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digitalmars.D.learn - #import mapi.h

reply Martin Tschierschke <mt smartdolphin.de> writes:
Is there an step by step introduction how to convert a C header 
of an external lib into the right extern(C){} block?

A blog post or tutorial, or chapter in a D book? (I have those 
from Packt Publishing)

(Especially I am trying to get this used with D:
Montetdb C-API 
https://www.monetdb.org/Documentation/Manuals/SQLreference/Programming/MAPI
With: 
https://github.com/snaga/monetdb/blob/master/clients/mapilib/mapi.h)

The page: https://dlang.org/spec/interfaceToC.html is known, but 
not detailed enough for me.
Mar 21 2018
next sibling parent ketmar <ketmar ketmar.no-ip.org> writes:
Martin Tschierschke wrote:


 or tutorial


ok, tutorial:

1. learn C.
2. learn D.
3. DO IT!

;-)
Mar 21 2018
prev sibling next sibling parent reply Timoses <timosesu gmail.com> writes:
On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin Tschierschke 
wrote:

 Is there an step by step introduction how to convert a C header 
 of an external lib into the right extern(C){} block?

 A blog post or tutorial, or chapter in a D book? (I have those 
 from Packt Publishing)


While googling I found this:
https://dlang.org/blog/2017/12/05/interfacing-d-with-c-getting-started/

Haven't read it yet, but might give you some more insight.

For automatic conversion I stumbled across Dstep which I so far 
like a lot:
https://github.com/jacob-carlborg/dstep
Mar 21 2018
parent reply Martin Tschierschke <mt smartdolphin.de> writes:
On Wednesday, 21 March 2018 at 17:12:07 UTC, Timoses wrote:

 On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin 
 Tschierschke wrote:

 Is there an step by step introduction how to convert a C 
 header of an external lib into the right extern(C){} block?

 A blog post or tutorial, or chapter in a D book? (I have those 
 from Packt Publishing)


 While googling I found this:
 https://dlang.org/blog/2017/12/05/interfacing-d-with-c-getting-started/

 Haven't read it yet, but might give you some more insight.

 For automatic conversion I stumbled across Dstep which I so far 
 like a lot:
 https://github.com/jacob-carlborg/dstep


Thank you! I will have a look at both, an Mike Parker is pointing 
to his book, too,
so now together with the post  from "nkm1" I should be able to 
make it!

 ketmar, I learned C but the counter of years from that time was 
stored in a nibble and so I got an overflow...error :-)
Mar 22 2018
parent Martin Tschierschke <mt smartdolphin.de> writes:
On Thursday, 22 March 2018 at 12:53:23 UTC, Martin Tschierschke 
wrote:

 On Wednesday, 21 March 2018 at 17:12:07 UTC, Timoses wrote:


[...]

I got it, my first mini test with C bindings!
Important missing at first: (stderr)

import core.stdc.stdio : stderr, FILE;
and use of toStringz inside:  mapi_query(dbh, toStringz(q) )

After installing monetdb and starting the server with:
https://www.monetdb.org/Documentation/UserGuide/Tutorial

My minimal version of the example compiled with
dmd app.d -I /usr/local/lib/libmapi.so

(My dub.json is still incomplete so the linking failed.)

Here is the code: (only the minimum of mapi.h is icluded!)

```
  std.stdio;
import std.string;

/* interfacing winth monetdb #include mapi.h */
/* minimum to run code of example at: 
https://www.monetdb.org/Documentation/Manuals/SQLreference/Programming/MAPI */
import core.stdc.stdio : stderr,FILE;
import core.stdc.stdlib;

struct MapiStruct;
alias Mapi = MapiStruct*;

struct MapiStatement;
alias MapiHdl = MapiStatement*;

enum MOK = 0 ;

alias MapiMsg = int;

extern(System){
Mapi mapi_connect(const char* host, int port, const char* 
username, const char* password, const char* lang, const char* 
dbname);
MapiHdl mapi_query(Mapi mid, const char *cmd);
int mapi_fetch_row(MapiHdl hdl);
char *mapi_fetch_field(MapiHdl hdl, int fnr);
MapiMsg mapi_error(Mapi mid);
MapiMsg mapi_explain(Mapi mid, FILE* fd);
MapiMsg mapi_destroy(Mapi mid);
MapiMsg mapi_close_handle(MapiHdl hdl);
MapiMsg mapi_explain_result(MapiHdl hdl, FILE* fd);
MapiMsg mapi_next_result(MapiHdl hdl);
MapiMsg mapi_explain_query(MapiHdl hdl, FILE* fd);
char *mapi_result_error(MapiHdl hdl);
}


void die(Mapi dbh, MapiHdl hdl) {
   if (hdl != null) {
     mapi_explain_query(hdl, stderr);
     do {
       if (mapi_result_error(hdl) != null)
         mapi_explain_result(hdl, stderr);
     } while (mapi_next_result(hdl) == 1);
     mapi_close_handle(hdl);
     mapi_destroy(dbh);
   } else if (dbh != null) {
     mapi_explain(dbh, stderr);
     mapi_destroy(dbh);
   } else {
     fprintf(stderr, "command failed\n");
   }
   exit(-1);
}


MapiHdl query(Mapi dbh, string q) {
   MapiHdl ret = null;
   if ((ret = mapi_query(dbh, toStringz(q) )) == null || 
mapi_error(dbh) != MOK)
     die(dbh, ret);
   return(ret);
}

void update(Mapi dbh, string q) {
   MapiHdl ret = query(dbh, q);
   if (mapi_close_handle(ret) != MOK)
     die(dbh, ret);
}

void main()
{

auto  dbh = mapi_connect("localhost", 50000, "monetdb", 
"monetdb", "sql", "voc");
       writeln("DB-connect");
       update(dbh, "CREATE TABLE emp (name VARCHAR(20), age INT)");
       writeln("create");
       update(dbh, "INSERT INTO emp VALUES ('John', 23)");
       update(dbh, "INSERT INTO emp VALUES ('Mary', 22)");
auto hdl = query(dbh, "SELECT * FROM emp");
   while (mapi_fetch_row(hdl)) {
     auto name = mapi_fetch_field(hdl, 0);
     auto age = mapi_fetch_field(hdl, 1);
     printf("%s is %s\n", name, age);
   }
}
```

Will try to make a complete binding available later...
Mar 22 2018
prev sibling next sibling parent reply nkm1 <t4nk074 openmailbox.org> writes:
On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin Tschierschke 
wrote:

 Is there an step by step introduction how to convert a C header 
 of an external lib into the right extern(C){} block?

 A blog post or tutorial, or chapter in a D book? (I have those 
 from Packt Publishing)

 (Especially I am trying to get this used with D:
 Montetdb C-API 
 https://www.monetdb.org/Documentation/Manuals/SQLreference/Programming/MAPI
 With: 
 https://github.com/snaga/monetdb/blob/master/clients/mapilib/mapi.h)

 The page: https://dlang.org/spec/interfaceToC.html is known, 
 but not detailed enough for me.


The easiest thing to do is to write a wrapper in C. The wrapper 
will include all necessary headers and provide some easy to use 
functions that you can call from D. Of course, you'll need to use 
a C compiler to compile it.
Anyway, this header looks very straightforwar, no particular 
tricks with the preprocessor. It should be something like this 
(untested, obviously):

import core.stdc.stdio : FILE;

enum
{
     MAPI_AUTO      = 0,  /* automatic type detection */
     MAPI_TINY      = 1,
     MAPI_UTINY     = 2,
     MAPI_SHORT     = 3,
     MAPI_USHORT    = 4,
     MAPI_INT       = 5,
     MAPI_UINT      = 6,
     MAPI_LONG      = 7,
     MAPI_ULONG     = 8,
     MAPI_LONGLONG  = 9,
     MAPI_ULONGLONG = 10,
     MAPI_CHAR      = 11,
     MAPI_VARCHAR   = 12,
     MAPI_FLOAT     = 13,
     MAPI_DOUBLE    = 14,
     MAPI_DATE      = 15,
     MAPI_TIME      = 16,
     MAPI_DATETIME  = 17,
     MAPI_NUMERIC   = 18,
}

enum int PLACEHOLDER = '?';

enum
{
     MAPI_SEEK_SET = 0,
     MAPI_SEEK_CUR = 1,
     MAPI_SEEK_END = 2,
}

enum
{
     MAPI_TRACE      = 1,
     MAPI_TRACE_LANG = 2,
}

alias MapiMsg = int;

enum
{
     MOK         =  0,
     MERROR      = -1,
     MTIMEOUT    = -2,
     MMORE       = -3,
     MSERVER     = -4,
}

enum
{
     LANG_MAL    = 0,
     LANG_SQL    = 2,
     LANG_JAQL   = 3,
}

/* prompts for MAPI protocol */
enum int PROMPTBEG = '\001'; /* start prompt bracket */

  /* prompt: ready for new query */
const(char)* PROMPT1 = "\001\001\n".ptr;

/* prompt: more data needed */
const(char)* PROMTP2 = "\001\002\n".ptr;

/*
  * The table field information is extracted from the table headers
  * obtained from the server. This list may be extended in the 
future.
  * The type of both the 'param' and 'binding'
  * variables refer to their underlying C-type. They are used for
  * automatic type coercion between back-end and application.
  */
struct MapiStruct;
alias Mapi = MapiStruct*;

/* this definition is a straight copy from 
sql/include/sql_query.h */
enum
{
     Q_PARSE     = 0,
     Q_TABLE     = 1,
     Q_UPDATE    = 2,
     Q_SCHEMA    = 3,
     Q_TRANS     = 4,
     Q_PREPARE   = 5,
     Q_BLOCK     = 6,
}

struct MapiStatement;
alias MapiHdl = MapiStatement*;

alias mapi_uint64 = ulong;
alias mapi_int64 = long;

/* three structures used for communicating date/time information 
*/
/* these structs are deliberately compatible with the ODBC 
versions
    SQL_DATE_STRUCT, SQL_TIME_STRUCT, and SQL_TIMESTAMP_STRUCT */

/* used by MAPI_DATE */
struct MapiDate
{
     short year;
     ushort month;
     ushort day;
}

/* used by MAPI_TIME */
struct MapiTime
{
     ushort hour;
     ushort minute;
     ushort second;
}

/* used by MAPI_DATETIME */
struct MapiDateTime
{
     short year;
     ushort month;
     ushort day;
     ushort hour;
     ushort minute;
     ushort second;
     uint fraction;  /* in 1000 millionths of a second (10e-9) */
}

/* connection-oriented functions */
extern (C)
{
     Mapi mapi_mapi(const char *host,
                    int port,
                    const char *username,
                    const char *password,
                    const char *lang,
                    const char *dbname);


     // and so on...
}
Mar 21 2018
parent Martin Tschierschke <mt smartdolphin.de> writes:
On Wednesday, 21 March 2018 at 18:42:43 UTC, nkm1 wrote:

 On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin 
 Tschierschke wrote:

 [...]


 The easiest thing to do is to write a wrapper in C. The wrapper 
 will include all necessary headers and provide some easy to use 
 functions that you can call from D. Of course, you'll need to 
 use a C compiler to compile it.
 Anyway, this header looks very straightforwar, no particular 
 tricks with the preprocessor. It should be something like this 
 (untested, obviously):

 [...]


Thank you!
Especially this was a missing link:

struct MapiStruct;
alias Mapi = MapiStruct*;
Mar 22 2018
prev sibling next sibling parent Kagamin <spam here.lot> writes:
On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin Tschierschke 
wrote:

 Is there an step by step introduction how to convert a C header 
 of an external lib into the right extern(C){} block?


In short, they should be binary compatible: where is a pointer on 
C side, should be a pointer on D side, same for integer sizes, 
data layout an calling conventions.
Mar 22 2018
prev sibling parent reply Paul Backus <snarwin gmail.com> writes:
On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin Tschierschke 
wrote:

 Is there an step by step introduction how to convert a C header 
 of an external lib into the right extern(C){} block?


In addition to what others have said, I found the following 
article on the D Wiki useful:

https://wiki.dlang.org/D_binding_for_C
Mar 22 2018
parent reply Martin Tschierschke <mt smartdolphin.de> writes:
On Thursday, 22 March 2018 at 17:42:46 UTC, Paul Backus wrote:

 On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin 
 Tschierschke wrote:

 Is there an step by step introduction how to convert a C 
 header of an external lib into the right extern(C){} block?


 In addition to what others have said, I found the following 
 article on the D Wiki useful:

 https://wiki.dlang.org/D_binding_for_C


Thank you, this one is very good!
Mar 22 2018
parent reply Mike Parker <aldacron gmail.com> writes:
On Thursday, 22 March 2018 at 21:45:40 UTC, Martin Tschierschke 
wrote:

 On Thursday, 22 March 2018 at 17:42:46 UTC, Paul Backus wrote:

 On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin 
 Tschierschke wrote:

 Is there an step by step introduction how to convert a C 
 header of an external lib into the right extern(C){} block?


 In addition to what others have said, I found the following 
 article on the D Wiki useful:

 https://wiki.dlang.org/D_binding_for_C


 Thank you, this one is very good!


If you have Learning D, chapter 9 is all about interface D with C.
Mar 22 2018
parent Martin Tschierschke <mt smartdolphin.de> writes:
On Friday, 23 March 2018 at 01:12:58 UTC, Mike Parker wrote:

 On Thursday, 22 March 2018 at 21:45:40 UTC, Martin Tschierschke 
 wrote:

 On Thursday, 22 March 2018 at 17:42:46 UTC, Paul Backus wrote:

 On Wednesday, 21 March 2018 at 16:22:45 UTC, Martin 
 Tschierschke wrote:

 Is there an step by step introduction how to convert a C 
 header of an external lib into the right extern(C){} block?


 In addition to what others have said, I found the following 
 article on the D Wiki useful:

 https://wiki.dlang.org/D_binding_for_C


 Thank you, this one is very good!


 If you have Learning D, chapter 9 is all about interface D with 
 C.


I will look at it! I have seen your hint already, you have 
mentioned it in the beginning of your blogpost. The discussion in 
an other thread [1] about direct integration of an C/C++ 
preprocessor into the D complier(s) is very interesting, I think 
this will push the adoption of the language, because you just can 
start immediately to use D as a replacement for C or C++. It is 
very fascinating to see how D is evolving all the time. Now I 
hope that with the survey and more donations the D Foundation get 
the ability to push this even more.

[1] 
https://forum.dlang.org/post/hvanbsyrydsxpizltkca forum.dlang.org
Mar 23 2018