On Friday 30 November 2007 12:13:09 Glynn Clements wrote: > I don't know if it's "major", but one thing to bear in mind is that > the map must have been opened with G_open_cell_new_random() in order > to be able to use that function. >
OK, this is noted, it means I have to create a function to open a floating point cell: G_open_fp_cell_new_random(). In opencell.c, G_open_cell_new_random() returns a call to G__open_raster_new(name, type of Open). Where is this function located please, and does it need modification in this case? > This has several consequences: the map is stored uncompressed, it > cannot contain nulls, and it cannot be floating-point (essentially, > when FP and null values were added in 5.x, the random-access case > wasn't upgraded). > > Neither of these factors would be particularly hard to change. > Could you direct me a bit on changing those? > The raster file contains a table of row pointers, so the rows don't > actually have to be stored in sequence in the file, even if they're > compressed. They could be written out in an arbitrary order (although > not concurrently). > > The null bitmap isn't compressed, so it would be possible to write out > rows in an arbitrary order, or even concurrently. The existing code > can't handle this because it caches a block of consecutive rows and > writes them all out at once. Changing this would introduce > inefficiency, as the null file is opened and closed for each write (to > avoid doubling the number of open file descriptors). Thank you, Yann -- Yann Chemin International Rice Research Institute Los Banos, Laguna The Philippines _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
