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 ofSeekableStreamthat 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), theMemoryCacheSeekableStreamclass 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[]bufThe read buffer.private intbufLenThe length of the read buffer.private java.io.RandomAccessFilecacheThe cache as a RandomAcessFile.private java.io.FilecacheFileThe cache File.private booleanfoundEOFTrue if we've encountered the end of the source stream.private longlengthNumber of bytes in the cache.private longpointerNext byte to be read.private java.io.InputStreamstreamThe 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 aMemoryCacheSeekableStreamthat takes its source data from a regularInputStream.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description booleancanSeekBackwards()Returnstruesince allFileCacheSeekableStreaminstances support seeking backwards.voidclose()Closes this stream and releases any system resources associated with the stream.longgetFilePointer()Returns the current offset in this file.intread()Reads the next byte of data from the input stream.intread(byte[] b, int off, int len)Reads up tolenbytes of data from the input stream into an array of bytes.private longreadUntil(long pos)Ensures that at leastposbytes are cached, or the end of the source is reached.voidseek(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.IOExceptionConstructs aMemoryCacheSeekableStreamthat takes its source data from a regularInputStream. Seeking backwards is supported by means of an file cache.An
IOExceptionwill 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.IOExceptionEnsures that at leastposbytes are cached, or the end of the source is reached. The return value is equal to the smaller ofposand the length of the source file.- Throws:
java.io.IOException
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canSeekBackwards
public boolean canSeekBackwards()
Returnstruesince allFileCacheSeekableStreaminstances support seeking backwards.- Overrides:
canSeekBackwardsin classSeekableStream
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getFilePointer
public long getFilePointer()
Returns the current offset in this file.- Specified by:
getFilePointerin 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.IOExceptionSets the file-pointer offset, measured from the beginning of this file, at which the next read occurs.- Specified by:
seekin 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- ifposis less than0or if an I/O error occurs.
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read
public int read() throws java.io.IOExceptionReads the next byte of data from the input stream. The value byte is returned as anintin the range0to255. If no byte is available because the end of the stream has been reached, the value-1is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.- Specified by:
readin classSeekableStream- Returns:
- the next byte of data, or
-1if 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.IOExceptionReads up tolenbytes of data from the input stream into an array of bytes. An attempt is made to read as many aslenbytes, 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
bisnull, aNullPointerExceptionis thrown.If
offis negative, orlenis negative, oroff+lenis greater than the length of the arrayb, then anIndexOutOfBoundsExceptionis thrown.If
lenis zero, then no bytes are read and0is 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-1is 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
IOExceptionis thrown. In particular, anIOExceptionis thrown if the input stream has been closed.- Specified by:
readin classSeekableStream- Parameters:
b- the buffer into which the data is read.off- the start offset in arraybat which the data is written.len- the maximum number of bytes to read.- Returns:
- the total number of bytes read into the buffer, or
-1if 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.IOExceptionCloses this stream and releases any system resources associated with the stream.- Specified by:
closein interfacejava.lang.AutoCloseable- Specified by:
closein interfacejava.io.Closeable- Overrides:
closein classjava.io.InputStream- Throws:
java.io.IOException- if an I/O error occurs.
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