[GRASS-dev] from v6 to v7: G_get_cellhd -> Rast_get_cellhd ?

[Yann Chemin]

Thank you Glynn for those nice explanations
Yann

On 13 October 2010 16:27, Glynn Clements <glynn at gclements.plus.com> wrote:
>
> Yann Chemin wrote:
>
>> some confusion you may clarify.
>>
>> Looking into some v6 to v7 coding translation, how would you test for
>> readability of raster cell header in v7
>>
>> <from grass-addons: i.landsat.toar>
>>
>>           mapset = G_find_cell2(band_in, "");
>>           if (mapset == NULL) {
>>               G_warning(_("Raster map <%s> not found"), band_in);
>>               continue;
>>           }
>>           if ((infd = G_open_cell_old(band_in, mapset)) < 0)
>>               G_fatal_error(_("Unable to open raster map <%s>"), band_in);
>>           if (G_get_cellhd(band_in, mapset, &cellhd) < 0)
>>               G_fatal_error(_("Unable to read header of raster map <%s>"), band_in);
>>           if (G_set_window(&cellhd) < 0)
>>               G_fatal_error(_("Cannot reset current region"));
>>
>> The Last 4 lines I am trying to see if Rast_get_cellhd should be used...
>>
>>             if (Rast_get_cellhd(band_in, "", &cellhd) < 0)
>>                 G_fatal_error(_("Unable to read header of raster map <%s>"), band_in);
>>             if (G_set_window(&cellhd) < 0)
>>                 G_fatal_error(_("Cannot reset current region"));
>>
>> These 4 lines above are returning errors because the two functions
>> Rast_get_cellhd and G_set_window both return void, and they are tested
>> for a return value.
>>
>> How would you rewrite that initial code within version 7?
>
> Remove the test. If a 6.x function returned a status and the 7.x
> version doesn't return anything, it means that the 7.x version calls
> G_fatal_error() itself.
>
> I made this change for almost every lib/raster function where the only
> consequence of an error return was to call G_fatal_error() (assuming
> that the code bothered to check the return value in the first place).
>
> Also, note that Rast_open_* will only ever return a valid descriptor.
> If something goes wrong, it results in a fatal error, so there's no
> point in explicitly checking for "fd < 0".
>
> Functions which read metadata files which may or may not exist
> (categories, colour tables, etc) still return status codes.
>
> --
> Glynn Clements <glynn at gclements.plus.com>
>



-- 
Yann Chemin
Senior Spatial Hydrologist
www.csu.edu.au/research/icwater
M +61-4-3740 7019