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Language/OS - Multiplatform Resource Library
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LANGUAGE OS.iso
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idioms.lha
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ev3tric.c
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C/C++ Source or Header
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1993-08-08
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3KB
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91 lines
/* Copyright (c) 1992 by AT&T Bell Laboratories. */
/* Advanced C++ Programming Styles and Idioms */
/* James O. Coplien */
/* All rights reserved. */
//************************************************************//
// //
// F I L E : E V 3 T R I C . C //
// //
// Cutover control code for version 3 Triangle code //
// //
//************************************************************//
#include "ev3tri.h"
#include "Map.h"
// --------------------------------------------------------------
class v2Triangle: public ShapeRep {
public:
Shape make();
Shape make(Coordinate, Coordinate, Coordinate);
v2Triangle();
void move(Coordinate);
void *operator new(size_t);
void operator delete(void *);
void gc(size_t = 0);
void draw();
v2Triangle(Exemplar);
static void init();
private:
friend Thing *Triangle::cutover(); // put in for conversion
static void poolInit(size_t);
Shape make(Coordinate) { return *aShape; }
Shape make(Coordinate, Coordinate) { return *aShape; }
Coordinate p1, p2, p3;
};
// --------------------------------------------------------------
// Use this map to keep track of all old objects we are
// asked to convert, and of the new ones they were converted to.
// That way, if we are asked to convert the same object
// several times, we map all requests onto the same return
// value.
Map<Thingp, Thingp> objectMap;
Thing *
Triangle::cutover() {
// we are going to return a pointer to a converted triangle
Triangle *retval = this;
// instance passed in is really old triangle
// the old triangle declaration is preserved
// under the name v2Triangle; class Triangle
// is the version 3 one
v2Triangle *old = (v2Triangle *)this;
Thingp oldtp = this;
ShapeRep *oldsr = (ShapeRep*)this;
if (objectMap.element(oldtp)) {
// if we've converted it already, don't
// convert it again--just return old
// converted value
retval = (Triangle*)(objectMap[oldtp]);
} else {
// create a new (version 3) triangle to return
// store it in several different kinds of pointers
retval = new Triangle;
ShapeRep *newsr = retval;
Thingp newtp = retval;
// copy over just the base class (ShapeRep) part
*newsr = *oldsr;
// now set up the fields of the new object
retval->exemplarPointer = triangle;
retval->p1 = old->p1;
retval->p2 = old->p2;
retval->p3 = old->p3;
retval->color = Black;
// save converted one for later
objectMap[oldtp] = newtp;
}
return retval;
}
Triangle::Triangle() { }