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package org.apache.poi.ss.formula;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import org.apache.poi.ss.formula.eval.BlankEval;
import org.apache.poi.ss.formula.eval.ErrorEval;
import org.apache.poi.ss.formula.eval.ValueEval;
/**
* Instances of this class keep track of multiple dependent cell evaluations due
* to recursive calls to {@link WorkbookEvaluator#evaluate(EvaluationCell)}}
* The main purpose of this class is to detect an attempt to evaluate a cell
* that is already being evaluated. In other words, it detects circular
* references in spreadsheet formulas.
*
* @author Josh Micich
*/
final class EvaluationTracker {
// TODO - consider deleting this class and letting CellEvaluationFrame take care of itself
private final List _evaluationFrames;
private final Set _currentlyEvaluatingCells;
private final EvaluationCache _cache;
public EvaluationTracker(EvaluationCache cache) {
_cache = cache;
_evaluationFrames = new ArrayList();
_currentlyEvaluatingCells = new HashSet();
}
/**
* Notifies this evaluation tracker that evaluation of the specified cell is
* about to start.
*
* In the case of a true return code, the caller should
* continue evaluation of the specified cell, and also be sure to call
* endEvaluate() when complete.
*
* In the case of a null return code, the caller should
* return an evaluation result of
* ErrorEval.CIRCULAR_REF_ERROR, and not call endEvaluate().
*
* @return false if the specified cell is already being evaluated
*/
public boolean startEvaluate(FormulaCellCacheEntry cce) {
if (cce == null) {
throw new IllegalArgumentException("cellLoc must not be null");
}
if (_currentlyEvaluatingCells.contains(cce)) {
return false;
}
_currentlyEvaluatingCells.add(cce);
_evaluationFrames.add(new CellEvaluationFrame(cce));
return true;
}
public void updateCacheResult(ValueEval result) {
int nFrames = _evaluationFrames.size();
if (nFrames < 1) {
throw new IllegalStateException("Call to endEvaluate without matching call to startEvaluate");
}
CellEvaluationFrame frame = _evaluationFrames.get(nFrames-1);
if (result == ErrorEval.CIRCULAR_REF_ERROR && nFrames > 1) {
// Don't cache a circular ref error result if this cell is not the top evaluated cell.
// A true circular ref error will propagate all the way around the loop. However, it's
// possible to have parts of the formula tree (/ parts of the loop) to evaluate to
// CIRCULAR_REF_ERROR, and that value not get used in the final cell result (see the
// unit tests for a simple example). Thus, the only CIRCULAR_REF_ERROR result that can
// safely be cached is that of the top evaluated cell.
return;
}
frame.updateFormulaResult(result);
}
/**
* Notifies this evaluation tracker that the evaluation of the specified cell is complete.
*
* Every successful call to startEvaluate must be followed by a call to endEvaluate (recommended in a finally block) to enable
* proper tracking of which cells are being evaluated at any point in time.
*
* Assuming a well behaved client, parameters to this method would not be
* required. However, they have been included to assert correct behaviour,
* and form more meaningful error messages.
*/
public void endEvaluate(CellCacheEntry cce) {
int nFrames = _evaluationFrames.size();
if (nFrames < 1) {
throw new IllegalStateException("Call to endEvaluate without matching call to startEvaluate");
}
nFrames--;
CellEvaluationFrame frame = _evaluationFrames.get(nFrames);
if (cce != frame.getCCE()) {
throw new IllegalStateException("Wrong cell specified. ");
}
// else - no problems so pop current frame
_evaluationFrames.remove(nFrames);
_currentlyEvaluatingCells.remove(cce);
}
public void acceptFormulaDependency(CellCacheEntry cce) {
// Tell the currently evaluating cell frame that it has a dependency on the specified
int prevFrameIndex = _evaluationFrames.size()-1;
if (prevFrameIndex < 0) {
// Top level frame, there is no 'cell' above this frame that is using the current cell
} else {
CellEvaluationFrame consumingFrame = _evaluationFrames.get(prevFrameIndex);
consumingFrame.addSensitiveInputCell(cce);
}
}
public void acceptPlainValueDependency(int bookIndex, int sheetIndex,
int rowIndex, int columnIndex, ValueEval value) {
// Tell the currently evaluating cell frame that it has a dependency on the specified
int prevFrameIndex = _evaluationFrames.size() - 1;
if (prevFrameIndex < 0) {
// Top level frame, there is no 'cell' above this frame that is using the current cell
} else {
CellEvaluationFrame consumingFrame = _evaluationFrames.get(prevFrameIndex);
if (value == BlankEval.instance) {
consumingFrame.addUsedBlankCell(bookIndex, sheetIndex, rowIndex, columnIndex);
} else {
PlainValueCellCacheEntry cce = _cache.getPlainValueEntry(bookIndex, sheetIndex,
rowIndex, columnIndex, value);
consumingFrame.addSensitiveInputCell(cce);
}
}
}
}