Package org.apache.derby.impl.jdbc

Class UpdatableBlobStream

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable
    class UpdatableBlobStream
extends java.io.InputStream
    Updatable blob stream is a wrapper stream over dvd stream and LOBInputStream. It detects if blob data has moved from dvd to clob control. If this happens, it will update itself to point to LOBInputStream and reflect changes made to the Blob after the current position of the stream.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private EmbedBlob blob  
      private boolean materialized
      Flag to check if it is using stream from LOBStreamControl or from DVD.
      private long maxPos
      Position in Blob where to stop reading unless EOF is reached first.
      private long pos  
      private java.io.InputStream stream  

    • Constructor Summary

      Constructors 
      Constructor Description
      UpdatableBlobStream​(EmbedBlob blob, java.io.InputStream is)
      Constructs UpdatableBlobStream using the the InputStream receives as the parameter.
      UpdatableBlobStream​(EmbedBlob blob, java.io.InputStream is, long pos, long len)
      Construct an UpdatableBlobStream using the InputStream received as parameter.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int read()
      Reads the next byte of data from the input stream.
      int read​(byte[] b)
      Reads some number of bytes from the input stream and stores them into the buffer array b.
      int read​(byte[] b, int off, int len)
      Reads up to len bytes of data from the input stream into an array of bytes.
      long skip​(long n)
      Skips over and discards n bytes of data from this input stream.
      private void updateIfRequired()
      Checks if this object is using materialized blob if not it checks if the blob was materialized since this stream was last access.

      • Methods inherited from class java.io.InputStream

        available, close, mark, markSupported, nullInputStream, readAllBytes, readNBytes, readNBytes, reset, transferTo

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • materialized

        private boolean materialized
        Flag to check if it is using stream from LOBStreamControl or from DVD. true means data is read from LOBStreamControl, false means data is read from the DVD.

      • stream

        private java.io.InputStream stream

      • pos

        private long pos

      • maxPos

        private final long maxPos
        Position in Blob where to stop reading unless EOF is reached first.

    • Constructor Detail

      • UpdatableBlobStream

        UpdatableBlobStream​(EmbedBlob blob,
                    java.io.InputStream is)
             throws java.io.IOException
        Constructs UpdatableBlobStream using the the InputStream receives as the parameter. The initial position is set to the 0.
        Parameters:
        blob - EmbedBlob this stream is associated with.
        is - InputStream this class is going to use internally.
        Throws:
        java.io.IOException - if an I/O error occurs

      • UpdatableBlobStream

        UpdatableBlobStream​(EmbedBlob blob,
                    java.io.InputStream is,
                    long pos,
                    long len)
             throws java.io.IOException
        Construct an UpdatableBlobStream using the InputStream received as parameter. The initial position in the stream is set to pos and the stream is restricted to a length of len.
        Parameters:
        blob - EmbedBlob this stream is associated with.
        is - InputStream this class is going to use internally.
        pos - initial position
        len - The length to which the underlying InputStream has to be restricted.
        Throws:
        java.io.IOException

    • Method Detail

      • updateIfRequired

        private void updateIfRequired()
                       throws java.io.IOException
        Checks if this object is using materialized blob if not it checks if the blob was materialized since this stream was last access. If the blob was materialized (due to one of the set methods) it gets the stream again and sets the position to current read position.
        Throws:
        java.io.IOException

      • read

        public int read()
         throws java.io.IOException
        Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. 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.

        A subclass must provide an implementation of this method.

        Note that this stream will reflect changes made to the underlying Blob at positions equal to or larger then the current position.

        Specified by:
        read in class java.io.InputStream
        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.
        See Also:
        InputStream.read()

      • read

        public int read​(byte[] b,
                int off,
                int len)
         throws java.io.IOException
        Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer.

        Note that this stream will reflect changes made to the underlying Blob at positions equal to or larger then the current position .

        Overrides:
        read in class java.io.InputStream
        Parameters:
        b - the buffer into which the data is read.
        off - the start offset in array b 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 the first byte cannot be read for any reason other than end of file, or if the input stream has been closed, or if some other I/O error occurs.
        java.lang.NullPointerException - If b is null.
        java.lang.IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off
        See Also:
        InputStream.read(byte[],int,int)

      • read

        public int read​(byte[] b)
         throws java.io.IOException
        Reads some number of bytes from the input stream and stores them into the buffer array b. 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.

        Note that this stream will reflect changes made to the underlying Blob at positions equal to or larger then the current position .

        Overrides:
        read in class java.io.InputStream
        Parameters:
        b - the buffer into which the data is read.
        Returns:
        the total number of bytes read into the buffer, or -1 is there is no more data because the end of the stream has been reached.
        Throws:
        java.io.IOException - If the first byte cannot be read for any reason other than the end of the file, if the input stream has been closed, or if some other I/O error occurs.
        java.lang.NullPointerException - if b is null.
        See Also:
        InputStream.read(byte[])

      • skip

        public long skip​(long n)
          throws java.io.IOException
        Skips over and discards n bytes of data from this input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped.

        Note that this stream will reflect changes made to the underlying Blob at positions equal to or larger then the current position .

        Overrides:
        skip in class java.io.InputStream
        Parameters:
        n - the number of bytes to be skipped.
        Returns:
        the actual number of bytes skipped.
        Throws:
        java.io.IOException - if the stream does not support seek, or if some other I/O error occurs.
        See Also:
        InputStream.skip(long)