bufferedreadernew.java

来自「一个eclipse插件源代码。用于web开发」· Java 代码 · 共 496 行

/*
 * $Header: /home/cvs/WEBPUMP2.0/WebPumpIDE_Src/WebPumpIDE/src/com/webpump/ui/sql/BufferedReaderNew.java,v 1.1.1.1 2004/07/01 09:07:52 wang_j Exp $
 * $Revision: 1.1.1.1 $
 * $Date: 2004/07/01 09:07:52 $
 *
 * ====================================================================
 *
 * The NanJing HopeRun(IT-FOREST) Software License, Version 2.0.0
 *
 * Copyright 2003-2004 by NanJing HopeRun(IT-FOREST) Information System Co., Ltd, CHINA and
 *                        IT Forest Corporation
 * All rights reserved.
 *
 * This software is the confidential and proprietary information of
 * HopeRun(IT-FOREST) Information System Co., Ltd, CHINA and IT Forest Corporation.
 * You shall not disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into with
 * HopeRun(IT-FOREST) Information System Co., Ltd, CHINA and IT Forest Corporation.
 */
 
package com.webpump.ui.sql;

import java.io.Reader;
import java.io.IOException;
/**
 * Read text from a character-input stream, buffering characters so as to
 * provide for the efficient reading of characters, arrays, and lines..
 * 
 * @author luo_sa
 * @version 2.0.0 2004-2-24
 */
public class BufferedReaderNew extends Reader {

	private Reader in;

	private char cb[];
	private int nChars, nextChar;

	private static final int INVALIDATED = -2;
	private static final int UNMARKED = -1;
	private int markedChar = UNMARKED;
	private int readAheadLimit = 0; /* Valid only when markedChar > 0 */

	/** If the next character is a line feed, skip it */
	private boolean skipLF = false;

	/** The skipLF flag when the mark was set */
	private boolean markedSkipLF = false;

	private static int defaultCharBufferSize = 8192;
	private static int defaultExpectedLineLength = 80;

	/**
	 * Create a buffering character-input stream that uses an input buffer of
	 * the specified size.
	 *
	 * @param  in   A Reader
	 * @param  sz   Input-buffer size
	 *
	 * @exception  IllegalArgumentException  If sz is <= 0
	 */
	public BufferedReaderNew(Reader in, int sz) {
		super(in);
		if (sz <= 0)
			throw new IllegalArgumentException("Buffer size <= 0");
		this.in = in;
		cb = new char[sz];
		nextChar = nChars = 0;
	}

	/**
	 * Create a buffering character-input stream that uses a default-sized
	 * input buffer.
	 *
	 * @param  in   A Reader
	 */
	public BufferedReaderNew(Reader in) {
	this(in, defaultCharBufferSize);
	}

	/** Check to make sure that the stream has not been closed */
	private void ensureOpen() throws IOException {
	if (in == null)
		throw new IOException("Stream closed");
	}

	/**
	 * Fill the input buffer, taking the mark into account if it is valid.
	 */
	private void fill() throws IOException {
	int dst;
	if (markedChar <= UNMARKED) {
		/* No mark */
		dst = 0;
	} else {
		/* Marked */
		int delta = nextChar - markedChar;
		if (delta >= readAheadLimit) {
		/* Gone past read-ahead limit: Invalidate mark */
		markedChar = INVALIDATED;
		readAheadLimit = 0;
		dst = 0;
		} else {
		if (readAheadLimit <= cb.length) {
			/* Shuffle in the current buffer */
			System.arraycopy(cb, markedChar, cb, 0, delta);
			markedChar = 0;
			dst = delta;
		} else {
			/* Reallocate buffer to accomodate read-ahead limit */
			char ncb[] = new char[readAheadLimit];
			System.arraycopy(cb, markedChar, ncb, 0, delta);
			cb = ncb;
			markedChar = 0;
			dst = delta;
		}
				nextChar = nChars = delta;
		}
	}

	int n;
	do {
		n = in.read(cb, dst, cb.length - dst);
	} while (n == 0);
	if (n > 0) {
		nChars = dst + n;
		nextChar = dst;
	}
	}

	/**
	 * Read a single character.
	 *
	 * @return The character read, as an integer in the range
	 *         0 to 65535 (<tt>0x00-0xffff</tt>), or -1 if the
	 *         end of the stream has been reached
	 * @exception  IOException  If an I/O error occurs
	 */
	public int read() throws IOException {
	synchronized (lock) {
		ensureOpen();
		for (;;) {
		if (nextChar >= nChars) {
			fill();
			if (nextChar >= nChars)
			return -1;
		}
		if (skipLF) {
			skipLF = false;
			if (cb[nextChar] == '\n') {
			nextChar++;
			continue;
			}
		}
		return cb[nextChar++];
		}
	}
	}

	/**
	 * Read characters into a portion of an array, reading from the underlying
	 * stream if necessary.
	 */
	private int read1(char[] cbuf, int off, int len) throws IOException {
	if (nextChar >= nChars) {
		/* If the requested length is at least as large as the buffer, and
		   if there is no mark/reset activity, and if line feeds are not
		   being skipped, do not bother to copy the characters into the
		   local buffer.  In this way buffered streams will cascade
		   harmlessly. */
		if (len >= cb.length && markedChar <= UNMARKED && !skipLF) {
		return in.read(cbuf, off, len);
		}
		fill();
	}
	if (nextChar >= nChars) return -1;
	if (skipLF) {
		skipLF = false;
		if (cb[nextChar] == '\n') {
		nextChar++;
		if (nextChar >= nChars)
			fill();
		if (nextChar >= nChars)
			return -1;
		}
	}
	int n = Math.min(len, nChars - nextChar);
	System.arraycopy(cb, nextChar, cbuf, off, n);
	nextChar += n;
	return n;
	}

	/**
	 * Read characters into a portion of an array.
	 *
	 * <p> This method implements the general contract of the corresponding
	 * <code>{@link Reader#read(char[], int, int) read}</code> method of the
	 * <code>{@link Reader}</code> class.  As an additional convenience, it
	 * attempts to read as many characters as possible by repeatedly invoking
	 * the <code>read</code> method of the underlying stream.  This iterated
	 * <code>read</code> continues until one of the following conditions becomes
	 * true: <ul>
	 *
	 *   <li> The specified number of characters have been read,
	 *
	 *   <li> The <code>read</code> method of the underlying stream returns
	 *   <code>-1</code>, indicating end-of-file, or
	 *
	 *   <li> The <code>ready</code> method of the underlying stream
	 *   returns <code>false</code>, indicating that further input requests
	 *   would block.
	 *
	 * </ul> If the first <code>read</code> on the underlying stream returns
	 * <code>-1</code> to indicate end-of-file then this method returns
	 * <code>-1</code>.  Otherwise this method returns the number of characters
	 * actually read.
	 *
	 * <p> Subclasses of this class are encouraged, but not required, to
	 * attempt to read as many characters as possible in the same fashion.
	 *
	 * <p> Ordinarily this method takes characters from this stream's character
	 * buffer, filling it from the underlying stream as necessary.  If,
	 * however, the buffer is empty, the mark is not valid, and the requested
	 * length is at least as large as the buffer, then this method will read
	 * characters directly from the underlying stream into the given array.
	 * Thus redundant <code>BufferedReader</code>s will not copy data
	 * unnecessarily.
	 *
	 * @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 -1 if the end of the
	 *             stream has been reached
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	public int read(char cbuf[], int off, int len) throws IOException {
		synchronized (lock) {
		ensureOpen();
			if ((off < 0) || (off > cbuf.length) || (len < 0) ||
				((off + len) > cbuf.length) || ((off + len) < 0)) {
				throw new IndexOutOfBoundsException();
			} else if (len == 0) {
				return 0;
			}

		int n = read1(cbuf, off, len);
		if (n <= 0) return n;
		while ((n < len) && in.ready()) {
		int n1 = read1(cbuf, off + n, len - n);
		if (n1 <= 0) break;
		n += n1;
		}
		return n;
	}
	}

	/**
	 * Read a line of text.  A line is considered to be terminated by any one
	 * of a line feed ('\n'), a carriage return ('\r'), or a carriage return
	 * followed immediately by a linefeed.
	 *
	 * @param      ignoreLF  If true, the next '\n' will be skipped
	 *
	 * @return     A String containing the contents of the line, not including
	 *             any line-termination characters, or null if the end of the
	 *             stream has been reached
	 * 
	 * @see        java.io.LineNumberReader#readLine()
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	String readLine(boolean ignoreLF) throws IOException {
	StringBuffer s = null;
	int startChar;
	boolean omitLF = ignoreLF || skipLF;

		synchronized (lock) {
			ensureOpen();

	bufferLoop:
		for (;;) {

		if (nextChar >= nChars)
			fill();
		if (nextChar >= nChars) { /* EOF */
			if (s != null && s.length() > 0)
			return s.toString();
			else
			return null;
		}
		boolean eol = false;
		char c = 0;
		int i;

				/* Skip a leftover '\n', if necessary */
		if (omitLF && (cb[nextChar] == '\n')) 
					nextChar++;
		skipLF = false;
		omitLF = false;

		charLoop:
		for (i = nextChar; i < nChars; i++) {
			c = cb[i];
			if (c == '\r') {
			eol = true;
			break charLoop;
			}
		}

		startChar = nextChar;
		nextChar = i;

		if (eol) {
			String str;
			if (s == null) {
			str = new String(cb, startChar, i - startChar);
			} else {
			s.append(cb, startChar, i - startChar);
			str = s.toString();
			}
			nextChar++;
			if (c == '\r') {
			skipLF = true;
			}
			return str;
		}
		
		if (s == null) 
			s = new StringBuffer(defaultExpectedLineLength);
		s.append(cb, startChar, i - startChar);
		}
		}
	}

	/**
	 * Read a line of text.  A line is considered to be terminated by any one
	 * of a line feed ('\n'), a carriage return ('\r'), or a carriage return
	 * followed immediately by a linefeed.
	 *
	 * @return     A String containing the contents of the line, not including
	 *             any line-termination characters, or null if the end of the
	 *             stream has been reached
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	public String readLine() throws IOException {
		return readLine(true);
	}

	/**
	 * Skip characters.
	 *
	 * @param  n  The number of characters to skip
	 *
	 * @return    The number of characters actually skipped
	 *
	 * @exception  IllegalArgumentException  If <code>n</code> is negative.
	 * @exception  IOException  If an I/O error occurs
	 */
	public long skip(long n) throws IOException {
	if (n < 0L) {
		throw new IllegalArgumentException("skip value is negative");
	}
	synchronized (lock) {
		ensureOpen();
		long r = n;
		while (r > 0) {
		if (nextChar >= nChars)
			fill();
		if (nextChar >= nChars)	/* EOF */
			break;
		if (skipLF) {
			skipLF = false;
			if (cb[nextChar] == '\n') {
			nextChar++;
			}
		}
		long d = nChars - nextChar;
		if (r <= d) {
			nextChar += r;
			r = 0;
			break;
		}
		else {
			r -= d;
			nextChar = nChars;
		}
		}
		return n - r;
	}
	}

	/**
	 * Tell whether this stream is ready to be read.  A buffered character
	 * stream is ready if the buffer is not empty, or if the underlying
	 * character stream is ready.
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	public boolean ready() throws IOException {
	synchronized (lock) {
		ensureOpen();

		/* 
		 * If newline needs to be skipped and the next char to be read
		 * is a newline character, then just skip it right away.
		 */
		if (skipLF) {
		/* Note that in.ready() will return true if and only if the next 
		 * read on the stream will not block.
		 */
		if (nextChar >= nChars && in.ready()) {
			fill();
		}
		if (nextChar < nChars) {
			if (cb[nextChar] == '\n') 
			nextChar++;
			skipLF = false;
		} 
		}
		return (nextChar < nChars) || in.ready();
	}
	}

	/**
	 * Tell whether this stream supports the mark() operation, which it does.
	 */
	public boolean markSupported() {
	return true;
	}

	/**
	 * Mark the present position in the stream.  Subsequent calls to reset()
	 * will attempt to reposition the stream to this point.
	 *
	 * @param readAheadLimit   Limit on the number of characters that may be
	 *                         read while still preserving the mark.  After
	 *                         reading this many characters, attempting to
	 *                         reset the stream may fail.  A limit value larger
	 *                         than the size of the input buffer will cause a
	 *                         new buffer to be allocated whose size is no
	 *                         smaller than limit.  Therefore large values
	 *                         should be used with care.
	 *
	 * @exception  IllegalArgumentException  If readAheadLimit is < 0
	 * @exception  IOException  If an I/O error occurs
	 */
	public void mark(int readAheadLimit) throws IOException {
	if (readAheadLimit < 0) {
		throw new IllegalArgumentException("Read-ahead limit < 0");
	}
	synchronized (lock) {
		ensureOpen();
		this.readAheadLimit = readAheadLimit;
		markedChar = nextChar;
		markedSkipLF = skipLF;
	}
	}

	/**
	 * Reset the stream to the most recent mark.
	 *
	 * @exception  IOException  If the stream has never been marked,
	 *                          or if the mark has been invalidated
	 */
	public void reset() throws IOException {
	synchronized (lock) {
		ensureOpen();
		if (markedChar < 0)
		throw new IOException((markedChar == INVALIDATED)
					  ? "Mark invalid"
					  : "Stream not marked");
		nextChar = markedChar;
		skipLF = markedSkipLF;
	}
	}

	/**
	 * Close the stream.
	 *
	 * @exception  IOException  If an I/O error occurs
	 */
	public void close() throws IOException {
	synchronized (lock) {
		if (in == null)
		return;
		in.close();
		in = null;
		cb = null;
	}
	}

}