FilterReader buffers input from an
- * underlying implementation to provide a possibly more efficient read
- * mechanism. It maintains the buffer and buffer state in instance
- * variables that are available to subclasses. The default buffer size
- * of 512 chars can be overridden by the creator of the stream.
- *
- * This class also implements mark/reset functionality. It is capable
- * of remembering any number of input chars, to the limits of
- * system memory or the size of
- * Note that the number of chars that can be remembered by this method
- * can be greater than the size of the internal read buffer. It is also
- * not dependent on the subordinate stream supporting mark/reset
- * functionality.
- *
- * @param readlimit The number of chars that can be read before the mark
- * becomes invalid
- *
- * @exception IOException If an error occurs
- */
- public void mark(int readLimit) throws IOException
- {
- synchronized (lock)
- {
- checkStatus();
- // In this method we need to be aware of the special case where
- // pos + 1 == limit. This indicates that a '\r' was the last char
- // in the buffer during a readLine. We'll want to maintain that
- // condition after we shift things around and if a larger buffer is
- // needed to track readLimit, we'll have to make it one element
- // larger to ensure we don't invalidate the mark too early, if the
- // char following the '\r' is NOT a '\n'. This is ok because, per
- // the spec, we are not required to invalidate when passing readLimit.
- //
- // Note that if 'pos > limit', then doing 'limit -= pos' will cause
- // limit to be negative. This is the only way limit will be < 0.
-
- if (pos + readLimit > limit)
- {
- char[] old_buffer = buffer;
- int extraBuffSpace = 0;
- if (pos > limit)
- extraBuffSpace = 1;
- if (readLimit + extraBuffSpace > limit)
- buffer = new char[readLimit + extraBuffSpace];
- limit -= pos;
- if (limit >= 0)
- {
- System.arraycopy(old_buffer, pos, buffer, 0, limit);
- pos = 0;
- }
- }
-
- if (limit < 0)
- {
- // Maintain the relationship of 'pos > limit'.
- pos = 1;
- limit = markPos = 0;
- }
- else
- markPos = pos;
- // Now pos + readLimit <= buffer.length. thus if we need to read
- // beyond buffer.length, then we are allowed to invalidate markPos.
- }
- }
-
- /**
- * Reset the stream to the point where the
- * This method will throw an IOException if the number of chars read from
- * the stream since the call to
- * This method will block until some data can be read.
- *
- * @param buf The array into which the chars read should be stored
- * @param offset The offset into the array to start storing chars
- * @param count The requested number of chars to read
- *
- * @return The actual number of chars read, or -1 if end of stream.
- *
- * @exception IOException If an error occurs.
- */
- public int read(char[] buf, int offset, int count) throws IOException
- {
- synchronized (lock)
- {
- checkStatus();
- // Once again, we need to handle the special case of a readLine
- // that has a '\r' at the end of the buffer. In this case, we'll
- // need to skip a '\n' if it is the next char to be read.
- // This special case is indicated by 'pos > limit'.
- boolean retAtEndOfBuffer = false;
-
- int avail = limit - pos;
- if (count > avail)
- {
- if (avail > 0)
- count = avail;
- else // pos >= limit
- {
- if (limit == buffer.length)
- markPos = -1; // read too far - invalidate the mark.
- if (pos > limit)
- {
- // Set a boolean and make pos == limit to simplify things.
- retAtEndOfBuffer = true;
- --pos;
- }
- if (markPos < 0)
- {
- // Optimization: can read directly into buf.
- if (count >= buffer.length && !retAtEndOfBuffer)
- return in.read(buf, offset, count);
- pos = limit = 0;
- }
- avail = in.read(buffer, limit, buffer.length - limit);
- if (retAtEndOfBuffer && avail > 0 && buffer[limit] == '\n')
- {
- --avail;
- limit++;
- }
- if (avail < count)
- {
- if (avail <= 0)
- return avail;
- count = avail;
- }
- limit += avail;
- }
- }
- System.arraycopy(buffer, pos, buf, offset, count);
- pos += count;
- return count;
- }
- }
-
- /* Read more data into the buffer. Update pos and limit appropriately.
- Assumes pos==limit initially. May invalidate the mark if read too much.
- Return number of chars read (never 0), or -1 on eof. */
- private int fill() throws IOException
- {
- checkStatus();
- // Handle the special case of a readLine that has a '\r' at the end of
- // the buffer. In this case, we'll need to skip a '\n' if it is the
- // next char to be read. This special case is indicated by 'pos > limit'.
- boolean retAtEndOfBuffer = false;
- if (pos > limit)
- {
- retAtEndOfBuffer = true;
- --pos;
- }
-
- if (markPos >= 0 && limit == buffer.length)
- markPos = -1;
- if (markPos < 0)
- pos = limit = 0;
- int count = in.read(buffer, limit, buffer.length - limit);
- if (count > 0)
- limit += count;
-
- if (retAtEndOfBuffer && buffer[pos] == '\n')
- {
- --count;
- pos++;
- }
-
- return count;
- }
-
- public int read() throws IOException
- {
- synchronized (lock)
- {
- checkStatus();
- if (pos >= limit && fill () <= 0)
- return -1;
- return buffer[pos++];
- }
- }
-
- /* Return the end of the line starting at this.pos and ending at limit.
- * The index returns is *before* any line terminators, or limit
- * if no line terminators were found.
- */
- private int lineEnd(int limit)
- {
- int i = pos;
- for (; i < limit; i++)
- {
- char ch = buffer[i];
- if (ch == '\n' || ch == '\r')
- break;
- }
- return i;
- }
-
- /**
- * This method reads a single line of text from the input stream, returning
- * it as a
- * This method first discards chars in the buffer, then calls the
- * Integer.MAX_VALUE
- *
- * @author Per Bothner BufferedReader that will read from the
- * specified subordinate stream with a default buffer size of 4096 chars.
- *
- * @param in The subordinate stream to read from
- */
- public BufferedReader(Reader in)
- {
- this(in, DEFAULT_BUFFER_SIZE);
- }
-
- /**
- * Create a new BufferedReader that will read from the
- * specified subordinate stream with a buffer size that is specified by the
- * caller.
- *
- * @param in The subordinate stream to read from
- * @param bufsize The buffer size to use
- */
- public BufferedReader(Reader in, int size)
- {
- super(in.lock);
- this.in = in;
- buffer = new char[size];
- }
-
- /**
- * This method closes the stream
- *
- * @exception IOException If an error occurs
- */
- public void close() throws IOException
- {
- synchronized (lock)
- {
- if (in != null)
- in.close();
- in = null;
- buffer = null;
- }
- }
-
- /**
- * Returns true to indicate that this class supports mark/reset
- * functionality.
- *
- * @return true
- */
- public boolean markSupported()
- {
- return true;
- }
-
- /**
- * Mark a position in the input to which the stream can be
- * "reset" by calling the reset() method. The parameter
- * readlimit is the number of chars that can be read from the
- * stream after setting the mark before the mark becomes invalid. For
- * example, if mark() is called with a read limit of 10, then
- * when 11 chars of data are read from the stream before the
- * reset() method is called, then the mark is invalid and the
- * stream object instance is not required to remember the mark.
- * mark() method
- * was called. Any chars that were read after the mark point was set will
- * be re-read during subsequent reads.
- * mark() exceeds the mark limit
- * passed when establishing the mark.
- *
- * @exception IOException If an error occurs;
- */
- public void reset() throws IOException
- {
- synchronized (lock)
- {
- checkStatus();
- if (markPos < 0)
- throw new IOException("mark never set or invalidated");
-
- // Need to handle the extremely unlikely case where a readLine was
- // done with a '\r' as the last char in the buffer; which was then
- // immediately followed by a mark and a reset with NO intervening
- // read of any sort. In that case, setting pos to markPos would
- // lose that info and a subsequent read would thus not skip a '\n'
- // (if one exists). The value of limit in this rare case is zero.
- // We can assume that if limit is zero for other reasons, then
- // pos is already set to zero and doesn't need to be readjusted.
- if (limit > 0)
- pos = markPos;
- }
- }
-
- /**
- * This method determines whether or not a stream is ready to be read. If
- * This method returns false then this stream could (but is
- * not guaranteed to) block on the next read attempt.
- *
- * @return true if this stream is ready to be read, false otherwise
- *
- * @exception IOException If an error occurs
- */
- public boolean ready() throws IOException
- {
- synchronized (lock)
- {
- checkStatus();
- return pos < limit || in.ready();
- }
- }
-
- /**
- * This method read chars from a stream and stores them into a caller
- * supplied buffer. It starts storing the data at index offset into
- * the buffer and attempts to read len chars. This method can
- * return before reading the number of chars requested. The actual number
- * of chars read is returned as an int. A -1 is returned to indicate the
- * end of the stream.
- * String. A line is terminated by "\n", a "\r", or
- * an "\r\n" sequence. The system dependent line separator is not used.
- * The line termination characters are not returned in the resulting
- * String.
- *
- * @return The line of text read, or null if end of stream.
- *
- * @exception IOException If an error occurs
- */
- public String readLine() throws IOException
- {
- checkStatus();
- // Handle the special case where a previous readLine (with no intervening
- // reads/skips) had a '\r' at the end of the buffer.
- // In this case, we'll need to skip a '\n' if it's the next char to be read.
- // This special case is indicated by 'pos > limit'.
- if (pos > limit)
- {
- int ch = read();
- if (ch < 0)
- return null;
- if (ch != '\n')
- --pos;
- }
- int i = lineEnd(limit);
- if (i < limit)
- {
- String str = new String(buffer, pos, i - pos);
- pos = i + 1;
- // If the last char in the buffer is a '\r', we must remember
- // to check if the next char to be read after the buffer is refilled
- // is a '\n'. If so, skip it. To indicate this condition, we set pos
- // to be limit + 1, which normally is never possible.
- if (buffer[i] == '\r')
- if (pos == limit || buffer[pos] == '\n')
- pos++;
- return str;
- }
- StringBuffer sbuf = new StringBuffer(200);
- sbuf.append(buffer, pos, i - pos);
- pos = i;
- // We only want to return null when no characters were read before
- // EOF. So we must keep track of this separately. Otherwise we
- // would treat an empty `sbuf' as an EOF condition, which is wrong
- // when there is just a newline.
- boolean eof = false;
- for (;;)
- {
- int ch = read();
- if (ch < 0)
- {
- eof = true;
- break;
- }
- if (ch == '\n' || ch == '\r')
- {
- // Check here if a '\r' was the last char in the buffer; if so,
- // mark it as in the comment above to indicate future reads
- // should skip a newline that is the next char read after
- // refilling the buffer.
- if (ch == '\r')
- if (pos == limit || buffer[pos] == '\n')
- pos++;
- break;
- }
- i = lineEnd(limit);
- sbuf.append(buffer, pos - 1, i - (pos - 1));
- pos = i;
- }
- return (sbuf.length() == 0 && eof) ? null : sbuf.toString();
- }
-
- /**
- * This method skips the specified number of chars in the stream. It
- * returns the actual number of chars skipped, which may be less than the
- * requested amount.
- * skip method on the underlying stream to skip the remaining chars.
- *
- * @param num_chars The requested number of chars to skip
- *
- * @return The actual number of chars skipped.
- *
- * @exception IOException If an error occurs
- */
- public long skip(long count) throws IOException
- {
- synchronized (lock)
- {
- checkStatus();
- if (count <= 0)
- return 0;
- // Yet again, we need to handle the special case of a readLine
- // that has a '\r' at the end of the buffer. In this case, we need
- // to ignore a '\n' if it is the next char to be read.
- // This special case is indicated by 'pos > limit' (i.e. avail < 0).
- // To simplify things, if we're dealing with the special case for
- // readLine, just read the next char (since the fill method will
- // skip the '\n' for us). By doing this, we'll have to back up pos.
- // That's easier than trying to keep track of whether we've skipped
- // one element or not.
- int ch;
- if (pos > limit)
- if ((ch = read()) < 0)
- return 0;
- else
- --pos;
-
- int avail = limit - pos;
-
- if (count < avail)
- {
- pos += count;
- return count;
- }
-
- pos = limit;
- long todo = count - avail;
- if (todo > buffer.length)
- {
- markPos = -1;
- todo -= in.skip(todo);
- }
- else
- {
- while (todo > 0)
- {
- avail = fill();
- if (avail <= 0)
- break;
- if (avail > todo)
- avail = (int) todo;
- pos += avail;
- todo -= avail;
- }
- }
- return count - todo;
- }
- }
-
- private void checkStatus() throws IOException
- {
- if (in == null)
- throw new IOException("Stream closed");
- }
-}