java 数据库管理系统 DBMS

/* * Created on 2005-1-24 * * TODO To change the template for this generated file go to * Window - Preferences - Java - Code Style - Code Templates */ package buffer; import java.util.Arrays; import recordmanagement.AttributeType; import dataitem.BooleanItem; import dataitem.CharItem; import dataitem.DataItem; import dataitem.DoubleItem; import dataitem.IntegerItem; import dataitem.LongItem; import dataitem.StringItem; import dataitem.TimeItem; import diskaccess.DiskManagement; /** * @author zh * * TODO To change the template for this generated type comment go to * Window - Preferences - Java - Code Style - Code Templates */ public class IndexBlock extends Block { private static final int NOT_NULL_OFFSET = 1; private static final int POINTER_OFFSET = 4; private static final int KEY_NUMBER_OFFSET = 0; private static final int LAST_POINTER_OFFSET = 2; private static final int STARTING_OFFSET = LAST_POINTER_OFFSET + POINTER_OFFSET; /** * 节点中key的个数 */ private short keyNum; /** * 子节点地址 */ private int[] pointerArray; /** * 键类型 */ private AttributeType type; /** * 数据 */ private DataItem[] keyArray; /** * @param buffer * @param id */ IndexBlock(byte[] buffer, IDEntry id) { super(buffer, id); } public void initialize(AttributeType type, boolean byExternal) { if (initialized()) { if (byExternal) { throw new IllegalArgumentException("new block has an error"); } return; } this.type = type; int n = type.getIndexCapacity(); // 两个数组都加一，方便插入，实际上只能有n个指针，n-1个键 pointerArray = new int[n + 2]; keyArray = new DataItem[n + 1]; if (byExternal) { setData(null); keyNum = 0; // 叶节点中最后一个顺序指针初始化 pointerArray[n + 1] = -1; modified = true; return; } keyNum = getShort(KEY_NUMBER_OFFSET); pointerArray[n + 1] = getInt(LAST_POINTER_OFFSET); int offset = STARTING_OFFSET; for (int i = 0; i <= keyNum; i++) { pointerArray[i] = getInt(offset); offset += POINTER_OFFSET; } // 读入键 readKey(offset); // 不需要如此大的空间了 setData(null); } private void readKey(int offset) { int keyByteAndNullFlagLength = type.getByteLength() + NOT_NULL_OFFSET; switch (type.getType()) { case AttributeType.BOOLEAN: for (int i = 0; i < keyNum; i++) { if (getBoolean(offset)) keyArray[i] = new BooleanItem(getBoolean(offset + NOT_NULL_OFFSET)); offset += keyByteAndNullFlagLength; } break; case AttributeType.CHAR: for (int i = 0; i < keyNum; i++) { if (getBoolean(offset)) keyArray[i] = new CharItem( getChar(offset + NOT_NULL_OFFSET)); offset += keyByteAndNullFlagLength; } break; case AttributeType.INTEGER: for (int i = 0; i < keyNum; i++) { if (getBoolean(offset)) keyArray[i] = new IntegerItem(getInt(offset + NOT_NULL_OFFSET)); offset += keyByteAndNullFlagLength; } break; case AttributeType.LONG: for (int i = 0; i < keyNum; i++) { if (getBoolean(offset)) keyArray[i] = new LongItem( getLong(offset + NOT_NULL_OFFSET)); offset += keyByteAndNullFlagLength; } break; case AttributeType.DOUBLE: for (int i = 0; i < keyNum; i++) { if (getBoolean(offset)) keyArray[i] = new DoubleItem(getDouble(offset + NOT_NULL_OFFSET)); offset += keyByteAndNullFlagLength; } break; case AttributeType.TIME: for (int i = 0; i < keyNum; i++) { if (getBoolean(offset)) keyArray[i] = new TimeItem( getTime(offset + NOT_NULL_OFFSET)); offset += keyByteAndNullFlagLength; } break; case AttributeType.STRING: for (int i = 0; i < keyNum; i++) { if (getBoolean(offset)) keyArray[i] = new StringItem(getString(offset + NOT_NULL_OFFSET, keyByteAndNullFlagLength / 2)); offset += keyByteAndNullFlagLength; } break; default: System.out.println("illegal argument"); break; } } protected void releaseMemory(DiskManagement disk) { if (modified) { int size = STARTING_OFFSET + (keyNum + 1) * POINTER_OFFSET + keyNum * (type.getByteLength() + NOT_NULL_OFFSET); byte[] dt = new byte[size]; setData(dt); setShort(KEY_NUMBER_OFFSET, keyNum); setInt(LAST_POINTER_OFFSET, pointerArray[pointerArray.length - 1]); int offset = STARTING_OFFSET; for (int i = 0; i <= keyNum; i++) { setInt(offset, pointerArray[i]); offset += POINTER_OFFSET; } writeKey(offset); modified = false; super.writeBlock(disk); } // 清空内存空间 pointerArray = null; keyArray = null; } private void writeKey(int offset) { int keyByteAndNullFlagLength = type.getByteLength() + NOT_NULL_OFFSET; switch (type.getType()) { case AttributeType.BOOLEAN: for (int i = 0; i < keyNum; i++) { if (keyArray[i] != null) { setBoolean(offset, true); setBoolean(offset + NOT_NULL_OFFSET, ((BooleanItem)keyArray[i]).getData() ); } else { setBoolean(offset, false); } offset += keyByteAndNullFlagLength; } break; case AttributeType.CHAR: for (int i = 0; i < keyNum; i++) { if (keyArray[i] != null) { setBoolean(offset, true); setChar(offset + NOT_NULL_OFFSET, ((CharItem)keyArray[i]).getData() ); } else { setBoolean(offset, false); } offset += keyByteAndNullFlagLength; } break; case AttributeType.INTEGER: for (int i = 0; i < keyNum; i++) { if (keyArray[i] != null) { setBoolean(offset, true); setInt(offset + NOT_NULL_OFFSET, ((IntegerItem)keyArray[i]).getData() ); } else { setBoolean(offset, false); } offset += keyByteAndNullFlagLength; } break; case AttributeType.LONG: for (int i = 0; i < keyNum; i++) { if (keyArray[i] != null) { setBoolean(offset, true); setLong(offset + NOT_NULL_OFFSET, ((LongItem)keyArray[i]).getData() ); } else { setBoolean(offset, false); } offset += keyByteAndNullFlagLength; } break;