public class PipedInputStream extends InputStream
PipedOutputStream
Modifier and Type | Field and Description |
---|---|
protected byte[] |
buffer
The circular buffer through which data is passed.
|
protected int |
in
The index in
buffer where the next byte will be written. |
protected int |
out
The index in
buffer where the next byte will be read. |
protected static int |
PIPE_SIZE
The size of the default pipe in bytes.
|
Constructor and Description |
---|
PipedInputStream()
Constructs a new unconnected
PipedInputStream . |
PipedInputStream(int pipeSize)
Constructs a new unconnected
PipedInputStream with the given
buffer size. |
PipedInputStream(PipedOutputStream out)
|
PipedInputStream(PipedOutputStream out,
int pipeSize)
Constructs a new
PipedInputStream connected to the given PipedOutputStream ,
with the given buffer size. |
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 |
connect(PipedOutputStream src)
Connects this
PipedInputStream to a PipedOutputStream . |
int |
read()
Reads a single byte from this stream and returns it as an integer in the
range from 0 to 255.
|
int |
read(byte[] bytes,
int offset,
int byteCount)
Reads at most
byteCount bytes from this stream and stores them in the
byte array bytes starting at offset . |
protected void |
receive(int oneByte)
Receives a byte and stores it in this stream's
buffer . |
mark, markSupported, read, reset, skip
protected byte[] buffer
[out, in)
and written to the range [in, out)
.
Data in the buffer is either sequential: { - - - X X X X X X X - - - - - } ^ ^ | | out in...or wrapped around the buffer's end:
{ X X X X - - - - - - - - X X X } ^ ^ | | in outWhen the buffer is empty,
in == -1
. Reading when the buffer is
empty will block until data is available. When the buffer is full,
in == out
. Writing when the buffer is full will block until free
space is available.protected int in
buffer
where the next byte will be written.protected int out
buffer
where the next byte will be read.protected static final int PIPE_SIZE
public PipedInputStream()
PipedInputStream
. The resulting
stream must be connected to a PipedOutputStream
before data may
be read from it.public PipedInputStream(PipedOutputStream out) throws IOException
PipedInputStream
connected to the
PipedOutputStream
out
. Any data written to the output
stream can be read from the this input stream.out
- the piped output stream to connect to.IOException
- if this stream or out
are already connected.public PipedInputStream(int pipeSize)
PipedInputStream
with the given
buffer size. The resulting stream must be connected to a
PipedOutputStream
before data may be read from it.pipeSize
- the size of the buffer in bytes.IllegalArgumentException
- if pipeSize is less than or equal to zero.public PipedInputStream(PipedOutputStream out, int pipeSize) throws IOException
PipedInputStream
connected to the given PipedOutputStream
,
with the given buffer size. Any data written to the output stream can be read from this
input stream.out
- the PipedOutputStream
to connect to.pipeSize
- the size of the buffer in bytes.IOException
- if an I/O error occurs.IllegalArgumentException
- if pipeSize is less than or equal to zero.public int available() throws IOException
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, 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.
Unlike most streams, PipedInputStream
returns 0 rather than throwing
IOException
if the stream has been closed. Unconnected and broken pipes also
return 0.
available
in class InputStream
IOException
- if an I/O error occurspublic void close() throws IOException
close
in interface Closeable
close
in interface AutoCloseable
close
in class InputStream
IOException
- if an error occurs while closing this stream.public void connect(PipedOutputStream src) throws IOException
PipedInputStream
to a PipedOutputStream
.
Any data written to the output stream becomes readable in this input
stream.src
- the source output stream.IOException
- if either stream is already connected.public int read() throws IOException
Separate threads should be used to read from a PipedInputStream
and to write to the connected PipedOutputStream
. If the same
thread is used, a deadlock may occur.
read
in class InputStream
IOException
- if this stream is closed or not connected to an output
stream, or if the thread writing to the connected output
stream is no longer alive.public int read(byte[] bytes, int offset, int byteCount) throws IOException
byteCount
bytes from this stream and stores them in the
byte array bytes
starting at offset
. Blocks until at
least one byte has been read, the end of the stream is detected or an
exception is thrown.
Separate threads should be used to read from a PipedInputStream
and to write to the connected PipedOutputStream
. If the same
thread is used, a deadlock may occur.
read
in class InputStream
bytes
- the byte array in which to store the bytes read.offset
- the initial position in buffer
to store the bytes read
from this stream.byteCount
- the maximum number of bytes to store in b
.IndexOutOfBoundsException
- if offset < 0
or byteCount < 0
, or if offset + byteCount
is greater than the size of bytes
.InterruptedIOException
- if the thread reading from this stream is interrupted.IOException
- if this stream is closed or not connected to an output
stream, or if the thread writing to the connected output
stream is no longer alive.NullPointerException
- if bytes
is null
.protected void receive(int oneByte) throws IOException
buffer
. This
method is called by PipedOutputStream.write(int)
. The least
significant byte of the integer oneByte
is stored at index
in
in the buffer
.
This method blocks as long as buffer
is full.
oneByte
- the byte to store in this pipe.InterruptedIOException
- if the buffer
is full and the thread that has called
this method is interrupted.IOException
- if this stream is closed or the thread that has last read
from this stream is no longer alive.