Interface DataFileHandle

  • All Known Implementing Classes:
    LocalDataFileHandle

    public interface DataFileHandle
    DataFileHandle provides a random-access handle to a file.
    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      void close()
      Closes this random access file stream and releases any system resources associated with the stream.
      boolean isReadOnly()
      Returns true if this data file handle is open read-only.
      long length()
      Returns the length of this file.
      void read​(byte[] b)
      Reads b.length bytes from this file into the byte array, starting at the current file pointer.
      void read​(byte[] b, int off, int len)
      Reads exactly len bytes from this file into the byte array, starting at the current file pointer.
      void seek​(long pos)
      Sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs.
      void setLength​(long newLength)
      Sets the length of this file.
      int skipBytes​(int n)
      Attempts to skip over n bytes of input discarding the skipped bytes.
      void write​(byte[] b)
      Writes b.length bytes from the specified byte array to this file, starting at the current file pointer.
      void write​(byte[] b, int off, int len)
      Writes len bytes from the specified byte array starting at offset off to this file.
      void write​(int b)
      Writes the specified byte to this file.
    • Method Detail

      • isReadOnly

        boolean isReadOnly()
                    throws java.io.IOException
        Returns true if this data file handle is open read-only.
        Throws:
        java.io.IOException - if an I/O error occurs.
      • read

        void read​(byte[] b)
           throws java.io.IOException
        Reads b.length bytes from this file into the byte array, starting at the current file pointer. This method reads repeatedly from the file until the requested number of bytes are read. This method blocks until the requested number of bytes are read, the end of the stream is detected, or an exception is thrown.
        Parameters:
        b - the buffer into which the data is read.
        Throws:
        java.io.EOFException - if this file reaches the end before reading all the bytes.
        java.io.IOException - if an I/O error occurs.
      • read

        void read​(byte[] b,
                  int off,
                  int len)
           throws java.io.IOException
        Reads exactly len bytes from this file into the byte array, starting at the current file pointer. This method reads repeatedly from the file until the requested number of bytes are read. This method blocks until the requested number of bytes are read, the end of the stream is detected, or an exception is thrown.
        Parameters:
        b - the buffer into which the data is read.
        off - the start offset of the data.
        len - the number of bytes to read.
        Throws:
        java.io.EOFException - if this file reaches the end before reading all the bytes.
        java.io.IOException - if an I/O error occurs.
      • skipBytes

        int skipBytes​(int n)
               throws java.io.IOException
        Attempts to skip over n bytes of input discarding the skipped bytes.

        This method may skip over some smaller number of bytes, possibly zero. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. This method never throws an EOFException. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped.

        Parameters:
        n - the number of bytes to be skipped.
        Returns:
        the actual number of bytes skipped.
        Throws:
        java.io.IOException - if an I/O error occurs.
      • write

        void write​(int b)
            throws java.io.IOException
        Writes the specified byte to this file. The write starts at the current file pointer.
        Parameters:
        b - the byte to be written.
        Throws:
        java.io.IOException - if an I/O error occurs.
      • write

        void write​(byte[] b)
            throws java.io.IOException
        Writes b.length bytes from the specified byte array to this file, starting at the current file pointer.
        Parameters:
        b - the data.
        Throws:
        java.io.IOException - if an I/O error occurs.
      • write

        void write​(byte[] b,
                   int off,
                   int len)
            throws java.io.IOException
        Writes len bytes from the specified byte array starting at offset off to this file.
        Parameters:
        b - the data.
        off - the start offset in the data.
        len - the number of bytes to write.
        Throws:
        java.io.IOException - if an I/O error occurs.
      • seek

        void seek​(long pos)
           throws java.io.IOException
        Sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs. The offset may be set beyond the end of the file. Setting the offset beyond the end of the file does not change the file length. The file length will change only by writing after the offset has been set beyond the end of the file.
        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 - if pos is less than 0 or if an I/O error occurs.
      • length

        long length()
             throws java.io.IOException
        Returns the length of this file.
        Returns:
        the length of this file, measured in bytes.
        Throws:
        java.io.IOException - if an I/O error occurs.
      • setLength

        void setLength​(long newLength)
                throws java.io.IOException
        Sets the length of this file.

        If the present length of the file as returned by the length method is greater than the newLength argument then the file will be truncated. In this case, if the file offset as returned by the getFilePointer method is greater then newLength then after this method returns the offset will be equal to newLength.

        If the present length of the file as returned by the length method is smaller than the newLength argument then the file will be extended. In this case, the contents of the extended portion of the file are not defined.

        Parameters:
        newLength - The desired length of the file
        Throws:
        java.io.IOException - If an I/O error occurs
      • close

        void close()
            throws java.io.IOException
        Closes this random access file stream and releases any system resources associated with the stream. A closed random access file cannot perform input or output operations and cannot be reopened.
        Throws:
        java.io.IOException - if an I/O error occurs.