package java.io;
/**
- * This subclass of <code>FilterReader</code> provides the ability to
- * unread data from a stream. It maintains an internal buffer of unread
- * data that is supplied to the next read operation. This is conceptually
- * similar to mark/reset functionality, except that in this case the
- * position to reset the stream to does not need to be known in advance.
- * <p>
- * The default pushback buffer size one char, but this can be overridden
- * by the creator of the stream.
- *
- * @version 0.0
- *
- * @author Aaron M. Renn (arenn@urbanophile.com)
- * @author Warren Levy <warrenl@cygnus.com>
- */
-public class PushbackReader extends FilterReader
-{
-
-/*************************************************************************/
-
-/*
- * Class Variables
- */
-
-/**
- * This is the default buffer size
- */
-private static final int DEFAULT_BUFFER_SIZE = 1;
-
-/*************************************************************************/
-
-/*
- * Instance Variables
- */
-
-/**
- * This is the buffer that is used to store the pushed back data
- */
-private char[] buf;
-
-/**
- * This is the position in the buffer from which the next char will be
- * read. Bytes are stored in reverse order in the buffer, starting from
- * <code>buf[buf.length - 1]</code> to <code>buf[0]</code>. Thus when
- * <code>pos</code> is 0 the buffer is full and <code>buf.length</code> when
- * it is empty
- */
-private int pos;
-
-/*************************************************************************/
-
-/*
- * Constructors
- */
-
-/**
- * This method initializes a <code>PushbackReader</code> to read from the
- * specified subordinate <code>Reader</code> with a default pushback buffer
- * size of 1.
- *
- * @code in The subordinate stream to read from
- */
-public
-PushbackReader(Reader in)
-{
- this(in, DEFAULT_BUFFER_SIZE);
-}
-
-/*************************************************************************/
-
-/**
- * This method initializes a <code>PushbackReader</code> to read from the
- * specified subordinate <code>Reader</code> with the specified buffer
- * size
- *
- * @param in The subordinate <code>Reader</code> to read from
- * @param bufsize The pushback buffer size to use
- */
-public
-PushbackReader(Reader in, int bufsize)
-{
- super(in);
-
- if (bufsize < 0)
- throw new IllegalArgumentException("buffer size must be positive");
-
- buf = new char[bufsize];
- pos = bufsize;
-}
-
-/*************************************************************************/
-
-/*
- * Instance Methods
+ * This subclass of <code>FilterReader</code> provides the ability to
+ * unread data from a stream. It maintains an internal buffer of unread
+ * data that is supplied to the next read operation. This is conceptually
+ * similar to mark/reset functionality, except that in this case the
+ * position to reset the stream to does not need to be known in advance.
+ * <p>
+ * The default pushback buffer size one char, but this can be overridden
+ * by the creator of the stream.
+ *
+ * @version 0.0
+ *
+ * @author Aaron M. Renn (arenn@urbanophile.com)
+ * @author Warren Levy <warrenl@cygnus.com>
*/
-
-/**
- * This method closes the stream and frees any associated resources.
- *
- * @exception IOException If an error occurs.
- */
-public void
-close() throws IOException
-{
- synchronized (lock)
- {
- buf = null;
- super.close();
- }
-}
-
-/*************************************************************************/
-
-/**
- * This method throws an exception when called since this class does
- * not support mark/reset.
- *
- * @param read_limit Not used.
- *
- * @exception IOException Always thrown to indicate mark/reset not supported.
- */
-public void
-mark(int read_limit) throws IOException
-{
- throw new IOException("mark not supported in this class");
-}
-
-/*************************************************************************/
-
-/**
- * This method returns <code>false</code> to indicate that it does not support
- * mark/reset functionality.
- *
- * @return This method returns <code>false</code> to indicate that this class does not support mark/reset functionality
- *
- */
-public boolean
-markSupported()
-{
- return(false);
-}
-
-/*************************************************************************/
-
-/**
- * This method always throws an IOException in this class because
- * mark/reset functionality is not supported.
- *
- * @exception IOException Always thrown for this class
- */
-public void
-reset() throws IOException
-{
- throw new IOException("reset not supported in this class");
-}
-
-/*************************************************************************/
-
-/**
- * This method determines whether or not this stream is ready to be read.
- * If it returns <code>false</code> to indicate that the stream is not
- * ready, any attempt to read from the stream could (but is not
- * guaranteed to) block.
- * <p>
- * This stream is ready to read if there are either chars waiting to be
- * read in the pushback buffer or if the underlying stream is ready to
- * be read.
- *
- * @return <code>true</code> if this stream is ready to be read, <code>false</code> otherwise
- *
- * @exception IOException If an error occurs
- */
-public boolean
-ready() throws IOException
-{
- synchronized (lock)
- {
- if (buf == null)
- throw new IOException ("stream closed");
-
- if (((buf.length - pos) > 0) || super.ready())
- return(true);
- else
- return(false);
- }
-}
-
-/*************************************************************************/
-
-// Don't delete this method just because the spec says it shouldn't be there!
-// See the CVS log for details.
-/**
- * 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.
- * <p>
- * This method first discards chars from the buffer, then calls the
- * <code>skip</code> method on the underlying <code>Reader</code> to
- * skip additional chars if necessary.
- *
- * @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 num_chars) throws IOException
-{
- synchronized (lock)
- {
- if (num_chars <= 0)
- return(0);
-
- if ((buf.length - pos) >= num_chars)
- {
- pos += num_chars;
- return(num_chars);
- }
-
- int chars_discarded = buf.length - pos;
- pos = buf.length;
-
- long chars_skipped = in.skip(num_chars - chars_discarded);
-
- return(chars_discarded + chars_skipped);
- } // synchronized
-}
-
-/*************************************************************************/
-
-/**
- * This method reads an unsigned char from the input stream and returns it
- * as an int in the range of 0-65535. This method also will return -1 if
- * the end of the stream has been reached. The char returned will be read
- * from the pushback buffer, unless the buffer is empty, in which case
- * the char will be read from the underlying stream.
- * <p>
- * This method will block until the char can be read.
- *
- * @return The char read or -1 if end of stream
- *
- * @exception IOException If an error occurs
- */
-public int
-read() throws IOException
-{
- synchronized (lock)
- {
- if (buf == null)
- throw new IOException("stream closed");
-
- if (pos == buf.length)
- return(super.read());
-
- ++pos;
- return((buf[pos - 1] & 0xFFFF));
- }
-}
-
-/*************************************************************************/
-
-/**
- * This method read chars from a stream and stores them into a caller
- * supplied buffer. It starts storing the data at index <code>offset</code> into
- * the buffer and attempts to read <code>len</code> 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.
- * <p>
- * This method will block until some data can be read.
- * <p>
- * This method first reads chars from the pushback buffer in order to
- * satisfy the read request. If the pushback buffer cannot provide all
- * of the chars requested, the remaining chars are read from the
- * underlying stream.
- *
- * @param buf The array into which the chars read should be stored
- * @param offset The offset into the array to start storing chars
- * @param len 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 synchronized int
-read(char[] b, int offset, int len) throws IOException
-{
- synchronized (lock)
- {
- if (buf == null)
- throw new IOException("stream closed");
-
- if (offset < 0 || len < 0 || offset + len > b.length)
- throw new ArrayIndexOutOfBoundsException();
-
- int numBytes = Math.min(buf.length - pos, len);
- if (numBytes > 0)
- {
- System.arraycopy (buf, pos, b, offset, numBytes);
- pos += numBytes;
- return numBytes;
- }
-
- return super.read(b, offset, len);
- }
-}
-
-/*************************************************************************/
-
-/**
- * This method pushes a single char of data into the pushback buffer.
- * The char pushed back is the one that will be returned as the first char
- * of the next read.
- * <p>
- * If the pushback buffer is full, this method throws an exception.
- * <p>
- * The argument to this method is an <code>int</code>. Only the low eight bits
- * of this value are pushed back.
- *
- * @param b The char to be pushed back, passed as an int
- *
- * @exception IOException If the pushback buffer is full.
- */
-public void
-unread(int b) throws IOException
-{
- synchronized (lock)
- {
- if (buf == null)
- throw new IOException("stream closed");
- if (pos == 0)
- throw new IOException("Pushback buffer is full");
-
- --pos;
- buf[pos] = (char)(b & 0xFFFF);
- } // synchronized
-}
-
-/*************************************************************************/
-
-/**
- * This method pushes all of the chars in the passed char array into
- * the pushback buffer. These chars are pushed in reverse order so that
- * the next char read from the stream after this operation will be
- * <code>buf[0]</code> followed by <code>buf[1]</code>, etc.
- * <p>
- * If the pushback buffer cannot hold all of the requested chars, an
- * exception is thrown.
- *
- * @param buf The char array to be pushed back
- *
- * @exception IOException If the pushback buffer is full
- */
-public synchronized void
-unread(char[] buf) throws IOException
-{
- unread(buf, 0, buf.length);
-}
-
-/*************************************************************************/
-
-/**
- * This method pushed back chars from the passed in array into the pushback
- * buffer. The chars from <code>buf[offset]</code> to <code>buf[offset + len]</code>
- * are pushed in reverse order so that the next char read from the stream
- * after this operation will be <code>buf[offset]</code> followed by
- * <code>buf[offset + 1]</code>, etc.
- * <p>
- * If the pushback buffer cannot hold all of the requested chars, an
- * exception is thrown.
- *
- * @param buf The char array to be pushed back
- * @param offset The index into the array where the chars to be push start
- * @param len The number of chars to be pushed.
- *
- * @exception IOException If the pushback buffer is full
- */
-public synchronized void
-unread(char[] b, int offset, int len) throws IOException
+public class PushbackReader extends FilterReader
{
- synchronized (lock)
- {
- if (buf == null)
- throw new IOException("stream closed");
- if (pos < len)
- throw new IOException("Pushback buffer is full");
-
- // Note the order that these chars are being added is the opposite
- // of what would be done if they were added to the buffer one at a time.
- // See the Java Class Libraries book p. 1397.
- System.arraycopy(b, offset, buf, pos - len, len);
-
- // Don't put this into the arraycopy above, an exception might be thrown
- // and in that case we don't want to modify pos.
- pos -= len;
- }
+ /**
+ * This is the default buffer size
+ */
+ private static final int DEFAULT_BUFFER_SIZE = 1;
+
+ /**
+ * This is the buffer that is used to store the pushed back data
+ */
+ private char[] buf;
+
+ /**
+ * This is the position in the buffer from which the next char will be
+ * read. Bytes are stored in reverse order in the buffer, starting from
+ * <code>buf[buf.length - 1]</code> to <code>buf[0]</code>. Thus when
+ * <code>pos</code> is 0 the buffer is full and <code>buf.length</code> when
+ * it is empty
+ */
+ private int pos;
+
+ /**
+ * This method initializes a <code>PushbackReader</code> to read from the
+ * specified subordinate <code>Reader</code> with a default pushback buffer
+ * size of 1.
+ *
+ * @code in The subordinate stream to read from
+ */
+ public PushbackReader(Reader in)
+ {
+ this(in, DEFAULT_BUFFER_SIZE);
+ }
+
+ /**
+ * This method initializes a <code>PushbackReader</code> to read from the
+ * specified subordinate <code>Reader</code> with the specified buffer
+ * size
+ *
+ * @param in The subordinate <code>Reader</code> to read from
+ * @param bufsize The pushback buffer size to use
+ */
+ public PushbackReader(Reader in, int bufsize)
+ {
+ super(in);
+
+ if (bufsize < 0)
+ throw new IllegalArgumentException("buffer size must be positive");
+
+ buf = new char[bufsize];
+ pos = bufsize;
+ }
+
+ /**
+ * This method closes the stream and frees any associated resources.
+ *
+ * @exception IOException If an error occurs.
+ */
+ public void close() throws IOException
+ {
+ synchronized (lock)
+ {
+ buf = null;
+ super.close();
+ }
+ }
+
+ /**
+ * This method throws an exception when called since this class does
+ * not support mark/reset.
+ *
+ * @param read_limit Not used.
+ *
+ * @exception IOException Always thrown to indicate mark/reset not supported.
+ */
+ public void mark(int read_limit) throws IOException
+ {
+ throw new IOException("mark not supported in this class");
+ }
+
+ /**
+ * This method returns <code>false</code> to indicate that it does not support
+ * mark/reset functionality.
+ *
+ * @return This method returns <code>false</code> to indicate that this class does not support mark/reset functionality
+ *
+ */
+ public boolean markSupported()
+ {
+ return(false);
+ }
+
+ /**
+ * This method always throws an IOException in this class because
+ * mark/reset functionality is not supported.
+ *
+ * @exception IOException Always thrown for this class
+ */
+ public void reset() throws IOException
+ {
+ throw new IOException("reset not supported in this class");
+ }
+
+ /**
+ * This method determines whether or not this stream is ready to be read.
+ * If it returns <code>false</code> to indicate that the stream is not
+ * ready, any attempt to read from the stream could (but is not
+ * guaranteed to) block.
+ * <p>
+ * This stream is ready to read if there are either chars waiting to be
+ * read in the pushback buffer or if the underlying stream is ready to
+ * be read.
+ *
+ * @return <code>true</code> if this stream is ready to be read, <code>false</code> otherwise
+ *
+ * @exception IOException If an error occurs
+ */
+ public boolean ready() throws IOException
+ {
+ synchronized (lock)
+ {
+ if (buf == null)
+ throw new IOException ("stream closed");
+
+ if (((buf.length - pos) > 0) || super.ready())
+ return(true);
+ else
+ return(false);
+ }
+ }
+
+ // Don't delete this method just because the spec says it shouldn't be there!
+ // See the CVS log for details.
+ /**
+ * 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.
+ * <p>
+ * This method first discards chars from the buffer, then calls the
+ * <code>skip</code> method on the underlying <code>Reader</code> to
+ * skip additional chars if necessary.
+ *
+ * @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 num_chars) throws IOException
+ {
+ synchronized (lock)
+ {
+ if (num_chars <= 0)
+ return(0);
+
+ if ((buf.length - pos) >= num_chars)
+ {
+ pos += num_chars;
+ return(num_chars);
+ }
+
+ int chars_discarded = buf.length - pos;
+ pos = buf.length;
+
+ long chars_skipped = in.skip(num_chars - chars_discarded);
+
+ return(chars_discarded + chars_skipped);
+ }
+ }
+
+ /**
+ * This method reads an unsigned char from the input stream and returns it
+ * as an int in the range of 0-65535. This method also will return -1 if
+ * the end of the stream has been reached. The char returned will be read
+ * from the pushback buffer, unless the buffer is empty, in which case
+ * the char will be read from the underlying stream.
+ * <p>
+ * This method will block until the char can be read.
+ *
+ * @return The char read or -1 if end of stream
+ *
+ * @exception IOException If an error occurs
+ */
+ public int read() throws IOException
+ {
+ synchronized (lock)
+ {
+ if (buf == null)
+ throw new IOException("stream closed");
+
+ if (pos == buf.length)
+ return(super.read());
+
+ ++pos;
+ return((buf[pos - 1] & 0xFFFF));
+ }
+ }
+
+ /**
+ * This method read chars from a stream and stores them into a caller
+ * supplied buffer. It starts storing the data at index <code>offset</code> into
+ * the buffer and attempts to read <code>len</code> 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.
+ * <p>
+ * This method will block until some data can be read.
+ * <p>
+ * This method first reads chars from the pushback buffer in order to
+ * satisfy the read request. If the pushback buffer cannot provide all
+ * of the chars requested, the remaining chars are read from the
+ * underlying stream.
+ *
+ * @param buf The array into which the chars read should be stored
+ * @param offset The offset into the array to start storing chars
+ * @param len 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 synchronized int read(char[] b, int offset, int len) throws IOException
+ {
+ synchronized (lock)
+ {
+ if (buf == null)
+ throw new IOException("stream closed");
+
+ if (offset < 0 || len < 0 || offset + len > b.length)
+ throw new ArrayIndexOutOfBoundsException();
+
+ int numBytes = Math.min(buf.length - pos, len);
+ if (numBytes > 0)
+ {
+ System.arraycopy (buf, pos, b, offset, numBytes);
+ pos += numBytes;
+ return numBytes;
+ }
+
+ return super.read(b, offset, len);
+ }
+ }
+
+ /**
+ * This method pushes a single char of data into the pushback buffer.
+ * The char pushed back is the one that will be returned as the first char
+ * of the next read.
+ * <p>
+ * If the pushback buffer is full, this method throws an exception.
+ * <p>
+ * The argument to this method is an <code>int</code>. Only the low eight bits
+ * of this value are pushed back.
+ *
+ * @param b The char to be pushed back, passed as an int
+ *
+ * @exception IOException If the pushback buffer is full.
+ */
+ public void unread(int b) throws IOException
+ {
+ synchronized (lock)
+ {
+ if (buf == null)
+ throw new IOException("stream closed");
+ if (pos == 0)
+ throw new IOException("Pushback buffer is full");
+
+ --pos;
+ buf[pos] = (char)(b & 0xFFFF);
+ }
+ }
+
+ /**
+ * This method pushes all of the chars in the passed char array into
+ * the pushback buffer. These chars are pushed in reverse order so that
+ * the next char read from the stream after this operation will be
+ * <code>buf[0]</code> followed by <code>buf[1]</code>, etc.
+ * <p>
+ * If the pushback buffer cannot hold all of the requested chars, an
+ * exception is thrown.
+ *
+ * @param buf The char array to be pushed back
+ *
+ * @exception IOException If the pushback buffer is full
+ */
+ public synchronized void unread(char[] buf) throws IOException
+ {
+ unread(buf, 0, buf.length);
+ }
+
+ /**
+ * This method pushed back chars from the passed in array into the pushback
+ * buffer. The chars from <code>buf[offset]</code> to <code>buf[offset + len]</code>
+ * are pushed in reverse order so that the next char read from the stream
+ * after this operation will be <code>buf[offset]</code> followed by
+ * <code>buf[offset + 1]</code>, etc.
+ * <p>
+ * If the pushback buffer cannot hold all of the requested chars, an
+ * exception is thrown.
+ *
+ * @param buf The char array to be pushed back
+ * @param offset The index into the array where the chars to be push start
+ * @param len The number of chars to be pushed.
+ *
+ * @exception IOException If the pushback buffer is full
+ */
+ public synchronized void unread(char[] b, int offset, int len)
+ throws IOException
+ {
+ synchronized (lock)
+ {
+ if (buf == null)
+ throw new IOException("stream closed");
+ if (pos < len)
+ throw new IOException("Pushback buffer is full");
+
+ // Note the order that these chars are being added is the opposite
+ // of what would be done if they were added to the buffer one at a time.
+ // See the Java Class Libraries book p. 1397.
+ System.arraycopy(b, offset, buf, pos - len, len);
+
+ // Don't put this into the arraycopy above, an exception might be thrown
+ // and in that case we don't want to modify pos.
+ pos -= len;
+ }
+ }
}
-
-} // class PushbackReader
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