Convert std::string to LV path to apply to an dll generated from labview

[egon456]

Hi.

I am working with a dll-function generated from LV which needs an path type.

I would like to convert a std::string to LV-path and tried the following code.

    std::string v_PathAsString_o = "C:\\_work\\PowerSupply.ini";
    const char * v_path_pc = v_PathAsString_o.c_str();
    const char ** v_path_ppc = &v_path_pc;
    Path * v_Path_po = NULL;
    char **filename = 0;
    MgErr v_status_o = FStringToPath((ConstLStrH)v_path_ppc, v_Path_po);
    // v_status_o will be set to 2 (mFullErr)
    // v_Path_po remains 0x00000000

After sucessful compile and run I got status from FStringToPath() back and was set to mFullErr.

I cannot imagine that my Windows 7 PC is having trouble with memory space.

What is the right way to get a LV path variable?

[rolfk]

---

@egon456 wrote:

Hi.

I am working with a dll-function generated from LV which needs an path type.

I would like to convert a std::string to LV-path and tried the following code.

    std::string v_PathAsString_o = "C:\\_work\\PowerSupply.ini";
    const char * v_path_pc = v_PathAsString_o.c_str();
    const char ** v_path_ppc = &v_path_pc;
    Path * v_Path_po = NULL;
    char **filename = 0;
    MgErr v_status_o = FStringToPath((ConstLStrH)v_path_ppc, v_Path_po);
    // v_status_o will be set to 2 (mFullErr)
    // v_Path_po remains 0x00000000

After sucessful compile and run I got status from FStringToPath() back and was set to mFullErr.

I cannot imagine that my Windows 7 PC is having trouble with memory space.

What is the right way to get a LV path variable?

---

A LStrHandle is a pointer to a pointer, but not to a C string buffer but instead to a memory buffer that first contains an int32 that indicates the number of bytes, followed by the 8bit MCBS data string (without appended 0 char but having one in the buffer as long as it is not counted in the length is not a problem).

So you really first need to convert your C String into a LStrHandle.

And once you do that you would run into the next error (mgArgErr) since you don't allocate a space for the returned path but only for a pointer to one and initialize it to NULL, then pass it to FStringToPath() like that. And FStringToPath() receives a null pointer to return the path in! That can't work!

Something like this would work:

char *cstr = "something";
LStrHandle lstr = NULL;
Path path = NULL;

err = NumericArrayResize(uB, 1, (UHandle*)&lstr, strlen(cstr));
if (!err)
{
     MoveBlock(cstr, LStrBuf(*lstr), strlen(cstr));
     LStrLen(*lstr) = strlen(cstr);
     err = FStringToPath(lstr, &path);
     DSDisposeHandle((UHandle)lstr);
}