Class MemoryCacheSeekableStream
- All Implemented Interfaces:
Closeable
,DataInput
,AutoCloseable
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.
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate List
A Vector of source sectors.(package private) boolean
True if we've previously reached the end of the source stream(package private) int
Number of bytes read.private long
Position of first unread byte.private static final int
A mask to determine the offset within a sector.private static final int
Log_2 of the sector size.private static final int
The sector size.private InputStream
The source input stream.Fields inherited from class org.apache.xmlgraphics.image.codec.util.SeekableStream
markPos
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Constructor Summary
ConstructorsConstructorDescriptionConstructs aMemoryCacheSeekableStream
that takes its source data from a regularInputStream
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Method Summary
Modifier and TypeMethodDescriptionboolean
Returnstrue
since allMemoryCacheSeekableStream
instances support seeking backwards.long
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 tolen
bytes of data from the input stream into an array of bytes.private long
readUntil
(long pos) Ensures that at leastpos
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.Methods inherited from class org.apache.xmlgraphics.image.codec.util.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, nullInputStream, read, readAllBytes, readNBytes, readNBytes, skip, skipNBytes, transferTo
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Field Details
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src
The source input stream. -
pointer
private long pointerPosition of first unread byte. -
SECTOR_SHIFT
private static final int SECTOR_SHIFTLog_2 of the sector size.- See Also:
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SECTOR_SIZE
private static final int SECTOR_SIZEThe sector size.- See Also:
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SECTOR_MASK
private static final int SECTOR_MASKA mask to determine the offset within a sector.- See Also:
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data
A Vector of source sectors. -
length
int lengthNumber of bytes read. -
foundEOS
boolean foundEOSTrue if we've previously reached the end of the source stream
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Constructor Details
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MemoryCacheSeekableStream
Constructs aMemoryCacheSeekableStream
that takes its source data from a regularInputStream
. Seeking backwards is supported by means of an in-memory cache.
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Method Details
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readUntil
Ensures that at leastpos
bytes are cached, or the end of the source is reached. The return value is equal to the smaller ofpos
and the length of the source stream.- Throws:
IOException
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canSeekBackwards
public boolean canSeekBackwards()Returnstrue
since allMemoryCacheSeekableStream
instances support seeking backwards.- Overrides:
canSeekBackwards
in classSeekableStream
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getFilePointer
public long getFilePointer()Returns the current offset in this file.- Specified by:
getFilePointer
in classSeekableStream
- Returns:
- the offset from the beginning of the file, in bytes, at which the next read occurs.
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seek
Sets the file-pointer offset, measured from the beginning of this file, at which the next read occurs.- Specified by:
seek
in classSeekableStream
- Parameters:
pos
- the offset position, measured in bytes from the beginning of the file, at which to set the file pointer.- Throws:
IOException
- ifpos
is less than0
or if an I/O error occurs.
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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 classSeekableStream
- 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 file 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 file, 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 file, then an
IOException
is thrown. In particular, anIOException
is thrown if the input stream has been closed.- Specified by:
read
in classSeekableStream
- 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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