public class FilterInputStream extends InputStream
InputStream and performs some transformation on
the input data while it is being read. Transformations can be anything from a
simple byte-wise filtering input data to an on-the-fly compression or
decompression of the underlying stream. Input streams that wrap another input
stream and provide some additional functionality on top of it usually inherit
from this class.FilterOutputStream| Modifier and Type | Field and Description |
|---|---|
protected InputStream |
in
The source input stream that is filtered.
|
| Modifier | Constructor and Description |
|---|---|
protected |
FilterInputStream(InputStream in)
Constructs a new
FilterInputStream with the specified input
stream as source. |
| Modifier and Type | Method and Description |
|---|---|
int |
available()
Returns an estimated number of bytes that can be read or skipped without blocking for more
input.
|
void |
close()
Closes this stream.
|
void |
mark(int readlimit)
Sets a mark position in this stream.
|
boolean |
markSupported()
Indicates whether this stream supports
mark() and reset(). |
int |
read()
Reads a single byte from the filtered stream and returns it as an integer
in the range from 0 to 255.
|
int |
read(byte[] buffer,
int offset,
int count)
Reads at most
count bytes from this stream and stores them in the
byte array buffer starting at offset. |
void |
reset()
Resets this stream to the last marked location.
|
long |
skip(long byteCount)
Skips
byteCount bytes in this stream. |
readprotected volatile InputStream in
protected FilterInputStream(InputStream in)
FilterInputStream with the specified input
stream as source.
Warning: passing a null source creates an invalid
FilterInputStream, that fails on every method that is not
overridden. Subclasses should check for null in their constructors.
in - the input stream to filter reads on.public int available()
throws IOException
InputStreamNote 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, 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.
available in class InputStreamIOException - if this stream is closed or an error occurspublic void close()
throws IOException
close in interface Closeableclose in interface AutoCloseableclose in class InputStreamIOException - if an error occurs while closing this stream.public void mark(int readlimit)
readlimit
indicates how many bytes can be read before the mark is invalidated.
Sending reset() will reposition this stream back to the marked
position, provided that readlimit has not been surpassed.
This implementation sets a mark in the filtered stream.
mark in class InputStreamreadlimit - the number of bytes that can be read from this stream before
the mark is invalidated.markSupported(),
reset()public boolean markSupported()
mark() and reset().
This implementation returns whether or not the filtered stream supports
marking.markSupported in class InputStreamtrue if mark() and reset() are supported,
false otherwise.mark(int),
reset(),
skip(long)public int read()
throws IOException
read in class InputStreamIOException - if the stream is closed or another IOException occurs.public int read(byte[] buffer,
int offset,
int count)
throws IOException
count bytes from this stream and stores them in the
byte array buffer starting at offset. Returns the number
of bytes actually read or -1 if no bytes have been read and the end of
this stream has been reached. This implementation reads bytes from the
filtered stream.read in class InputStreambuffer - the byte array in which to store the bytes read.offset - the initial position in buffer to store the bytes
read from this stream.count - the maximum number of bytes to store in buffer.IOException - if this stream is closed or another I/O error occurs.public void reset()
throws IOException
reset in class InputStreamIOException - if this stream is already closed, no mark has been set or the
mark is no longer valid because more than readlimit
bytes have been read since setting the mark.mark(int),
markSupported()public long skip(long byteCount)
throws IOException
byteCount bytes in this stream. Subsequent
calls to read will not return these bytes unless reset is
used. This implementation skips byteCount bytes in the
filtered stream.skip in class InputStreambyteCount - the number of bytes to skip.IOException - if this stream is closed or another IOException occurs.mark(int),
reset()