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package java.awt.image;

/** 
 * Class that manages arrays of data elements. A data buffer consists
 * of one or more banks.  A bank is a continuous region of data
 * elements.
 *
 * @author Rolf W. Rasmussen (rolfwr@ii.uib.no)
 */
public abstract class DataBuffer
{
  /**
   * A constant representing a data type that uses <code>byte</code> primitives
   * as the storage unit.
   */
  public static final int TYPE_BYTE      =  0;

  /**
   * A constant representing a data type that uses <code>short</code> 
   * primitives as the storage unit.
   */
  public static final int TYPE_USHORT    =  1;

  /**
   * A constant representing a data type that uses <code>short</code> 
   * primitives as the storage unit.
   */
  public static final int TYPE_SHORT     =  2;

  /**
   * A constant representing a data type that uses <code>int</code> 
   * primitives as the storage unit.
   */
  public static final int TYPE_INT       =  3;
  
  /**
   * A constant representing a data type that uses <code>float</code> 
   * primitives as the storage unit.
   */
  public static final int TYPE_FLOAT     =  4;

  /**
   * A constant representing a data type that uses <code>double</code> 
   * primitives as the storage unit.
   */
  public static final int TYPE_DOUBLE    =  5;

  /**
   * A constant representing an undefined data type.
   */
  public static final int TYPE_UNDEFINED = 32;
  
  /** The type of the data elements stored in the data buffer.  */
  protected int dataType;
  
  /** The number of banks in this buffer.  */
  protected int banks = 1;
  
  /** Offset into the default (0'th) bank). */
  protected int offset; // FIXME: Is offsets[0] always mirrored in offset?
  
  /** The size of the banks.  */
  protected int size;
  
  /** Offset into each bank.  */
  protected int[] offsets;
  
  /**
   * Creates a new <code>DataBuffer</code> with the specified data type and
   * size.  The <code>dataType</code> should be one of the constants 
   * {@link #TYPE_BYTE}, {@link #TYPE_SHORT}, {@link #TYPE_USHORT}, 
   * {@link #TYPE_INT}, {@link #TYPE_FLOAT} and {@link #TYPE_DOUBLE}.
   * <p>
   * The physical (array-based) storage is allocated by a subclass.
   * 
   * @param dataType the data type.
   * @param size the number of elements in the buffer.
   */
  protected DataBuffer(int dataType, int size)
  {
    this(dataType, size, 1);
  }

  /**
   * Creates a new <code>DataBuffer</code> with the specified data type,
   * size and number of banks.  The <code>dataType</code> should be one of 
   * the constants {@link #TYPE_BYTE}, {@link #TYPE_SHORT}, 
   * {@link #TYPE_USHORT}, {@link #TYPE_INT}, {@link #TYPE_FLOAT} and 
   * {@link #TYPE_DOUBLE}.
   * <p>
   * The physical (array-based) storage is allocated by a subclass.
   * 
   * @param dataType the data type.
   * @param size the number of elements in the buffer.
   * @param numBanks the number of data banks.
   */
  protected DataBuffer(int dataType, int size, int numBanks) {
    this(dataType, size, numBanks, 0);
  }

  /**
   * Creates a new <code>DataBuffer</code> with the specified data type,
   * size and number of banks.  An offset (which applies to all banks) is
   * also specified.  The <code>dataType</code> should be one of 
   * the constants {@link #TYPE_BYTE}, {@link #TYPE_SHORT}, 
   * {@link #TYPE_USHORT}, {@link #TYPE_INT}, {@link #TYPE_FLOAT} and 
   * {@link #TYPE_DOUBLE}.
   * <p>
   * The physical (array-based) storage is allocated by a subclass.
   * 
   * @param dataType the data type.
   * @param size the number of elements in the buffer.
   * @param numBanks the number of data banks.
   * @param offset the offset to the first element for all banks.
   */
  protected DataBuffer(int dataType, int size, int numBanks, int offset) {
    banks = numBanks;
    this.dataType = dataType;
    this.size = size;
    this.offset = offset;

    offsets = new int[ numBanks ];
    for(int i = 0; i < numBanks; i++ )
      offsets[i] = offset;
  }

  /**
   * Creates a new <code>DataBuffer</code> with the specified data type,
   * size and number of banks.  An offset (which applies to all banks) is
   * also specified.  The <code>dataType</code> should be one of 
   * the constants {@link #TYPE_BYTE}, {@link #TYPE_SHORT}, 
   * {@link #TYPE_USHORT}, {@link #TYPE_INT}, {@link #TYPE_FLOAT} and 
   * {@link #TYPE_DOUBLE}.
   * <p>
   * The physical (array-based) storage is allocated by a subclass.
   * 
   * @param dataType the data type.
   * @param size the number of elements in the buffer.
   * @param numBanks the number of data banks.
   * @param offsets the offsets to the first element for all banks.
   * 
   * @throws ArrayIndexOutOfBoundsException if 
   *         <code>numBanks != offsets.length</code>.
   */
  protected DataBuffer(int dataType, int size, int numBanks, int[] offsets) {
    if (numBanks != offsets.length) 
      throw new ArrayIndexOutOfBoundsException();

    this.dataType = dataType;
    this.size = size;
    banks = numBanks;
    this.offsets = offsets;
    
    offset = offsets[0];
  }
  
  /**
   * Returns the size (number of bits) of the specified data type. Valid types
   * are defined by the constants {@link #TYPE_BYTE}, {@link #TYPE_SHORT}, 
   * {@link #TYPE_USHORT}, {@link #TYPE_INT}, {@link #TYPE_FLOAT} and 
   * {@link #TYPE_DOUBLE}.
   * 
   * @param dataType the data type.
   * @return The number of bits for the specified data type.
   * @throws IllegalArgumentException if <code>dataType < 0</code> or 
   *         <code>dataType > TYPE_DOUBLE</code>.
   */
  public static int getDataTypeSize(int dataType) {
    // Maybe this should be a lookup table instead.
    switch (dataType)
      {
      case TYPE_BYTE:
	return 8;
      case TYPE_USHORT:
      case TYPE_SHORT:
	return 16;
      case TYPE_INT:
      case TYPE_FLOAT:
	return 32;
      case TYPE_DOUBLE:
	return 64;
      default:
	throw new IllegalArgumentException();
      }
  }

  /**
   * Returns the type of the data elements in the data buffer.  Valid types
   * are defined by the constants {@link #TYPE_BYTE}, {@link #TYPE_SHORT}, 
   * {@link #TYPE_USHORT}, {@link #TYPE_INT}, {@link #TYPE_FLOAT} and 
   * {@link #TYPE_DOUBLE}.
   * 
   * @return The type.
   */
  public int getDataType()
  {
    return dataType;
  }
  
  /**
   * Returns the size of the data buffer.
   * 
   * @return The size.
   */
  public int getSize()
  {
    return size;
  }
  
  /**
   * Returns the element offset for the first data bank.
   * 
   * @return The element offset.
   */
  public int getOffset()
  {
    return offset;
  }
  
  /**
   * Returns the offsets for all the data banks used by this 
   * <code>DataBuffer</code>.
   * 
   * @return The offsets.
   */
  public int[] getOffsets()
  {
    if (offsets == null)
    {
      // is this necessary?
      offsets = new int[1];
      offsets[0] = offset;
    }
    return offsets;
  }

  /**
   * Returns the number of data banks for this <code>DataBuffer</code>.
   * @return The number of data banks.
   */
  public int getNumBanks()
  {
    return banks;
  }

  /**
   * Returns an element from the first data bank.  The offset (specified in
   * the constructor) is added to <code>i</code> before accessing the 
   * underlying data array.
   * 
   * @param i the element index.
   * @return The element.
   */
  public int getElem(int i)
  {
    return getElem(0, i);
  }

  /**
   * Returns an element from a particular data bank.  The offset (specified in
   * the constructor) is added to <code>i</code> before accessing the 
   * underlying data array.
   * 
   * @param bank the bank index.
   * @param i the element index.
   * @return The element.
   */
  public abstract int getElem(int bank, int i);
  
  /**
   * Sets an element in the first data bank.  The offset (specified in the
   * constructor) is added to <code>i</code> before updating the underlying
   * data array.
   * 
   * @param i the element index.
   * @param val the new element value.
   */
  public void setElem(int i, int val)
  {
    setElem(0, i, val);
  }

  /**
   * Sets an element in a particular data bank.  The offset (specified in the
   * constructor) is added to <code>i</code> before updating the underlying
   * data array.
   * 
   * @param bank the data bank index.
   * @param i the element index.
   * @param val the new element value.
   */
  public abstract void setElem(int bank, int i, int val);
  
  /**
   * Returns an element from the first data bank, converted to a 
   * <code>float</code>.  The offset (specified in the constructor) is added 
   * to <code>i</code> before accessing the underlying data array.
   * 
   * @param i the element index.
   * @return The element.
   */
  public float getElemFloat(int i)
  {
    return getElem(i);
  }
    
  /**
   * Returns an element from a particular data bank, converted to a 
   * <code>float</code>.  The offset (specified in the constructor) is 
   * added to <code>i</code> before accessing the underlying data array.
   * 
   * @param bank the bank index.
   * @param i the element index.
   * @return The element.
   */
  public float getElemFloat(int bank, int i)
  {
    return getElem(bank, i);
  }

  /**
   * Sets an element in the first data bank.  The offset (specified in the
   * constructor) is added to <code>i</code> before updating the underlying
   * data array. 
   * 
   * @param i the element index.
   * @param val the new element value.
   */
  public void setElemFloat(int i, float val)
  {
    setElem(i, (int) val);
  }

  /**
   * Sets an element in a particular data bank.  The offset (specified in the
   * constructor) is added to <code>i</code> before updating the underlying
   * data array.
   * 
   * @param bank the data bank index.
   * @param i the element index.
   * @param val the new element value.
   */
  public void setElemFloat(int bank, int i, float val)
  {
    setElem(bank, i, (int) val);
  }

  /**
   * Returns an element from the first data bank, converted to a 
   * <code>double</code>.  The offset (specified in the constructor) is added
   * to <code>i</code> before accessing the underlying data array.
   * 
   * @param i the element index.
   * @return The element.
   */
  public double getElemDouble(int i)
  {
    return getElem(i);
  }
    
  /**
   * Returns an element from a particular data bank, converted to a 
   * <code>double</code>.  The offset (specified in the constructor) is 
   * added to <code>i</code> before accessing the underlying data array.
   * 
   * @param bank the bank index.
   * @param i the element index.
   * @return The element.
   */
  public double getElemDouble(int bank, int i)
  {
    return getElem(bank, i);
  }

  /**
   * Sets an element in the first data bank.  The offset (specified in the
   * constructor) is added to <code>i</code> before updating the underlying
   * data array. 
   * 
   * @param i the element index.
   * @param val the new element value.
   */
  public void setElemDouble(int i, double val)
  {
    setElem(i, (int) val);
  }

  /**
   * Sets an element in a particular data bank.  The offset (specified in the
   * constructor) is added to <code>i</code> before updating the underlying
   * data array.
   * 
   * @param bank the data bank index.
   * @param i the element index.
   * @param val the new element value.
   */
  public void setElemDouble(int bank, int i, double val)
  {
    setElem(bank, i, (int) val);
  }
}