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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Xml;
namespace Anoto
{
/// <remarks>
/// This class implements a table-driven finite state machine.
/// The table is defined by an XML document. The System.Xml.XmlTextReader
/// class is used for fast scanning of the table and allows larger tables
/// to be used as opposed to System.Xml.XmlDocument.
/// </remarks>
class XMLStateMachine
{
private XmlTextReader tableParser;
private string stateCurrent;
private string stateTable;
private string action;
public XMLStateMachine()
{
tableParser = null;
stateCurrent = String.Empty;
stateTable = String.Empty;
action = String.Empty;
}
/// <summary>
/// The CurrentState property contains the current state in the table.
/// </summary>
public string CurrentState
{
get
{
return stateCurrent;
}
set
{
stateCurrent = value;
}
}
/// <summary>
/// The Action property contains a user-defined string
/// that indicates an action to be performed on the current transition.
/// </summary>
public string Action
{
get
{
return action;
}
}
/// <summary>
/// The StateTable property contains the state table file name.
/// </summary>
public string StateTable
{
get
{
return stateTable;
}
set
{
stateTable = value;
}
}
/// <summary>
/// The Next method gets the next valid state given
/// the current state and the supplied input.
/// </summary>
/// <param name="inputArg">The input used to trigger a state transition.</param>
/// <returns>A string that identifies the next state</returns>
public string Next(string inputArg)
{
string nextState = String.Empty;
if (CurrentState != String.Empty)
{
try
{
tableParser = new XmlTextReader(StateTable);
while (true == tableParser.Read())
{
if (XmlNodeType.Element == tableParser.NodeType)
{
if (true == tableParser.HasAttributes)
{
string state = tableParser.GetAttribute("name");
if (state == CurrentState)
{
// Get transition data
while (true == tableParser.Read())
{
if ((XmlNodeType.Element == tableParser.NodeType) && ("transition" == tableParser.Name))
{
if (true == tableParser.HasAttributes)
{
string input = tableParser.GetAttribute("input");
if (input == inputArg)
{
CurrentState = tableParser.GetAttribute("next");
nextState = CurrentState;
action = tableParser.GetAttribute("action");
return nextState;
}
}
}
}
}
}
}
}
}
catch (XmlException e)
{
// Eliminate default trace listener
Trace.Listeners.RemoveAt(0);
// Add console trace listener
TextWriterTraceListener myWriter = new TextWriterTraceListener(System.Console.Out);
Trace.Listeners.Add(myWriter);
Trace.WriteLine("[XMLStateMachine] Could not load state table definition.");
Trace.Indent();
Trace.WriteLine(e.Message);
Trace.Unindent();
// Clean up object
tableParser.Close();
tableParser = null;
stateCurrent = String.Empty;
action = String.Empty;
}
}
return nextState;
}
}
}
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