Hello again,
I hope this is an easy question:
I took this chunk of r.drain which reads single int CELL values given
a row and col:
CELL direction;
CELL *dir;
dir = G_allocate_c_raster_buf();
next_row = list->row;
next_col = list->col;
...
lseek(fd, (off_t) list->row * ncol * sizeof(CELL), SEEK_SET);
read(fd, dir, ncol * sizeof(CELL));
direction = *(dir + list->col);
G_message(_("row:%i, col:%i, direction:%i"), next_row, next_col,
direction);
And tried to replicate it for use with a double DCELL like this:
int row, col, next_row, next_col;
DCELL direction;
DCELL *dir_buf;
dir_buf = G_allocate_d_raster_buf();
next_row = list->row;
next_col = list->col;
lseek(dir_fd, (off_t) list->row * ncol * sizeof(DCELL), SEEK_SET);
read(dir_fd, dir_buf, ncol * sizeof(DCELL));
direction = *(dir_buf + list->col);
G_message(_("row:%i, col:%i, direction:%lf"), next_row, next_col,
direction);
Somehow the top int section functions properly, while my modified
section for doubles does not (ie. it returns the wrong "direction"
value). I suspect it has something to do with the offset in lseek, but
I can't figure it out. Does it matter that the row and col are int,
while the value is double?
Is there an easier way to read a single cell value given that you know
the row and col?
Thanks,
-Colin
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