First (untested) pass at handling GL Style Spec filters

evaluator.cpp

@@ -0,0 +1,196 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <map>
+#include "mvt.hpp"
+#include "evaluator.hpp"
+
+int compare(mvt_value one, json_object *two, bool &fail) {
+	if (one.type == mvt_string) {
+		if (two->type != JSON_STRING) {
+			fail = true;
+			return false; // string vs non-string
+		}
+
+		return strcmp(one.string_value.c_str(), two->string);
+	}
+
+	if (one.type == mvt_double || one.type == mvt_float || one.type == mvt_int || one.type == mvt_uint || one.type == mvt_sint) {
+		if (two->type != JSON_NUMBER) {
+			fail = true;
+			return false; // number vs non-number
+		}
+
+		double v;
+		if (one.type == mvt_double) {
+			v = one.numeric_value.double_value;
+		} else if (one.type == mvt_float) {
+			v = one.numeric_value.float_value;
+		} else if (one.type == mvt_int) {
+			v = one.numeric_value.int_value;
+		} else if (one.type == mvt_uint) {
+			v = one.numeric_value.uint_value;
+		} else if (one.type == mvt_sint) {
+			v = one.numeric_value.sint_value;
+		} else {
+			fprintf(stderr, "Internal error: bad mvt type %d\n", one.type);
+			exit(EXIT_FAILURE);
+		}
+
+		if (v < two->number) {
+			return -1;
+		} else if (v > two->number) {
+			return 1;
+		} else {
+			return 0;
+		}
+	}
+
+	if (one.type == mvt_bool) {
+		if (two->type != JSON_TRUE && two->type != JSON_FALSE) {
+			fail = true;
+			return false; // bool vs non-bool
+		}
+
+		bool b = two->type = JSON_TRUE;
+		return one.numeric_value.bool_value > b;
+	}
+
+	fprintf(stderr, "Internal error: bad mvt type %d\n", one.type);
+	exit(EXIT_FAILURE);
+}
+
+bool eval(std::map<std::string, mvt_value> const &feature, json_object *f) {
+	if (f == NULL || f->type != JSON_ARRAY) {
+		fprintf(stderr, "Filter is not an array: %s\n", json_stringify(f));
+		exit(EXIT_FAILURE);
+	}
+
+	if (f->length < 2) {
+		fprintf(stderr, "Array too small in filter: %s\n", json_stringify(f));
+		exit(EXIT_FAILURE);
+	}
+
+	if (f->array[0]->type != JSON_STRING) {
+		fprintf(stderr, "Filter operation is not a string: %s\n", json_stringify(f));
+		exit(EXIT_FAILURE);
+	}
+
+	if (strcmp(f->array[0]->string, "has") == 0) {
+		if (f->array[1]->type != JSON_STRING) {
+			fprintf(stderr, "\"has\" key is not a string: %s\n", json_stringify(f));
+			exit(EXIT_FAILURE);
+		}
+		return feature.count(std::string(f->array[1]->string)) != 0;
+	}
+
+	if (strcmp(f->array[0]->string, "!has") == 0) {
+		if (f->array[1]->type != JSON_STRING) {
+			fprintf(stderr, "\"!has\" key is not a string: %s\n", json_stringify(f));
+			exit(EXIT_FAILURE);
+		}
+		return feature.count(std::string(f->array[1]->string)) == 0;
+	}
+
+	if (strcmp(f->array[0]->string, "==") == 0 ||
+	    strcmp(f->array[0]->string, "!=") == 0 ||
+	    strcmp(f->array[0]->string, ">") == 0 ||
+	    strcmp(f->array[0]->string, ">=") == 0 ||
+	    strcmp(f->array[0]->string, "<") == 0 ||
+	    strcmp(f->array[0]->string, "<=") == 0) {
+		if (f->length < 3) {
+			fprintf(stderr, "Array too small in filter: %s\n", json_stringify(f));
+			exit(EXIT_FAILURE);
+		}
+		if (f->array[1]->type != JSON_STRING) {
+			fprintf(stderr, "\"!has\" key is not a string: %s\n", json_stringify(f));
+			exit(EXIT_FAILURE);
+		}
+
+		auto ff = feature.find(std::string(f->array[1]->string));
+		if (ff == feature.end()) {
+			return false; // not found: comparison is false
+		}
+
+		bool fail = false;
+		int cmp = compare(ff->second, f->array[2], fail);
+
+		if (fail) {
+			return false;
+		}
+
+		if (strcmp(f->array[0]->string, "==") == 0) {
+			return cmp == 0;
+		}
+		if (strcmp(f->array[0]->string, "!=") == 0) {
+			return cmp != 0;
+		}
+		if (strcmp(f->array[0]->string, ">") == 0) {
+			return cmp > 0;
+		}
+		if (strcmp(f->array[0]->string, ">=") == 0) {
+			return cmp >= 0;
+		}
+		if (strcmp(f->array[0]->string, "<") == 0) {
+			return cmp < 0;
+		}
+		if (strcmp(f->array[0]->string, "<=") == 0) {
+			return cmp <= 0;
+		}
+
+		fprintf(stderr, "Internal error: can't happen: %s\n", json_stringify(f));
+		exit(EXIT_FAILURE);
+	}
+
+	if (strcmp(f->array[0]->string, "all") == 0 ||
+	    strcmp(f->array[0]->string, "any") == 0 ||
+	    strcmp(f->array[0]->string, "none") == 0) {
+		bool v;
+
+		if (strcmp(f->array[0]->string, "all") == 0) {
+			v = true;
+		} else {
+			v = false;
+		}
+
+		for (size_t i = 1; i < f->length; i++) {
+			bool out = eval(feature, f->array[i]);
+
+			if (strcmp(f->array[0]->string, "all") == 0) {
+				v = v && out;
+			} else {
+				v = v || out;
+			}
+		}
+
+		if (strcmp(f->array[0]->string, "none") == 0) {
+			return !v;
+		} else {
+			return v;
+		}
+	}
+
+	fprintf(stderr, "Unknown filter %s\n", json_stringify(f));
+	exit(EXIT_FAILURE);
+}
+
+bool evaluate(std::map<std::string, mvt_value> const &feature, std::string const &layer, json_object *filter) {
+	json_object *layers = json_hash_get(filter, "layers");
+
+	if (layers == NULL) {
+		fprintf(stderr, "Filter: no \"layers\" key at top level\n");
+		exit(EXIT_FAILURE);
+	}
+
+	if (layers->type != JSON_HASH) {
+		fprintf(stderr, "Filter: \"layers\" is not a hash\n");
+		exit(EXIT_FAILURE);
+	}
+
+	json_object *f = json_hash_get(layers, layer.c_str());
+
+	if (f != NULL) {
+		return eval(feature, f);
+	} else {
+		return true; // no filter for this layer;
+	}
+}