Re: A Little Help

[Eric McDonald <mcdonald@phy.cmich.edu>]

D. Cooper Stevenson wrote:

>   * I haven't written (but do respect) the C language in a long time and it 
> shows; I've had a tough go of it getting the application to work.
> 
> I think it's time to ask for help.
> 
> As I mentioned above, the GIS ASCII file format is simple. Here's a 
> description:
> 
>  The first 7 or so lines represent the header of the file. The most relevant 
> numbers for our purposes are the "rows" and "cols" numbers. The last line is 
> the actual elevation (or landcover) data. Here's an example:
> 
>   north: 3980319.16466812
>   south: 3978824.85093895
>   east: 443960
>   west: 442296

If you don't need these values, you might want to just toss them. That 
way you wouldn't have to tell your parser to ignore them.

>   rows: 747
>   cols: 832

You'll probably want to keep this information. The number of rows is 
probably a better termination condition than EOF. And the number of 
columns is useful for determining how many times to call strtok(3), for 
example.

Here is a vague handwaving outline of how one might go about some of 
this. This is not guaranteed to be the best way. Just some spewing off 
the top of my head...:

/* Some definitions earlier on. */
#define BUFSIZE 256
#define DATAWIDTH 5
char data [BUFSIZE]
int numrows = numcols = 0;

/* Some code.... */

/* Part of your parser. (One possible way; there are others. Assumes you 
are inside some sort of loop.) */
if (numrows && numcols)
   break;
fgets(data, BUFSIZE, ifp);
if (!strncmp("rows: ", data, 6)) {
   numrows = atoi(data+6);
   continue;
}
else if (!strncmp("cols: ", data, 6)) {
   numcols = atoi(data+6);
   continue;
}

/* Some code...? */

/* Another part of your parser. */
data2 = malloc(numcols*DATAWIDTH);
boxrowsz = numcols / BOXWIDTH;
elevbox = malloc(numcols * BOXHEIGHT * sizeof(int));
for (i = 0; i < numrows; ++i) {
   fgets(data2, numcols * DATAWIDTH, ifp);
   memset(elevrow, 0, numcols * sizeof(int));
   for (j = 0; j < numcols; ++j) {
     if (!j)
       nextdata = strtok(data2, " ");
     else
       nextdata = strtok(NULL, " ");
     /* Stuff the data into the appropriate elev row box and slot(s) 
within the box. */
     /* You can use / and % (div and mod) to help determine which box to 
stuff things in. */
   }
   if (i && (0 == (i % BOXHEIGHT)))
      /* Take median, mean, or whatever. */
}

/* More code.... */

/* You can use existing functions in libconq.a or maybe even just 
libconqlow.a to help in writing out Xconq-readable forms, including 
layer data. */

/* Hope this helps,
    Eric */