I don't know how to use the parameter of some functions in libcsv

Question

So I have an ongoing project where I am trying to use libcsv . From the doc , I understand that csv_parse() takes

"a pointer to a callback function (cb1) that will be called from csv_parse()
 after an entire field has been read. cb1 will be called with a pointer to the
 parsed data (which is NOT nul-terminated unless the CSV_APPEND_NULL option is 
set), the number of bytes in the data, and the pointer that was passed 
to csv_parse()."

The function I gave to csv_parse to call as a callback (while reading an existing file, and trying to populate a struct with it) is :

void cb1_db_populate(void *s, size_t len, void *data)
{
    int row = ((struct DB *)data)->currRow, field = ((struct DB *)data)->currField;
    str = (char *)s;
    printf("%s\n", str);
}

And I have no clue on how to use that void *s since there is several data type in my data base , like char * and int and so on... For the moment I would just like to be able to print it properly, the code I have works the first time the function is called, but after that, there is a problem with the string's (array of char of course) length.

Sample :
2014-11-04
07.5011-04
courses soirée
eourses soirée
2014-11-05irée
30.5011-05irée
carburant5irée

How can I know which of pointer hides behind _void_ , and how to use it properly (print it, make operations with it...) ?

Hope I'm being clear, thank you very much :)

---

The solution I now use that gets me a proper string, that I can print without error or pass to atoi()/atof() when I need to :

char *str = malloc(sizeof(char)*len);
memcpy(str, (char *)s, len);  
printf("%s\n", str);  

Answer 1

There's a nice example in the documentation you linked to on page 7 that shows how to use it.

The callback function cb1 looks like this :

void cb1 (void *s, size_t len, void *data) {
}

So you'd be passing a pointer to a void(*)(void*, size_t, void*) .

EDIT:

For the moment I would just like to be able to print it properly, the code I have works the first time the function is called, but after that, there is a problem with the string's (array of char of course) length.

Those strings are not null-terminated, you can't just pass them to printf like normal cstrings. Try printf("%.*s\\n", len, str); instead.

And I have no clue on how to use that void *s since there is several data type in my data base, like char * and int and so on...

The void* is a pointer to the data field of a csv_parser struct. It points to the raw data read from the file/database. If your CSV contains text, then this data is text and you can cast the void* to char*. If your CSV contains numbers encoded in raw 32bit binary form (so, not text), then you can cast that void* to a uint32_t*.

Most of the time, you'll probably want to read it as a char*, but it's your job to know what's inside those files. All the parser sees is a bunch of bytes.

Answer 2

You don't need to use the void *s

but it's likely you may find it useful later on like if you discover that using global variables in the callback function was a bad idea.