374 lines
10 KiB
Java
374 lines
10 KiB
Java
/* Copyright (C) 1998, 1999 Cygnus Solutions
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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package java.io;
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/**
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* @author Per Bothner <bothner@cygnus.com>
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* @date April 22, 1998.
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*/
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/* Written using "Java Class Libraries", 2nd edition, plus online
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* API docs for JDK 1.2 beta from http://www.javasoft.com.
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* Status: Believed complete and correct.
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*/
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public class BufferedReader extends Reader
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{
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Reader in;
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char[] buffer;
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/* Index of current read position. Must be >= 0 and <= limit. */
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/* There is a special case where pos may be equal to limit+1; this
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* is used as an indicator that a readLine was done with a '\r' was
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* the very last char in the buffer. Since we don't want to read-ahead
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* and potentially block, we set pos this way to indicate the situation
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* and deal with it later. Doing it this way rather than having a
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* separate boolean field to indicate the condition has the advantage
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* that it is self-clearing on things like mark/reset.
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*/
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int pos;
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/* Limit of valid data in buffer. Must be >= pos and <= buffer.length. */
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/* This can be < pos in the one special case described above. */
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int limit;
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/* The value -1 means there is no mark, or the mark has been invalidated.
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Otherwise, markPos is the index in the buffer of the marked position.
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Must be >= 0 and <= pos.
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Note we do not explicitly store the read-limit.
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The implicit read-limit is (buffer.length - markPos), which is
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guaranteed to be >= the read-limit requested in the call to mark. */
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int markPos = -1;
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public BufferedReader(Reader in)
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{
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this(in, 8192);
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}
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public BufferedReader(Reader in, int size)
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{
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super(in.lock);
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this.in = in;
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buffer = new char[size];
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}
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public void close() throws IOException
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{
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synchronized (lock)
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{
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if (in != null)
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in.close();
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in = null;
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buffer = null;
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}
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}
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public boolean markSupported()
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{
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return true;
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}
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public void mark(int readLimit) throws IOException
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{
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synchronized (lock)
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{
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// In this method we need to be aware of the special case where
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// pos + 1 == limit. This indicates that a '\r' was the last char
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// in the buffer during a readLine. We'll want to maintain that
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// condition after we shift things around and if a larger buffer is
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// needed to track readLimit, we'll have to make it one element
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// larger to ensure we don't invalidate the mark too early, if the
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// char following the '\r' is NOT a '\n'. This is ok because, per
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// the spec, we are not required to invalidate when passing readLimit.
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//
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// Note that if 'pos > limit', then doing 'limit -= pos' will cause
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// limit to be negative. This is the only way limit will be < 0.
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if (pos + readLimit > limit)
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{
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char[] old_buffer = buffer;
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int extraBuffSpace = 0;
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if (pos > limit)
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extraBuffSpace = 1;
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if (readLimit + extraBuffSpace > limit)
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buffer = new char[readLimit + extraBuffSpace];
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limit -= pos;
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if (limit >= 0)
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{
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System.arraycopy(old_buffer, pos, buffer, 0, limit);
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pos = 0;
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}
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}
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if (limit < 0)
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{
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// Maintain the relationship of 'pos > limit'.
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pos = 1;
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limit = markPos = 0;
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}
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else
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markPos = pos;
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// Now pos + readLimit <= buffer.length. thus if we need to read
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// beyond buffer.length, then we are allowed to invalidate markPos.
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}
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}
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public void reset() throws IOException
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{
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synchronized (lock)
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{
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if (markPos < 0)
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throw new IOException("mark never set or invalidated");
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// Need to handle the extremely unlikely case where a readLine was
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// done with a '\r' as the last char in the buffer; which was then
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// immediately followed by a mark and a reset with NO intervening
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// read of any sort. In that case, setting pos to markPos would
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// lose that info and a subsequent read would thus not skip a '\n'
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// (if one exists). The value of limit in this rare case is zero.
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// We can assume that if limit is zero for other reasons, then
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// pos is already set to zero and doesn't need to be readjusted.
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if (limit > 0)
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pos = markPos;
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}
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}
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public boolean ready() throws IOException
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{
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synchronized (lock)
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{
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return pos < limit || in.ready();
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}
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}
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public int read(char[] buf, int offset, int count) throws IOException
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{
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synchronized (lock)
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{
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// Once again, we need to handle the special case of a readLine
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// that has a '\r' at the end of the buffer. In this case, we'll
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// need to skip a '\n' if it is the next char to be read.
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// This special case is indicated by 'pos > limit'.
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boolean retAtEndOfBuffer = false;
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int avail = limit - pos;
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if (count > avail)
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{
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if (avail > 0)
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count = avail;
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else // pos >= limit
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{
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if (limit == buffer.length)
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markPos = -1; // read too far - invalidate the mark.
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if (pos > limit)
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{
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// Set a boolean and make pos == limit to simplify things.
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retAtEndOfBuffer = true;
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--pos;
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}
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if (markPos < 0)
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{
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// Optimization: can read directly into buf.
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if (count >= buffer.length && !retAtEndOfBuffer)
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return in.read(buf, offset, count);
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pos = limit = 0;
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}
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avail = in.read(buffer, limit, buffer.length - limit);
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if (retAtEndOfBuffer && avail > 0 && buffer[limit] == '\n')
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{
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--avail;
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limit++;
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}
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if (avail < count)
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{
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if (avail <= 0)
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return avail;
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count = avail;
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}
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limit += avail;
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}
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}
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System.arraycopy(buffer, pos, buf, offset, count);
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pos += count;
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return count;
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}
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}
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/* Read more data into the buffer. Update pos and limit appropriatly.
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Assumes pos==limit initially. May invalidate the mark if read too much.
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Return number of chars read (never 0), or -1 on eof. */
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private int fill() throws IOException
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{
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// Handle the special case of a readLine that has a '\r' at the end of
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// the buffer. In this case, we'll need to skip a '\n' if it is the
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// next char to be read. This special case is indicated by 'pos > limit'.
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boolean retAtEndOfBuffer = false;
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if (pos > limit)
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{
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retAtEndOfBuffer = true;
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--pos;
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}
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if (markPos >= 0 && limit == buffer.length)
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markPos = -1;
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if (markPos <= 0)
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pos = limit = 0;
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int count = in.read(buffer, limit, buffer.length - limit);
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if (count > 0)
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limit += count;
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if (retAtEndOfBuffer && buffer[pos] == '\n')
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{
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--count;
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pos++;
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}
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return count;
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}
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public int read() throws IOException
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{
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synchronized (lock)
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{
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if (pos >= limit && fill () <= 0)
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return -1;
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return buffer[pos++];
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}
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}
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/* Return the end of the line starting at this.pos and ending at limit.
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* The index returns is *before* any line terminators, or limit
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* if no line terminators were found.
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*/
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private int lineEnd(int limit)
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{
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int i = pos;
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for (; i < limit; i++)
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{
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char ch = buffer[i];
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if (ch == '\n' || ch == '\r')
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break;
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}
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return i;
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}
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public String readLine() throws IOException
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{
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// Handle the special case where a previous readLine (with no intervening
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// reads/skips) had a '\r' at the end of the buffer.
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// In this case, we'll need to skip a '\n' if it's the next char to be read.
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// This special case is indicated by 'pos > limit'.
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if (pos > limit)
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{
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int ch = read();
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if (ch < 0)
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return null;
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if (ch != '\n')
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--pos;
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}
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int i = lineEnd(limit);
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if (i < limit)
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{
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String str = new String(buffer, pos, i - pos);
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pos = i + 1;
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// If the last char in the buffer is a '\r', we must remember
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// to check if the next char to be read after the buffer is refilled
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// is a '\n'. If so, skip it. To indicate this condition, we set pos
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// to be limit + 1, which normally is never possible.
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if (buffer[i] == '\r')
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if (pos == limit || buffer[pos] == '\n')
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pos++;
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return str;
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}
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StringBuffer sbuf = new StringBuffer(200);
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sbuf.append(buffer, pos, i - pos);
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pos = i;
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// We only want to return null when no characters were read before
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// EOF. So we must keep track of this separately. Otherwise we
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// would treat an empty `sbuf' as an EOF condition, which is wrong
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// when there is just a newline.
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boolean eof = false;
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for (;;)
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{
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int ch = read();
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if (ch < 0)
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{
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eof = true;
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break;
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}
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if (ch == '\n' || ch == '\r')
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{
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// Check here if a '\r' was the last char in the buffer; if so,
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// mark it as in the comment above to indicate future reads
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// should skip a newline that is the next char read after
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// refilling the buffer.
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if (ch == '\r')
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if (pos == limit || buffer[pos] == '\n')
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pos++;
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break;
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}
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i = lineEnd(limit);
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sbuf.append(buffer, pos - 1, i - (pos - 1));
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pos = i;
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}
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return (sbuf.length() == 0 && eof) ? null : sbuf.toString();
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}
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public long skip(long count) throws IOException
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{
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if (count <= 0)
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return 0;
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synchronized (lock)
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{
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// Yet again, we need to handle the special case of a readLine
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// that has a '\r' at the end of the buffer. In this case, we need
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// to ignore a '\n' if it is the next char to be read.
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// This special case is indicated by 'pos > limit' (i.e. avail < 0).
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// To simplify things, if we're dealing with the special case for
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// readLine, just read the next char (since the fill method will
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// skip the '\n' for us). By doing this, we'll have to back up pos.
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// That's easier than trying to keep track of whether we've skipped
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// one element or not.
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int ch;
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if (pos > limit)
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if ((ch = read()) < 0)
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return 0;
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else
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--pos;
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int avail = limit - pos;
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if (count < avail)
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{
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pos += count;
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return count;
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}
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pos = limit;
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long todo = count - avail;
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if (todo > buffer.length)
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{
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markPos = -1;
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todo -= in.skip(todo);
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}
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else
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{
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while (todo > 0)
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{
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avail = fill();
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if (avail <= 0)
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break;
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if (avail > todo)
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avail = (int) todo;
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pos += avail;
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todo -= avail;
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}
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}
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return count - todo;
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}
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}
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}
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