[Gambas-user] external functions and structs

[T Lee Davidson]

On 11/28/18 11:49 AM, T Lee Davidson wrote:
> When I try to run your code, I get:
> Cannot find dynamic library 'libais.so.1.9.so': libais.so.1.9.so: cannot open shared object file: No such file or directory in
> Main:61.
> 
> In addition to your:
> Library "libais.so.1.9"
> 
> I tried:
> Library "./libais.so.1.9"
> Library "../libais.so.1.9"
> 
> No love. I don't know why Gambas is changing the name I specified.
> 
> 
> ___
> Lee

I forgot to mention. In the sixbit structure, there is "char *p; //!< pointer to current character in bits". You have p defined
as a string instead of as a pointer. Maybe it needs to be the way you have it. I couldn't test it.


> 
> On 11/28/18 7:39 AM, gen braga wrote:
>> 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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