Package org.apache.derby.io

Interface StorageRandomAccessFile

  • All Superinterfaces:
    java.io.DataInput, java.io.DataOutput
    All Known Implementing Classes:
    DirRandomAccessFile, VirtualRandomAccessFile
    public interface StorageRandomAccessFile
extends java.io.DataInput, java.io.DataOutput
    This interface abstracts an object that implements reading and writing on a random access file. It extends DataInput and DataOutput, so it implicitly contains all the methods of those interfaces. Any method in this interface that also appears in the java.io.RandomAccessFile class should behave as the java.io.RandomAccessFile method does.

    Each StorageRandomAccessFile has an associated file pointer, a byte offset in the file. All reading and writing takes place at the file pointer offset and advances it.

    An implementation of StorageRandomAccessFile need not be thread safe. The database engine single-threads access to each StorageRandomAccessFile instance. Two threads will not access the same StorageRandomAccessFile instance at the same time.

    See Also:
    java.io.RandomAccessFile

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      StorageRandomAccessFile clone()
      Clone this file abstraction
      void close()
      Closes this file.
      long getFilePointer()
      Get the current offset in this file.
      long length()
      Gets the length of this file.
      int read​(byte[] b, int off, int len)
      Reads up to len bytes of data from this file into an array of bytes.
      void seek​(long newFilePointer)
      Set the file pointer.
      void setLength​(long newLength)
      Sets the length of this file, either extending or truncating it.
      void sync()
      Force any changes out to the persistent store.

      • Methods inherited from interface java.io.DataInput

        readBoolean, readByte, readChar, readDouble, readFloat, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedShort, readUTF, skipBytes

      • Methods inherited from interface java.io.DataOutput

        write, write, write, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF

    • Method Detail

      • close

        void close()
    throws java.io.IOException
        Closes this file.
        Throws:
        java.io.IOException - - if an I/O error occurs.

      • getFilePointer

        long getFilePointer()
             throws java.io.IOException
        Get the current offset in this file.
        Returns:
        the current file pointer.
        Throws:
        java.io.IOException - - if an I/O error occurs.

      • length

        long length()
     throws java.io.IOException
        Gets the length of this file.
        Returns:
        the number of bytes this file.
        Throws:
        java.io.IOException - - if an I/O error occurs.

      • seek

        void seek​(long newFilePointer)
   throws java.io.IOException
        Set the file pointer. It may be moved beyond the end of the file, but this does not change the length of the file. The length of the file is not changed until data is actually written..
        Parameters:
        newFilePointer - the new file pointer, measured in bytes from the beginning of the file.
        Throws:
        java.io.IOException - - if newFilePointer is less than 0 or an I/O error occurs.

      • setLength

        void setLength​(long newLength)
        throws java.io.IOException
        Sets the length of this file, either extending or truncating it.

        If the file is extended then the contents of the extension are not defined.

        If the file is truncated and the file pointer is greater than the new length then the file pointer is set to the new length.

        Parameters:
        newLength - The new file length.
        Throws:
        java.io.IOException - If an I/O error occurs.

      • sync

        void sync()
   throws java.io.IOException
        Force any changes out to the persistent store. If the database is to be transient, that is, if the database does not survive a restart, then the sync method implementation need not do anything.
        Throws:
        java.io.SyncFailedException - if a possibly recoverable error occurs.
        java.io.IOException - If an IO error occurs.

      • read

        int read​(byte[] b,
         int off,
         int len)
  throws java.io.IOException
        Reads up to len bytes of data from this file into an array of bytes. This method blocks until at least one byte of input is available.

        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 read.
        Returns:
        the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file 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 random access file 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