r.external speed-up (#1305)

 * faster linking with r.external
 * super-fast mode for r.external
 * warning for fast mode
 * update r.info if range is missing
 * fix r.support to re-compute range for fp maps

Co-authored-by: Markus Neteler <neteler@gmail.com>

lib/raster/range.c

@@ -120,6 +120,12 @@ int Rast_read_fp_range(const char *name, const char *mapset,
 	Rast_update_fp_range(dcell2, drange);
 	close(fd);
     }
+    else {
+	/* "f_range" file does not exist */
+	G_warning(_("Missing fp range file for <%s> (run r.support -s)"),
+		  G_fully_qualified_name(name, mapset));
+	return -1;
+    }
 
     return 1;
 }
@@ -237,6 +243,12 @@ int Rast_read_range(const char *name, const char *mapset, struct Range *range)
 	}
 	fclose(fd);
     }
+    else {
+	/* "range" file does not exist */
+	G_warning(_("Missing range file for <%s> (run r.support -s)"),
+		  G_fully_qualified_name(name, mapset));
+	return -1;
+    }
 
     return 1;
 }

raster/r.external/link.c

@@ -47,6 +47,9 @@ void query_band(GDALRasterBandH hBand, const char *output,
 	break;
     }
 
+    if (info->have_minmax)
+	GDALComputeRasterMinMax(hBand, 0, info->minmax);
+
     Rast_init_colors(&info->colors);
 
     if (GDALGetRasterColorTable(hBand) != NULL) {
@@ -184,7 +187,6 @@ void create_map(const char *input, int band, const char *output,
     struct History history;
     struct Categories cats;
     char buf[1024];
-    int outfd;
 
     Rast_put_cellhd(output, cellhd);
 
@@ -211,39 +213,24 @@ void create_map(const char *input, int band, const char *output,
     if (title)
 	Rast_put_cell_title(output, title);
 
-    /* get stats for this raster band */
-    G_remove_misc("cell_misc", "stats", output);
-
-    outfd = Rast_open_old(output, G_mapset());
-    if (info->data_type == CELL_TYPE) {
-	int r;
-	struct Range range;
-	CELL *rbuf = Rast_allocate_buf(CELL_TYPE);
+    if (info->have_minmax) {
+	if (info->data_type == CELL_TYPE) {
+	    struct Range range;
 
-	G_remove_misc("cell_misc", "range", output);
-	Rast_init_range(&range);
-	for (r = 0; r < cellhd->rows; r++) {
-	    Rast_get_row(outfd, rbuf, r, CELL_TYPE);
-	    Rast_row_update_range(rbuf, cellhd->cols, &range);
+	    Rast_init_range(&range);
+	    Rast_update_range((CELL)info->minmax[0], &range);
+	    Rast_update_range((CELL)info->minmax[1], &range);
+	    Rast_write_range(output, &range);
 	}
-	Rast_write_range(output, &range);
-	G_free(rbuf);
-    }
-    else {
-	int r;
-	struct FPRange fprange;
-	void *rbuf = Rast_allocate_buf(info->data_type);
-
-	G_remove_misc("cell_misc", "f_range", output);
-	Rast_init_fp_range(&fprange);
-	for (r = 0; r < cellhd->rows; r++) {
-	    Rast_get_row(outfd, rbuf, r, info->data_type);
-	    Rast_row_update_fp_range(rbuf, cellhd->cols, &fprange, info->data_type);
+	else {
+	    struct FPRange fprange;
+
+	    Rast_init_fp_range(&fprange);
+	    Rast_update_fp_range(info->minmax[0], &fprange);
+	    Rast_update_fp_range(info->minmax[1], &fprange);
+	    Rast_write_fp_range(output, &fprange);
 	}
-	Rast_write_fp_range(output, &fprange);
-	G_free(rbuf);
     }
-    Rast_unopen(outfd);
 
     G_message(_("Link to raster map <%s> created."), output);
 }

raster/r.external/main.c

@@ -44,7 +44,7 @@ int main(int argc, char *argv[])
 	struct Option *input, *source, *output, *band, *title;
     } parm;
     struct {
-	struct Flag *o, *j, *f, *e, *h, *v, *t, *a;
+	struct Flag *o, *j, *f, *e, *h, *v, *t, *a, *r;
     } flag;
     int min_band, max_band, band;
     struct band_info info;
@@ -135,6 +135,11 @@ int main(int argc, char *argv[])
     flag.t->guisection = _("Print");
     flag.t->suppress_required = YES;
 
+    flag.r = G_define_flag();
+    flag.r->key = 'r';
+    flag.r->label = _("Create fast link without data range");
+    flag.r->description = _("WARNING: some modules do not work correctly without known data range");
+
     if (G_parser(argc, argv))
 	exit(EXIT_FAILURE);
 
@@ -219,6 +224,7 @@ int main(int argc, char *argv[])
 	I_init_group_ref(&reference);
     }
 
+    info.have_minmax = !flag.r->answer;
     for (band = min_band; band <= max_band; band++) {
 	char *output2, *title2 = NULL;
 

raster/r.external/proto.h

@@ -11,6 +11,8 @@ struct band_info
     GDALDataType gdal_type;
     int has_null;
     double null_val;
+    DCELL minmax[2];
+    int have_minmax;
     struct Colors colors;
 };