Class SegmentedImageInputStream
- All Implemented Interfaces:
Closeable
,DataInput
,AutoCloseable
,ImageInputStream
SegmentedImageInputStream
provides a view of a
subset of another ImageInputStream
consiting of a series
of segments with given starting positions in the source stream and
lengths. The resulting stream behaves like an ordinary
ImageInputStream
.
For example, given a ImageInputStream
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 SegmentedImageInputStream
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 SegmentedImageInputStream
, who see a
separate ImageInputStream
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 SegmentedImageInputStream
. 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.
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate StreamSegmentMapper
private ImageInputStream
private StreamSegment
Fields inherited from class javax.imageio.stream.ImageInputStreamImpl
bitOffset, byteOrder, flushedPos, streamPos
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Constructor Summary
ConstructorsConstructorDescriptionSegmentedImageInputStream
(ImageInputStream stream, long[] segmentPositions, int[] segmentLengths) Constructs aSegmentedImageInputStream
given aImageInputStream
as input and a list of the starting positions and lengths of the segments of the source stream.SegmentedImageInputStream
(ImageInputStream stream, long[] segmentPositions, int segmentLength, int totalLength) Constructs aSegmentedImageInputStream
given aImageInputStream
as input, a list of the starting positions of the segments of the source stream, the common length of each segment, and the total length of the segments.SegmentedImageInputStream
(ImageInputStream stream, StreamSegmentMapper mapper) Constructs aSegmentedImageInputStream
given aImageInputStream
as input and an instance ofStreamSegmentMapper
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Method Summary
Methods inherited from class javax.imageio.stream.ImageInputStreamImpl
checkClosed, close, finalize, flush, flushBefore, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, isCached, isCachedFile, isCachedMemory, mark, read, readBit, readBits, readBoolean, readByte, readBytes, readChar, readDouble, readFloat, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedInt, readUnsignedShort, readUTF, reset, seek, setBitOffset, setByteOrder, skipBytes, skipBytes
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Field Details
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stream
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mapper
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streamSegment
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Constructor Details
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SegmentedImageInputStream
Constructs aSegmentedImageInputStream
given aImageInputStream
as input and an instance ofStreamSegmentMapper
.- Parameters:
stream
- A sourceImageInputStream
mapper
- An instance of theStreamSegmentMapper
interface.
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SegmentedImageInputStream
public SegmentedImageInputStream(ImageInputStream stream, long[] segmentPositions, int[] segmentLengths) Constructs aSegmentedImageInputStream
given aImageInputStream
as input and a list of the starting positions and lengths of the segments of the source stream.- Parameters:
stream
- A sourceImageInputStream
segmentPositions
- An array oflong
s giving the starting positions of the segments in the source stream.segmentLengths
- An array ofint
s giving the lengths of segments in the source stream.
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SegmentedImageInputStream
public SegmentedImageInputStream(ImageInputStream stream, long[] segmentPositions, int segmentLength, int totalLength) Constructs aSegmentedImageInputStream
given aImageInputStream
as input, a list of the starting positions of the segments of the source stream, the common length of each segment, and the total length of the segments.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.
- Parameters:
stream
- A sourceImageInputStream
segmentPositions
- An array oflong
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.
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Method Details
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read
Reads the next byte of data from the input stream. The value byte is returned as anint
in the range0
to255
. 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.- Specified by:
read
in interfaceImageInputStream
- Specified by:
read
in classImageInputStreamImpl
- Returns:
- the next byte of data, or
-1
if the end of the stream is reached. - Throws:
IOException
- if an I/O error occurs.
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read
Reads up tolen
bytes of data from the input stream into an array of bytes. An attempt is made to read as many aslen
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
isnull
, aNullPointerException
is thrown.If
off
is negative, orlen
is negative, oroff+len
is greater than the length of the arrayb
, then anIndexOutOfBoundsException
is thrown.If
len
is zero, then no bytes are read and0
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 intob
.The first byte read is stored into element
b[off]
, the next one intob[off+1]
, and so on. The number of bytes read is, at most, equal tolen
. Let k be the number of bytes actually read; these bytes will be stored in elementsb[off]
throughb[off+
k-1]
, leaving elementsb[off+
k]
throughb[off+len-1]
unaffected.In every case, elements
b[0]
throughb[off]
and elementsb[off+len]
throughb[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, anIOException
is thrown if the input stream has been closed.- Specified by:
read
in interfaceImageInputStream
- Specified by:
read
in classImageInputStreamImpl
- Parameters:
b
- the buffer into which the data is read.off
- the start offset in arrayb
at which the data is written.len
- the maximum number of bytes to read.- Returns:
- 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. - Throws:
IOException
- if an I/O error occurs.
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length
public long length()- Specified by:
length
in interfaceImageInputStream
- Overrides:
length
in classImageInputStreamImpl
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