[GRASS5] readsites() TODO list...

[Bill Brown - staff]

Hi Eric, 

just a few suggestions...

1. We already have a struct Site, so to avoid confusion how about using 
   "xyz_site" instead of "site" ? (If typedef'd then the convention would 
   be to capitalize), e.g.
   typedef struct{
     double x, y, z;
   } XYZ_site;
   This typedef would then be added to site.h

2. I think that Z-dim is not really defined by the sites interface - only
   the first 2 dimensions are recognized as X and Y and any others dimensions
   are just referred to as dim[2], dim[3], ...  so a user might have a sites
   file with 5 dimensions and no attributes, and want to use the 4th dimension
   as Z.  From your example, I'd guess that I'd call readsites with type=0 and
   index=2 (2nd extra dimension?)  That might need to be clarified.

3. num should probably be a *num so that the number actually read can be
   returned in it (in case file ends) Or else add another parameter. You might 
   be able to eliminate done then (*num = 0).

4. What about the cat?  User might want to use that as Z.

5. I suggest having a G_allocate_xyz_sites(numsites) so the allocation 
   and freeing would be handled outside readsites, allowing 
   users to re-use a block within a loop without re-allocating. 

6. type should be defined and added to site.h, e.g.:
   #define SITE_DIM   0
   #define SITE_CAT   1
   #define SITE_DBL   2
   #define SITE_STR   3

- Bill

>
>/* readsites: Reads a sites file converting to a site struct of xyz values.
> * The Z value can come from one of the z-dimensions, a double attribute,
> * or a string attribute converted to a double with strtod().
> * If 'num' is less than one, attempt to read entire site file, otherwise
> * read 'num' records.  The number of records read is returned.  If an
> * error occurs, a negative value is returned.  The caller can decide to
> * abort or retry.  Error values are:
> *	Couldn't allocate memory  				-1
> *	Attribute 'type' not found				-2
> *      Attribute 'index' out of range				-3
> *	Format error in file (includes conversion error)	-4
> *	Something else (probably never happen)  		-5
> */
>
>typedef struct _site {
>	double x, y, z;
>} site;
>
>int readsites(
>	FILE * fdsite,  /* The FILE stream to the sites file */
>	int    num,     /* Number of records to read */
>	int    type,    /* Attribute type: 0 =3D Z-dim, 1 =3D double, 2 =3D string=
> */
>	int    index,   /* The field index (1 based) for the attribute */
>	int  * done,    /* No more records in file? 0 =3D false, 1 =3D true */
>	site **xyz      /* The site array, caller must free between calls */
>	);
>

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