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java.lang.Object | +--java.io.InputStream | +--com.sun.media.jai.codec.SeekableStream | +--com.sun.media.jai.codec.SegmentedSeekableStream
A SegmentedSeekableStream
provides a view of a
subset of another SeekableStream
consiting of a series
of segments with given starting positions in the source stream and
lengths. The resulting stream behaves like an ordinary
SeekableStream
.
For example, given a SeekableStream
containing
data in a format consisting of a number of sub-streams stored in
non-contiguous sectors indexed by a directory, it is possible to
construct a set of SegmentedSeekableStream
s, one for
each sub-stream, that each provide a view of the sectors comprising
a particular stream by providing the positions and lengths of the
stream's sectors as indicated by the directory. The complex
multi-stream structure of the original stream may be ignored by
users of the SegmentedSeekableStream
, who see a
separate SeekableStream
for each sub-stream and do not
need to understand the directory structure at all.
For further efficiency, a directory structure such as in the
example described above need not be fully parsed in order to build
a SegmentedSeekableStream
. Instead, the
StreamSegmentMapper
interface allows the association
between a desired region of the output and an input segment to be
provided dynamically. This mapping might be computed by reading
from a directory in piecemeal fashion in order to avoid consuming
memory resources.
It is the responsibility of the user of this class to determine
whether backwards seeking should be enabled. If the source stream
supports only forward seeking, backwards seeking must be disabled
and the StreamSegmentMapper
must be monotone; that is,
forward motion in the destination must always result in forward
motion within the source. If the source stream supports backwards
seeking, there are no restrictions on the
StreamSegmentMapper
and backwards seeking may always
be enabled for the SegmentedSeekableStream
.
This class is not a committed part of the JAI API. It may be removed or changed in future releases of JAI.
Fields inherited from class com.sun.media.jai.codec.SeekableStream |
markPos |
Constructor Summary | |
SegmentedSeekableStream(SeekableStream stream,
long[] segmentPositions,
int[] segmentLengths,
boolean canSeekBackwards)
Constructs a SegmentedSeekableStream given a
SeekableStream as input, a list of the starting
positions and lengths of the segments of the source stream, and
a boolean indicating whether the output
SegmentedSeekableStream should support seeking
backwards. |
|
SegmentedSeekableStream(SeekableStream stream,
long[] segmentPositions,
int segmentLength,
int totalLength,
boolean canSeekBackwards)
Constructs a SegmentedSeekableStream given a
SeekableStream as input, a list of the starting
positions of the segments of the source stream, the common
length of each segment, the total length of the segments and
a boolean indicating whether the output
SegmentedSeekableStream should support seeking
backwards. |
|
SegmentedSeekableStream(SeekableStream stream,
StreamSegmentMapper mapper,
boolean canSeekBackwards)
Constructs a SegmentedSeekableStream
given a SeekableStream as input,
an instance of StreamSegmentMapper ,
and a boolean indicating whether the
output SegmentedSeekableStream should
support seeking backwards. |
Method Summary | |
boolean |
canSeekBackwards()
Returns true if seeking backwards is supported. |
long |
getFilePointer()
Returns the current offset in this stream. |
int |
read()
Reads the next byte of data from the input stream. |
int |
read(byte[] b,
int off,
int len)
Reads up to len bytes of data from the input stream into
an array of bytes. |
void |
seek(long pos)
Sets the offset, measured from the beginning of this stream, at which the next read occurs. |
Methods inherited from class com.sun.media.jai.codec.SeekableStream |
finalize, mark, markSupported, readBoolean, readByte, readChar, readCharLE, readDouble, readDoubleLE, readFloat, readFloatLE, readFully, readFully, readInt, readIntLE, readLine, readLong, readLongLE, readShort, readShortLE, readUnsignedByte, readUnsignedInt, readUnsignedIntLE, readUnsignedShort, readUnsignedShortLE, readUTF, reset, skipBytes, wrapInputStream |
Methods inherited from class java.io.InputStream |
available, close, read, skip |
Methods inherited from class java.lang.Object |
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public SegmentedSeekableStream(SeekableStream stream, StreamSegmentMapper mapper, boolean canSeekBackwards)
SegmentedSeekableStream
given a SeekableStream
as input,
an instance of StreamSegmentMapper
,
and a boolean
indicating whether the
output SegmentedSeekableStream
should
support seeking backwards. If canSeekBackwards
is true
, the source stream must itself
support seeking backwards.stream
- A source SeekableStream
mapper
- An instance of the StreamSegmentMapper
interface.canSeekBackwards
- true
if the ability to
seek backwards is desired.public SegmentedSeekableStream(SeekableStream stream, long[] segmentPositions, int[] segmentLengths, boolean canSeekBackwards)
SegmentedSeekableStream
given a
SeekableStream
as input, a list of the starting
positions and lengths of the segments of the source stream, and
a boolean
indicating whether the output
SegmentedSeekableStream
should support seeking
backwards. If canSeekBakckwards
is
true
, the source stream must itself support
seeking backwards.stream
- A source SeekableStream
segmentPositions
- An array of long
s
giving the starting positions of the segments in the
source stream.segmentLengths
- An array of int
s
giving the lengths of segments in the source stream.canSeekBackwards
- true
if the ability to
seek backwards is desired.public SegmentedSeekableStream(SeekableStream stream, long[] segmentPositions, int segmentLength, int totalLength, boolean canSeekBackwards)
SegmentedSeekableStream
given a
SeekableStream
as input, a list of the starting
positions of the segments of the source stream, the common
length of each segment, the total length of the segments and
a boolean
indicating whether the output
SegmentedSeekableStream
should support seeking
backwards. If canSeekBakckwards
is
true
, the source stream must itself support
seeking backwards.
This constructor is useful for selecting substreams of sector-oriented file formats in which each segment of the substream (except possibly the final segment) occupies a fixed-length sector.
stream
- A source SeekableStream
segmentPositions
- An array of long
s
giving the starting positions of the segments in the
source stream.segmentLength
- The common length of each segment.totalLength
- The total length of the source segments.canSeekBackwards
- true
if the ability to
seek backwards is desired.Method Detail |
public long getFilePointer()
getFilePointer
in class SeekableStream
public boolean canSeekBackwards()
true
if seeking backwards is supported.
Support is determined by the value of the
canSeekBackwards
parameter at construction time.canSeekBackwards
in class SeekableStream
public void seek(long pos) throws IOException
If canSeekBackwards()
returns false
,
then setting pos
to an offset smaller than
the current value of getFilePointer()
will have
no effect.
seek
in class SeekableStream
pos
- the offset position, measured in bytes from the
beginning of the stream, at which to set the stream
pointer.IOException
- if pos
is less than
0
or if an I/O error occurs.public int read() throws IOException
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.read
in class SeekableStream
-1
if the end of the
stream is reached.IOException
- if an I/O error occurs.public int read(byte[] b, int off, int len) throws IOException
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, possibly
zero. The number of bytes actually read is returned as an integer.
This method blocks until input data is available, end of stream is detected, or an exception is thrown.
If b
is null
, a
NullPointerException
is thrown.
If off
is negative, or len
is negative, or
off+len
is greater than the length of the array
b
, then an IndexOutOfBoundsException
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
stream, 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.
If the first byte cannot be read for any reason other than end of
stream, then an IOException
is thrown. In particular, an
IOException
is thrown if the input stream has been closed.
read
in class SeekableStream
b
- the buffer into which the data is read.off
- the start offset in array b
at which the data is written.len
- 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 an I/O error occurs.
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