New example

git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk/SWIG@736 626c5289-ae23-0410-ae9c-e8d60b6d4f22

Examples/tcl/index.html

@@ -16,6 +16,8 @@ The following examples illustrate the use of SWIG with Tcl.
 be used to wrap a C function and a global variable.
 <li><a href="constants/index.html">constants</a>.  This shows how preprocessor macros and
 certain C declarations are turned into constants.
+<li><a href="variables/index.html">variables</a>.  How SWIG can be used to wrap C global variables.
+
 </ul>
 
 <h2>Compilation Issues</h2>

Examples/tcl/simple/example.i

@@ -3,3 +3,5 @@
 
 extern int    gcd(int x, int y);
 extern double Foo;
+
+

Examples/tcl/variables/example.c

@@ -4,6 +4,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include "example.h"
 
 int              ivar = 0;                    
 short            svar = 0;
@@ -17,8 +18,15 @@ char             cvar = 0;
 float            fvar = 0;
 double           dvar = 0;
 char            *strvar = 0;
+const char      *cstrvar = 0;
 int             *iptrvar = 0;
 char             name[256] = "Dave";
+char             path[256] = "/home/beazley";
+
+
+/* Global variables involving a structure */
+Point           *ptptr = 0;
+Point            pt = { 10, 20 };
 
 /* A variable that we will make read-only in the interface */
 int              status = 1;
@@ -38,8 +46,11 @@ void print_vars() {
   printf("dvar      = %g\n", dvar);
   printf("cvar      = %c\n", cvar);
   printf("strvar    = %s\n", strvar ? strvar : "(null)");
+  printf("cstrvar   = %s\n", cstrvar ? cstrvar : "(null)");
   printf("iptrvar   = %x\n", iptrvar);
   printf("name      = %s\n", name);
+  printf("ptptr     = %x (%d, %d)\n", ptptr, ptptr ? ptptr->x : 0, ptptr ? ptptr->y : 0);
+  printf("pt        = (%d, %d)\n", pt.x, pt.y);
   printf("status    = %d\n", status);
 }
 
@@ -51,4 +62,25 @@ int *new_int(int value) {
   return ip;
 }
 
+/* A function to create a point */
 
+Point *new_Point(int x, int y) {
+  Point *p = (Point *) malloc(sizeof(Point));
+  p->x = x;
+  p->y = y;
+  return p;
+}
+
+char * Point_print(Point *p) {
+  static char buffer[256];
+  if (p) {
+    sprintf(buffer,"(%d,%d)", p->x,p->y);
+  } else {
+    sprintf(buffer,"null");
+  }
+  return buffer;
+}
+
+void pt_print() {
+  printf("(%d, %d)\n", pt.x, pt.y);
+}

Examples/tcl/variables/example.h

@@ -0,0 +1,6 @@
+/* File: example.h */
+
+typedef struct {
+  int x,y;
+} Point;
+

Examples/tcl/variables/example.i

@@ -1,5 +1,8 @@
 /* File : example.i */
 %module example
+%{
+#include "example.h"
+%}
 
 /* Some global variable declarations */
 extern int              ivar;
@@ -14,18 +17,28 @@ extern char             cvar;
 extern float            fvar;
 extern double           dvar;
 extern char            *strvar;
+extern const char      *cstrvar;
 extern int             *iptrvar;
 extern char             name[256];
 
+extern Point           *ptptr;
+extern Point            pt;
+
+
+/* Some read-only variables */
+
+%readonly
+extern int  status;
+extern char path[256];
+%readwrite
+
 /* Some helper functions to make it easier to test */
 extern void  print_vars();
 extern int  *new_int(int value);
-
-/* A read-only variable */
-
-%readonly
-extern int  status;
-%readwrite
+extern Point *new_Point(int x, int y);
+extern char  *Point_print(Point *p);
+extern void  pt_print();
+
 
 
 

Examples/tcl/variables/example.tcl

@@ -17,7 +17,10 @@ set cvar    "S"
 set fvar    3.14159
 set dvar    2.1828
 set strvar  "Hello World"
+set cstrvar "Goodbye"
 set iptrvar [new_int 37]
+set ptptr [new_Point 37 42]
+set name    "Bill"
 
 # Now print out the values of the variables
 
@@ -35,8 +38,11 @@ puts "fvar      = $fvar"
 puts "dvar      = $dvar"
 puts "cvar      = $cvar"
 puts "strvar    = $strvar"
+puts "cstrvar   = $cstrvar"
 puts "iptrvar   = $iptrvar"
 puts "name      = $name"
+puts "ptptr     = $ptptr [Point_print $ptptr]"
+puts "pt        = $pt [Point_print $pt]"
 
 puts "\nVariables (values printed from C)"
 
@@ -44,9 +50,9 @@ print_vars
 
 puts "\nNow I'm going to try and modify some read only variables";
 
-puts "     Tring to set 'name'";
+puts "     Tring to set 'path'";
 if { [catch {
-    set name "Whoa!"
+    set path "Whoa!"
     puts "Hey, what's going on?!?! This shouldn't work"
 }]} {
     puts "Good."
@@ -60,4 +66,13 @@ if { [catch {
     puts "Good."
 }
 
+puts "\nI'm going to try and update a structure variable.\n"
+
+set pt $ptptr
+
+puts "The new value is"
+pt_print
+puts "You should see the value [Point_print $ptptr]"
+
+
 

Examples/tcl/variables/index.html

@@ -39,20 +39,10 @@ string.   However, whenever the value of such a variable is set from Tcl, the ol
 value is destroyed using <tt>free()</tt> or <tt>delete</tt> (the choice of which depends
 on whether or not SWIG was run with the -c++ option).
 <li><tt>signed char</tt> and <tt>unsigned char</tt> are handled as small 8-bit integers.
-<li>Array variables such as '<tt>char name[256]</tt>' are read-only variables because
-SWIG doesn't really know how to change the "value" of an array.   You can work
-around this by writing some kind of helper function in the SWIG interface.
-For example:
-
-<blockquote>
-<pre>
-%inline %{
-void set_name(char *newname) {
-    strncpy(name,newname,256);
-}
-%}
-</pre>
-</blockquote>
+<li>String array variables such as '<tt>char name[256]</tt>' are managed as Tcl strings, but
+when setting the value, the result is truncated to the maximum length of the array.  Furthermore, the string is assumed to be null-terminated.
+<li>When structures and classes are used as global variables, they are mapped into pointers.
+Getting the "value" returns a pointer to the global variable.  Setting the value of a structure results in a memory copy from a pointer to the global.
 </ul>
 
 <h2>Creating read-only variables</h2>