perlcall for dummies

frazap has asked for the wisdom of the Perl Monks concerning the following question:

I have the following files for a embryonic keyboard hook on windows

lib/Kbh.pm

package Kbh;
our $VERSION = '0.01';
require XSLoader;
XSLoader::load('Kbh', $VERSION);
sub process_key {
    print "process_key in perl\n";
    
}
1;
[download]

Makefile.pl

use ExtUtils::MakeMaker;
WriteMakefile (
    NAME => 'Kbh',
    VERSION => '0.01',
    OBJECT => 'hook.o Kbh.o',
);
[download]

hook.h

LRESULT CALLBACK HookCallback(int nCode, WPARAM wParam, LPARAM lParam)
+;
void processKey();
void register_hook();
void unregister_hook();
void MsgLoop();
[download]

hook.c

#include <windows.h>
#include <WinAble.h>
#include "stdio.h"
#include "hook.h"

HHOOK hook;

LRESULT CALLBACK HookCallback( int nCode, WPARAM wParam, LPARAM lParam
+ ) {
    processKey();
    return CallNextHookEx( hook, nCode, wParam, lParam );
}

void processKey() {
    printf("processKey  in C\n");

}

void MsgLoop() {
    MSG message;

    while ( GetMessage( &message, NULL, 0, 0 ) ) {
        TranslateMessage(&message);
        DispatchMessage(&message);
    }
}

void register_hook() {
    HMODULE hMod = (HMODULE) GetModuleHandle(NULL);
    hook = SetWindowsHookEx( WH_KEYBOARD_LL, HookCallback, hMod, 0 );

}

void unregister_hook() {
    UnhookWindowsHookEx(hook);

}
[download]

and Kbh.xs

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include "ppport.h"
#include "hook.h"

MODULE = Kbh               PACKAGE = Kbh

PROTOTYPES: DISABLE

void
MsgLoop()

void
register_hook()

void
unregister_hook()

void 
processKey()

    INIT:
        int count;
    PPCODE:
        dSP;
        PUSHMARK(SP);
        count= call_pv("Kbh::process_key", G_DISCARD|G_NOARGS); 
    if (count != 0)
        croak("Big trouble\n");
[download]

When I run

Perl Makefile.pl
dmake
[download]

the things compile.

When I run runit.pl from the main directory(use ctrl+c to quit)

runit.pl

use lib qw(./lib ./blib/arch/auto/Kbh);
use Kbh;
Kbh::register_hook();
Kbh::MsgLoop;
Kbh::unregister_hook();
[download]

I see that the hook is installed, I get two messages from processKey when I hit a key, but I don't have msg "process_key from perl"

What am I missing ?

Thanks

François

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Replies are listed 'Best First'.
Re: perlcall for dummies by RMGir (Prior) on Sep 22, 2017 at 18:05 UTC
I haven't done anything with XS in years, so I may be missing something. But wouldn't the "C" processKey hide the "XS" processKey, depending on your link line order? I see you're printing a trace in your C processKey, and in the perl process_key. Have you tried adding a trace to the xs routine to make sure it's being invoked? Mike	[reply]
Re^2: perlcall for dummies by frazap (Monk) on Sep 25, 2017 at 13:57 UTC
Good idea: and it's not called. The suggestion of beech get me in the right direction.	[reply]
Re^3: perlcall for dummies by RMGir (Prior) on Sep 25, 2017 at 17:44 UTC
That works, but I'm betting that just deleting `void processKey() { printf("processKey in C\n"); }` [download] would have worked, too - then your XS 'processKey' would have been called instead of this one. Mike	[reply] [d/l]
Re: perlcall for dummies by beech (Parson) on Sep 22, 2017 at 20:04 UTC
Hi, I think you need to have that call_pv stuff inside HookCallback	[reply]
Re^2: perlcall for dummies by frazap (Monk) on Sep 25, 2017 at 14:02 UTC
Yes, thanks and this code works: hook.c #include <windows.h> #include <WinAble.h> #include "stdio.h" #include "EXTERN.h" #include "perl.h" #include "XSUB.h" #include "ppport.h" #include "hook.h" HHOOK hook; LRESULT CALLBACK HookCallback( int nCode, WPARAM wParam, LPARAM lParam + ) { processKey(); return CallNextHookEx( hook, nCode, wParam, lParam ); } void processKey() { printf("processKey in C\n"); dSP; PUSHMARK(SP); int count= call_pv("Kbh::process_key", G_DISCARD\|G_NOARGS); if (count != 0) croak("Big trouble\n"); } void MsgLoop() { MSG message; while ( GetMessage( &message, NULL, 0, 0 ) ) { TranslateMessage(&message); DispatchMessage(&message); } } void register_hook() { HMODULE hMod = (HMODULE) GetModuleHandle(NULL); hook = SetWindowsHookEx( WH_KEYBOARD_LL, HookCallback, hMod, 0 ); } void unregister_hook() { UnhookWindowsHookEx(hook); } [download] Kbh.xs `#include "EXTERN.h" #include "perl.h" #include "XSUB.h" #include "ppport.h" #include "hook.h" MODULE = Kbh PACKAGE = Kbh PROTOTYPES: DISABLE void MsgLoop() void register_hook() void unregister_hook()` [download] The tricky part for me was to put the header in hook.c files in the right order. François	[reply] [d/l] [select]