File	Doc	Category	Size	Date	Package
CharsetDecode.java	API Doc	Example	4242	Mon May 20 00:24:30 BST 2002	com.ronsoft.books.nio.charset

CharsetDecode

• java.lang.Object

Fields Summary

Constructors Summary

Methods Summary
public static void	decodeChannel(java.nio.channels.ReadableByteChannel source, java.io.Writer writer, java.nio.charset.Charset charset) General purpose static method which reads bytes from a Channel, decodes them according param source A ReadableByteChannel object which will be read to EOF as a source of encoded bytes. param writer A Writer object to which decoded chars will be written. param charset A Charset object, whose CharsetDecoder will be used to do the character set decoding. // get a decoder instance from the Charset CharsetDecoder decoder = charset.newDecoder(); // tell decoder to replace bad chars with default marker decoder.onMalformedInput (CodingErrorAction.REPLACE); decoder.onUnmappableCharacter (CodingErrorAction.REPLACE); // allocate radically different input and output buffer sizes // for testing purposes ByteBuffer bb = ByteBuffer.allocateDirect (16 * 1024); CharBuffer cb = CharBuffer.allocate (57); // buffer starts empty, indicate input is needed CoderResult result = CoderResult.UNDERFLOW; boolean eof = false; while ( ! eof) { // input buffer underflow, decoder wants more input if (result == CoderResult.UNDERFLOW) { // decoder consumed all input, prepare to refill bb.clear(); // fill the input buffer, watch for EOF eof = (source.read (bb) == -1); // prepare the buffer for reading by decoder bb.flip(); } // decode input bytes to output chars, pass EOF flag result = decoder.decode (bb, cb, eof); // if output buffer is full, drain output if (result == CoderResult.OVERFLOW) { drainCharBuf (cb, writer); } } // flush any remaining state from the decoder, being careful // to detect output buffer overflow(s). while (decoder.flush (cb) == CoderResult.OVERFLOW) { drainCharBuf (cb, writer); } // drain any chars remaining in the output buffer drainCharBuf (cb, writer); // close the channel, push out any buffered data to stdout source.close(); writer.flush();
static void	drainCharBuf(java.nio.CharBuffer cb, java.io.Writer writer) Helper method to drain the char buffer and write its content to the given Writer object. Upon return, the buffer is empty and ready to be refilled. param cb A CharBuffer containing chars to be written. param writer A Writer object to consume the chars in cb. cb.flip(); // prepare buffer for draining // This writes the chars contained in the CharBuffer but // doesn't actually modify the state of the buffer. // If the char buffer was being drained by calls to get(), // a loop might be needed here. if (cb.hasRemaining()) { writer.write (cb.toString()); } cb.clear(); // prepare buffer to be filled again
public static void	main(java.lang.String[] argv) Test charset decoding in the general case, detecting and handling buffer under/overflow and flushing the decoder state at end of input. This code reads from stdin and decodes the ASCII-encoded byte stream to chars. The decoded chars are written to stdout. This is effectively a 'cat' for input ascii files, but another charset encoding could be used by simply specifying it on the command line. // default charset is standard ASCII String charsetName = "ISO-8859-1"; // charset name can be specified on the command line if (argv.length > 0) { charsetName = argv [0]; } // wrap a Channel around stdin, wrap a channel around stdout, // find the named Charset and pass them to the decode method. // If the named charset is not valid, an exception of type // UnsupportedCharsetException will be thrown. decodeChannel (Channels.newChannel (System.in), new OutputStreamWriter (System.out), Charset.forName (charsetName));