public final class MemoryCacheSeekableStream extends SeekableStream
SeekableStream
that may be used to wrap
a regular InputStream
. Seeking backwards is supported
by means of an in-memory cache. For greater efficiency,
FileCacheSeekableStream
should be used in
circumstances that allow the creation of a temporary file.
The mark()
and reset()
methods are
supported.
This class is not a committed part of the JAI API. It may be removed or changed in future releases of JAI.
Modifier and Type | Field and Description |
---|---|
private java.util.List |
data
A Vector of source sectors.
|
(package private) boolean |
foundEOS
True if we've previously reached the end of the source stream
|
(package private) int |
length
Number of bytes read.
|
private long |
pointer
Position of first unread byte.
|
private static int |
SECTOR_MASK
A mask to determine the offset within a sector.
|
private static int |
SECTOR_SHIFT
Log_2 of the sector size.
|
private static int |
SECTOR_SIZE
The sector size.
|
private java.io.InputStream |
src
The source input stream.
|
markPos
Constructor and Description |
---|
MemoryCacheSeekableStream(java.io.InputStream src)
Constructs a
MemoryCacheSeekableStream that takes
its source data from a regular InputStream . |
Modifier and Type | Method and Description |
---|---|
boolean |
canSeekBackwards()
Returns
true since all
MemoryCacheSeekableStream instances support seeking
backwards. |
long |
getFilePointer()
Returns the current offset in this file.
|
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. |
private long |
readUntil(long pos)
Ensures that at least
pos bytes are cached,
or the end of the source is reached. |
void |
seek(long pos)
Sets the file-pointer offset, measured from the beginning of this
file, at which the next read occurs.
|
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
private java.io.InputStream src
private long pointer
private static final int SECTOR_SHIFT
private static final int SECTOR_SIZE
private static final int SECTOR_MASK
private java.util.List data
int length
boolean foundEOS
public MemoryCacheSeekableStream(java.io.InputStream src)
MemoryCacheSeekableStream
that takes
its source data from a regular InputStream
.
Seeking backwards is supported by means of an in-memory cache.private long readUntil(long pos) throws java.io.IOException
pos
bytes are cached,
or the end of the source is reached. The return value
is equal to the smaller of pos
and the
length of the source stream.java.io.IOException
public boolean canSeekBackwards()
true
since all
MemoryCacheSeekableStream
instances support seeking
backwards.canSeekBackwards
in class SeekableStream
public long getFilePointer()
getFilePointer
in class SeekableStream
public void seek(long pos) throws java.io.IOException
seek
in class SeekableStream
pos
- the offset position, measured in bytes from the
beginning of the file, at which to set the file
pointer.java.io.IOException
- if pos
is less than
0
or if an I/O error occurs.public int read() throws java.io.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.java.io.IOException
- if an I/O error occurs.public int read(byte[] b, int off, int len) throws java.io.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 file 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
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.
If the first byte cannot be read for any reason other than end of
file, 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.java.io.IOException
- if an I/O error occurs.