World: r3wp

Jocko, here's an "add-mul" sample extension that works with A102: 
https://gist.github.com/bc820cc3eb301c79c1ef

Compiled with `gcc -shared -fpack-struct=4 -Isrc/include/ -o sample.so 
sample.c`.

You'll possibly want to adapt the -I, make sure it points to the 
A102 hostkit's src/include/ directory. For Win32, you'll also want 
"-o sample.dll".

thhanks, I will try. But my problem is not here. I have two concerns 
:  for the extensions dealing with strings (not the simple example 
where one reverse the order of chars), the compatibility is no more 
achieved (because of changes in the representation or processing 
of strings ?) Then I have to compile using the new headers. And when 
I do so, the extension is no more loadable (even a simple one like 
your example)

I dont't follow.

The example I have given above needs to be compiled with the "new" 
headers, the headers of the A102 hostkit, that is.

And as demonstrated: it compiles _and_ loads just fine.

Note that while my sample.c it may _look_ just like the example given 
in http://www.rebol.com/r3/docs/concepts/extensions-making.html#section-2, 
it differs in that `RX_Call` takes three arguments instead of two.

I added a second file, sample2.c, to demonstrate working with strings 
in A102: https://gist.github.com/bc820cc3eb301c79c1ef#file_sample2.c

Also compiles and loads fine for me.

thanks, ill have a look

Well, I had the same problem that some months ago :  

 in my application, I must compile in c++, and there is a difference 
 in labelling the function calls in c and c++.  
The simplest solution is to modify a line in reb-ext-lib.h:  
#define RXIEXT _declspec(dllexport) to
#define extern "C" RXIEXT _declspec(dllexport) 

One shoud definitly insert in this header a condition like  
#ifdef _cplusplus   
 #define extern "C" RXIEXT _declspec(dllexport)

This done, everything works correctly

So C++ name mangling was the issue?

yes

Good to know. Thank for posting!

Yes, that's a good note. Should be used. I forward it to Carl.

Done.

http://www.rebol.com/r3/docs/concepts/extensions-making.html#section-17
says it's out of date and I'm really having trouble including words 
as symbols in a result block of an extension command. 

It works fine with an *INIT_BLOCK defined as


 const char *init_block = "REBOL [\nTitle: {Power Management}\nName: 
 power\nType: extension\nExports: [power-status]\n]\n"

     "lib-boot:           does [map-words words] ;-- Is that a good idea?\n"

     "words:             [ac-line battery remains of high low critical 
     charging]\n"
	    "map-words:    command [words [block!]]\n"
	    "power-status: command []\n"
;

if after IMPORT %power.dll I call SYSTEM/MODULES/POWER/LIB-BOOT.


Is there a way to have IMPORT automatically execute the LIB-BOOT 
code with a simple extension not included into the host code with 
host-kit?

Sorry, don't get what you want to do. You can run some init code 
when the extension is loaded.

I'm trying to return a block containg a word not taken from a commands 
arguments. Say, I want to return a block like [BATTERY CHARGING]: 

That works with

	u32 *word_ids = 0; // used to hold word identifiers
	enum power_words {W_POWER_BATTERY = 1, W_POWER_CHARGING};

	RXIEXT int RX_Call(int cmd, RXIFRM *frm, void *data) {
		/* .... */

		v.int32a = word_ids[W_POWER_BATTERY];
		RXI_SET_VALUE(s, pos++, v, RXT_WORD); 
		v.int32a = word_ids[W_POWER_CHARGING];
		RXI_SET_VALUE(s, pos++, v, RXT_WORD);
	
		/* .... */
   	}


only after importing the DLL I "manually" init the words with a MAP-WORDS 
command. I was thinking that IMPORT eventually triggers LIB-BOOT 
init-code from the INIT_BLOCK. It seems like the init code is not 
executed.

That MAP-WORDS command only does:

	word_ids = RXI_MAP_WORDS(RXA_SERIES(frm, 1));
	return RXR_TRUE;

How does your RX_Init look like?

RXIEXT const char *RX_Init(int opts, RXILIB *lib) {
    RXI = lib;
    if (lib->version == RXI_VERSION) return init_block;
    return 0;
}

Straight from the samples, since I have about zero knowledge of C 
and only am exploring how extensions work.

Ok, you need to make a call to your lob-boot function out of this 
init function.

Ouch! Now that problem above has a really simple solution: Just putting 
the module init code in the CONST CHAR *INIT_BLOCK works great:

	const char *init_block =
	    "REBOL [\n"
	        "Title:   {Power Management}\n"
	        "Name:    power\n"
	        "Type:    extension\n"
	        "Exports: [power-status capture-screen]\n"
	    "]\n"

     "words:          [ac-line battery remains of high low critical charging]\n"
	    "map-words:      command [words [block!]]\n"

     "power-status:   command [{Returns ac-line and battery status information.}]\n"

     "capture-screen: command [{Returns screenshot as an image.}]\n"
	    "map-words words\n";


The "magic" is the last line, where MAP_WORDS WORDS is evaluated 
ofter loading the module, that command inits the dll with the word 
ids used by the extension.

I have built a simple R3 extension for ODBC database access. Although 
more work needs to be done in the unicode area and configurable rowset 
max-rows retrieval as well as catching some GC-related bugs, basic 
functionality like selects, inserts, updates and statement parameters 
is there and working for most major types like LOGIC!, INTEGER!, 
DECIMAL!, TIME! and STRING! I have to test with more databases / 
odbc database drivers. 


I have, however, major problems in working with date values. I just 
don't manage to retrieve date values passed to a command or to return 
a proper date value. So, has anybody succeeded in working with date 
values and probably knows how to create, access and calculate them? 
Sadly, I've found no example code related to date values and there 
isn't much documentation too. Any info is greatly appreciated!

absolutly cool :-)

Do you have some examples of the date values you get back with their 
actual value?

I would say it's absolutely necessary to find the definitions of 
the date values. Reverse engineering can work, but may hide subtle 
bugs, and take much longer before you're sure about the correctness 
of the implementation.

Where have you looked so far?

If you mean that it is difficult or impossible to work with date 
values in extensions, bring the issue to Robert, who can communicate 
it with Carl, to get the answer ASAP imo ....

Ah, good question, now I think Christian meant the binary format 
of rebol's date! values, not any database's date format, which should 
be available as a string at least.

I suspect the passing of rebol date values may not have been implemented 
in R3 extensions yet (not that I've tried anything there yet).

I've looked in DevBase, but haven't asked questions there yet. I've 
scanned all the extensions documentation on DocBase and the header 
files in the host-lib/extension packages. 


I didn't even manage to read a date value in a simple command like 
   TEST-DATE: COMMAND [DATE [DATE!]]      About every member n the 
REBOL value c-union type seemed to only contain zero values.

I have no idea on how date values are stored in C, all that the docs 
say is that date values are 32 bit encoded date and time zone values, 
so I mainly tried with value.int32a but tried other members too. 
I have no idea about how the encoding is done and - as Anton said 
- I really don't want to reverse engineer it.

Hmm.. that doesn't look very promising.

Anton, yes, I can get date values from databases if I ask for string 
values, but I'd rather like DATE! results.

Yes, it should be faster performance.

But I suppose if you need it badly enough and can't find how to move 
dates then you parse and transform between the string formats.

On the rebol side, should just need a MOLD and a LOAD / TO-DATE...

Surely *someone* will illuminate the situation soon...

ChristianE - either post on R3 Chat, or post to Robert - he might 
be the most direct channel to Carl, so I think you might get your 
answer faster that way ....

Hmm, I think I've to check this again. At least, a simple 

    RXIEXT int RX_Call(int cmd, RXIFRM *frm, void *data) {
        return RXR_VALUE
    }
    
returns a proper date value for

    test-date: command [date [date!]]
    
I'll see if I can find some time to work on this evening.

Using external extensions with a104, I get an error when using these 
series macros :

RL_SERIES_INFO(ser, RXI_SER_TAIL) ,  RL_GET_CHAR(ser, idx) , and 
RL_MAKE_STRING. Did someone noticed this ?

ChristianE, can we see your extension .. even if it is a WIP?

There are things that have to be cleaned up a bit first, Graham, 
but I hope I can publish it very soon (counting days, not weeks).

It really should only depend on the time I can piut aside to work 
on the driver.

Hmm, I somehow don't manage to compile my odbc extension with a109, 
on import I get the following error

>> import %../lib/odbc.dll
** Script error: make-scheme has no value
** Where: do -apply- make catch case case -apply- apply import
** Near: do body obj


I do understand that it's related to MAKE-SCHEME moving into SYS 
context,. Do I have to import SYS into my extension module's context 
first and, if so, how? NEEDS: [SYS] doesn't work, my extension is 
already declared with TYPE: MODULE OPTIONS: [EXTENSION DELAY], trying 
to access MAKE-SCHEME directly thru SYS/MAKE-SCHEME makes the intepreter 
crash.

Maybe your extension is loaded faster than mezz-code?

That's why I'm trying to DELAY. Delaying doesn't seem to work for 
embedded extensions according to curecode, but here it's a simple 
dll import ...