Class LOBInputStream
- java.lang.Object
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- java.io.InputStream
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- org.apache.derby.impl.jdbc.LOBInputStream
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- All Implemented Interfaces:
java.io.Closeable,java.lang.AutoCloseable,PositionedStream
public class LOBInputStream extends java.io.InputStream implements PositionedStream
This input stream is built on top ofLOBStreamControl.All the read methods are routed to
LOBStreamControl.
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Field Summary
Fields Modifier and Type Field Description private booleanclosedprivate LOBStreamControlcontrolprivate longposprivate longupdateCount
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Constructor Summary
Constructors Constructor Description LOBInputStream(LOBStreamControl control, long position)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.io.InputStreamasInputStream()Returns a reference to self as anInputStream.voidclose()Closes this input stream and releases any system resources associated with the stream.longgetPosition()Returns the current byte position.(package private) booleanisObsolete()Checks if underlying StreamControl has been updated.(package private) longlength()Returns size of stream in bytes.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.(package private) voidreInitialize()Reinitializes the stream and sets the current pointer to zero.voidreposition(long requestedPos)Repositions the stream to the requested byte position.
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Field Detail
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closed
private boolean closed
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control
private final LOBStreamControl control
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pos
private long pos
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updateCount
private long updateCount
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Constructor Detail
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LOBInputStream
LOBInputStream(LOBStreamControl control, long position)
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Method Detail
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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. 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.The
read(b,off,len)method for classInputStreamsimply calls the methodread()repeatedly. If the first such call results in anIOException, that exception is returned from the call to theread(b,off,len)method. If any subsequent call toread()results in aIOException, the exception is caught and treated as if it were end of file; the bytes read up to that point are stored intoband the number of bytes read before the exception occurred is returned. Subclasses are encouraged to provide a more efficient implementation of this method.- Overrides:
readin classjava.io.InputStream- 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.java.lang.NullPointerException- ifbisnull.- See Also:
InputStream.read()
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close
public void close() throws java.io.IOExceptionCloses this input stream and releases any system resources associated with the stream.The
closemethod ofInputStreamdoes nothing.- 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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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.A subclass must provide an implementation of this method.
- Specified by:
readin classjava.io.InputStream- 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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isObsolete
boolean isObsolete()
Checks if underlying StreamControl has been updated.- Returns:
- if stream is modified since created
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reInitialize
void reInitialize()
Reinitializes the stream and sets the current pointer to zero.
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length
long length() throws java.io.IOExceptionReturns size of stream in bytes.- Returns:
- size of stream.
- Throws:
java.io.IOException
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asInputStream
public java.io.InputStream asInputStream()
Description copied from interface:PositionedStreamReturns a reference to self as anInputStream.This method is not allowed to return
null.- Specified by:
asInputStreamin interfacePositionedStream- Returns:
- An
InputStreamreference to self.
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getPosition
public long getPosition()
Returns the current byte position.- Specified by:
getPositionin interfacePositionedStream- Returns:
- The current byte position.
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reposition
public void reposition(long requestedPos) throws java.io.IOExceptionRepositions the stream to the requested byte position.- Specified by:
repositionin interfacePositionedStream- Parameters:
requestedPos- the requested position, starting at0- Throws:
java.io.EOFException- if the requested position is larger than the lengthjava.io.IOException- if obtaining the stream length fails
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