Re: [Vala] Problems retrieving binary data from a sqlite3 database BLOB column

[Iñigo Serna <inigoserna gmail com>]

Hi Alexandre,

thanks for your comments, I'm closer to the solution.

On 26 June 2011 21:18, Alexandre Rosenfeld
<alexandre rosenfeld gmail com> wrote:
> On Sun, Jun 26, 2011 at 13:18, Iñigo Serna <inigoserna gmail com> wrote:
> > if I include a line like:
> >
> > uint8[]? data = (uint8[]) stmt.column_blob(3);
> >
> > it's translated as next C code:
> >
> > _tmp11_ = (_tmp10_ = (guint8*) _tmp9_, (_tmp10_ == NULL) ? ((gpointer)
> > _tmp10_) : _vala_array_dup3 (_tmp10_, -1));
>
> I had this problem a lot of times before I realized that Vala arrays must
> have a length, but this length is not always retrieved by the API, so Vala
> has no idea of the size of the array returned from Sqlite. The -1 ilustrated
> at the C code shows this, because Vala thinks this array has -1 items.
> You can use stmt.column_bytes to retrieve the number of items in the array
> (at this case, the number of bytes) and assign it to the array length such
> as:
>
> data.length = stmt.column_bytes(3);
>
> So now Vala knows the size of the array and you can use it anyway you want
> to.
>
> Alexandre Rosenfeld

VALA code:
var data = new uint8[stmt.column_bytes(4)];
data = (uint8[]) stmt.column_blob(4);
FileUtils.set_data("image2.png", data);


Generated C code:
gint _tmp8_;
guint8* _tmp9_ = NULL;
guint8* data;
gint data_length1;
gint _data_size_;
void* _tmp10_ = NULL;
guint8* _tmp11_;
guint8* _tmp12_;
_tmp8_ = sqlite3_column_bytes (stmt, 4);
_tmp9_ = g_new0 (guint8, _tmp8_);
data = _tmp9_;
data_length1 = _tmp8_;
data_size_ = data_length1;
_tmp10_ = sqlite3_column_blob (stmt, 4);
_tmp12_ = (_tmp11_ = (guint8*) _tmp10_, (_tmp11_ == NULL) ?
((gpointer) _tmp11_) : _vala_array_dup3 (_tmp11_, -1));
data = (g_free (data), NULL);
data = _tmp12_;
data_length1 = -1;
_data_size_ = data_length1;
g_file_set_contents ("image2.png", (const char*) data, (size_t)
data_length1, &_inner_error_);

And it crash with the same error.


But if I edit C code and change to:
_tmp12_ = (_tmp11_ = (guint8*) _tmp10_, (_tmp11_ == NULL) ?
((gpointer) _tmp11_) : _vala_array_dup3 (_tmp11_, _tmp8_));
...
data_length1 = _tmp8_;

it works correctly.
Am I missing something more? is this a bug in the code generated by vala?


Regards,
Iñigo Serna