X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=simgear%2Fmisc%2Fprops.hxx;h=b9a0157ac4bca01f341913748546a7357ce5c5cd;hb=5bab565cfe4c30d6cf08ecaba50af74d5e4f0c98;hp=ebaaf7f29e40f4b3973e8d24da5ad08a34ae5993;hpb=a1bf8d22297416de9524370f4c0d4f0f0c9e89d4;p=simgear.git

diff --git a/simgear/misc/props.hxx b/simgear/misc/props.hxx
index ebaaf7f2..b9a0157a 100644
--- a/simgear/misc/props.hxx
+++ b/simgear/misc/props.hxx
@@ -1,34 +1,45 @@
-// props.hxx -- declaration of SimGear Property Manager.
-//
-// Written by David Megginson - david@megginson.com
-//
-// This module is in the PUBLIC DOMAIN.
-//
-// 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 props.html for documentation [replace with URL when available].
-//
-// $Id$
+/**
+ * \file props.hxx
+ * Interface definition for a property list.
+ * Started Fall 2000 by David Megginson, david@megginson.com
+ * This code is released into the Public Domain.
+ *
+ * See props.html for documentation [replace with URL when available].
+ *
+ * $Id$
+ */
 
 #ifndef __PROPS_HXX
 #define __PROPS_HXX
 
+#include <simgear/compiler.h>
+
 #include <stdio.h>
 
-#include <string>
-#include <map>
-#include <iostream>
+#include STL_STRING
+#include <vector>
+#include STL_IOSTREAM
 
-using std::string;
-using std::map;
-using std::istream;
-using std::ostream;
+SG_USING_STD(string);
+SG_USING_STD(vector);
+#if !defined(SG_HAVE_NATIVE_SGI_COMPILERS)
+SG_USING_STD(istream);
+SG_USING_STD(ostream);
+#endif
+
+#ifdef NONE
+#pragma warn A sloppy coder has defined NONE as a macro!
+#undef NONE
+#endif
+
+#ifdef ALIAS
+#pragma warn A sloppy coder has defined ALIAS as a macro!
+#undef ALIAS
+#endif
 
-#ifdef UNKNOWN
-#pragma warn A sloppy coder has defined UNKNOWN as a macro!
-#undef UNKNOWN
+#ifdef UNSPECIFIED
+#pragma warn A sloppy coder has defined UNSPECIFIED as a macro!
+#undef UNSPECIFIED
 #endif
 
 #ifdef BOOL
@@ -41,6 +52,11 @@ using std::ostream;
 #undef INT
 #endif
 
+#ifdef LONG
+#pragma warn A sloppy coder has defined LONG as a macro!
+#undef LONG
+#endif
+
 #ifdef FLOAT
 #pragma warn A sloppy coder has defined FLOAT as a macro!
 #undef FLOAT
@@ -59,364 +75,1051 @@ using std::ostream;
 
 
 ////////////////////////////////////////////////////////////////////////
-// Values.
+// A raw value.
+//
+// This is the mechanism that information-providing routines can
+// use to link their own values to the property manager.  Any
+// SGValue can be tied to a raw value and then untied again.
 ////////////////////////////////////////////////////////////////////////
 
+
 /**
- * Abstract representation of a FlightGear value.
+ * Abstract base class for a raw value.
  *
- * This value is designed to be fairly robust -- it can exist without
- * a specified value, it can be any of several types, and it can
- * be tied to an external variable without disrupting any existing
- * pointers or references to the value.  Some basic type conversions
- * are also handled automatically.
+ * The property manager is implemented in three layers.  The {@link
+ * SGPropertyNode} is the highest and most abstract layer,
+ * representing * an LValue/RValue pair: it * records the position
+ * of the property in the property tree and * contains facilities
+ * for navigation to other nodes.  Each node * may contain an {@link
+ * SGValue}, which is guaranteed persistent: the * {@link SGValue}
+ * will not change during a session, even if the * property is bound
+ * and unbound multiple times.  The SGValue is the * abstraction of
+ * an RValue: it allows for conversion among all of the different
+ * types, and can be bound to external pointers, functions, methods,
+ * or other data sources.  Every SGValue contains an SGRawValue of
+ * a specific type.  The SGRawValue (this class) may change frequently
+ * during a session as a value is retyped or bound and unbound to
+ * various data source, but the abstract SGValue layer insulates
+ * the application from those changes.  The raw value contains no
+ * facilities for data binding or for type conversion: it is simply
+ * the abstraction of a primitive data type (or a compound data
+ * type, in the case of a string).
  *
- * Values also have attributes that control whether they can be read
- * from, written to, or archived (i.e. saved to disk).
- */
-class SGValue
+ * The SGValue class always keeps a *copy* of a raw value, not the
+ * original one passed to it; if you override a derived class but do
+ * not replace the {@link #clone} method, strange things will happen.
+ *
+ * All raw values must implement {@link #getValue}, {@link #setValue},
+ * and {@link #clone} for the appropriate type.
+ *
+ * @see SGValue
+ * @see SGPropertyNode */
+template <class T>
+class SGRawValue
 {
 public:
 
-				// External getters
-  typedef bool (*bool_getter)();
-  typedef int (*int_getter)();
-  typedef float (*float_getter)();
-  typedef double (*double_getter)();
-  typedef const string &(*string_getter)();
+  /**
+   * The default underlying value for this type.
+   *
+   * Every raw value has a default; the default is false for a
+   * boolean, 0 for the various numeric values, and "" for a string.
+   * If additional types of raw values are added in the future, they
+   * may need different kinds of default values (such as epoch for a
+   * date type).  The default value is used when creating new values.
+   */
+  static const T DefaultValue;	// Default for this kind of raw value.
+
+
+  /**
+   * Constructor.
+   *
+   * Use the default value for this type.
+   */
+  SGRawValue () {}
+
+
+  /**
+   * Destructor.
+   */
+  virtual ~SGRawValue () {}
+
+
+  /**
+   * Return the underlying value.
+   *
+   * @return The actual value for the property.
+   * @see #setValue
+   */
+  virtual T getValue () const = 0;
+
+
+  /**
+   * Assign a new underlying value.
+   *
+   * If the new value cannot be set (because this is a read-only
+   * raw value, or because the new value is not acceptable for
+   * some reason) this method returns false and leaves the original
+   * value unchanged.
+   *
+   * @param value The actual value for the property.
+   * @return true if the value was set successfully, false otherwise.
+   * @see #getValue
+   */
+  virtual bool setValue (T value) = 0;
+
+
+  /**
+   * Create a new deep copy of this raw value.
+   *
+   * The copy will contain its own version of the underlying value
+   * as well.
+   *
+   * @return A deep copy of the current object.
+   */
+  virtual SGRawValue * clone () const = 0;
+};
 
-				// External setters
-  typedef void (*bool_setter)(bool);
-  typedef void (*int_setter)(int);
-  typedef void (*float_setter)(float);
-  typedef void (*double_setter)(double);
-  typedef void (*string_setter)(const string &);
 
-  enum Type {
-    UNKNOWN,			// no value assigned yet
-    BOOL,			// boolean
-    INT,			// integer
-    FLOAT,			// floating point
-    DOUBLE,			// double precision
-    STRING			// text
-  };
+/**
+ * An unbound raw value, stored internally.
+ *
+ * Instances of this class are created automatically, by default,
+ * by the SGValue class; ordinarily the application should not
+ * need to touch it.
+ */
+template <class T>
+class SGRawValueInternal : public SGRawValue<T>
+{
+public:
 
-  SGValue ();
-  virtual ~SGValue ();
-
-				// Meta information.
-  virtual Type getType () const { return _type; }
-  virtual bool isTied () const { return _tied; }
-
-				// Accessors.
-  virtual bool getBoolValue () const;
-  virtual int getIntValue () const;
-  virtual float getFloatValue () const;
-  virtual double getDoubleValue () const;
-  virtual const string & getStringValue () const;
-
-				// Setters.
-  virtual bool setBoolValue (bool value);
-  virtual bool setIntValue (int value);
-  virtual bool setFloatValue (float value);
-  virtual bool setDoubleValue (double value);
-  virtual bool setStringValue (const string &value);
-  virtual bool setUnknownValue (const string &value);
-
-				// Tie to external variables.
-  virtual bool tieBool (bool_getter getter,
-			bool_setter setter = 0,
-			bool useDefault = true);
-  virtual bool tieInt (int_getter getter,
-		       int_setter setter = 0,
-		       bool useDefault = true);
-  virtual bool tieFloat (float_getter getter,
-			 float_setter setter = 0,
-			 bool useDefault = true);
-  virtual bool tieDouble (double_getter getter,
-			  double_setter setter = 0,
-			  bool useDefault = true);
-  virtual bool tieString (string_getter getter,
-			  string_setter setter = 0,
-			  bool useDefault = true);
-
-				// Untie from external variables.
-  virtual bool untie ();
+  /**
+   * Default constructor.
+   *
+   * Initialize with the default value for this type.
+   */
+  SGRawValueInternal () {}
+
+  /**
+   * Explicit value constructor.
+   *
+   * Initialize with the underlying value provided.
+   *
+   * @param value The initial value for this property.
+   */
+  SGRawValueInternal (T value) : _value(value) {}
+
+  /**
+   * Destructor.
+   */
+  virtual ~SGRawValueInternal () {}
+
+  /**
+   * Get the underlying value.
+   */
+  virtual T getValue () const { return _value; }
+
+  /**
+   * Set the underlying value.
+   */
+  virtual bool setValue (T value) { _value = value; return true; }
+
+  /**
+   * Create a deep copy of this raw value.
+   */
+  virtual SGRawValue<T> * clone () const {
+    return new SGRawValueInternal<T>(_value);
+  }
+
+private:
+  T _value;
+};
 
-protected:
 
-  bool getRawBool () const;
-  int getRawInt () const;
-  float getRawFloat () const;
-  double getRawDouble () const;
-  const string &getRawString () const;
+/**
+ * A raw value bound to a pointer.
+ *
+ * This is the most efficient way to tie an external value, but also
+ * the most dangerous, because there is no way for the supplier to
+ * perform bounds checking and derived calculations except by polling
+ * the variable to see if it has changed.  There is no default
+ * constructor, because this class would be meaningless without a
+ * pointer.
+ */
+template <class T>
+class SGRawValuePointer : public SGRawValue<T>
+{
+public:
 
-  bool setRawBool (bool value);
-  bool setRawInt (int value);
-  bool setRawFloat (float value);
-  bool setRawDouble (double value);
-  bool setRawString (const string & value);
+  /**
+   * Explicit pointer constructor.
+   *
+   * Create a new raw value bound to the value of the variable
+   * referenced by the pointer.
+   *
+   * @param ptr The pointer to the variable to which this raw value
+   * will be bound.
+   */
+  SGRawValuePointer (T * ptr) : _ptr(ptr) {}
+
+  /**
+   * Destructor.
+   */
+  virtual ~SGRawValuePointer () {}
+
+  /**
+   * Get the underlying value.
+   *
+   * This method will dereference the pointer and return the
+   * variable's value.
+   */
+  virtual T getValue () const { return *_ptr; }
+
+  /**
+   * Set the underlying value.
+   *
+   * This method will dereference the pointer and change the
+   * variable's value.
+   */
+  virtual bool setValue (T value) { *_ptr = value; return true; }
+
+  /**
+   * Create a copy of this raw value.
+   *
+   * The copy will use the same external pointer as the original.
+   */
+  virtual SGRawValue<T> * clone () const {
+    return new SGRawValuePointer<T>(_ptr);
+  }
 
 private:
+  T * _ptr;
+};
 
-  Type _type;
-  bool _tied;
 
-  mutable string string_val;
+/**
+ * A value managed through static functions.
+ *
+ * A read-only value will not have a setter; a write-only value will
+ * not have a getter.
+ */
+template <class T>
+class SGRawValueFunctions : public SGRawValue<T>
+{
+public:
 
-				// The value is one of the following...
-  union {
+  /**
+   * The template type of a static getter function.
+   */
+  typedef T (*getter_t)();
+
+  /**
+   * The template type of a static setter function.
+   */
+  typedef void (*setter_t)(T);
+
+  /**
+   * Explicit constructor.
+   *
+   * Create a new raw value bound to the getter and setter supplied.
+   *
+   * @param getter A static function for getting a value, or 0
+   * to read-disable the value.
+   * @param setter A static function for setting a value, or 0
+   * to write-disable the value.
+   */
+  SGRawValueFunctions (getter_t getter = 0, setter_t setter = 0)
+    : _getter(getter), _setter(setter) {}
+
+  /**
+   * Destructor.
+   */
+  virtual ~SGRawValueFunctions () {}
+
+  /**
+   * Get the underlying value.
+   *
+   * This method will invoke the getter function to get a value.
+   * If no getter function was supplied, this method will always
+   * return the default value for the type.
+   */
+  virtual T getValue () const {
+    if (_getter) return (*_getter)();
+    else return SGRawValue<T>::DefaultValue;
+  }
 
-    bool bool_val;
-    int int_val;
-    float float_val;
-    double double_val;
-
-    struct {
-      bool_setter setter;
-      bool_getter getter;
-    } bool_func;
-
-    struct {
-      int_setter setter;
-      int_getter getter;
-    } int_func;
-
-    struct {
-      void * obj;
-      float_setter setter;
-      float_getter getter;
-    } float_func;
-
-    struct {
-      void * obj;
-      double_setter setter;
-      double_getter getter;
-    } double_func;
-
-    struct {
-      string_setter setter;
-      string_getter getter;
-    } string_func;
+  /**
+   * Set the underlying value.
+   *
+   * This method will invoke the setter function to change the
+   * underlying value.  If no setter function was supplied, this
+   * method will return false.
+   */
+  virtual bool setValue (T value) {
+    if (_setter) { (*_setter)(value); return true; }
+    else return false;
+  }
 
-  } _value;
+  /**
+   * Create a copy of this raw value, bound to the same functions.
+   */
+  virtual SGRawValue<T> * clone () const {
+    return new SGRawValueFunctions<T>(_getter,_setter);
+  }
 
+private:
+  getter_t _getter;
+  setter_t _setter;
 };
 
 
-
-////////////////////////////////////////////////////////////////////////
-// Top-level manager.
-////////////////////////////////////////////////////////////////////////
+/**
+ * An indexed value bound to static functions.
+ *
+ * A read-only value will not have a setter; a write-only value will
+ * not have a getter.  An indexed value is useful for binding one
+ * of a list of possible values (such as multiple engines for a
+ * plane).  The index is hard-coded at creation time.
+ */
+template <class T>
+class SGRawValueFunctionsIndexed : public SGRawValue<T>
+{
+public:
+  typedef T (*getter_t)(int);
+  typedef void (*setter_t)(int,T);
+  SGRawValueFunctionsIndexed (int index, getter_t getter = 0, setter_t setter = 0)
+    : _index(index), _getter(getter), _setter(setter) {}
+  virtual ~SGRawValueFunctionsIndexed () {}
+  virtual T getValue () const {
+    if (_getter) return (*_getter)(_index);
+    else return SGRawValue<T>::DefaultValue;
+  }
+  virtual bool setValue (T value) {
+    if (_setter) { (*_setter)(_index, value); return true; }
+    else return false;
+  }
+  virtual SGRawValue<T> * clone () const {
+    return new SGRawValueFunctionsIndexed<T>(_index, _getter, _setter);
+  }
+private:
+  int _index;
+  getter_t _getter;
+  setter_t _setter;
+};
 
 
 /**
- * A list of FlightGear properties.
- *
- * This list associates names (conventional written as paths,
- * i.e. "/foo/bar/hack") with SGValue classes.  Once an SGValue
- * object is associated with the name, the association is
- * permanent -- it is safe to keep a pointer or reference.
- * however, that the type of a value may change if it is tied
- * to a variable.
+ * A value managed through an object and access methods.
  *
- * When iterating through the list, the value type is
- *
- *   pair<string,SGValue>
- *
- * To get the name from a const_iterator, use
- *
- *   it->first
- *
- * and to get the value from a const_iterator, use
- *
- *   it->second
+ * A read-only value will not have a setter; a write-only value will
+ * not have a getter.
  */
-class SGPropertyList
+template <class C, class T>
+class SGRawValueMethods : public SGRawValue<T>
 {
 public:
-  typedef map<string, SGValue> value_map;
-
-  typedef SGValue::bool_getter bool_getter;
-  typedef SGValue::int_getter int_getter;
-  typedef SGValue::float_getter float_getter;
-  typedef SGValue::double_getter double_getter;
-  typedef SGValue::string_getter string_getter;
-
-  typedef SGValue::bool_setter bool_setter;
-  typedef SGValue::int_setter int_setter;
-  typedef SGValue::float_setter float_setter;
-  typedef SGValue::double_setter double_setter;
-  typedef SGValue::string_setter string_setter;
-
-  typedef value_map::value_type value_type;
-  typedef value_map::size_type size_type;
-  typedef value_map::const_iterator const_iterator;
-
-  SGPropertyList ();
-  virtual ~SGPropertyList ();
-
-  virtual size_type size () const { return _props.size(); }
-
-  virtual const_iterator begin () const { return _props.begin(); }
-  virtual const_iterator end () const { return _props.end(); }
-
-  virtual SGValue * getValue (const string &name, bool create = false);
-  virtual const SGValue * getValue (const string &name) const;
-
-  virtual bool getBoolValue (const string &name,
-			     bool defaultValue = false) const;
-  virtual int getIntValue (const string &name,
-			   int defaultValue = 0) const;
-  virtual float getFloatValue (const string &name,
-			       float defaultValue = 0.0) const;
-  virtual double getDoubleValue (const string &name,
-				 double defaultValue = 0.0L) const;
-  virtual const string & getStringValue (const string &name,
-					 const string &defaultValue = "")
-    const;
-
-  virtual bool setBoolValue (const string &name, bool value);
-  virtual bool setIntValue (const string &name, int value);
-  virtual bool setFloatValue (const string &name, float value);
-  virtual bool setDoubleValue (const string &name, double value);
-  virtual bool setStringValue (const string &name, const string &value);
-  virtual bool setUnknownValue (const string &name, const string &value);
-
-  virtual bool tieBool (const string &name,
-			bool_getter getter,
-			bool_setter setter = 0,
-			bool useDefault = true);
-  virtual bool tieInt (const string &name,
-		       int_getter getter,
-		       int_setter setter = 0,
-		       bool useDefault = true);
-  virtual bool tieFloat (const string &name,
-			 float_getter getter,
-			 float_setter setter = 0,
-			 bool useDefault = true);
-  virtual bool tieDouble (const string &name,
-			  double_getter getter,
-			  double_setter setter = 0,
-			  bool useDefault = true);
-  virtual bool tieString (const string &name,
-			  string_getter getter,
-			  string_setter setter = 0,
-			  bool useDefault = true);
-
-  virtual bool untie (const string &name);
-
+  typedef T (C::*getter_t)() const;
+  typedef void (C::*setter_t)(T);
+  SGRawValueMethods (C &obj, getter_t getter = 0, setter_t setter = 0)
+    : _obj(obj), _getter(getter), _setter(setter) {}
+  virtual ~SGRawValueMethods () {}
+  virtual T getValue () const {
+    if (_getter) { return (_obj.*_getter)(); }
+    else { return SGRawValue<T>::DefaultValue; }
+  }
+  virtual bool setValue (T value) {
+    if (_setter) { (_obj.*_setter)(value); return true; }
+    else return false;
+  }
+  virtual SGRawValue<T> * clone () const {
+    return new SGRawValueMethods<C,T>(_obj, _getter, _setter);
+  }
 private:
-  value_map _props;
+  C &_obj;
+  getter_t _getter;
+  setter_t _setter;
 };
 
 
-
-////////////////////////////////////////////////////////////////////////
-// Tree/node/directory view.
-////////////////////////////////////////////////////////////////////////
+/**
+ * An indexed value managed through an object and access methods.
+ *
+ * A read-only value will not have a setter; a write-only value will
+ * not have a getter.
+ */
+template <class C, class T>
+class SGRawValueMethodsIndexed : public SGRawValue<T>
+{
+public:
+  typedef T (C::*getter_t)(int) const;
+  typedef void (C::*setter_t)(int, T);
+  SGRawValueMethodsIndexed (C &obj, int index,
+		     getter_t getter = 0, setter_t setter = 0)
+    : _obj(obj), _index(index), _getter(getter), _setter(setter) {}
+  virtual ~SGRawValueMethodsIndexed () {}
+  virtual T getValue () const {
+    if (_getter) { return (_obj.*_getter)(_index); }
+    else { return SGRawValue<T>::DefaultValue; }
+  }
+  virtual bool setValue (T value) {
+    if (_setter) { (_obj.*_setter)(_index, value); return true; }
+    else return false;
+  }
+  virtual SGRawValue<T> * clone () const {
+    return new SGRawValueMethodsIndexed<C,T>(_obj, _index, _getter, _setter);
+  }
+private:
+  C &_obj;
+  int _index;
+  getter_t _getter;
+  setter_t _setter;
+};
 
 
+
 /**
- * Tree view of a property list.
- *
- * This class provides a virtual tree view of a property list, without
- * actually constructing a tree -- the view always stays in sync with
- * the property list itself.
- *
- * This class is designed to be used for setup and configuration; it is
- * optimized for ease of use rather than performance, and shouldn't be
- * used inside a tight loop.
- *
- * Every node is actually just a path together with a pointer to
- * the real property list and a few convenient operations; to the
- * user, however, it looks like a node in a tree or a file system,
- * with the regular operations such as getChild and getParent.
- *
- * Note that a node may be both a branch and a leaf -- that is, it
- * may have a value itself and it may have children.  Here is a simple
- * example that prints the names of all of the different nodes inside 
- * "/controls":
- *
- *   SGPropertyNode controls("/controls", current_property_list);
- *   SGPropertyNode child;
- *   int size = controls.size();
- *   for (int i = 0; i < size; i++) {
- *     if (controls.getChild(child, i))
- *       cout << child.getName() << endl;
- *     else
- *       cerr << "Failed to read child " << i << endl;
- *   }
+ * A node in a property tree.
  */
 class SGPropertyNode
 {
+
 public:
-				// Constructor and destructor
-  SGPropertyNode (const string &path = "", SGPropertyList * props = 0);
+
+
+  /**
+   * Property value types.
+   */
+  enum Type {
+    NONE,
+    ALIAS,
+    BOOL,
+    INT,
+    LONG,
+    FLOAT,
+    DOUBLE,
+    STRING,
+    UNSPECIFIED
+  };
+
+
+  /**
+   * Access mode attributes.
+   *
+   * <p>The ARCHIVE attribute is strictly advisory, and controls
+   * whether the property should normally be saved and restored.</p>
+   */
+  enum Attribute {
+    READ = 1,
+    WRITE = 2,
+    ARCHIVE = 4,
+    TRACE_READ = 8,
+    TRACE_WRITE = 16
+  };
+
+
+  /**
+   * Default constructor.
+   */
+  SGPropertyNode ();
+
+
+  /**
+   * Copy constructor.
+   */
+  SGPropertyNode (const SGPropertyNode &node);
+
+
+  /**
+   * Destructor.
+   */
   virtual ~SGPropertyNode ();
 
-				// Accessor and setter for the internal
-				// path.
-  virtual const string &getPath () const { return _path; }
-  virtual void setPath (const string &path);
 
-				// Accessor and setter for the real
-				// property list.
-  virtual SGPropertyList * getPropertyList () { return _props; }
-  virtual void setPropertyList (SGPropertyList * props) {
-    _props = props;
+
+  //
+  // Basic properties.
+  //
+
+  /**
+   * Test whether this node contains a primitive leaf value.
+   */
+  bool hasValue () const { return (_type != NONE); }
+
+
+  /**
+   * Get the node's simple (XML) name.
+   */
+  const string &getName () const { return _name; }
+
+
+  /**
+   * Get the node's integer index.
+   */
+  const int getIndex () const { return _index; }
+
+
+  /**
+   * Get a non-const pointer to the node's parent.
+   */
+  SGPropertyNode * getParent () { return _parent; }
+
+
+  /**
+   * Get a const pointer to the node's parent.
+   */
+  const SGPropertyNode * getParent () const { return _parent; }
+
+
+  //
+  // Children.
+  //
+
+
+  /**
+   * Get the number of child nodes.
+   */
+  const int nChildren () const { return _children.size(); }
+
+
+  /**
+   * Get a child node by position (*NOT* index).
+   */
+  SGPropertyNode * getChild (int position);
+
+
+  /**
+   * Get a const child node by position (*NOT* index).
+   */
+  const SGPropertyNode * getChild (int position) const;
+
+
+  /**
+   * Get a child node by name and index.
+   */
+  SGPropertyNode * getChild (const string &name, int index = 0,
+			     bool create = false);
+
+
+  /**
+   * Get a const child node by name and index.
+   */
+  const SGPropertyNode * getChild (const string &name, int index = 0) const;
+
+
+  /**
+   * Get a vector of all children with the specified name.
+   */
+  vector<SGPropertyNode *> getChildren (const string &name);
+
+
+  /**
+   * Get a vector all all children (const) with the specified name.
+   */
+  vector<const SGPropertyNode *> getChildren (const string &name) const;
+
+
+  //
+  // Alias support.
+  //
+
+
+  /**
+   * Alias this node's leaf value to another's.
+   */
+  bool alias (SGPropertyNode * target);
+
+
+  /**
+   * Alias this node's leaf value to another's by relative path.
+   */
+  bool alias (const string &path);
+
+
+  /**
+   * Remove any alias for this node.
+   */
+  bool unalias ();
+
+
+  /**
+   * Test whether the node's leaf value is aliased to another's.
+   */
+  bool isAlias () const { return (_type == ALIAS); }
+
+
+  /**
+   * Get a non-const pointer to the current alias target, if any.
+   */
+  SGPropertyNode * getAliasTarget ();
+
+
+  /**
+   * Get a const pointer to the current alias target, if any.
+   */
+  const SGPropertyNode * getAliasTarget () const;
+
+
+  //
+  // Path information.
+  //
+
+
+  /**
+   * Get the path to this node from the root.
+   */
+  string getPath (bool simplify = false) const;
+
+
+  /**
+   * Get a pointer to the root node.
+   */
+  SGPropertyNode * getRootNode ();
+
+
+  /**
+   * Get a const pointer to the root node.
+   */
+  const SGPropertyNode * getRootNode () const;
+
+
+  /**
+   * Get a pointer to another node by relative path.
+   */
+  SGPropertyNode * getNode (const string &relative_path, bool create = false);
+
+
+  /**
+   * Get a const pointer to another node by relative path.
+   */
+  const SGPropertyNode * getNode (const string &relative_path) const;
+
+
+  //
+  // Access Mode.
+  //
+
+  /**
+   * Check a single mode attribute for the property node.
+   */
+  bool getAttribute (Attribute attr) const { return ((_attr & attr) != 0); }
+
+
+  /**
+   * Set a single mode attribute for the property node.
+   */
+  void setAttribute (Attribute attr, bool state) {
+    (state ? _attr |= attr : _attr &= ~attr);
   }
 
-				// Accessors for derived information.
-  virtual int size () const;
-  virtual const string &getName () const;
-  virtual SGPropertyNode &getParent () const;
-  virtual SGPropertyNode &getChild (int n) const;
-  virtual SGPropertyNode &getSubNode (const string &subpath) const;
-
-				// Get values directly.
-  virtual SGValue * getValue (const string &subpath = "");
-  virtual bool getBoolValue (const string &subpath = "",
-			     bool defaultValue = false) const;
-  virtual int getIntValue (const string &subpath = "",
-			   int defaultValue = 0) const;
-  virtual float getFloatValue (const string &subpath = "",
-			       float defaultValue = 0.0) const;
-  virtual double getDoubleValue (const string &subpath = "",
-				 double defaultValue = 0.0L) const;
-  virtual const string &
-  getStringValue (const string &subpath = "",
-		  const string &defaultValue = "") const;
+
+  /**
+   * Get all of the mode attributes for the property node.
+   */
+  int getAttributes () const { return _attr; }
+
+
+  /**
+   * Set all of the mode attributes for the property node.
+   */
+  void setAttributes (int attr) { _attr = attr; }
+  
+
+  //
+  // Leaf Value (primitive).
+  //
+
+
+  /**
+   * Get the type of leaf value, if any, for this node.
+   */
+  Type getType () const;
+
+
+  /**
+   * Get a bool value for this node.
+   */
+  bool getBoolValue () const;
+
+
+  /**
+   * Get an int value for this node.
+   */
+  int getIntValue () const;
+
+
+  /**
+   * Get a long int value for this node.
+   */
+  long getLongValue () const;
+
+
+  /**
+   * Get a float value for this node.
+   */
+  float getFloatValue () const;
+
+
+  /**
+   * Get a double value for this node.
+   */
+  double getDoubleValue () const;
+
+
+  /**
+   * Get a string value for this node.
+   */
+  string getStringValue () const;
+
+
+
+  /**
+   * Set a bool value for this node.
+   */
+  bool setBoolValue (bool value);
+
+
+  /**
+   * Set an int value for this node.
+   */
+  bool setIntValue (int value);
+
+
+  /**
+   * Set a long int value for this node.
+   */
+  bool setLongValue (long value);
+
+
+  /**
+   * Set a float value for this node.
+   */
+  bool setFloatValue (float value);
+
+
+  /**
+   * Set a double value for this node.
+   */
+  bool setDoubleValue (double value);
+
+
+  /**
+   * Set a string value for this node.
+   */
+  bool setStringValue (string value);
+
+
+  /**
+   * Set a value of unspecified type for this node.
+   */
+  bool setUnspecifiedValue (string value);
+
+
+  //
+  // Data binding.
+  //
+
+
+  /**
+   * Test whether this node is bound to an external data source.
+   */
+  bool isTied () const { return _tied; }
+
+
+  /**
+   * Bind this node to an external bool source.
+   */
+  bool tie (const SGRawValue<bool> &rawValue, bool useDefault = true);
+
+
+  /**
+   * Bind this node to an external int source.
+   */
+  bool tie (const SGRawValue<int> &rawValue, bool useDefault = true);
+
+
+  /**
+   * Bind this node to an external long int source.
+   */
+  bool tie (const SGRawValue<long> &rawValue, bool useDefault = true);
+
+
+  /**
+   * Bind this node to an external float source.
+   */
+  bool tie (const SGRawValue<float> &rawValue, bool useDefault = true);
+
+
+  /**
+   * Bind this node to an external double source.
+   */
+  bool tie (const SGRawValue<double> &rawValue, bool useDefault = true);
+
+
+  /**
+   * Bind this node to an external string source.
+   */
+  bool tie (const SGRawValue<string> &rawValue, bool useDefault = true);
+
+
+  /**
+   * Unbind this node from any external data source.
+   */
+  bool untie ();
+
+
+  //
+  // Convenience methods using paths.
+  // TODO: add attribute methods
+  //
+
+
+  /**
+   * Get another node's type.
+   */
+  Type getType (const string &relative_path) const;
+
+
+  /**
+   * Test whether another node has a leaf value.
+   */
+  bool hasValue (const string &relative_path) const;
+
+
+  /**
+   * Get another node's value as a bool.
+   */
+  bool getBoolValue (const string &relative_path,
+		     bool defaultValue = false) const;
+
+
+  /**
+   * Get another node's value as an int.
+   */
+  int getIntValue (const string &relative_path,
+		   int defaultValue = 0) const;
+
+
+  /**
+   * Get another node's value as a long int.
+   */
+  long getLongValue (const string &relative_path,
+		     long defaultValue = 0L) const;
+
+
+  /**
+   * Get another node's value as a float.
+   */
+  float getFloatValue (const string &relative_path,
+		       float defaultValue = 0.0) const;
+
+
+  /**
+   * Get another node's value as a double.
+   */
+  double getDoubleValue (const string &relative_path,
+			 double defaultValue = 0.0L) const;
+
+
+  /**
+   * Get another node's value as a string.
+   */
+  string getStringValue (const string &relative_path,
+			 string defaultValue = "") const;
+
+
+  /**
+   * Set another node's value as a bool.
+   */
+  bool setBoolValue (const string &relative_path, bool value);
+
+
+  /**
+   * Set another node's value as an int.
+   */
+  bool setIntValue (const string &relative_path, int value);
+
+
+  /**
+   * Set another node's value as a long int.
+   */
+  bool setLongValue (const string &relative_path, long value);
+
+
+  /**
+   * Set another node's value as a float.
+   */
+  bool setFloatValue (const string &relative_path, float value);
+
+
+  /**
+   * Set another node's value as a double.
+   */
+  bool setDoubleValue (const string &relative_path, double value);
+
+
+  /**
+   * Set another node's value as a string.
+   */
+  bool setStringValue (const string &relative_path, string value);
+
+
+  /**
+   * Set another node's value with no specified type.
+   */
+  bool setUnspecifiedValue (const string &relative_path, string value);
+
+
+  /**
+   * Test whether another node is bound to an external data source.
+   */
+  bool isTied (const string &relative_path) const;
+
+
+  /**
+   * Bind another node to an external bool source.
+   */
+  bool tie (const string &relative_path, const SGRawValue<bool> &rawValue,
+	    bool useDefault = true);
+
+
+  /**
+   * Bind another node to an external int source.
+   */
+  bool tie (const string &relative_path, const SGRawValue<int> &rawValue,
+	    bool useDefault = true);
+
+
+  /**
+   * Bind another node to an external long int source.
+   */
+  bool tie (const string &relative_path, const SGRawValue<long> &rawValue,
+	    bool useDefault = true);
+
+
+  /**
+   * Bind another node to an external float source.
+   */
+  bool tie (const string &relative_path, const SGRawValue<float> &rawValue,
+	    bool useDefault = true);
+
+
+  /**
+   * Bind another node to an external double source.
+   */
+  bool tie (const string &relative_path, const SGRawValue<double> &rawValue,
+	    bool useDefault = true);
+
+
+  /**
+   * Bind another node to an external string source.
+   */
+  bool tie (const string &relative_path, const SGRawValue<string> &rawValue,
+	    bool useDefault = true);
+
+
+  /**
+   * Unbind another node from any external data source.
+   */
+  bool untie (const string &relative_path);
+
+
+protected:
+
+
+  /**
+   * Protected constructor for making new nodes on demand.
+   */
+  SGPropertyNode (const string &name, int index, SGPropertyNode * parent);
+
 
 private:
-  string _path;
-  SGPropertyList * _props;
-				// for pointer persistence...
-				// NOT THREAD SAFE!!!
-				// (each thread must have its own node
-				// object)
-  mutable string _name;
-  mutable SGPropertyNode * _node;
+
+
+  /**
+   * Clear any existing value and set the type to NONE.
+   */
+  void clear_value ();
+
+
+  /**
+   * Get the value as a string.
+   */
+  string get_string () const;
+
+
+  /**
+   * Trace a read access.
+   */
+  void trace_read (Type accessType) const;
+
+
+  /**
+   * Trace a write access.
+   */
+  void trace_write (Type accessType) const;
+
+  string _name;
+  int _index;
+  SGPropertyNode * _parent;
+  vector<SGPropertyNode *> _children;
+
+
+  Type _type;
+  bool _tied;
+  int _attr;
+
+				// The right kind of pointer...
+  union {
+    SGPropertyNode * alias;
+    SGRawValue<bool> * bool_val;
+    SGRawValue<int> * int_val;
+    SGRawValue<long> * long_val;
+    SGRawValue<float> * float_val;
+    SGRawValue<double> * double_val;
+    SGRawValue<string> * string_val;
+  } _value;
+
+
 };
 
 
 
 ////////////////////////////////////////////////////////////////////////
-// Input and output.
+// I/O functions.
 ////////////////////////////////////////////////////////////////////////
 
-extern bool readPropertyList (istream &input, SGPropertyList * props);
-extern bool writePropertyList (ostream &output, const SGPropertyList * props);
 
+/**
+ * Read properties from an XML input stream.
+ */
+void readProperties (istream &input, SGPropertyNode * start_node,
+		     const string &base = "");
 
-
-////////////////////////////////////////////////////////////////////////
-// Global property manager.
-////////////////////////////////////////////////////////////////////////
 
-extern SGPropertyList current_properties;
+/**
+ * Read properties from an XML file.
+ */
+void readProperties (const string &file, SGPropertyNode * start_node);
+
+
+/**
+ * Write properties to an XML output stream.
+ */
+void writeProperties (ostream &output, const SGPropertyNode * start_node);
+
+
+/**
+ * Write properties to an XML file.
+ */
+void writeProperties (const string &file, const SGPropertyNode * start_node);
+
+
+/**
+ * Copy properties from one node to another.
+ */
+bool copyProperties (const SGPropertyNode *in, SGPropertyNode *out);
 
 
-#endif __PROPS_HXX
+#endif // __PROPS_HXX
 
 // end of props.hxx