X-Git-Url: http://gitweb.fperrin.net/?p=GpsPrune.git;a=blobdiff_plain;f=src%2Ftim%2Fprune%2Fundo%2FUndoStack.java;fp=src%2Ftim%2Fprune%2Fundo%2FUndoStack.java;h=d3e85e02e3f5d078eb49ac612e084528d34eae1c;hp=0000000000000000000000000000000000000000;hb=ce6f2161b8596f7018d6a76bff79bc9e571f35fd;hpb=2d8cb72e84d5cc1089ce77baf1e34ea3ea2f8465

diff --git a/src/tim/prune/undo/UndoStack.java b/src/tim/prune/undo/UndoStack.java
new file mode 100644
index 0000000..d3e85e0
--- /dev/null
+++ b/src/tim/prune/undo/UndoStack.java
@@ -0,0 +1,62 @@
+package tim.prune.undo;
+
+import java.util.Stack;
+
+/**
+ * Class to hold an undo operation together with a counter
+ */
+class UndoOpWithState
+{
+	public UndoOperation _undoOperation = null;
+	public int           _undoCounter = 0;
+	/** Constructor */
+	public UndoOpWithState(UndoOperation inOp, int inCounter)
+	{
+		_undoOperation = inOp;
+		_undoCounter   = inCounter;
+	}
+}
+
+/**
+ * Stack of undo operations
+ * which also remembers how many undos have been performed
+ */
+public class UndoStack extends Stack<UndoOpWithState>
+{
+	/** Number of undos (and clears) already performed */
+	private int _numUndos = 0;
+
+	@Override
+	public void clear()
+	{
+		_numUndos++;
+		super.clear();
+	}
+
+	/** Add an undo operation to the stack */
+	public synchronized boolean add(UndoOperation inOp)
+	{
+		return super.add(new UndoOpWithState(inOp, _numUndos));
+	}
+
+	/** Pop the latest operation from the stack */
+	public synchronized UndoOperation popOperation()
+	{
+		_numUndos++;
+		return super.pop()._undoOperation;
+	}
+
+	/** Get the operation at the given index */
+	public UndoOperation getOperationAt(int inIndex)
+	{
+		return super.elementAt(inIndex)._undoOperation;
+	}
+
+	/** @return number of undos */
+	public int getNumUndos()
+	{
+		if (isEmpty()) {return 0;}
+		// Get the number of undos stored by the last operation on the stack
+		return peek()._undoCounter;
+	}
+}