getting C STRUCTURES and C++ classes and JSON

[bigbass]

for me there is no better way to understand (and remember)
than seeing some working code example the easier the better

so here is a C program struct source as a reference ported to BaCon below
You will notice how I combined the library with the struct code and a nice example of gets
some may complain so I also did an example with fgets below


source code
www.9wy.net/onlinebook/CPrimerPlus5/ch14lev1sec1.html#ch14list01




BaConized struct code


'-- book.c -- one-book inventory  ported to BaCon by bigbass




CONST MAXTITL =  41    
CONST MAXAUTL = 31    



PROTO struct
PROTO printf,gets,scanf


DECLARE title TYPE char ARRAY 41
DECLARE author TYPE char ARRAY 31



struct book { char title[MAXTITL]; char author[MAXAUTL]; float value;}(library)

   
printf("Please enter the book title.\n");

gets(library.title);

printf("Now enter the author.\n");

gets(library.author);

printf("Now enter the value.\n");

scanf("%f", &library.value);

printf("%s by %s: $%.2f\n",library.title, library.author, library.value);

printf("Done.\n");






fgets version


'-- book.c -- one-book inventory ported to BaCon by bigbass
'--- updated with fgets note fgets adds the enter key to the input



CONST MAXTITL = 41
CONST MAXAUTL = 31



PROTO struct
PROTO printf,fgets,scanf

DECLARE title TYPE char ARRAY 41
DECLARE author TYPE char ARRAY 31



struct book { char title[MAXTITL]; char author[MAXAUTL]; float value;}(library)


printf("Please enter the book title.\n");

fgets(library.title, 41, stdin);

printf("Now enter the author.\n");

fgets(library.author,31,stdin);

printf("Now enter the value.\n");

scanf("%f", &library.value);

printf("\n");
printf(" TITLE : %s ",library.title);
printf("AUTHOR : %s ",library.author);
printf("COST : $%.2f", library.value);  
printf("\n");    








[bigbass]

some more practice with structs

removing the need to DECLARE thus shortening code




original C code

#include <stdio.h>

struct programming
{
   float constant;
   char *pointer;
};

main()
{
  struct programming variable;
  char string[] = "Programming in Software Development.";  

  variable.constant = 1.23;
  variable.pointer = string;

  printf("%f\n", variable.constant);
  printf("%s\n", variable.pointer);

  return 0;
}


bacon ported code pointer doesnt need to be a pointer anymore in bacon


PROTO struct
PROTO printf

'--- use a struct declare floating point member and a string member
struct programming { double constant; char * pointer; } (variable) ;    

variable.constant = 1.23
variable.pointer = "Programming in Software Development."

printf("%f\n", variable.constant);
printf("%s\n", variable.pointer);





[bigbass]

We can finally get any info from low level structs!!

this is a major break though I had tried to solve this
many, many times before so this is like winning a trophy for me


We are now able to read the low level header structs
and print the data in BaCon

This is an advanced topic but shows some new untapped
power of what BaCon can do


and look no need for USEC /END USEC

kernel-ver.bac


'---Joe Arose aka..bigbass  finally solved using structs reading
'---the low level sys headers directly and getting the data July 25 2013
'---example with printf and BaCons PRINT to see the differences



PRAGMA INCLUDE <sys/utsname.h>

'--- import C functions used
PROTO printf
PROTO struct
PROTO uname

struct utsname (u)
uname (&u)
printf ("%s kernel %s (version %s) on %s\n", u.sysname, u.release, u.version, u.machine)
PRINT  u.sysname, u.release, u.version, u.machine FORMAT "%s kernel %s (version %s) on %s\n"







./kernel-ver
Linux kernel 3.2.29-smp (version #2 SMP Mon Sep 17 13:16:43 CDT 2012) on i686
Linux kernel 3.2.29-smp (version #2 SMP Mon Sep 17 13:16:43 CDT 2012) on i686


[vovchik]

Dear Joe,

That is fabulous work. Thanks.

With kind regards,
Vovchik

[bigbass]

Now with porting even more code from C for external libraries

structure can be difficult to port
so having several examples will make it easier

this is plain C first then we will see the BaCon version ported


#include <glib.h>

struct test_struct { gint32 gint32_member1;
gchar  gchar_member2;
gint8  gint8_member3;
};


int main(int argc, char *argv[])
{
struct test_struct *tsptr, ts;

ts.gint32_member1 = 32;
ts.gchar_member2  = 's';
ts.gint8_member3  = 8;

tsptr = &ts;

g_printf("ts.gint32_member1: %d\n", G_STRUCT_MEMBER(gint32, tsptr, 0));
g_printf("ts.gchar_member2:  %c\n", G_STRUCT_MEMBER(gchar, tsptr, 4));
g_printf("ts.gint8_member3:  %d\n", G_STRUCT_MEMBER(gint8, tsptr, 5));


return 0;
}






PRAGMA INCLUDE glib-2.0/glib.h
PRAGMA OPTIONS -I /usr/include/glib-2.0/
PRAGMA OPTIONS -I /usr/lib/i386-linux-gnu/glib-2.0/include/


PROTO printf
PROTO struct

struct { gint32 gint32_member1; gchar  gchar_member2; gint8  gint8_member3; } (ts )



ts.gint32_member1 = 32
ts.gchar_member2  = 's'
ts.gint8_member3  = 8


printf("ts.gint32_member1: %d\n", G_STRUCT_MEMBER(gint32, &ts, 0));
printf("ts.gchar_member2:  %c\n", G_STRUCT_MEMBER(gchar, &ts, 4));
printf("ts.gint8_member3:  %d\n", G_STRUCT_MEMBER(gint8, &ts, 5));






[bigbass]

Converting structs to BaCon in steps look at the prior post
to see that we went from an UGLY hardware struct using glib
and embedded it in BaCon (not fun but it can be done when needed)

now we go one step more and convert it to use BaCon's RECORD command
I will comment more what is happening in the next post

this macro will become useful for us G_STRUCT_MEMBER
just trying to get it into BaCon cleanly

I shortened the code a little not using pointers or the struct alias
just using the struct name "ts" directly
Joe




PRAGMA INCLUDE glib-2.0/glib.h
PRAGMA OPTIONS -I /usr/include/glib-2.0/
PRAGMA OPTIONS -I /usr/lib/i386-linux-gnu/glib-2.0/include/

'--- import functions
PROTO printf



'--- name the struct "ts" and decalare it
'--- with the TYPEs that will be used
RECORD ts
    LOCAL gint32_member1 TYPE gint32
    LOCAL gchar_member2 TYPE gchar
    LOCAL gint8_member3 TYPE gint8
END RECORD


ts.gint32_member1 = 32
ts.gchar_member2  = 's'
ts.gint8_member3  = 8


printf("ts.gint32_member1: %d\n", G_STRUCT_MEMBER(gint32, &ts, 0))
printf("ts.gchar_member2:  %c\n", G_STRUCT_MEMBER(gchar, &ts, 4))
printf("ts.gint8_member3:  %d\n", G_STRUCT_MEMBER(gint8, &ts, 5))



[vovchik]

Dear Joe,

It's a nice example. Thanks.

With kind regards,
vovchik

[bigbass]

kernel-uevents

Connect a USB and get real time info from it


I will only focus on the documentation of the port


Before I start forum member barryk
did an excellent port of kernel-uevents
it only lacked a link to the original source code used
however he overcame some difficult problems with the structs
when porting the code to bacon which was a very important step
that I feel needs to be documented this is really a complex
code example because it uses low level structs
Thank you barryk for the hard work you did on this to get the code to
compile and run !
*I just want to document this based on some C source code for educational reasons


For the documentation we will base everything off this source code to port to BaCon
www.kernel.org/doc/pending/hotplug.txt

landley.net/kdocs/pending/hotplug.txt

since I don't know exactly what code was used before and this looks like a good example


I reused a lot of code from barryk to make this documentation part possible
basic-converter.proboards.com/thread/502

RECORD pfd converted from struct pollfd pfd;
basic-converter.proboards.com/post/4279




Joe


just compile the code the connect or disconnect a usb to see the
information in the terminal

hotplug3.bac






'--- from linux/netlink.h
CONST NETLINK_KOBJECT_UEVENT = 15

'--- linux/poll.h, only includes asm/poll.h, which only includes asm-generic/poll.h
CONST POLLIN = 1

'--- C functions PROTO them to make them available in BaCon
PROTO getpid, socket, bind, poll, recv, printf,write,memset,exit

'--- defined in linux/netlink.h
'--- struct sockaddr_nl nls;
RECORD nls
   LOCAL nl_family TYPE unsigned short
   LOCAL nl_pad TYPE unsigned short
   LOCAL nl_pid TYPE unsigned int
   LOCAL nl_groups TYPE unsigned int
END RECORD

'--- defined in asm-generic/poll.h
'--- struct pollfd pfd;
RECORD pfd
   LOCAL fd TYPE int
   LOCAL events TYPE short
   LOCAL revents TYPE short
END RECORD


DECLARE buf[512] TYPE char

'================
SUB SEND_OUT()
'================  
PRINT "poll"
PRINT "Use ctrl+c to break and quit "
END SUB



'--- Open hotplug event netlink socket
memset(&nls,0,SIZEOF(nls))
nls.nl_family = AF_NETLINK
nls.nl_pid = getpid()
nls.nl_groups = -1

pfd.events = POLLIN
pfd.fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT)
IF (pfd.fd==-1) THEN
PRINT "***No permission or no root***"
SEND_OUT
END IF

'--- Listen to netlink socket
IF (bind(pfd.fd, (void *)&nls, SIZEOF(nls))) THEN
PRINT "***Bind failed***"
SEND_OUT
END IF

PRINT "Connect or disconnect something to the USB port"
WHILE (-1!=poll(&pfd, 1, -1))

i = 0
len = recv(pfd.fd, buf, SIZEOF(buf), MSG_DONTWAIT)
IF (len == -1) THEN
PRINT "recv"
SEND_OUT
END IF
'--- Print the data to stdout.
i = 0
WHILE (i<len)
printf("%s\n", buf+i)
i  = i + strlen(buf+i)+1
WEND

SEND_OUT

WEND





[bigbass]

Now the detailed explination
I will append more info to this post


Produce header free code
of those C code headers only a few constants
,enums and structs are needed

1.) remove the #include <sys/poll.h>
www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/include/asm/poll.h?v=2.6.11.8

The first step convert the hex value to decimal
#define POLLIN          0x0001

In BaCon
CONST POLLIN = 1

2.) convert the C struct to a RECORD this has a typedef pfd

struct pollfd {
int fd;
short events;
short revents;
};


'--- struct pollfd pfd;
RECORD pfd
LOCAL fd TYPE int
LOCAL events TYPE short
LOCAL revents TYPE short
END RECORD

----------------------------------------------------------------------
3.)Remove the netlink.h
by supplying only what is needed from the header

dyxa.com/code.php?file=linux/netlink.h

We will have to convert this struct
struct sockaddr_nl
{
sa_family_t nl_family; /* AF_NETLINK */
unsigned short nl_pad; /* zero */
__u32 nl_pid; /* process pid */
__u32 nl_groups; /* multicast groups mask */
};

In BaCon we use the typedef nls

'--- struct sockaddr_nl nls;
RECORD nls
LOCAL nl_family TYPE unsigned short
LOCAL nl_pad TYPE unsigned short
LOCAL nl_pid TYPE unsigned int
LOCAL nl_groups TYPE unsigned int
END RECORD


4.) convert the #define to a BaCon CONST

#define NETLINK_KOBJECT_UEVENT 15 /* Kernel messages to userspace */

In BaCon this is
'--- from linux/netlink.h
CONST NETLINK_KOBJECT_UEVENT = 15


----------------------------------------------------------------------

[bigbass]

I first began documenting structs May 29, 2013
and now *finally* we can do typedef structures with a pointer too!
which means the low level stuff can be done without USEC

I hope we can get a typedef RECORD in bacon to
improve the syntax even more

This was first tested in HUG then converted to a "hybrid"
using header free stand alone code with PROTO/PRAGMA


gtkhelp how to use typedef structs in bacon
wiki.basic-converter.org/index.php?title=Gtkhelp

here is some working demo code
wiki.basic-converter.org/index.php?title=Gdk-events.bac

[bigbass]

developer.gnome.org/gdk3/stable/gdk3-Event-Structures.html

In bacon we have reduced and modified several things that we need our own
help file for structs


Let's focus on typdef structs
A new GUI called zahnrad uses its own typedefs
Porting to BaCon could be tricky but doable
Using gtk as an example only

struct GdkEventKey in C




struct GdkEventKey {
 GdkEventType type;
 GdkWindow *window;
 gint8 send_event;
 guint32 time;
 guint state;
 guint keyval;
 gint length;
 gchar *string;
 guint16 hardware_keycode;
 guint8 group;
 guint is_modifier : 1;
};



BaCon code we can embed a typedef struct
however the syntax is a bit different
notice the types and that int type; and void *window;
replaces the GdkEventType type; GdkWindow *window;
because those are declared only in the headers and were changed for HUG


typedef struct { \
int type; \
void *window; \
signed char send_event; \
unsigned int time; \
unsigned int state; \
unsigned int keyval;}(GdkEventKey)




Describes a key press or key release event.




int type; the type of the event (GDK_KEY_PRESS or GDK_KEY_RELEASE).

void *window; the window which received the event.

signed char send_event; TRUE if the event was sent explicitly.

unsigned int time; the time of the event in milliseconds

unsigned int state; a bit-mask representing the state of the modifier keys
(e.g. Control, Shift and Alt) and the pointer
buttons. See GdkModifierType.[type GdkModifierType]

unsigned int keyval; the key that was pressed or released.
See the gdk/gdkkeysyms.h header file
for a complete list of GDK key codes.



THESE WERE REMOVED but could be added back by changing the types

length;

*string;

guint16 hardware_keycode;

guint8 group;

guint is_modifier : 1;




GTK does this differently because of the union

A GdkEvent contains a union of all of the event types,
and allows access to the data fields in a number of ways.

The event type is always the first field in all of the event types,
and can always be accessed with the following code,
no matter what type of event it is:



GdkEvent *event;
GdkEventType type;

type = event->type



In BaCon there is no *event because we dont use the union
we get around this by using a typedef struct
called GdkEventKey directly then point to it
in this example we use keypress
the reason we use (char *) is for BaCon's PRINT to work


'---GdkEventKey* keypress;
LOCAL keypress TYPE GdkEventKey*

key_name$=(char *)gdk_keyval_name(keypress->keyval)
PRINT key_name$






Now a real example



'Note: Gdk-events.bac gets the low 'level keypress,mouse buttons and 'scroll wheel
'but this is header free code with 'typedef structs for the first 'time stand alone code  



'--- Needed for gtk2
PRAGMA LDFLAGS gtk-x11-2.0
PRAGMA LDFLAGS gdk-x11-2.0
'--- Needed to connect signals
PRAGMA LDFLAGS gobject-2.0

'--- GTK
PROTO gtk_init ALIAS INIT
PROTO gtk_main ALIAS DISPLAY
PROTO gtk_widget_show ALIAS SHOW
PROTO gtk_window_new ALIAS WINDOW
PROTO gtk_exit ALIAS QUIT
PROTO gtk_window_set_title ALIAS TITLE
PROTO gtk_window_set_default_size    ALIAS WINDOW_SIZE

'---extras
PROTO g_signal_connect_data ALIAS CALLBACK

'--- GDK
PROTO gdk_keyval_name
PROTO gdk_event_get_type
PROTO gdk_keyval_to_unicode

'--- set undeclared values
GTK_WINDOW_TOPLEVEL = 0
GTK_ORIENTATION_VERTICAL = 1

CONST GDK_KEY_PRESS_MASK = 1 << 10
CONST GDK_POINTER_MOTION_MASK = 1 << 2
CONST GDK_SCROLL_MASK = 1 << 21
CONST GDK_BUTTON_PRESS_MASK = 1 << 8
CONST GDK_BUTTON_RELEASE_MASK = 1 << 9
CONST G_CONNECT_AFTER = 1 << 0
GLOBAL NUL TYPE STRING

'---Global properties of the HUG GUI
GLOBAL RECORD hug_gui_properties
LOCAL last_key_pressed, timeout_id, canvas, freeze, canvasid
LOCAL mousex, mousey, scroll, button TYPE int
LOCAL options$, gl$, clip$ TYPE STRING
END RECORD


'======================================================================
FUNCTION hug_key_press(NUMBER hug_widget, void *hug_data1, NUMBER hug_data2)  
'======================================================================
REM should work for GTK 1.x and 2.x  3.x

'--- The big problem of typedef structs with pointers !
PROTO typedef,struct

typedef struct { int type; \
void *window; \
signed char send_event; \
unsigned int time; \
unsigned int state; \
unsigned int keyval;}(GdkEventKey)

'---GdkEventKey* keypress;
LOCAL keypress TYPE GdkEventKey*
keypress = (GdkEventKey*)hug_data1
hug_gui_properties.last_key_pressed = keypress->keyval

key_name$=(char *)gdk_keyval_name(keypress->keyval)
PRINT key_name$
TITLE(window, key_name$)

RETURN FALSE

END FUNCTION


'======================================================================
SUB hug_mouse_event (NUMBER hug_widget, NUMBER hug_data, long hug_user)
'======================================================================

PROTO  gtk_widget_set_events
PROTO gdk_window_get_pointer

LOCAL gdk, x, y

'---leave-notify-event
IF hug_user = 30 THEN
hug_gui_properties.scroll = -1
hug_gui_properties.button = -1
hug_gui_properties.mousex = -1
hug_gui_properties.mousey = -1
ELSE

hug_gui_properties.canvasid = hug_widget

REM Works for GTK 2.x
'--- The big problem of typedef structs with pointers !
PROTO typedef,struct

typedef struct {int type; \
void *window; \
signed char send_event; \
unsigned int time; \
double x; \
double y; \
unsigned int state; \
int direction; }(GdkEventScroll)

LOCAL mousescroll TYPE GdkEventScroll*
mousescroll = (GdkEventScroll*)hug_data

IF (hug_user == 10) THEN hug_gui_properties.scroll = mousescroll->direction
ELSE hug_gui_properties.scroll = -1

'--- The big problem of typedef structs with pointers !
typedef struct {int type; \
void *window; \
signed char send_event; \
unsigned int time; \
double x; \
double y; \
double *axes; \
unsigned int state; \
unsigned int button; \
void *device;} (GdkEventButton)

LOCAL mousebutton TYPE GdkEventButton*
mousebutton = (GdkEventButton*)hug_data
IF (hug_user == 40) THEN hug_gui_properties.button = mousebutton->button
ELSE IF (hug_user == 20) THEN  hug_gui_properties.button = -1

REM always get position
gdk = gdk_window_at_pointer(ADDRESS(x), ADDRESS(y))
gdk_window_get_pointer(gdk, ADDRESS(hug_gui_properties.mousex), ADDRESS(hug_gui_properties.mousey),0)
END IF


'PRINT "Mouse x = ",hug_gui_properties.mousex
'PRINT "Mouse y = ",hug_gui_properties.mousey

SELECT hug_gui_properties.scroll
CASE 0
PRINT "UP"
TITLE(window, "UP")

CASE 1
PRINT "DOWN"
TITLE(window, "DOWN")

DEFAULT 0
END SELECT



SELECT hug_gui_properties.button
CASE 1
PRINT "one"
TITLE(window, "Mouse one")

CASE 2
PRINT "two"
TITLE(window, "Mouse two")

CASE 3
PRINT "three"
TITLE(window, "Mouse three")

DEFAULT 0
END SELECT

END SUB




'=====================
SUB exit_prog
'=====================
PRINT "QUIT"
QUIT
END SUB


INIT (0, 0)
window = WINDOW(GTK_WINDOW_TOPLEVEL)
WINDOW_SIZE(window, 230, 150)
TITLE(window, "get key press")
gtk_widget_set_events(window,  GDK_KEY_PRESS_MASK |GDK_BUTTON_PRESS_MASK |GDK_BUTTON_RELEASE_MASK | GDK_SCROLL_MASK)

CALLBACK(window, "delete-event", exit_prog, 0, 0, 0)
CALLBACK(window, "key-release-event", hug_key_press, 0, 0, 0)

'CALLBACK(window, "button-press-event", hug_mouse_event, 20, 0, 0)
CALLBACK(window, "button-release-event", hug_mouse_event, 40, 0, 0)
CALLBACK(window, "motion-notify-event", hug_mouse_event, 0, 0, 0)
CALLBACK(window, "scroll-event", hug_mouse_event, 10, 0, 0)
CALLBACK(window, "leave-notify-event", hug_mouse_event, 30, 0, 0)
SHOW(window)
DISPLAY




[bigbass]

Hey guys

Now that we can compile c++ code to some degree
We need to be able to get the structs
to do some tests and also to test the compiler directly and cleanly
without a GUI lib


PRAGMA INCLUDE  <iostream>
PRAGMA LDFLAGS
PRAGMA COMPILER g++
PRAGMA OPTIONS -Wno-write-strings -Wno-pointer-arith
PRAGMA BACONLIB

OPTION PARSE FALSE

std::cout << "Hello BaCon c++ World";

PRINT

'--- use a struct declare floating point member and a string member
struct programming { double constant; char * pointer; } (variable) ;    

variable.constant = 1.23
variable.pointer = "Programming in Software Development."

std::cout <<variable.constant ;  
 
PRINT

std::cout <<variable.pointer ;  
 




[vovchik]

Dear Joe,

Thanks for the example. It works. You only need that "Rebuild Bacon archive" option the first time during a compile session. Subsequent compiles will use the existing .a file, if it exists and "cough" if it doesn't.

With kind regards,
vovchik

[Pjot]

Folks,

There also is a way to force the BaCon library creation programmatically by using this line of code:


PRAGMA BACONLIB


In the next release there will be a C++ version of the BaCOn library archive, created by default during installation time. We then can use the '-lbacon++' link flag instead. Or use the PRAGMA directive again:

PRAGMA LDFLAGS -lfltk -lfltk_images -lbacon++


This will work starting from 3.6.1.

BR
peter

[bigbass]

Hello Peter

Thanks

I Think that adding PRAGMA BACONLIB to the code is the best solution
I will edit my above post with the new line of code

sorry for a late response

P.S
I would imagine you have some test snippets for bacon compiling pure c++ code

A humble suggestion if you do have some test code could you link to it / post some basic stuff
I would like to see how you get around with using Bacons PRINT

the only way I could get it to work is like this
convertprint$ = (char*)Book1.title
PRINT convertprint$

Is there a better way ?

or maybe a new command PRINTC that prints it as a string without manually adding (char*)

PRINTC Book1.title

Thanks

Joe