PushbackInputStream

The buffer that contains pushed-back bytes.

The current position within buf. A value equal to buf.length indicates that no bytes are available. A value of 0 indicates that the buffer is full.

Constructs a new PushbackInputStream with the specified input stream as source. The size of the pushback buffer is set to the default value of 1 byte.

Warning: passing a null source creates an invalid PushbackInputStream. All read operations on such a stream will fail.

Constructs a new PushbackInputStream with in as source input stream. The size of the pushback buffer is set to size.

Warning: passing a null source creates an invalid PushbackInputStream. All read operations on such a stream will fail.

Returns an estimated number of bytes that can be read or skipped without blocking for more input.

Note that this method provides such a weak guarantee that it is not very useful in practice.

Firstly, the guarantee is "without blocking for more input" rather than "without blocking": a read may still block waiting for I/O to complete — the guarantee is merely that it won't have to wait indefinitely for data to be written. The result of this method should not be used as a license to do I/O on a thread that shouldn't be blocked.

Secondly, the result is a conservative estimate and may be significantly smaller than the actual number of bytes available. In particular, an implementation that always returns 0 would be correct. In general, callers should only use this method if they'd be satisfied with treating the result as a boolean yes or no answer to the question "is there definitely data ready?".

Thirdly, the fact that a given number of bytes is "available" does not guarantee that a read or skip will actually read or skip that many bytes: they may read or skip fewer.

It is particularly important to realize that you must not use this method to size a container and assume that you can read the entirety of the stream without needing to resize the container. Such callers should probably write everything they read to a ByteArrayOutputStream and convert that to a byte array. Alternatively, if you're reading from a file, length() returns the current length of the file (though assuming the file's length can't change may be incorrect, reading a file is inherently racy).

The default implementation of this method in InputStream always returns 0. Subclasses should override this method if they are able to indicate the number of bytes available.

Closes this stream. This implementation closes the source stream and releases the pushback buffer.

Marks the current position in this stream. Setting a mark is not supported in this class; this implementation does nothing.

Indicates whether this stream supports the mark(int) and reset() methods. PushbackInputStream does not support them, so it returns false.

Reads a single byte from this stream and returns it as an integer in the range from 0 to 255. If the pushback buffer does not contain any available bytes then a byte from the source input stream is returned. Blocks until one byte has been read, the end of the source stream is detected or an exception is thrown.

Reads up to byteCount bytes from this stream and stores them in the byte array buffer starting at byteOffset. Bytes are read from the pushback buffer first, then from the source stream if more bytes are required. Blocks until byteCount bytes have been read, the end of the source stream is detected or an exception is thrown. Returns the number of bytes read, or -1 if the end of the source stream has been reached.

Resets this stream to the last marked position. Resetting the stream is not supported in this class; this implementation always throws an IOException.

Skips byteCount bytes in this stream. This implementation skips bytes in the pushback buffer first and then in the source stream if necessary.

Pushes a subset of the bytes in buffer back to this stream. The subset is defined by the start position offset within buffer and the number of bytes specified by length. The bytes are pushed back in such a way that the next byte read from this stream is buffer[offset], then buffer[1] and so on.

If this stream's internal pushback buffer cannot store the selected subset of buffer, an IOException is thrown. Parts of buffer may have already been copied to the pushback buffer when the exception is thrown.

Pushes all the bytes in buffer back to this stream. The bytes are pushed back in such a way that the next byte read from this stream is buffer[0], then buffer[1] and so on.

If this stream's internal pushback buffer cannot store the entire contents of buffer, an IOException is thrown. Parts of buffer may have already been copied to the pushback buffer when the exception is thrown.

Pushes the specified byte oneByte back to this stream. Only the least significant byte of the integer oneByte is pushed back. This is done in such a way that the next byte read from this stream is (byte) oneByte.

If this stream's internal pushback buffer cannot store the byte, an IOException is thrown.