[gdal-dev] Driver pointer NULL

[Even Rouault]

Would you mind reading the "OGR C++ API Read/Write Tutorial" available on 
http://gdal.org/ogr/ogr_apitut.html ? The answer is in the first code 
snippet ;-)

Le Wednesday 03 March 2010 21:43:49 deadpickle, vous avez écrit :
> I have finally compiled my C program and tried running it for the
> first time. When I ran the file I got the error:
> [thor at updraft ~/Programs]$ ./gdal_test_convert
> ERROR 10: Pointer 'hDriver' is NULL in 'OGR_Dr_CreateDataSource'.
> I'm trying to load the ESRI Shapefile driver. When I compiled it I
> linked it to the libgdal.a library. Is there something I'm missing?
>
> #include "ogr_api.h"
> #include "ogr_srs_api.h"
> #include "stdio.h"
>
> int main()
> {
> 	//~ variable declaration
> 	const char *name = "testc.shp", *dir = "C:\\Users\\deadpickle\\Desktop
> \\case study\\verify\\";
> 	char *source, *target;
> 	const char *sprj = "+proj=lcc +lat_1=33.000000 +lat_2=45.000000
> +lat_0=39.000000 +lon_0=-96.000000 +x_0=0.0 +y_0=0.0 +datum=NAD83";
> 	const char *tprj = "WGS84";
> 	char c[100];
> 	OGRSFDriverH driver;
> 	OGRDataSourceH ds;
> 	OGRCoordinateTransformationH ctrans;
> 	OGRLayerH layer;
> 	OGRFieldDefnH fieldDefn;
> 	OGRGeometryH line;
> 	OGRFeatureDefnH featureDefn;
> 	OGRFeatureH feature;
> 	FILE *file;
>
> 	//~ working directory
> 	chdir(dir);
>
> 	//~ get driver and create ds
> 	driver = OGRGetDriverByName("ESRI Shapefile");
> 	ds = OGR_Dr_CreateDataSource(driver, "testc.shp", NULL);
>
> 	//~ create spatrefs and trans
> 	OSRNewSpatialReference(source);
> 	OSRNewSpatialReference(target);
> 	OSRSetFromUserInput(source, sprj);
> 	OSRSetFromUserInput(target, tprj);
> 	ctrans = OCTNewCoordinateTransformation(target, source);
>
> 	//~ create the layer
> 	layer = OGR_DS_CreateLayer(ds, "test", source, wkbMultiLineString,
> NULL);
>
> 	//~ add an id field
> 	fieldDefn = OGR_Fld_Create("id", OFTInteger);
> 	OGR_L_CreateField(layer, fieldDefn, FALSE);
>
> 	//~ create geometry
> 	line = OGR_G_CreateGeometry(wkbMultiLineString);
>
> 	//~ layer def and create feature
> 	featureDefn = OGR_L_GetLayerDefn(layer);
> 	feature = OGR_F_Create(featureDefn);
>
> 	//~ open file
> 	file = fopen("2006track.csv","r");
>
> 	if(file==NULL) {
> 		printf("Error: can't open file.\n");
> 		/* fclose(file); DON'T PASS A NULL POINTER TO fclose !! */
> 		return 1;
> 	}
> 	else {
> 		printf("File opened successfully. Contents:\n\n");
>
> 		while(fgets(c, 100, file)!=NULL) {
> 			/* keep looping until NULL pointer... */
> 			printf("String: %s", c);
> 			/* print the file one line at a time  */
> 		}
>
> 		printf("\n\nNow closing file...\n");
> 	}
>
> 	//~ close file
> 	fclose(file);
> }
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