Hi,
----- Original Message -----
From: "Derick Smith" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Friday, February 28, 2003 9:09 PM
Subject: Re: HELP mysql_server_init embedded in a DLL?
> Attempts at creating an embedded mySQL DLL for VB:
>
> I can successfully use the mysql_init() function from libmysql.lib to
create
> a DLL for VB. However, when I use this function (in a DLL or lib)linked
> against the libmysqld.lib or mysqlserver.lib it crashes the VB application
> but not the C application.
>
> I tried hard coding the arguments and servergroups for mysql_server_init
(I
> also used memset to initialize the strings to 0), I get the same result.
>
> The lib I create will always work with a C program, but the DLL will not
> work with VB.
You must take care with CALLING CONVENTIONS(__stdcall).This is be one reason
for crash.
>
> Does anyone have any more suggestions on how to use the embedded library
in
> a Visual C DLL to link with VB?
You can not access directly the mysql api function from VB.Are ,at least,two
big problems :the VB type STRING which is UNICODE ; passing the data
structure (like MYSQL which contain node lists) from VB to C or reverse.In
my opinion you should make functions which will be interface between MYSQL C
API and VB.Also you should make your own function to convert char to unicode
and reverse.It's better if you don't use MultiByteToWideChar()...you will
get a lot of "unpleasure surprises".
Of course you can do some improvisation (like in mysql_init or to convert a
STRING into ARRAY of BYTE) but is not a solution because VB imediatly will
give you some error like "OUT OF MEMORY".
Regards,
Gelu
_____________________________________________________
G.NET SOFTWARE COMPANY
Permanent e-mail address : [EMAIL PROTECTED]
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>
> Thanks
> Eric
>
>
> p.s: Email received from another individual (Thanks!!):
>
> Put the libMySql.dll in the wint\system32 directory (or in the directory
> where
> your executable is!)
>
>
> In vb, I use this one
>
> the declares:
>
> Public Declare Function mysql_init Lib "libmySQL" (ByVal lMYSQL As Long)
> As
> Long
> Public Declare Function mysql_real_connect Lib "libmySQL" _
> (ByVal lMYSQL As Long, _
> ByVal sHostName As String, _
> ByVal sUserName As String, _
> ByVal sPassword As String, _
> ByVal sDbName As String, _
> ByVal lPortNum As Long, _
> ByVal sSocketName As String, _
> ByVal lFlags As Long) As Long
>
>
> Public Function OpenConnection(ByVal sHostName As String, _
> ByVal sUserName As String, _
> ByVal sPassword As String, _
> ByVal sDbName As String, _
> Optional ByVal lPortNum As Long = 3306, _
> Optional ByVal lFlags As MYSQL_FLAG) As
> MYSQL_CONNECTION_STATE
>
> ........
> mlMYSQL = mysql_init(mlMYSQL)
> If mlMYSQL = 0 Then
> no connection handler
> Else
>
> 'connect to server
> If mysql_real_connect(mlMYSQL, msHostname, msUsername, msPassword,
> msDbName, mlPortNum, "", mlFlags) = 0 Then
> ' oops
> Else
> 'connection established ... state is now open
> End If
> End If
>
> 'setup the return value
> End Function
>
>
> I myselve created an dll (in vb) which encapsulates all the stuff to
connect
> to
> the database, use recordsets, .... (as close as possible to the ADO object
> model: so with connection, recordset - objects,
> bookmarks, fields, ...)
>
> Hope this helps.
>
>
>
>
>
>
>
> >From: "Gelu Gogancea" <[EMAIL PROTECTED]>
> >To: "Derick Smith"
> ><[EMAIL PROTECTED]>,<[EMAIL PROTECTED]>,<[EMAIL PROTECTED]>
> >Subject: Re: HELP mysql_server_init embedded in a DLL?
> >Date: Fri, 28 Feb 2003 14:40:31 +0200
> >
> >Hi,
> >----- Original Message -----
> >From: "Derick Smith" <[EMAIL PROTECTED]>
> >To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
> >Sent: Thursday, February 27, 2003 10:33 PM
> >Subject: Re: HELP mysql_server_init embedded in a DLL?
> >
> >
> > > I am posting this again, in hope that I will get a response.
> > >
> > > I tried doing the following (see VB code below. I got this code from
> >another
> > > site):
> > >
> > > I get the same error message as if I was calling the DLL I created in
C
> > > which calls mysql_server_init.
> > >
> > > Is it impossible to call this function from VB or embedded in another
> >DLL
> > > from VB?
> > > Can I only use the embedded mysql library in C or C++?
> > >
> > > Thanks
> > > Eric
> > >
> > > Public Declare Function mysql_server_init Lib
> > > "C:\mysql40\source\lib_release\libmysqld.dll" _
> > > (ByVal argc As Long, _
> > > ByVal argv As Byte, _
> > > ByVal groups As Byte) As Long
> > >
> > > Private Sub cmdmysq_server_init_Click()
> > > Dim argv(0) As Byte, groups(0) As Byte
> > > Dim i As Long
> > > argv(0) = Asc("0")
> > > groups(0) = Asc("0")
> > > i = mysql_server_init(0, argv, groups)
> > > End Sub
> >In my opinion,this will never work because argv and groups are pointed to
> >array which have a pointer ....char*(*);
> >But anyhow...if you wish to try again this formula, must declare argv and
> >groups ByRef because VB is responsable for the stack and the variable
must
> >be initialized before using like argument in function.Since argv and
> >groups
> >are byte is a non-sense to use ASC().
> >I'm very pessimistic that will be work.
> >
> > >
> > >
> > >
> > >
> > > >From: "Derick Smith" <[EMAIL PROTECTED]>
> > > >To: [EMAIL PROTECTED], [EMAIL PROTECTED]
> > > >Subject: mysql_server_init embedded in a DLL?
> > > >Date: Wed, 26 Feb 2003 14:34:28 +0000
> > > >
> > > >Hi!
> > > >
> > > >I am trying to create a DLL that will hide embedded mySQL functions
for
> >use
> > > >with VB. I am using mysqlserver.lib. I am able to compile and execute
> >the
> > > >following code. This has to be done in C because VB is too slow :-(
> > > >
> > > >If mysql_server_init function is run in the DLL from Visual Basic. I
> >get
> > > >the following error message: "..referenced memory at "0x000000". The
> > > >memory could not be read".
> > > >
> > > >Without the mysql_server_init function it will run correctly. It will
> >also
> > > >run correctly when this is compiled as a .lib file linked to a C
> >program.
> > > >
> > > >Is it possible to embed mysql_server_init in a DLL? (So the DLL can
be
> >used
> > > >in VB)
> > > >
> > > >Thanks in advance for any responses.
> > > >
> > > >Thanks
> > > >Eric
> > > >
> > > >
> > > >header1.h
> > > >
> > > >#define GPAPI __stdcall
> > > >
> > > >header2.h
> > > >
> > > >typedef unsigned long DBS;
> > > >#define NULLDBS (DBS)0
> > > >
> > > >api.c
> > > >
> > > >GPAPI DBS dbNewSet (char * basedir, char * datadir, char * dbname)
> > > >{
> > > > return NewSet(basedir,datadir,dbname);
> > > >}
> > > >
> > > >
> > > >newset.c
> > > >
> > > >extern DBS NewSet(char * basedir, char * datadir, char * dbname)
> > > >{
> > > > DBSET* pSet = CreateSet();
> > > > char *args[3];
> > > > char strArgs[3][1024];
> >I guess some problems can be elimanted if you initialize the variables
> >which
> >are declared or if you allocate some memory.
> >Anyhow you can use '\0' - termination string to be sure that you don't
have
> >*other garbage* after your string.This *garbage* can influence the
lenght
> >of the string.Bad thing.
> >
> > > > int iRtn;
> > > > int argc = 3;
> > > >
> > > > strcpy(strArgs[0],"this_program");
> >
> > > > sprintf(strArgs[1],"--basedir=%s",basedir);
> > > > sprintf(strArgs[2],"--datadir=%s",datadir);
> > > > args[0]= strArgs[0];
> > > > args[1]= strArgs[1];
> > > > args[2]= strArgs[2];
> > > >
> > > >/* If I comment out this line of code,
> > > >the DLL will run correctly.
> > > >If mysql_server_init function is run in the DLL. I get the following
> > > >error message: "..referenced memory at "0x000000". The
> >...this means that one of your variables is NULL.This error occur because
> >you don't *catch* the right pointer.By using equal sign you pass the
> >pointer
> >to lvalue and not the value.At the address of pointer you can find the
> >value.
> >
> > > >memory could not be read" */
> > > > iRtn = mysql_server_init(3, args, server_groups);
> > > >
> > > > if (pSet ==0 ) return NULLDBS;
> > > > memset(pSet, 0, sizeof(DBSET)); /* Zero the structure. */
> > > > pSet->size = sizeof(DBSET);/* Assign structure size. */
> > > > pSet->magic = DBS_MAGIC; /* Assign magic number. */
> > > >
> > > > return (DBS)(void*)pSet;
> > > >}
> >
> >If you have a little patience (maybe a week or two...i try to find some
> >available time for this) a new version of GMySQL(An interface between
MYSQL
> >C API function and VB or other development platform for Windows) will be
> >released.This new version, will contain the implementation of the new
> >replication functions and also will be able to work with libmysqld.
> >
> >Regards,
> >
> >Gelu
> >_____________________________________________________
> >G.NET SOFTWARE COMPANY
> >
> >Permanent e-mail address : [EMAIL PROTECTED]
> > [EMAIL PROTECTED]
> >
> > >
> > >
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