// HTMLParser Library $Name: v1_6_20060319 $ - A java-based parser for HTML
// http://sourceforge.org/projects/htmlparser
// Copyright (C) 2004 Derrick Oswald
//
// Revision Control Information
//
// $Source: /cvsroot/htmlparser/htmlparser/src/org/htmlparser/lexer/Source.java,v $
// $Author: derrickoswald $
// $Date: 2005/05/15 11:49:04 $
// $Revision: 1.20 $
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
package org.htmlparser.lexer;
import java.io.IOException;
import java.io.Reader;
import java.io.Serializable;
import org.htmlparser.util.ParserException;
/**
* A buffered source of characters.
* A Source is very similar to a Reader, like:
* <pre>
* new InputStreamReader (connection.getInputStream (), charset)
* </pre>
* It differs from the above, in three ways:
* <ul>
* <li>the fetching of bytes may be asynchronous</li>
* <li>the character set may be changed, which resets the input stream</li>
* <li>characters may be requested more than once, so in general they
* will be buffered</li>
* </ul>
*/
public abstract class Source
extends
Reader
implements
Serializable
{
/**
* Return value when the source is exhausted.
* Has a value of {@value}.
*/
public static final int EOF = -1;
/**
* Get the encoding being used to convert characters.
* @return The current encoding.
*/
public abstract String getEncoding ();
/**
* Set the encoding to the given character set.
* If the current encoding is the same as the requested encoding,
* this method is a no-op. Otherwise any subsequent characters read from
* this source will have been decoded using the given character set.<p>
* If characters have already been consumed from this source, it is expected
* that an exception will be thrown if the characters read so far would
* be different if the encoding being set was used from the start.
* @param character_set The character set to use to convert characters.
* @exception ParserException If a character mismatch occurs between
* characters already provided and those that would have been returned
* had the new character set been in effect from the beginning. An
* exception is also thrown if the character set is not recognized.
*/
public abstract void setEncoding (String character_set)
throws
ParserException;
//
// Reader overrides
//
/**
* Does nothing.
* It's supposed to close the source, but use {@link #destroy} instead.
* @exception IOException <em>not used</em>
* @see #destroy
*/
public abstract void close () throws IOException;
/**
* Read a single character.
* This method will block until a character is available,
* an I/O error occurs, or the source is exhausted.
* @return The character read, as an integer in the range 0 to 65535
* (<tt>0x00-0xffff</tt>), or {@link #EOF} if the source is exhausted.
* @exception IOException If an I/O error occurs.
*/
public abstract int read () throws IOException;
/**
* Read characters into a portion of an array. This method will block
* until some input is available, an I/O error occurs, or the source is
* exhausted.
* @param cbuf Destination buffer
* @param off Offset at which to start storing characters
* @param len Maximum number of characters to read
* @return The number of characters read, or {@link #EOF} if the source is
* exhausted.
* @exception IOException If an I/O error occurs.
*/
public abstract int read (char[] cbuf, int off, int len) throws IOException;
/**
* Read characters into an array.
* This method will block until some input is available, an I/O error occurs,
* or the source is exhausted.
* @param cbuf Destination buffer.
* @return The number of characters read, or {@link #EOF} if the source is
* exhausted.
* @exception IOException If an I/O error occurs.
*/
public abstract int read (char[] cbuf) throws IOException;
/**
* Tell whether this source is ready to be read.
* @return <code>true</code> if the next read() is guaranteed not to block
* for input, <code>false</code> otherwise.
* Note that returning false does not guarantee that the next read will block.
* @exception IOException If an I/O error occurs.
*/
public abstract boolean ready () throws IOException;
/**
* Reset the source.
* Repositions the read point to begin at zero.
*/
public abstract void reset ();
/**
* Tell whether this source supports the mark() operation.
* @return <code>true</code> if and only if this source supports the mark
* operation.
*/
public abstract boolean markSupported ();
/**
* Mark the present position.
* Subsequent calls to {@link #reset}
* will attempt to reposition the source to this point. Not all
* sources support the mark() operation.
* @param readAheadLimit The minimum number of characters that can be read
* before this mark becomes invalid.
* @exception IOException If an I/O error occurs.
*/
public abstract void mark (int readAheadLimit) throws IOException;
/**
* Skip characters.
* This method will block until some characters are available,
* an I/O error occurs, or the source is exhausted.
* <em>Note: n is treated as an int</em>
* @param n The number of characters to skip.
* @return The number of characters actually skipped
* @exception IOException If an I/O error occurs.
*/
public abstract long skip (long n) throws IOException;
//
// Methods not in your Daddy's Reader
//
/**
* Undo the read of a single character.
* @exception IOException If the source is closed or no characters have
* been read.
*/
public abstract void unread () throws IOException;
/**
* Retrieve a character again.
* @param offset The offset of the character.
* @return The character at <code>offset</code>.
* @exception IOException If the source is closed or the offset is beyond
* {@link #offset()}.
*/
public abstract char getCharacter (int offset) throws IOException;
/**
* Retrieve characters again.
* @param array The array of characters.
* @param offset The starting position in the array where characters are to be placed.
* @param start The starting position, zero based.
* @param end The ending position
* (exclusive, i.e. the character at the ending position is not included),
* zero based.
* @exception IOException If the source is closed or the start or end is
* beyond {@link #offset()}.
*/
public abstract void getCharacters (char[] array, int offset, int start, int end) throws IOException;
/**
* Retrieve a string comprised of characters already read.
* @param offset The offset of the first character.
* @param length The number of characters to retrieve.
* @return A string containing the <code>length</code> characters at <code>offset</code>.
* @exception IOException If the source is closed.
*/
public abstract String getString (int offset, int length) throws IOException;
/**
* Append characters already read into a <code>StringBuffer</code>.
* @param buffer The buffer to append to.
* @param offset The offset of the first character.
* @param length The number of characters to retrieve.
* @exception IOException If the source is closed or the offset or
* (offset + length) is beyond {@link #offset()}.
*/
public abstract void getCharacters (StringBuffer buffer, int offset, int length) throws IOException;
/**
* Close the source.
* Once a source has been closed, further {@link #read() read},
* {@link #ready ready}, {@link #mark mark}, {@link #reset reset},
* {@link #skip skip}, {@link #unread unread},
* {@link #getCharacter getCharacter} or {@link #getString getString}
* invocations will throw an IOException.
* Closing a previously-closed source, however, has no effect.
* @exception IOException If an I/O error occurs.
*/
public abstract void destroy () throws IOException;
/**
* Get the position (in characters).
* @return The number of characters that have already been read, or
* {@link #EOF} if the source is closed.
*/
public abstract int offset ();
/**
* Get the number of available characters.
* @return The number of characters that can be read without blocking.
*/
public abstract int available ();
}