public class InspectableFileCachedInputStream extends MeasurableInputStream implements RepositionableStream, WritableByteChannel
MeasurableInputStream based on
cached data received by a WritableByteChannel whose first bytes can be inspected directly.
An instance of this class acts as a buffer holding the bytes written through its
WritableByteChannel interface (which can be easily turned into an OutputStream using
Channels.newOutputStream(WritableByteChannel)). The data can be discarded at any time using
clear(). The first inspectable bytes of buffer contains the first
bytes written. When buffer is full, the bytes are written to an overflow
file.
At any time, the stream of bytes written since creation (or since the last clear())
are available as a fully implemented MeasurableInputStream which also implements
RepositionableStream and supports marking.
Note that you must arbitrate carefully write and read accesses,
as it is always possible to call write(ByteBuffer)
and thus modify the length of the MeasurableInputStream.
The method close() makes the MeasurableInputStream and WritableByteChannel state-changing methods temporarily throw an IOException, but
does not otherwise modify the state of the stream. You can reopen the stream
later, or clear it.
The method dispose() can be used to release
the resources associated with the stream.
This class provides no form of buffering except for the memory buffer described above, both
when reading and when writing. Users should consider wrapping instances of this class with a
FastBufferedInputStream, as reads after the buffer has been exhausted will be performed
directly on a RandomAccessFile.
| Modifier and Type | Field and Description |
|---|---|
byte[] |
buffer
The inspection buffer.
|
static boolean |
DEBUG |
static int |
DEFAULT_BUFFER_SIZE
The default buffer size (64KiB).
|
int |
inspectable
The number of valid bytes currently in
buffer. |
| Constructor and Description |
|---|
InspectableFileCachedInputStream()
Creates a new instance with default buffer size and overflow-file directory.
|
InspectableFileCachedInputStream(int bufferSize)
Creates a new instance with specified buffer size and default overflow-file directory.
|
InspectableFileCachedInputStream(int bufferSize,
File overflowFile)
Creates a new instance with specified buffer size and overlow-file directory.
|
| Modifier and Type | Method and Description |
|---|---|
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.
|
void |
clear()
Clears the content of this
InspectableFileCachedInputStream, zeroing the length of the represented
stream. |
void |
close()
Makes the stream unreadable until the next
clear(). |
void |
dispose()
Disposes this stream, deleting the overflow file.
|
boolean |
isOpen()
Tells whether or not this channel is open.
|
long |
length()
Returns the overall length of this stream (optional operation).
|
void |
mark(int readlimit)
Marks the current position in this input stream.
|
boolean |
markSupported()
Tests if this input stream supports the
mark and
reset methods. |
long |
position()
Returns the current stream position.
|
void |
position(long position)
Positions the input stream.
|
int |
read()
Reads the next byte of data from the input stream.
|
int |
read(byte[] b)
Reads some number of bytes from the input stream and stores them into
the buffer array
b. |
int |
read(byte[] b,
int offset,
int length)
Reads up to
len bytes of data from the input stream into
an array of bytes. |
void |
reopen()
Makes the stream readable again after a
close(). |
void |
reset()
Repositions this stream to the position at the time the
mark method was last called on this input stream. |
long |
skip(long n)
Skips over and discards
n bytes of data from this input
stream. |
void |
truncate(long size)
Truncates the overflow file to a given size if possible.
|
int |
write(ByteBuffer byteBuffer)
Appends the content of a specified buffer to the end of the currently represented stream.
|
public static final boolean DEBUG
public static final int DEFAULT_BUFFER_SIZE
public final byte[] buffer
inspectable bytes contain the first part of the input stream.
The buffer is available for inspection, but users should not modify its content.public int inspectable
buffer.public InspectableFileCachedInputStream(int bufferSize,
File overflowFile)
throws IOException
bufferSize - the buffer size, in bytes.overflowFile - the directory where the overflow file should be created, or null for the default temporary directory.IOExceptionpublic InspectableFileCachedInputStream(int bufferSize)
throws IOException
bufferSize - the buffer size, in bytes.IOExceptionpublic InspectableFileCachedInputStream()
throws IOException
IOExceptionpublic void clear()
throws IOException
InspectableFileCachedInputStream, zeroing the length of the represented
stream.IOExceptionpublic int write(ByteBuffer byteBuffer) throws IOException
write in interface WritableByteChannelbyteBuffer - a byte buffer.byteBuffer.remaining()).ClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the write operation is in progressIOException - If some other I/O error occurspublic void truncate(long size)
throws FileNotFoundException,
IOException
size - the new size; the final size is the maximum between the current write position (i.e., the length
of the represented stream minus the length of the inspection buffer) and this value.FileNotFoundExceptionIOExceptionpublic void close()
clear().close in interface Closeableclose in interface AutoCloseableclose in interface Channelclose in class InputStreamreopen()public void reopen()
throws IOException
close().IOExceptionclose()public void dispose()
throws IOException
IOExceptionpublic int available()
throws IOException
java.io.InputStream Note that while some implementations of InputStream will return
the total number of bytes in the stream, many will not. It is
never correct to use the return value of this method to allocate
a buffer intended to hold all data in this stream.
A subclass' implementation of this method may choose to throw an
IOException if this input stream has been closed by
invoking the InputStream.close() method.
The available method for class InputStream always
returns 0.
This method should be overridden by subclasses.
available in class InputStream0 when
it reaches the end of the input stream.IOException - if an I/O error occurs.public int read(byte[] b,
int offset,
int length)
throws IOException
java.io.InputStreamlen 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.
read in class InputStreamb - the buffer into which the data is read.offset - the start offset in array b
at which the data is written.length - the maximum number of bytes to read.-1 if there is no more data because the end of
the stream has been reached.IOException - If 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.InputStream.read()public int read(byte[] b)
throws IOException
java.io.InputStreamb. 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) read in class InputStreamb - the buffer into which the data is read.-1 if there is no more data because the end of
the stream has been reached.IOException - If 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.InputStream.read(byte[], int, int)public long skip(long n)
throws IOException
java.io.InputStreamn 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.
skip in class InputStreamn - the number of bytes to be skipped.IOException - if the stream does not support seek,
or if some other I/O error occurs.public int read()
throws IOException
java.io.InputStreamint 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.
read in class InputStream-1 if the end of the
stream is reached.IOException - if an I/O error occurs.public long length()
throws IOException
MeasurableStreamlength in interface MeasurableStreamIOExceptionpublic long position()
throws IOException
RepositionableStreamposition in interface MeasurableStreamposition in interface RepositionableStreamIOExceptionpublic void position(long position)
throws IOException
position in interface RepositionableStreamposition - the new position (will be minimized with length()).IOExceptionpublic boolean isOpen()
java.nio.channels.Channelpublic void mark(int readlimit)
java.io.InputStreamreset method repositions this stream at the last marked
position so that subsequent reads re-read the same bytes.
The readlimit arguments tells this input stream to
allow that many bytes to be read before the mark position gets
invalidated.
The general contract of mark is that, if the method
markSupported returns true, the stream somehow
remembers all the bytes read after the call to mark and
stands ready to supply those same bytes again if and whenever the method
reset is called. However, the stream is not required to
remember any data at all if more than readlimit bytes are
read from the stream before reset is called.
Marking a closed stream should not have any effect on the stream.
The mark method of InputStream does
nothing.
mark in class InputStreamreadlimit - the maximum limit of bytes that can be read before
the mark position becomes invalid.InputStream.reset()public void reset()
throws IOException
java.io.InputStreammark method was last called on this input stream.
The general contract of reset is:
markSupported returns
true, then:
mark has not been called since
the stream was created, or the number of bytes read from the stream
since mark was last called is larger than the argument
to mark at that last call, then an
IOException might be thrown.
IOException is not thrown, then the
stream is reset to a state such that all the bytes read since the
most recent call to mark (or since the start of the
file, if mark has not been called) will be resupplied
to subsequent callers of the read method, followed by
any bytes that otherwise would have been the next input data as of
the time of the call to reset. markSupported returns
false, then:
reset may throw an
IOException.
IOException is not thrown, then the stream
is reset to a fixed state that depends on the particular type of the
input stream and how it was created. The bytes that will be supplied
to subsequent callers of the read method depend on the
particular type of the input stream. The method reset for class InputStream
does nothing except throw an IOException.
reset in class InputStreamIOException - if this stream has not been marked or if the
mark has been invalidated.InputStream.mark(int),
IOExceptionpublic boolean markSupported()
java.io.InputStreammark and
reset methods. Whether or not mark and
reset are supported is an invariant property of a
particular input stream instance. The markSupported method
of InputStream returns false.markSupported in class InputStreamtrue if this stream instance supports the mark
and reset methods; false otherwise.InputStream.mark(int),
InputStream.reset()