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public class DynamicFilterByteSource extends InputStream implements ByteSource
ByteSource and InputStream implementation that dynamically chooses the actual output for each read operation.

this class forwards its read operations to a ByteSource that is chosen using the given function at construction time. If a read operation is requested, the function is called, which can choose the stream to execute the read operations on. If the function returns null, the fallback ByteSource will be used to complete the operation.

The chooser function can decide arbitrarily, but an useful implementation is that it returns a stream based on some thread local state.

Closing this stream will not close the fallback source, or any choosen inputs by the chooser function.

Constructors
public
DynamicFilterByteSource(Supplier<extends ByteSource> sourceProvider, ByteSource fallbackSource)
Creates a new instance.
Methods
public void
Closes this input stream and releases any system resources associated with the stream.
public ByteSource
Gets the fallback byte source that is used when the source chooser function fails to find an input.
public int
Reads the next byte of data from the input stream.
public int
Reads bytes from this byte source and writes them to the argument buffer.
public int
read(byte[] b)
Reads some number of bytes from the input stream and stores them into the buffer array b.
public int
read(byte[] b, int off, int len)
Reads up to len bytes of data from the input stream into an array of bytes.
public long
skip(long n)
Skips over and discards n bytes of data from this input stream.
public DynamicFilterByteSource(Supplier<extends ByteSource> sourceProvider, ByteSource fallbackSource) throws NullPointerException
Creates a new instance.
sourceProviderThe source provider function which is called when read operations are issued.
fallbackSourceThe fallback source which is used when the source provider fails to get an input.
NullPointerExceptionIf any of the arguments are null.
public void close() throws IOException
Overridden from: InputStream
Closes this input stream and releases any system resources associated with the stream.

The close method of InputStream does nothing.

IOExceptionif an I/O error occurs.
Gets the fallback byte source that is used when the source chooser function fails to find an input.
The fallback source.
public int read() throws IOException
Overridden from: InputStream
Reads the next byte of data from the 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.

A subclass must provide an implementation of this method.

the next byte of data, or -1 if the end of the stream is reached.
IOExceptionif an I/O error occurs.
public int read(ByteRegion buffer) throws IOException
Overridden from: ByteSource
Reads bytes from this byte source and writes them to the argument buffer.

The number of bytes read is based on the buffer length.

This method works similarly to InputStream.read(byte[], int, int).

RMI method calls to this method is redirected to ByteSource.redirectReadCall(ByteSource, ByteRegion).

bufferThe buffer to read the bytes to.
The number of bytes read and put into the buffer. Negative result means that the end of the byte source has been reached.
IOExceptionIn case of I/O error.
public int read(byte[] b) throws IOException
Overridden from: InputStream
Reads some number of bytes from the input stream and stores them into the buffer array b. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown.

If the length of b is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at the end of the file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[0], the next one into b[1], and so on. The number of bytes read is, at most, equal to the length of b. Let k be the number of bytes actually read; these bytes will be stored in elements b[0] through b[k-1], leaving elements b[k] through b[b.length-1] unaffected.

The read(b) method for class InputStream has the same effect as:

 read(b, 0, b.length) 
bthe buffer into which the data is read.
the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
IOExceptionIf the first byte cannot be read for any reason other than the end of the file, if the input stream has been closed, or if some other I/O error occurs.
public int read(byte[] b, int off, int len) throws IOException
Overridden from: InputStream
Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of file is detected, or an exception is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.

The read(b, off, len) method for class InputStream simply calls the method read() repeatedly. If the first such call results in an IOException, that exception is returned from the call to the read(b, off, len) method. If any subsequent call to read() results in a IOException, the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into b and the number of bytes read before the exception occurred is returned. The default implementation of this method blocks until the requested amount of input data len has been read, end of file is detected, or an exception is thrown. Subclasses are encouraged to provide a more efficient implementation of this method.

bthe buffer into which the data is read.
offthe start offset in array b at which the data is written.
lenthe maximum number of bytes to read.
the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
IOExceptionIf the first byte cannot be read for any reason other than end of file, or if the input stream has been closed, or if some other I/O error occurs.
public long skip(long n) throws IOException
Overridden from: InputStream
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 0. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. The actual number of bytes skipped is returned. If n is negative, the skip method for class InputStream always returns 0, and no bytes are skipped. Subclasses may handle the negative value differently.

The skip method of this class creates a byte array and then repeatedly reads into it until n bytes have been read or the end of the stream has been reached. Subclasses are encouraged to provide a more efficient implementation of this method. For instance, the implementation may depend on the ability to seek.

nthe number of bytes to be skipped.
the actual number of bytes skipped.
IOExceptionif the stream does not support seek, or if some other I/O error occurs.