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/**
* com.mckoi.database.CollatedBaseSearch 26 Aug 2002
*
* Mckoi SQL Database ( http://www.mckoi.com/database )
* Copyright (C) 2000, 2001, 2002 Diehl and Associates, Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* Version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License Version 2 for more details.
*
* You should have received a copy of the GNU General Public License
* Version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Change Log:
*
*
*/
package com.mckoi.database;
import java.io.*;
import com.mckoi.util.IntegerVector;
import com.mckoi.util.BlockIntegerList;
/**
* An implementation of SelectableScheme that is based on some collated set of
* data. This can be used to implement more advanced types of selectable
* schemes based on presistant indexes (see InsertSearch).
*
* The default implementation maintains no state,
*
* Derived classes are required to implement 'copy', 'searchFirst' and
* 'searchLast' methods. With these basic methods, a selectable scheme can
* be generated provided the column is sorted in ascending order (value of row i
* is <= value of row i+1). Overwrite 'firstInCollationOrder',
* 'lastInCollationOrder' and 'addRangeToSet' methods for non sorted underlying
* sets.
*
* Assumptions - the underlying column is sorted low to high (value of row i
* is <= value of row i+1).
*
* @author Tobias Downer
*/
public abstract class CollatedBaseSearch extends SelectableScheme {
/**
* The Constructor.
*/
public CollatedBaseSearch(TableDataSource table, int column) {
super(table, column);
}
/**
* This scheme doesn't take any notice of insertions or removals.
*/
public void insert(int row) {
// Ignore insert (no state to maintain)
if (isImmutable()) {
throw new Error("Tried to change an immutable scheme.");
}
}
/**
* This scheme doesn't take any notice of insertions or removals.
*/
public void remove(int row) {
// Ignore remove (no state to maintain)
if (isImmutable()) {
throw new Error("Tried to change an immutable scheme.");
}
}
/**
* Reads the entire state of the scheme from the input stream.
* This is a trivial case for BlindSearch which doesn't require any
* data to be stored.
*/
public void readFrom(InputStream in) throws IOException {
}
/**
* Writes the entire state of the scheme to the output stream.
* This is a trivial case for BlindSearch which doesn't require any
* data to be stored.
*/
public void writeTo(OutputStream out) throws IOException {
}
/**
* Disposes and invalidates the BlindSearch.
*/
public void dispose() {
// Nothing to do!
}
// -------- Abstract or overwrittable methods ----------
/**
* Finds the position in the collated set of the first value in the column
* equal to the given value. If the value is not to be found in the column,
* it returns -(insert_position + 1).
*/
protected abstract int searchFirst(TObject val);
/**
* Finds the position in the collated set of the last value in the column
* equal to the given value. If the value is not to be found in the column,
* it returns -(insert_position + 1).
*/
protected abstract int searchLast(TObject val);
/**
* The size of the set (the number of rows in this column).
*/
protected int setSize() {
return getTable().getRowCount();
}
/**
* Returns the first value of this column (in collated order). For
* example, if the column contains (1, 4, 8} then '1' is returned.
*/
protected TObject firstInCollationOrder() {
return getCellContents(0);
}
/**
* Returns the last value of this column (in collated order). For
* example, if the column contains (1, 4, 8} then '8' is returned.
*/
protected TObject lastInCollationOrder() {
return getCellContents(setSize() - 1);
}
/**
* Adds the set indexes to the list that represent the range of values
* between the start (inclusive) and end offset (inclusive) given.
*/
protected IntegerVector addRangeToSet(int start, int end,
IntegerVector ivec) {
if (ivec == null) {
ivec = new IntegerVector((end - start) + 2);
}
for (int i = start; i <= end; ++i) {
ivec.addInt(i);
}
return ivec;
}
// ---------- Range search methods ----------
public IntegerVector selectAll() {
return addRangeToSet(0, setSize() - 1, null);
}
/**
* Given a flag (FIRST_VALUE, LAST_VALUE, BEFORE_FIRST_VALUE or
* AFTER_LAST_VALUE) and a value which is either a place marker (first, last
* in set) or a TObject object, this will determine the position in this
* set of the range point. For example, we may want to know the index of
* the last instance of a particular number in a set of numbers which
* would be 'positionOfRangePoint(SelectableRange.LAST_VALUE,
* [number TObject])'.
*
* Note how the position is determined if the value is not found in the set.
*/
private int positionOfRangePoint(byte flag, TObject val) {
int p;
TObject cell;
switch(flag) {
case(SelectableRange.FIRST_VALUE):
if (val == SelectableRange.FIRST_IN_SET) {
return 0;
}
if (val == SelectableRange.LAST_IN_SET) {
// Get the last value and search for the first instance of it.
cell = lastInCollationOrder();
}
else {
cell = val;
}
p = searchFirst(cell);
// (If value not found)
if (p < 0) {
return -(p + 1);
}
return p;
case(SelectableRange.LAST_VALUE):
if (val == SelectableRange.LAST_IN_SET) {
return setSize() - 1;
}
if (val == SelectableRange.FIRST_IN_SET) {
// Get the first value.
cell = firstInCollationOrder();
}
else {
cell = val;
}
p = searchLast(cell);
// (If value not found)
if (p < 0) {
return -(p + 1) - 1;
}
return p;
case(SelectableRange.BEFORE_FIRST_VALUE):
if (val == SelectableRange.FIRST_IN_SET) {
return -1;
}
if (val == SelectableRange.LAST_IN_SET) {
// Get the last value and search for the first instance of it.
cell = lastInCollationOrder();
}
else {
cell = val;
}
p = searchFirst(cell);
// (If value not found)
if (p < 0) {
return -(p + 1) - 1;
}
return p - 1;
case(SelectableRange.AFTER_LAST_VALUE):
if (val == SelectableRange.LAST_IN_SET) {
return setSize();
}
if (val == SelectableRange.FIRST_IN_SET) {
// Get the first value.
cell = firstInCollationOrder();
}
else {
cell = val;
}
p = searchLast(cell);
// (If value not found)
if (p < 0) {
return -(p + 1);
}
return p + 1;
default:
throw new Error("Unrecognised flag.");
}
}
/**
* Adds a range from this set to the given IntegerVector. IntegerVector may
* be null if a list has not yet been allocated for the range.
*/
private IntegerVector addRange(SelectableRange range, IntegerVector ivec) {
int r1, r2;
// Select the range specified.
byte start_flag = range.getStartFlag();
TObject start = range.getStart();
byte end_flag = range.getEndFlag();
TObject end = range.getEnd();
r1 = positionOfRangePoint(start_flag, start);
r2 = positionOfRangePoint(end_flag, end);
if (r2 < r1) {
return ivec;
}
// Add the range to the set
return addRangeToSet(r1, r2, ivec);
}
public IntegerVector selectRange(SelectableRange range) {
// If no items in the set return an empty set
if (setSize() == 0) {
return new IntegerVector(0);
}
IntegerVector ivec = addRange(range, null);
if (ivec == null) {
return new IntegerVector(0);
}
return ivec;
}
public IntegerVector selectRange(SelectableRange[] ranges) {
// If no items in the set return an empty set
if (setSize() == 0) {
return new IntegerVector(0);
}
IntegerVector ivec = null;
for (int i = 0; i < ranges.length; ++i) {
SelectableRange range = ranges[i];
ivec = addRange(range, ivec);
}
if (ivec == null) {
return new IntegerVector(0);
}
return ivec;
}
}