopy2 (source, dest);
source.close();
dest.close();
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