Mega Code Archive
XML-related tasks and java io Readers
<![CDATA[
/*
* $Id: XmlReader.java,v 1.1 2004/08/19 05:30:22 aslom Exp $
*
* The Apache Software License, Version 1.1
*
*
* Copyright (c) 2000 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Crimson" and "Apache Software Foundation" must
* not be used to endorse or promote products derived from this
* software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* nor may "Apache" appear in their name, without prior written
* permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation and was
* originally based on software copyright (c) 1999, Sun Microsystems, Inc.,
* http://www.sun.com. For more information on the Apache Software
* Foundation, please see <http://www.apache.org/>.
*/
import java.io.*;
import java.util.Hashtable;
/**
* 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.
*
* <P> 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.
*
* <P> 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
* @version $Revision: 1.1 $
*/
final public class XmlReader extends Reader
{
private static final int MAXPUSHBACK = 512;
private Reader in;
private String assignedEncoding;
private boolean closed;
//
// This class always delegates I/O to a reader, which gets
// its data from the very beginning of the XML text. It needs
// to use a pushback stream since (a) autodetection can read
// partial UTF-8 characters which need to be fully processed,
// (b) the "Unicode" readers swallow characters that they think
// are byte order marks, so tests fail if they don't see the
// real byte order mark.
//
// It's got do this efficiently: character I/O is solidly on the
// critical path. (So keep buffer length over 2 Kbytes to avoid
// excess buffering. Many URL handlers stuff a BufferedInputStream
// between here and the real data source, and larger buffers keep
// that from slowing you down.)
//
/**
* Constructs the reader from an input stream, autodetecting
* the encoding to use according to the heuristic specified
* in the XML 1.0 recommendation.
*
* @param in the input stream from which the reader is constructed
* @exception IOException on error, such as unrecognized encoding
*/
public static Reader createReader (InputStream in) throws IOException
{
return new XmlReader (in);
}
/**
* Creates a reader supporting the given encoding, mapping
* from standard encoding names to ones that understood by
* Java where necessary.
*
* @param in the input stream from which the reader is constructed
* @param encoding the IETF standard name of the encoding to use;
* if null, autodetection is used.
* @exception IOException on error, including unrecognized encoding
*/
public static Reader createReader (InputStream in, String encoding)
throws IOException
{
if (encoding == null) {
return new XmlReader(in);
}
if ("UTF-8".equalsIgnoreCase (encoding)
|| "UTF8".equalsIgnoreCase (encoding)) {
return new Utf8Reader (in);
}
if ("US-ASCII".equalsIgnoreCase (encoding)
|| "ASCII".equalsIgnoreCase (encoding)) {
return new AsciiReader (in);
}
if ("ISO-8859-1".equalsIgnoreCase (encoding)
// plus numerous aliases ...
) {
return new Iso8859_1Reader (in);
}
// What we really want is an administerable resource mapping
// encoding names/aliases to classnames. For example a property
// file resource, "readers/mapping.props", holding and a set
// of readers in that (sub)package... defaulting to this call
// only if no better choice is available.
//
return new InputStreamReader (in, std2java (encoding));
}
// JDK doesn't know all of the standard encoding names, and
// in particular none of the EBCDIC ones IANA defines (and
// which IBM encourages).
static private final Hashtable charsets = new Hashtable (31);
static {
charsets.put ("UTF-16", "Unicode");
charsets.put ("ISO-10646-UCS-2", "Unicode");
// NOTE: no support for ISO-10646-UCS-4 yet.
charsets.put ("EBCDIC-CP-US", "cp037");
charsets.put ("EBCDIC-CP-CA", "cp037");
charsets.put ("EBCDIC-CP-NL", "cp037");
charsets.put ("EBCDIC-CP-WT", "cp037");
charsets.put ("EBCDIC-CP-DK", "cp277");
charsets.put ("EBCDIC-CP-NO", "cp277");
charsets.put ("EBCDIC-CP-FI", "cp278");
charsets.put ("EBCDIC-CP-SE", "cp278");
charsets.put ("EBCDIC-CP-IT", "cp280");
charsets.put ("EBCDIC-CP-ES", "cp284");
charsets.put ("EBCDIC-CP-GB", "cp285");
charsets.put ("EBCDIC-CP-FR", "cp297");
charsets.put ("EBCDIC-CP-AR1", "cp420");
charsets.put ("EBCDIC-CP-HE", "cp424");
charsets.put ("EBCDIC-CP-BE", "cp500");
charsets.put ("EBCDIC-CP-CH", "cp500");
charsets.put ("EBCDIC-CP-ROECE", "cp870");
charsets.put ("EBCDIC-CP-YU", "cp870");
charsets.put ("EBCDIC-CP-IS", "cp871");
charsets.put ("EBCDIC-CP-AR2", "cp918");
// IANA also defines two that JDK 1.2 doesn't handle:
// EBCDIC-CP-GR --> CP423
// EBCDIC-CP-TR --> CP905
}
// returns an encoding name supported by JDK >= 1.1.6
// for some cases required by the XML spec
private static String std2java (String encoding)
{
String temp = encoding.toUpperCase ();
temp = (String) charsets.get (temp);
return (temp != null) ? temp : encoding;
}
/** Returns the standard name of the encoding in use */
public String getEncoding ()
{
return assignedEncoding;
}
private XmlReader (InputStream stream) throws IOException
{
super (stream);
PushbackInputStream pb;
byte buf [];
int len;
/*if (stream instanceof PushbackInputStream)
pb = (PushbackInputStream) stream;
else*/
/**
* Commented out the above code to make sure it works when the
* document is accessed using http. URL connection in the code uses
* a PushbackInputStream with size 7 and when we try to push back
* MAX which default value is set to 512 we get and exception. So
* that's why we need to wrap the stream irrespective of what type
* of stream we start off with.
*/
pb = new PushbackInputStream (stream, MAXPUSHBACK);
//
// See if we can figure out the character encoding used
// in this file by peeking at the first few bytes.
//
buf = new byte [4];
len = pb.read (buf);
if (len > 0)
pb.unread (buf, 0, len);
if (len == 4) switch (buf [0] & 0x0ff) {
case 0:
// 00 3c 00 3f == illegal UTF-16 big-endian
if (buf [1] == 0x3c && buf [2] == 0x00 && buf [3] == 0x3f) {
setEncoding (pb, "UnicodeBig");
return;
}
// else it's probably UCS-4
break;
case '<': // 0x3c: the most common cases!
switch (buf [1] & 0x0ff) {
// First character is '<'; could be XML without
// an XML directive such as "<hello>", "<!-- ...",
// and so on.
default:
break;
// 3c 00 3f 00 == illegal UTF-16 little endian
case 0x00:
if (buf [2] == 0x3f && buf [3] == 0x00) {
setEncoding (pb, "UnicodeLittle");
return;
}
// else probably UCS-4
break;
// 3c 3f 78 6d == ASCII and supersets '<?xm'
case '?':
if (buf [2] != 'x' || buf [3] != 'm')
break;
//
// One of several encodings could be used:
// Shift-JIS, ASCII, UTF-8, ISO-8859-*, etc
//
useEncodingDecl (pb, "UTF8");
return;
}
break;
// 4c 6f a7 94 ... some EBCDIC code page
case 0x4c:
if (buf [1] == 0x6f
&& (0x0ff & buf [2]) == 0x0a7
&& (0x0ff & buf [3]) == 0x094) {
useEncodingDecl (pb, "CP037");
return;
}
// whoops, treat as UTF-8
break;
// UTF-16 big-endian
case 0xfe:
if ((buf [1] & 0x0ff) != 0xff)
break;
setEncoding (pb, "UTF-16");
return;
// UTF-16 little-endian
case 0xff:
if ((buf [1] & 0x0ff) != 0xfe)
break;
setEncoding (pb, "UTF-16");
return;
// default ... no XML declaration
default:
break;
}
//
// If all else fails, assume XML without a declaration, and
// using UTF-8 encoding.
//
setEncoding (pb, "UTF-8");
}
/*
* Read the encoding decl on the stream, knowing that it should
* be readable using the specified encoding (basically, ASCII or
* EBCDIC). The body of the document may use a wider range of
* characters than the XML/Text decl itself, so we switch to use
* the specified encoding as soon as we can. (ASCII is a subset
* of UTF-8, ISO-8859-*, ISO-2022-JP, EUC-JP, and more; EBCDIC
* has a variety of "code pages" that have these characters as
* a common subset.)
*/
private void useEncodingDecl (PushbackInputStream pb, String encoding)
throws IOException
{
byte buffer[] = new byte [MAXPUSHBACK];
int len;
Reader r;
int c;
//
// Buffer up a bunch of input, and set up to read it in
// the specified encoding ... we can skip the first four
// bytes since we know that "<?xm" was read to determine
// what encoding to use!
//
len = pb.read (buffer, 0, buffer.length);
pb.unread (buffer, 0, len);
r = new InputStreamReader (
new ByteArrayInputStream (buffer, 4, len),
encoding);
//
// Next must be "l" (and whitespace) else we conclude
// error and choose UTF-8.
//
if ((c = r.read ()) != 'l') {
setEncoding (pb, "UTF-8");
return;
}
//
// Then, we'll skip any
// S version="..." [or single quotes]
// bit and get any subsequent
// S encoding="..." [or single quotes]
//
// We put an arbitrary size limit on how far we read; lots
// of space will break this algorithm.
//
StringBuffer buf = new StringBuffer ();
StringBuffer keyBuf = null;
String key = null;
boolean sawEq = false;
char quoteChar = 0;
boolean sawQuestion = false;
XmlDecl:
for (int i = 0; i < MAXPUSHBACK - 5; ++i) {
if ((c = r.read ()) == -1)
break;
// ignore whitespace before/between "key = 'value'"
if (c == ' ' || c == '\t' || c == '\n' || c == '\r')
continue;
// ... but require at least a little!
if (i == 0)
break;
// terminate the loop ASAP
if (c == '?')
sawQuestion = true;
else if (sawQuestion) {
if (c == '>')
break;
sawQuestion = false;
}
// did we get the "key =" bit yet?
if (key == null || !sawEq) {
if (keyBuf == null) {
if (Character.isWhitespace ((char) c))
continue;
keyBuf = buf;
buf.setLength (0);
buf.append ((char)c);
sawEq = false;
} else if (Character.isWhitespace ((char) c)) {
key = keyBuf.toString ();
} else if (c == '=') {
if (key == null)
key = keyBuf.toString ();
sawEq = true;
keyBuf = null;
quoteChar = 0;
} else
keyBuf.append ((char)c);
continue;
}
// space before quoted value
if (Character.isWhitespace ((char) c))
continue;
if (c == '"' || c == '\'') {
if (quoteChar == 0) {
quoteChar = (char) c;
buf.setLength (0);
continue;
} else if (c == quoteChar) {
if ("encoding".equals (key)) {
assignedEncoding = buf.toString ();
// [81] Encname ::= [A-Za-z] ([A-Za-z0-9._]|'-')*
for (i = 0; i < assignedEncoding.length(); i++) {
c = assignedEncoding.charAt (i);
if ((c >= 'A' && c <= 'Z')
|| (c >= 'a' && c <= 'z'))
continue;
if (i == 0)
break XmlDecl;
if (i > 0 && (c == '-'
|| (c >= '0' && c <= '9')
|| c == '.' || c == '_'))
continue;
// map illegal names to UTF-8 default
break XmlDecl;
}
setEncoding (pb, assignedEncoding);
return;
} else {
key = null;
continue;
}
}
}
buf.append ((char) c);
}
setEncoding (pb, "UTF-8");
}
private void setEncoding (InputStream stream, String encoding)
throws IOException
{
assignedEncoding = encoding;
in = createReader (stream, encoding);
}
/**
* Reads the number of characters read into the buffer, or -1 on EOF.
*/
public int read(char buf [], int off, int len) throws IOException
{
int val;
if (closed)
return -1; // throw new IOException ("closed");
val = in.read (buf, off, len);
if (val == -1)
close ();
return val;
}
/**
* Reads a single character.
*/
public int read () throws IOException
{
int val;
if (closed) {
throw new IOException("Stream closed");
}
val = in.read();
if (val == -1) {
close();
}
return val;
}
/**
* Returns true iff the reader supports mark/reset.
*/
public boolean markSupported ()
{
return in == null ? false : in.markSupported ();
}
/**
* Sets a mark allowing a limited number of characters to
* be "peeked", by reading and then resetting.
* @param value how many characters may be "peeked".
*/
public void mark (int value) throws IOException
{
if (in != null) in.mark (value);
}
/**
* Resets the current position to the last marked position.
*/
public void reset () throws IOException
{
if (in != null) in.reset ();
}
/**
* Skips a specified number of characters.
*/
public long skip (long value) throws IOException
{
return in == null ? 0 : in.skip (value);
}
/**
* Returns true iff input characters are known to be ready.
*/
public boolean ready () throws IOException
{
return in == null ? false : in.ready ();
}
/**
* Closes the reader.
*/
public void close() throws IOException
{
if (closed)
return;
in.close ();
in = null;
closed = true;
}
//
// Delegating to a converter module will always be slower than
// direct conversion. Use a similar approach for any other
// readers that need to be particularly fast; only block I/O
// speed matters to this package. For UTF-16, separate readers
// for big and little endian streams make a difference, too;
// fewer conditionals in the critical path!
//
public static abstract class BaseReader extends Reader
{
protected InputStream instream;
protected byte buffer [];
protected int start, finish;
BaseReader (InputStream stream)
{
super (stream);
instream = stream;
buffer = new byte [8192];
}
public abstract String getEncoding();
public boolean ready () throws IOException
{
return instream == null
|| (finish - start) > 0
|| instream.available () != 0;
}
// caller shouldn't read again
public void close () throws IOException
{
if (instream != null) {
instream.close ();
start = finish = 0;
buffer = null;
instream = null;
}
}
}
//
// We want this reader, to make the default encoding be as fast
// as we can make it. JDK's "UTF8" (not "UTF-8" till JDK 1.2)
// InputStreamReader works, but 20+% slower speed isn't OK for
// the default/primary encoding.
//
static final class Utf8Reader extends BaseReader
{
// 2nd half of UTF-8 surrogate pair
private char nextChar;
Utf8Reader (InputStream stream)
{
super (stream);
}
public String getEncoding() { return "UTF-8"; }
public int read (char buf [], int offset, int len) throws IOException
{
int i = 0, c = 0;
if (len <= 0)
return 0;
// avoid many runtime bounds checks ... a good optimizer
// (static or JIT) will now remove checks from the loop.
if ((offset + len) > buf.length || offset < 0)
throw new ArrayIndexOutOfBoundsException ();
// Consume remaining half of any surrogate pair immediately
if (nextChar != 0) {
buf [offset + i++] = nextChar;
nextChar = 0;
}
while (i < len) {
// stop or read data if needed
if (finish <= start) {
if (instream == null) {
c = -1;
break;
}
start = 0;
finish = instream.read (buffer, 0, buffer.length);
if (finish <= 0) {
this.close ();
c = -1;
break;
}
}
// RFC 2279 describes UTF-8; there are six encodings.
// Each encoding takes a fixed number of characters
// (1-6 bytes) and is flagged by a bit pattern in the
// first byte. The five and six byte-per-character
// encodings address characters which are disallowed
// in XML documents, as do some four byte ones.
// Single byte == ASCII. Common; optimize.
//
c = buffer [start] & 0x0ff;
if ((c & 0x80) == 0x00) {
// 0x0000 <= c <= 0x007f
start++;
buf [offset + i++] = (char) c;
continue;
}
//
// Multibyte chars -- check offsets optimistically,
// ditto the "10xx xxxx" format for subsequent bytes
//
int off = start;
try {
// 2 bytes
if ((buffer [off] & 0x0E0) == 0x0C0) {
c = (buffer [off++] & 0x1f) << 6;
c += buffer [off++] & 0x3f;
// 0x0080 <= c <= 0x07ff
// 3 bytes
} else if ((buffer [off] & 0x0F0) == 0x0E0) {
c = (buffer [off++] & 0x0f) << 12;
c += (buffer [off++] & 0x3f) << 6;
c += buffer [off++] & 0x3f;
// 0x0800 <= c <= 0xffff
// 4 bytes
} else if ((buffer [off] & 0x0f8) == 0x0F0) {
c = (buffer [off++] & 0x07) << 18;
c += (buffer [off++] & 0x3f) << 12;
c += (buffer [off++] & 0x3f) << 6;
c += buffer [off++] & 0x3f;
// 0x0001 0000 <= c <= 0x001f ffff
// Unicode supports c <= 0x0010 ffff ...
if (c > 0x0010ffff)
throw new CharConversionException (
"UTF-8 encoding of character 0x00"
+ Integer.toHexString (c)
+ " can't be converted to Unicode."
);
else if (c > 0xffff) {
// Convert UCS-4 char to surrogate pair (UTF-16)
c -= 0x10000;
nextChar = (char) (0xDC00 + (c & 0x03ff));
c = 0xD800 + (c >> 10);
}
// 5 and 6 byte versions are XML WF errors, but
// typically come from mislabeled encodings
} else
throw new CharConversionException (
"Unconvertible UTF-8 character"
+ " beginning with 0x"
+ Integer.toHexString (
buffer [start] & 0xff)
);
} catch (ArrayIndexOutOfBoundsException e) {
// off > length && length >= buffer.length
c = 0;
}
//
// if the buffer held only a partial character,
// compact it and try to read the rest of the
// character. worst case involves three
// single-byte reads -- quite rare.
//
if (off > finish) {
System.arraycopy (buffer, start,
buffer, 0, finish - start);
finish -= start;
start = 0;
off = instream.read (buffer, finish,
buffer.length - finish);
if (off < 0) {
this.close ();
throw new CharConversionException (
"Partial UTF-8 char");
}
finish += off;
continue;
}
//
// check the format of the non-initial bytes
//
for (start++; start < off; start++) {
if ((buffer [start] & 0xC0) != 0x80) {
this.close ();
throw new CharConversionException (
"Malformed UTF-8 char -- "
+ "is an XML encoding declaration missing?"
);
}
}
//
// If this needed a surrogate pair, consume ASAP
//
buf [offset + i++] = (char) c;
if (nextChar != 0 && i < len) {
buf [offset + i++] = nextChar;
nextChar = 0;
}
}
if (i > 0)
return i;
return (c == -1) ? -1 : 0;
}
}
//
// We want ASCII and ISO-8859 Readers since they're the most common
// encodings in the US and Europe, and we don't want performance
// regressions for them. They're also easy to implement efficiently,
// since they're bitmask subsets of UNICODE.
//
// XXX haven't benchmarked these readers vs what we get out of JDK.
//
static final class AsciiReader extends BaseReader
{
AsciiReader (InputStream in) { super (in); }
public String getEncoding() { return "US-ASCII"; }
public int read (char buf [], int offset, int len) throws IOException
{
if (instream == null) {
return -1;
}
// avoid many runtime bounds checks ... a good optimizer
// (static or JIT) will now remove checks from the loop.
if ((offset + len) > buf.length || offset < 0)
throw new ArrayIndexOutOfBoundsException ();
/* 07-Mar-2006, TSa: Actually, it's bad idea to try to fill the
* whole buffer -- if this is a blocking source (network socket
* for example), we may be blocking too early.
*/
// So, do we need to try to read more?
int avail = (finish - start);
if (avail < 1) {
start = 0;
finish = instream.read (buffer, 0, buffer.length);
if (finish <= 0) {
this.close();
return -1;
}
if (len > finish) {
len = finish;
}
} else {
if (len > avail) {
len = avail;
}
}
for (int i = 0; i < len; i++) {
int c = buffer[start++];
if (c < 0) {
throw new CharConversionException ("Illegal ASCII character, 0x"
+ Integer.toHexString(c & 0xff));
}
buf [offset + i] = (char) c;
}
return len;
}
}
static final class Iso8859_1Reader extends BaseReader
{
Iso8859_1Reader (InputStream in) { super (in); }
public String getEncoding() { return "ISO-8859-1"; }
public int read (char buf [], int offset, int len) throws IOException
{
if (instream == null)
return -1;
// avoid many runtime bounds checks ... a good optimizer
// (static or JIT) will now remove checks from the loop.
if ((offset + len) > buf.length || offset < 0)
throw new ArrayIndexOutOfBoundsException ();
/* 07-Mar-2006, TSa: Actually, it's bad idea to try to fill the
* whole buffer -- if this is a blocking source (network socket
* for example), we may be blocking too early.
*/
// So, do we need to try to read more?
int avail = (finish - start);
if (avail < 1) {
start = 0;
finish = instream.read (buffer, 0, buffer.length);
if (finish <= 0) {
this.close();
return -1;
}
if (len > finish) {
len = finish;
}
} else {
if (len > avail) {
len = avail;
}
}
for (int i = 0; i < len; i++) {
buf [offset + i] = (char) (buffer[start++] & 0xFF);
}
return len;
}
}
}
]]>