Add a tippecanoe-decode option to restrict which attributes to decode

decode.cpp

@@ -28,6 +28,7 @@
 int minzoom = 0;
 int maxzoom = 32;
 bool force = false;
+std::set<std::string> include_attr;
 
 bool progress_time() {
 	return false;
@@ -217,7 +218,7 @@ void handle(std::string message, int z, unsigned x, unsigned y, std::set<std::st
 		} else if (coordinate_mode == 2) {  // integer
 			scale = 1;
 		}
-		layer_to_geojson(layer, z, x, y, !pipeline, pipeline, pipeline, false, 0, 0, 0, !force, state, scale);
+		layer_to_geojson(layer, z, x, y, !pipeline, pipeline, pipeline, false, 0, 0, 0, !force, state, scale, include_attr);
 
 		if (!pipeline) {
 			if (true) {
@@ -571,6 +572,7 @@ int main(int argc, char **argv) {
 		{"stats", no_argument, 0, 'S'},
 		{"force", no_argument, 0, 'f'},
 		{"exclude-metadata-row", required_argument, 0, 'x'},
+		{"include", required_argument, 0, 'y'},
 		{0, 0, 0, 0},
 	};
 
@@ -630,6 +632,10 @@ int main(int argc, char **argv) {
 			exclude_meta.insert(optarg);
 			break;
 
+		case 'y':
+			include_attr.insert(optarg);
+			break;
+
 		default:
 			usage(argv);
 		}

plugin.cpp

@@ -55,7 +55,7 @@ void *run_writer(void *a) {
 
 	json_writer state(fp);
 	for (size_t i = 0; i < wa->layers->size(); i++) {
-		layer_to_geojson((*(wa->layers))[i], wa->z, wa->x, wa->y, false, true, false, true, 0, 0, 0, true, state, 0);
+		layer_to_geojson((*(wa->layers))[i], wa->z, wa->x, wa->y, false, true, false, true, 0, 0, 0, true, state, 0, std::set<std::string>());
 	}
 
 	if (fclose(fp) != 0) {

tile.cpp

@@ -1358,7 +1358,7 @@ void *run_prefilter(void *v) {
 		decode_meta(sf, tmp_layer, tmp_feature);
 		tmp_layer.features.push_back(tmp_feature);
 
-		layer_to_geojson(tmp_layer, 0, 0, 0, false, true, false, true, sf.index, sf.seq, sf.extent, true, state, 0);
+		layer_to_geojson(tmp_layer, 0, 0, 0, false, true, false, true, sf.index, sf.seq, sf.extent, true, state, 0, std::set<std::string>());
 	}
 
 	if (fclose(rpa->prefilter_fp) != 0) {

write_json.cpp

@@ -268,7 +268,7 @@ void write_coords(json_writer &state, lonlat const &ll, double scale) {
 	}
 }
 
-void layer_to_geojson(mvt_layer const &layer, unsigned z, unsigned x, unsigned y, bool comma, bool name, bool zoom, bool write_dropped, unsigned long long index, long long sequence, long long extent, bool complain, json_writer &state, double scale) {
+void layer_to_geojson(mvt_layer const &layer, unsigned z, unsigned x, unsigned y, bool comma, bool name, bool zoom, bool write_dropped, unsigned long long index, long long sequence, long long extent, bool complain, json_writer &state, double scale, std::set<std::string> const &include_attr) {
 	for (size_t f = 0; f < layer.features.size(); f++) {
 		mvt_feature const &feat = layer.features[f];
 
@@ -334,6 +334,10 @@ void layer_to_geojson(mvt_layer const &layer, unsigned z, unsigned x, unsigned y
 				exit(EXIT_IMPOSSIBLE);
 			}
 
+			if (include_attr.size() > 0 && include_attr.find(layer.keys[feat.tags[t]]) == include_attr.end()) {
+				continue;
+			}
+
 			const char *key = layer.keys[feat.tags[t]].c_str();
 			mvt_value const &val = layer.values[feat.tags[t + 1]];
 

write_json.hpp

@@ -4,6 +4,7 @@
 #include <string>
 #include <vector>
 #include <stdio.h>
+#include <set>
 
 enum json_write_tok {
 	JSON_WRITE_HASH,
@@ -61,7 +62,7 @@ struct json_writer {
 	void adds(std::string const &s);
 };
 
-void layer_to_geojson(mvt_layer const &layer, unsigned z, unsigned x, unsigned y, bool comma, bool name, bool zoom, bool dropped, unsigned long long index, long long sequence, long long extent, bool complain, json_writer &state, double scale);
+void layer_to_geojson(mvt_layer const &layer, unsigned z, unsigned x, unsigned y, bool comma, bool name, bool zoom, bool dropped, unsigned long long index, long long sequence, long long extent, bool complain, json_writer &state, double scale, std::set<std::string> const &include_attr);
 void fprintq(FILE *f, const char *s);
 
 #endif