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git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk/SWIG@743 626c5289-ae23-0410-ae9c-e8d60b6d4f22
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Dave Beazley 2000-08-31 04:36:54 +00:00
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1
Examples/perl5/index.html
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@ -16,6 +16,7 @@ The following examples illustrate the use of SWIG with Perl.
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>. This example shows how to access C global variables from Perl.
</ul>
<h2>Compilation Issues</h2>

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Examples/perl5/variables/Makefile Normal file
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TOP = ../..
SWIG = $(TOP)/../swig
SRCS = example.c
TARGET = example
INTERFACE = example.i
SWIGOPT =
all::
$(MAKE) -f $(TOP)/Makefile SRCS='$(SRCS)' SWIG='$(SWIG)' \
SWIGOPT='$(SWIGOPT)' TARGET='$(TARGET)' INTERFACE='$(INTERFACE)' perl5
static::
$(MAKE) -f $(TOP)/Makefile SRCS='$(SRCS)' SWIG='$(SWIG)' \
SWIGOPT='$(SWIGOPT)' TARGET='myperl' INTERFACE='$(INTERFACE)' perl5_static
clean::
rm -f *_wrap* *.o core *~ *.so *.pm myperl
check: all

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/* File : example.c */
/* I'm a file containing some C global variables */
#include <stdio.h>
#include <stdlib.h>
#include "example.h"
int ivar = 0;
short svar = 0;
long lvar = 0;
unsigned int uivar = 0;
unsigned short usvar = 0;
unsigned long ulvar = 0;
signed char scvar = 0;
unsigned char ucvar = 0;
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;
/* A debugging function to print out their values */
void print_vars() {
printf("ivar = %d\n", ivar);
printf("svar = %d\n", svar);
printf("lvar = %ld\n", lvar);
printf("uivar = %u\n", uivar);
printf("usvar = %u\n", usvar);
printf("ulvar = %lu\n", ulvar);
printf("scvar = %d\n", scvar);
printf("ucvar = %u\n", ucvar);
printf("fvar = %g\n", fvar);
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);
}
/* A function to create an integer (to test iptrvar) */
int *new_int(int value) {
int *ip = (int *) malloc(sizeof(int));
*ip = 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);
}

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Examples/perl5/variables/example.h Normal file
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/* File: example.h */
typedef struct {
int x,y;
} Point;

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Examples/perl5/variables/example.i Normal file
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/* File : example.i */
%module example
%{
#include "example.h"
%}
/* Some global variable declarations */
extern int ivar;
extern short svar;
extern long lvar;
extern unsigned int uivar;
extern unsigned short usvar;
extern unsigned long ulvar;
extern signed char scvar;
extern unsigned char ucvar;
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);
extern Point *new_Point(int x, int y);
extern char *Point_print(Point *p);
extern void pt_print();

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Examples/perl5/variables/example.pl Normal file
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# file: example.pl
use example;
# Try to set the values of some global variables
$example::ivar = 42;
$example::svar = -31000;
$example::lvar = 65537;
$example::uivar = 123456;
$example::usvar = 61000;
$example::ulvar = 654321;
$example::scvar = -13;
$example::ucvar = 251;
$example::cvar = "S";
$example::fvar = 3.14159;
$example::dvar = 2.1828;
$example::strvar = "Hello World";
$example::cstrvar = "Goodbye";
$example::iptrvar= example::new_int(37);
$example::ptptr = example::new_Point(37,42);
$example::name = "Bill";
# Now print out the values of the variables
print "Variables (values printed from Python)";
print "ivar = $example::ivar\n";
print "svar = $example::svar\n";
print "lvar = $example::lvar\n";
print "uivar = $example::uivar\n";
print "usvar = $example::usvar\n";
print "ulvar = $example::ulvar\n";
print "scvar = $example::scvar\n";
print "ucvar = $example::ucvar\n";
print "fvar = $example::fvar\n";
print "dvar = $example::dvar\n";
print "cvar = $example::cvar\n";
print "strvar = $example::strvar\n";
print "cstrvar = $example::cstrvar\n";
print "iptrvar = $example::iptrvar\n";
print "name = $example::name\n";
print "ptptr = $example::ptptr", example::Point_print($example::ptptr), "\n";
print "pt = $example::pt", example::Point_print($example::pt), "\n";
print "\nVariables (values printed from C)\n";
example::print_vars();
print "\nI'm going to try and update a structure variable.\n";
$example::pt = $example::ptptr;
print "The new value is ";
example::pt_print();
print "You should see the value", example::Point_print($example::ptptr), "\n";
print "\nNow I'm going to try and modify some read only variables\n";
print " Tring to set 'path'\n";
$example::path = "Whoa!";
print " Trying to set 'status'\n";
$example::status = 0;

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<html>
<head>
<title>SWIG:Examples:perl5:variables</title>
</head>
<body bgcolor="#ffffff">
<tt>SWIG/Examples/perl5/variables/</tt>
<hr>
<H2>Wrapping C Global Variables</H2>
<tt>$Header$</tt><br>
<p>
When a C global variable appears in an interface file, SWIG tries to
wrap it using a technique known as "variable linking." The idea is
pretty simple---we try to create a Perl variable that magically
retrieves or updates the value of the underlying C variable when it is
accessed. Click <a href="example.i">here</a> to see a SWIG interface with some variable
declarations in it.
<h2>Manipulating Variables from Perl</h2>
Accessing a C global variable from Perl is easy---just reference it like a normal Perl variable.
Click <a href="example.pl">here</a> to see a script that updates and prints some global variables.
<h2>Creating read-only variables</h2>
The <tt>%readonly</tt> and <tt>%readwrite</tt> directives can be used to
specify a collection of read-only variables. For example:
<blockquote>
<pre>
%readonly
int status;
double blah;
...
%readwrite
</pre>
</blockquote>
The <tt>%readonly</tt> directive remains in effect until it is explicitly disabled
using the <tt>%readwrite</tt> directive.
<h2>Notes:</h2>
<ul>
<li>When a global variable has the type "<tt>char *</tt>", SWIG manages it as a character
string. However, whenever the value of such a variable is set from Perl, the old
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>String array variables such as '<tt>char name[256]</tt>' are managed as Perl 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.
<li>Variables are linked using Perl's magic mechanism. Take a look at the Advanced Perl Programming book to
find out more about this feature.
</ul>
</body>
</html>
<hr>