org.apache.crimson.parser
Class XmlReader

java.lang.Object
  java.io.Reader
      org.apache.crimson.parser.XmlReader

final class XmlReader

extends Reader

This handles several XML-related tasks that normal java.io Readers don't support, inluding use of IETF standard encoding names and automatic detection of most XML encodings. The former is needed for interoperability; the latter is needed to conform with the XML spec. This class also optimizes reading some common encodings by providing low-overhead unsynchronized Reader support.

Note that the autodetection facility should be used only on data streams which have an unknown character encoding. For example, it should never be used on MIME text/xml entities.

Note that XML processors are only required to support UTF-8 and UTF-16 character encodings. Autodetection permits the underlying Java implementation to provide support for many other encodings, such as US-ASCII, ISO-8859-5, Shift_JIS, EUC-JP, and ISO-2022-JP.

Author:

David Brownell

Nested Class Summary

(package private) static class	XmlReader.AsciiReader
(package private) static class	XmlReader.BaseReader
(package private) static class	XmlReader.Iso8859_1Reader
(package private) static class	XmlReader.Utf8Reader

Field Summary

private String	assignedEncoding
private static Hashtable	charsets
private boolean	closed
private Reader	in
private static int	MAXPUSHBACK

Fields inherited from class java.io.Reader

lock

Constructor Summary

private

XmlReader(InputStream stream)

Method Summary

void	close() Closes the reader.
static Reader	createReader(InputStream in) Constructs the reader from an input stream, autodetecting the encoding to use according to the heuristic specified in the XML 1.0 recommendation.
static Reader	createReader(InputStream in, String encoding) Creates a reader supporting the given encoding, mapping from standard encoding names to ones that understood by Java where necessary.
String	getEncoding() Returns the standard name of the encoding in use
void	mark(int value) Sets a mark allowing a limited number of characters to be "peeked", by reading and then resetting.
boolean	markSupported() Returns true iff the reader supports mark/reset.
int	read() Reads a single character.
int	read(char[] buf, int off, int len) Reads the number of characters read into the buffer, or -1 on EOF.
boolean	ready() Returns true iff input characters are known to be ready.
void	reset() Resets the current position to the last marked position.
private void	setEncoding(InputStream stream, String encoding)
long	skip(long value) Skips a specified number of characters.
private static String	std2java(String encoding)
private void	useEncodingDecl(PushbackInputStream pb, String encoding)

Methods inherited from class java.io.Reader

read

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MAXPUSHBACK

private static final int MAXPUSHBACK

See Also:

Constant Field Values

in

private Reader in

assignedEncoding

private String assignedEncoding

closed

private boolean closed

charsets

private static final Hashtable charsets

Constructor Detail

XmlReader

private XmlReader(InputStream stream)
           throws IOException

Method Detail

createReader

public static Reader createReader(InputStream in)
                           throws IOException

Constructs the reader from an input stream, autodetecting the encoding to use according to the heuristic specified in the XML 1.0 recommendation.

Parameters:

in - the input stream from which the reader is constructed

Throws:

IOException - on error, such as unrecognized encoding

createReader

public static Reader createReader(InputStream in,
                                  String encoding)
                           throws IOException

Creates a reader supporting the given encoding, mapping from standard encoding names to ones that understood by Java where necessary.

Parameters:

in - the input stream from which the reader is constructed

encoding - the IETF standard name of the encoding to use; if null, autodetection is used.

Throws:

IOException - on error, including unrecognized encoding

std2java

private static String std2java(String encoding)

getEncoding

public String getEncoding()

Returns the standard name of the encoding in use

useEncodingDecl

private void useEncodingDecl(PushbackInputStream pb,
                             String encoding)
                      throws IOException

Throws:

IOException

setEncoding

private void setEncoding(InputStream stream,
                         String encoding)
                  throws IOException

Throws:

IOException

read

public int read(char[] buf,
                int off,
                int len)
         throws IOException

Reads the number of characters read into the buffer, or -1 on EOF.

Specified by:

read in class Reader

Parameters:

buf - Destination buffer

off - Offset at which to start storing characters

len - Maximum number of characters to read

Returns:

The number of characters read, or -1 if the end of the stream has been reached

Throws:

IOException - If an I/O error occurs

read

public int read()
         throws IOException

Reads a single character.

Overrides:

read in class Reader

Returns:

The character read, as an integer in the range 0 to 65535 (0x00-0xffff), or -1 if the end of the stream has been reached

Throws:

IOException - If an I/O error occurs

markSupported

public boolean markSupported()

Returns true iff the reader supports mark/reset.

Overrides:

markSupported in class Reader

Returns:

true if and only if this stream supports the mark operation.

mark

public void mark(int value)
          throws IOException

Sets a mark allowing a limited number of characters to be "peeked", by reading and then resetting.

Overrides:

mark in class Reader

Parameters:

value - how many characters may be "peeked".

Throws:

IOException - If the stream does not support mark(), or if some other I/O error occurs

reset

public void reset()
           throws IOException

Resets the current position to the last marked position.

Overrides:

reset in class Reader

Throws:

IOException - If the stream has not been marked, or if the mark has been invalidated, or if the stream does not support reset(), or if some other I/O error occurs

skip

public long skip(long value)
          throws IOException

Skips a specified number of characters.

Overrides:

skip in class Reader

Parameters:

value - The number of characters to skip

Returns:

The number of characters actually skipped

Throws:

IOException - If an I/O error occurs

ready

public boolean ready()
              throws IOException

Returns true iff input characters are known to be ready.

Overrides:

ready in class Reader

Returns:

True if the next read() is guaranteed not to block for input, false otherwise. Note that returning false does not guarantee that the next read will block.

Throws:

IOException - If an I/O error occurs

close

public void close()
           throws IOException

Closes the reader.

Specified by:

close in class Reader

Throws:

IOException - If an I/O error occurs