Re: saving GArray contents to binary file

[Maciej Katafiasz <mnews22 wp pl>]

Dnia 03-10-2004, nie o godzinie 12:19 +0200, edward hage napisał(a):
> I want to save a GArray of struct to a binairy file, but I get stuck somehow.
> Just sequentially saving the structs is okay, but I want to save the complete array. Here 
> is a little program how I tried it, can anyone point out how to succesfully save and load 
> the GArray. The program is simple so self-explaining.
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <gtk/gtk.h>
>
> typedef struct // <=== structs like these need to be saved in GArray
> {
>    gchar *brand;
>    gchar *typenumber;
> } typDing;
>
> int main ()
> {
>    const gchar *FILENAME = "ding.txt";
>    FILE *fp;
>    GArray *array = g_array_sized_new (FALSE, FALSE, sizeof (typDing), 1);
>    typDing foo;
>    guint i;
>
>    //assign <== just 3 values with
>    foo.brand ="1branddasdsadsa";
>    foo.typenumber = "1typen m  asds adsa");
>    g_array_append_vals (array, &foo, 1);
>
>    foo.brand ="2branddasdsadsa";
>    foo.typenumber = "2typen m  asds adsa");
>    g_array_append_vals (array, &foo, 1);
>
>    foo.brand ="3branddasdsadsa";
>    foo.typenumber = "3typen m  asds adsa");
>    g_array_append_vals (array, &foo, 1);
>
>    if ((fp = fopen (FILENAME, "wb")) == NULL)
>    {
>      gchar label[90];
>      g_snprintf (label,90, "Not able to write to %s\n", FILENAME);
>      printf(label);
>      return (0);
>    }
>
>    for (i=0; i<array->len; i++)
>    {
>      fwrite(&array[i], sizeof (typDing), 1, fp);
              ^^^^^^^^^

I don't think that's right thing to do, GArray is not C array

>    }
>    fclose (fp);
>
>    /// read it back
>    GArray *read_array = g_array_sized_new (FALSE, FALSE, sizeof(typDing), 3);
>    if ((fp = fopen (FILENAME, "rb")) == NULL)
>    {
>      gchar label[90];
>      g_snprintf (label,90, "Not able to read from %s\n", FILENAME);
>      printf(label);
>      return (0);
>    }
>    typDing fooread;
>    for (i=0; i< 3; i++)
>    {
>      fread(&fooread, sizeof (typDing), 1, fp);
>      g_array_append_vals (read_array, &fooread, 1);
>      g_print("%d: brand:%s\n",i, g_array_index(read_array, typDing, i).brand);
>      g_print("%d: typen:%s\n",i, g_array_index(read_array, typDing, i).typenumber);
>    }
>    fclose (fp);
>
>   return (0);
> }
>
>
> I also want to save structs with GArrays inside them, like:
> typedef struct
> {
>    gchar *name;
>    GArray *attached;
> } typDing2;
>
> How to save those?

you need to save them struct-by-struct, and then read it back
reconstructing GArray, in general. You could also do some GValue
transformation foo, but that would be probably more hassle than gain, so
unless you have 1000 different types with GArrays that can change at
runtime, better go easy route and just manually save it

HTH,
Maciej

-- 
"Tautologizm to coś tautologicznego"
   Maciej Katafiasz <mnews2 wp pl>
       http://mathrick.blog.pl