[Gambas-user] external functions and structs

[gen braga]

Hi there,

I'm trying to use a method from an external library whose signature is as
follow

int __stdcall assemble_vdm( ais_state *state, char *str )

ais_state is:

#define SIXBIT_LEN   255

typedef struct {
    unsigned char msgid;               //!< Message ID 0-31
    unsigned int  sequence;            //!< VDM message sequence number
    unsigned int  total;               //!< Total # of parts for the message
    unsigned int  num;                 //!< Number of the last part stored
    char          channel;             //!< AIS Channel character
    sixbit        six_state;           //!< sixbit parser state
} ais_state;

six_state is:

typedef struct {
    char bits[SIXBIT_LEN];          //!< raw 6-bit ASCII data string
    char *p;                        //!< pointer to current character in
bits
    unsigned char remainder;        //!< Remainder bits
    unsigned char remainder_bits;   //!< Number of remainder bits
} sixbit;

I declared them all as follow:

Public Struct sixbit
  bits[255] As Byte                               'raw 6 - bit ASCII data
string --> era [SIXBIT_LEN - 1]
  p As String                                    'pointer To current
character In bits
  remainder As Byte                               'Remainder bits
  remainder_bits As Byte                          'Number Of remainder bits
End Struct

Public Struct AIS_State
    msgid As Byte                               'Message ID 0 - 31
    sequence As Short                         'era DWORD; / / ! < VDM
message sequence number
    total As Short                            'era DWORD; / / ! < Total #
Of parts For the message
    num As Short                              'era DWORD; / / ! < Number Of
the Last part stored
    channel As Byte                             ': Char; / / ! < AIS
Channel character
    six_state As SixBit                         '; / / ! < sixbit parser
state
End Struct

Private Extern assemble_vdm(state As AIS_State, str1 As String) As Integer

Ok....
In my Main method I call the assemble_vdm function and the result is as
expected, returning an integer between 0 and 5 meaning what's going on, I
can confirm it by changing the second parameter's contents. But that
method, modifies the first parameter (state) internally, and I should use
it afterwards to decide what do to, reading state.msgid

The fact is, when I read it, its empty and rises segfault.... Does anyone
knows how to deal with it?

The library's sources are at https://github.com/bcl/aisparser/tree/master/c

Attached are my sources.

Greetings,
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