Calling DLL function from C# and char** parameter type

[Siol]

I'm trying to call a dll function from C# which has the following form:

int some_function(i nt count, char **arg1, char **arg2)

Which parameter type I need to use in C# for C++ char** type? I tried
byte[][] (array of byte[]) but I get error "There is no marshaling support
for nested arrays."
regards
Tomaz

[Nicholas Paldino [.NET/C# MVP]]

Tomaz,

Are the strings being read from, or are they being written to? If they
are being read from, you should be able to pass it as an array of strings,
and it should work.

If they are being written to, then you will have to declare the
parameters as IntPtrs, allocate the memory for them, and then marshal the
data yourself (don't forget to unallocate the memory).
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Siol" <un*****@abc.co mwrote in message
news:zL******** ***********@new s.siol.net...

I'm trying to call a dll function from C# which has the following form:

int some_function(i nt count, char **arg1, char **arg2)

Which parameter type I need to use in C# for C++ char** type? I tried
byte[][] (array of byte[]) but I get error "There is no marshaling support
for nested arrays."
regards
Tomaz

[Rudy Velthuis]

Siol wrote:

I'm trying to call a dll function from C# which has the following
form:

int some_function(i nt count, char **arg1, char **arg2)

Which parameter type I need to use in C# for C++ char** type? I tried
byte[][] (array of byte[]) but I get error "There is no marshaling
support for nested arrays."

Probably something like:

[DllImport(yourd llname, CharSet=CharSet .Ansi)]
public static extern int some_function(i nt count,
string[] arg1, string[] arg2);

--
Rudy Velthuis http://rvelthuis.de

"Everyone is a genius at least once a year; a real genius has his
original ideas closer together."
-- Georg Lichtenberg (1742-1799)

[Tomaz Koritnik]

The strings are input parameters to the function (init parameters).

regards
Tomaz
"Nicholas Paldino [.NET/C# MVP]" <mv*@spam.guard .caspershouse.c omwrote in
message news:D4******** *************** ***********@mic rosoft.com...

Tomaz,

Are the strings being read from, or are they being written to? If they
are being read from, you should be able to pass it as an array of strings,
and it should work.

If they are being written to, then you will have to declare the
parameters as IntPtrs, allocate the memory for them, and then marshal the
data yourself (don't forget to unallocate the memory).
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Siol" <un*****@abc.co mwrote in message
news:zL******** ***********@new s.siol.net...

>I'm trying to call a dll function from C# which has the following form:

int some_function(i nt count, char **arg1, char **arg2)

Which parameter type I need to use in C# for C++ char** type? I tried
byte[][] (array of byte[]) but I get error "There is no marshaling
support for nested arrays."
regards
Tomaz

[Rudy Velthuis]

Tomaz Koritnik wrote:

The strings are input parameters to the function (init parameters).

Then (string[] arg1, string[] arg2) will do.

--
Rudy Velthuis http://rvelthuis.de

"Analyzing humor is like dissecting a frog. Few people are
interested and the frog dies of it."
-- E. B. White (1899-1985)

[TomazK]

I tried with string[] but as soon as I call the function, whole application
terminates instantly with no error message. I haven't tried with
CharSet=CharSet .Ansi yet.

from MySQL specification the dll function looks like this: int
mysql_library_i nit(int argc, char **argv, char **groups)

my implementation:

[DllImport("libm ysqld.dll")]
private static extern int mysql_server_in it(int argc, string[] argv,
string[] groups);
{
string[] argv = new string[1];
argv[0] = "mysql_test ";
string[] groups = new string[2];
groups[0] = "libmysqd_serve r";
groups[1] = "libmysqd_clien t";
mysql_server_in it(0, argv, groups);
}

regards

Tomaz


"Rudy Velthuis" <ne********@rve lthuis.dewrote in message
news:xn******** ********@news.m icrosoft.com...

Tomaz Koritnik wrote:

>The strings are input parameters to the function (init parameters).

Then (string[] arg1, string[] arg2) will do.

--
Rudy Velthuis http://rvelthuis.de

"Analyzing humor is like dissecting a frog. Few people are
interested and the frog dies of it."
-- E. B. White (1899-1985)

[Rudy Velthuis]

TomazK wrote:

[DllImport("libm ysqld.dll")]
private static extern int mysql_server_in it(int argc, string[] argv,
string[] groups);
{
string[] argv = new string[1];
argv[0] = "mysql_test ";
string[] groups = new string[2];
groups[0] = "libmysqd_serve r";
groups[1] = "libmysqd_clien t";
mysql_server_in it(0, argv, groups);
}

Assuming that argc is an argument count, it should probably not be 0,
and assuming that to each arg there is a group, you should probably
have argc=2, and also have two (2)strings in each array:

{
string[] argv = new string[2];
argv[0] = "mysql_test ";
argv[1] = argv[0];

string[] groups = new string[2];
groups[0] = "libmysqd_serve r";
groups[1] = "libmysqd_clien t";

mysql_server_in it(2, argv, groups);
}

Of course, I have no idea which strings are valid. Try to convert a C
or C++ example, if you have one, to C#.

--
Rudy Velthuis http://rvelthuis.de

"The object of war is not to die for your country but to make
the other bastard die for his."
-- General George Patton (1885-1945)

[TomazK]

Yes, argc is a count and it doesn't matter if I specify 2 or 0 or any other
number. It's the same in all cases.
regards
Tomaz
"Rudy Velthuis" <ne********@rve lthuis.dewrote in message
news:xn******** ********@news.m icrosoft.com...

TomazK wrote:

>[DllImport("libm ysqld.dll")]
private static extern int mysql_server_in it(int argc, string[] argv,
string[] groups);
{
string[] argv = new string[1];
argv[0] = "mysql_test ";
string[] groups = new string[2];
groups[0] = "libmysqd_serve r";
groups[1] = "libmysqd_clien t";
mysql_server_in it(0, argv, groups);
}

Assuming that argc is an argument count, it should probably not be 0,
and assuming that to each arg there is a group, you should probably
have argc=2, and also have two (2)strings in each array:

{
string[] argv = new string[2];
argv[0] = "mysql_test ";
argv[1] = argv[0];

string[] groups = new string[2];
groups[0] = "libmysqd_serve r";
groups[1] = "libmysqd_clien t";

mysql_server_in it(2, argv, groups);
}

Of course, I have no idea which strings are valid. Try to convert a C
or C++ example, if you have one, to C#.

--
Rudy Velthuis http://rvelthuis.de

"The object of war is not to die for your country but to make
the other bastard die for his."
-- General George Patton (1885-1945)

[Jesse McGrew]

On Jan 14, 10:10 am, "TomazK" <[e-mail] mwrote:

I tried with string[] but as soon as I call the function, whole application
terminates instantly with no error message. I haven't tried with
CharSet=CharSet .Ansi yet.

from MySQL specification the dll function looks like this: int
mysql_library_i nit(int argc, char **argv, char **groups)

my implementation:

[DllImport("libm ysqld.dll")]
private static extern int mysql_server_in it(int argc, string[] argv,
string[] groups);

{
string[] argv = new string[1];
argv[0] = "mysql_test ";

string[] groups = new string[2];
groups[0] = "libmysqd_serve r";
groups[1] = "libmysqd_clien t";

mysql_server_in it(0, argv, groups);

}

The function might expect groups and/or argv to be null-terminated.
Try adding an extra item to the end of each array and setting it to
null.

Jesse

[Rudy Velthuis]

Jesse McGrew wrote:

The function might expect groups and/or argv to be null-terminated.
Try adding an extra item to the end of each array and setting it to
null.

Could be. Good idea. But then I wonder what argc does there. <g>
--
Rudy Velthuis http://rvelthuis.de

"Wagner's music is better than it sounds."
-- Mark Twain (1835-1910)