Class MemoryCacheSeekableStream
- 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.MemoryCacheSeekableStream
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- All Implemented Interfaces:
java.io.Closeable,java.io.DataInput,java.lang.AutoCloseable
public final class MemoryCacheSeekableStream extends SeekableStream
A subclass ofSeekableStreamthat may be used to wrap a regularInputStream. Seeking backwards is supported by means of an in-memory cache. For greater efficiency,FileCacheSeekableStreamshould be used in circumstances that allow the creation of a temporary file.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: MemoryCacheSeekableStream.java 1733416 2016-03-03 07:07:13Z gadams $
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Field Summary
Fields Modifier and Type Field Description private java.util.ListdataA Vector of source sectors.(package private) booleanfoundEOSTrue if we've previously reached the end of the source stream(package private) intlengthNumber of bytes read.private longpointerPosition of first unread byte.private static intSECTOR_MASKA mask to determine the offset within a sector.private static intSECTOR_SHIFTLog_2 of the sector size.private static intSECTOR_SIZEThe sector size.(package private) intsectorsNumber of sectors stored.private java.io.InputStreamsrcThe source input stream.-
Fields inherited from class org.apache.batik.ext.awt.image.codec.util.SeekableStream
markPos
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Constructor Summary
Constructors Constructor Description MemoryCacheSeekableStream(java.io.InputStream src)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 allMemoryCacheSeekableStreaminstances support seeking backwards.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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src
private java.io.InputStream src
The source input stream.
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pointer
private long pointer
Position of first unread byte.
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SECTOR_SHIFT
private static final int SECTOR_SHIFT
Log_2 of the sector size.- See Also:
- Constant Field Values
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SECTOR_SIZE
private static final int SECTOR_SIZE
The sector size.- See Also:
- Constant Field Values
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SECTOR_MASK
private static final int SECTOR_MASK
A mask to determine the offset within a sector.- See Also:
- Constant Field Values
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data
private java.util.List data
A Vector of source sectors.
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sectors
int sectors
Number of sectors stored.
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length
int length
Number of bytes read.
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foundEOS
boolean foundEOS
True if we've previously reached the end of the source stream
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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 stream.- Throws:
java.io.IOException
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canSeekBackwards
public boolean canSeekBackwards()
Returnstruesince allMemoryCacheSeekableStreaminstances 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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