Class FileCacheSeekableStream
- java.lang.Object
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- java.io.InputStream
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- org.apache.batik.ext.awt.image.codec.util.SeekableStream
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- org.apache.batik.ext.awt.image.codec.util.FileCacheSeekableStream
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- All Implemented Interfaces:
java.io.Closeable
,java.io.DataInput
,java.lang.AutoCloseable
public final class FileCacheSeekableStream extends SeekableStream
A subclass ofSeekableStream
that may be used to wrap a regularInputStream
. Seeking backwards is supported by means of a file cache. In circumstances that do not allow the creation of a temporary file (for example, due to security consideration or the absence of local disk), theMemoryCacheSeekableStream
class may be used instead.The
mark()
andreset()
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.
- Version:
- $Id: FileCacheSeekableStream.java 1733416 2016-03-03 07:07:13Z gadams $
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Field Summary
Fields Modifier and Type Field Description private byte[]
buf
The read buffer.private int
bufLen
The length of the read buffer.private java.io.RandomAccessFile
cache
The cache as a RandomAcessFile.private java.io.File
cacheFile
The cache File.private boolean
foundEOF
True if we've encountered the end of the source stream.private long
length
Number of bytes in the cache.private long
pointer
Next byte to be read.private java.io.InputStream
stream
The source stream.-
Fields inherited from class org.apache.batik.ext.awt.image.codec.util.SeekableStream
markPos
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Constructor Summary
Constructors Constructor Description FileCacheSeekableStream(java.io.InputStream stream)
Constructs aMemoryCacheSeekableStream
that takes its source data from a regularInputStream
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
canSeekBackwards()
Returnstrue
since allFileCacheSeekableStream
instances support seeking backwards.void
close()
Closes this stream and releases any system resources associated with the stream.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 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.batik.ext.awt.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
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Field Detail
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stream
private java.io.InputStream stream
The source stream.
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cacheFile
private java.io.File cacheFile
The cache File.
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cache
private java.io.RandomAccessFile cache
The cache as a RandomAcessFile.
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bufLen
private int bufLen
The length of the read buffer.
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buf
private byte[] buf
The read buffer.
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length
private long length
Number of bytes in the cache.
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pointer
private long pointer
Next byte to be read.
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foundEOF
private boolean foundEOF
True if we've encountered the end of the source stream.
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Constructor Detail
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FileCacheSeekableStream
public FileCacheSeekableStream(java.io.InputStream stream) throws java.io.IOException
Constructs aMemoryCacheSeekableStream
that takes its source data from a regularInputStream
. Seeking backwards is supported by means of an file cache.An
IOException
will be thrown if the attempt to create the cache file fails for any reason.- Throws:
java.io.IOException
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Method Detail
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readUntil
private long readUntil(long pos) throws java.io.IOException
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 file.- Throws:
java.io.IOException
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canSeekBackwards
public boolean canSeekBackwards()
Returnstrue
since allFileCacheSeekableStream
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
public void seek(long pos) throws java.io.IOException
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:
java.io.IOException
- ifpos
is less than0
or if an I/O error occurs.
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read
public int read() throws java.io.IOException
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:
java.io.IOException
- if an I/O error occurs.
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read
public int read(byte[] b, int off, int len) throws java.io.IOException
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:
java.io.IOException
- if an I/O error occurs.
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close
public void close() throws java.io.IOException
Closes this stream and releases any system resources associated with the stream.- Specified by:
close
in interfacejava.lang.AutoCloseable
- Specified by:
close
in interfacejava.io.Closeable
- Overrides:
close
in classjava.io.InputStream
- Throws:
java.io.IOException
- if an I/O error occurs.
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