| java.lang.Object
 java.io.InputStream
java.io.FilterInputStream
java.io.PushbackInputStream
| PushbackInputStream | | public class PushbackInputStream extends FilterInputStream (Code) | | A PushbackInputStream adds
functionality to another input stream, namely
the ability to "push back" or "unread"
one byte. This is useful in situations where
it is convenient for a fragment of code
to read an indefinite number of data bytes
that are delimited by a particular byte
value; after reading the terminating byte,
the code fragment can "unread" it, so that
the next read operation on the input stream
will reread the byte that was pushed back.
For example, bytes representing the characters
constituting an identifier might be terminated
by a byte representing an operator character;
a method whose job is to read just an identifier
can read until it sees the operator and
then push the operator back to be re-read.
author:
David Connelly
author:
Jonathan Payne
version:
1.49, 05/05/07
since:
JDK1.0 |
| Field Summary | |
| protected byte[] | buf
The pushback buffer. | | protected int | pos
The position within the pushback buffer from which the next byte will
be read. |
| Constructor Summary | |
| public | PushbackInputStream(InputStream in, int size)
Creates a PushbackInputStream
with a pushback buffer of the specified size,
and saves its argument, the input stream
in, for later use. | | public | PushbackInputStream(InputStream in)
Creates a PushbackInputStream
and saves its argument, the input stream
in, for later use. |
| Method Summary | |
| public int | available()
Returns an estimate of the number of bytes that can be read (or
skipped over) from this input stream without blocking by the next
invocation of a method for this input stream. | | public synchronized void | close()
Closes this input stream and releases any system resources
associated with the stream. | | public synchronized void | mark(int readlimit)
Marks the current position in this input stream. | | public boolean | markSupported()
Tests if this input stream supports the mark and
reset methods, which it does not. | | public int | read()
Reads the next byte of data from this input stream. | | public int | read(byte[] b, int off, int len)
Reads up to len bytes of data from this input stream into
an array of bytes. | | public synchronized void | reset()
Repositions this stream to the position at the time the
mark method was last called on this input stream. | | public long | skip(long n)
Skips over and discards n bytes of data from this
input stream. | | public void | unread(int b)
Pushes back a byte by copying it to the front of the pushback buffer. | | public void | unread(byte[] b, int off, int len)
Pushes back a portion of an array of bytes by copying it to the front
of the pushback buffer. | | public void | unread(byte[] b)
Pushes back an array of bytes by copying it to the front of the
pushback buffer. |
| buf | | protected byte[] buf(Code) | | The pushback buffer.
since:
JDK1.1 |
| pos | | protected int pos(Code) | | The position within the pushback buffer from which the next byte will
be read. When the buffer is empty, pos is equal to
buf.length; when the buffer is full, pos is
equal to zero.
since:
JDK1.1 |
| PushbackInputStream | | public PushbackInputStream(InputStream in, int size)(Code) | | Creates a PushbackInputStream
with a pushback buffer of the specified size,
and saves its argument, the input stream
in, for later use. Initially,
there is no pushed-back byte (the field
pushBack is initialized to
-1).
Parameters:
in - the input stream from which bytes will be read.
Parameters:
size - the size of the pushback buffer.
exception:
IllegalArgumentException - if size is <= 0
since:
JDK1.1 |
| PushbackInputStream | | public PushbackInputStream(InputStream in)(Code) | | Creates a PushbackInputStream
and saves its argument, the input stream
in, for later use. Initially,
there is no pushed-back byte (the field
pushBack is initialized to
-1).
Parameters:
in - the input stream from which bytes will be read. |
| available | | public int available() throws IOException(Code) | | Returns an estimate of the number of bytes that can be read (or
skipped over) from this input stream without blocking by the next
invocation of a method for this input stream. The next invocation might be
the same thread or another thread. A single read or skip of this
many bytes will not block, but may read or skip fewer bytes.
The method returns the sum of the number of bytes that have been
pushed back and the value returned by
java.io.FilterInputStream.available available .
the number of bytes that can be read (or skipped over) fromthe input stream without blocking.
exception:
IOException - if this input stream has been closed byinvoking its PushbackInputStream.close() method,or an I/O error occurs.
See Also: java.io.FilterInputStream.in
See Also: java.io.InputStream.available |
| close | | public synchronized void close() throws IOException(Code) | | Closes this input stream and releases any system resources
associated with the stream.
Once the stream has been closed, further read(), unread(),
available(), reset(), or skip() invocations will throw an IOException.
Closing a previously closed stream has no effect.
exception:
IOException - if an I/O error occurs. |
| mark | | public synchronized void mark(int readlimit)(Code) | | Marks the current position in this input stream.
The mark method of PushbackInputStream
does nothing.
Parameters:
readlimit - the maximum limit of bytes that can be read beforethe mark position becomes invalid.
See Also: java.io.InputStream.reset |
| read | | public int read() throws IOException(Code) | | Reads the next byte of data from this input stream. The value
byte is returned as an int in the range
0 to 255. If no byte is available
because the end of the stream has been reached, the value
-1 is returned. This method blocks until input data
is available, the end of the stream is detected, or an exception
is thrown.
This method returns the most recently pushed-back byte, if there is
one, and otherwise calls the read method of its underlying
input stream and returns whatever value that method returns.
the next byte of data, or -1 if the end of thestream has been reached.
exception:
IOException - if this input stream has been closed byinvoking its PushbackInputStream.close() method,or an I/O error occurs.
See Also: java.io.InputStream.read |
| read | | public int read(byte[] b, int off, int len) throws IOException(Code) | | Reads up to len bytes of data from this input stream into
an array of bytes. This method first reads any pushed-back bytes; after
that, if fewer than len bytes have been read then it
reads from the underlying input stream. If len is not zero, the method
blocks until at least 1 byte of input is available; otherwise, no
bytes are read and 0 is returned.
Parameters:
b - the buffer into which the data is read.
Parameters:
off - the start offset in the destination array b
Parameters:
len - the maximum number of bytes read. the total number of bytes read into the buffer, or-1 if there is no more data because the end ofthe stream has been reached.
exception:
NullPointerException - If b is null.
exception:
IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off
exception:
IOException - if this input stream has been closed byinvoking its PushbackInputStream.close() method,or an I/O error occurs.
See Also: java.io.InputStream.read(byte[]intint) |
| skip | | public long skip(long n) throws IOException(Code) | | Skips over and discards n bytes of data from this
input stream. The skip method may, for a variety of
reasons, end up skipping over some smaller number of bytes,
possibly zero. If n is negative, no bytes are skipped.
The skip method of PushbackInputStream
first skips over the bytes in the pushback buffer, if any. It then
calls the skip method of the underlying input stream if
more bytes need to be skipped. The actual number of bytes skipped
is returned.
Parameters:
n -
exception:
IOException - if the stream does not support seek,or the stream has been closed byinvoking its PushbackInputStream.close() method,or an I/O error occurs.
See Also: java.io.FilterInputStream.in
See Also: java.io.InputStream.skip(long n)
since:
1.2 |
| unread | | public void unread(int b) throws IOException(Code) | | Pushes back a byte by copying it to the front of the pushback buffer.
After this method returns, the next byte to be read will have the value
(byte)b.
Parameters:
b - the int value whose low-order byte is to be pushed back.
exception:
IOException - If there is not enough room in the pushbackbuffer for the byte, or this input stream has been closed byinvoking its PushbackInputStream.close() method. |
| unread | | public void unread(byte[] b, int off, int len) throws IOException(Code) | | Pushes back a portion of an array of bytes by copying it to the front
of the pushback buffer. After this method returns, the next byte to be
read will have the value b[off], the byte after that will
have the value b[off+1], and so forth.
Parameters:
b - the byte array to push back.
Parameters:
off - the start offset of the data.
Parameters:
len - the number of bytes to push back.
exception:
IOException - If there is not enough room in the pushbackbuffer for the specified number of bytes,or this input stream has been closed byinvoking its PushbackInputStream.close() method.
since:
JDK1.1 |
| unread | | public void unread(byte[] b) throws IOException(Code) | | Pushes back an array of bytes by copying it to the front of the
pushback buffer. After this method returns, the next byte to be read
will have the value b[0], the byte after that will have the
value b[1], and so forth.
Parameters:
b - the byte array to push back
exception:
IOException - If there is not enough room in the pushbackbuffer for the specified number of bytes,or this input stream has been closed byinvoking its PushbackInputStream.close() method.
since:
JDK1.1 |
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