finished geonames.org lookup

src/Makefile.am

@@ -1,4 +1,10 @@
-bin_PROGRAMS = astro
+bin_PROGRAMS = astro sun geonames
 
 astro_SOURCES = calendar.c astro.c
 astro_LDADD = -lm
+
+sun_SOURCES = sun.c
+sun_LDADD = -lm
+
+geonames_SOURCES = geonames_test.c geonames.c
+geonames_LDADD = -lcurl -ljson

src/geonames.c

@@ -0,0 +1,106 @@
+#include <stdlib.h>
+#include <string.h>
+
+#include <curl/curl.h>
+#include <json/json.h>
+
+#include "geonames.h"
+
+const char* username = "libastro";
+const char* request_url_tpl = "http://api.geonames.org/search?name=%s&maxRows=1&username=%s&type=json&orderby=relevance";
+
+struct memory_block {
+	char *address;
+	size_t size;
+};
+
+static size_t json_parse_callback(void *contents, size_t size, size_t nmemb, void *userp) {
+	static struct json_tokener *jtok;
+	static struct json_object *jobj;
+	size_t realsize = size * nmemb;
+
+	/* initialize tokener */
+	if (jtok == NULL) {
+		jtok = json_tokener_new();
+		jtok->err = json_tokener_continue;
+	}
+
+	if (jtok->err == json_tokener_continue) {
+#ifdef DEBUG
+		printf("got chunk: %d * %d = %d bytes\r\n", size, nmemb, realsize);
+#endif
+
+		jobj = json_tokener_parse_ex(jtok, (char *) contents, realsize);
+
+		if (jtok->err == json_tokener_success) {
+			*(struct json_object **) userp = jobj;
+			json_tokener_free(jtok);
+		}
+		else if (jtok->err != json_tokener_continue) {
+			fprintf(stderr, "parse error: %s\r\n", json_tokener_errors[jtok->err]);
+			*(void **) userp = NULL;
+			json_tokener_free(jtok);
+		}
+	}
+
+	return realsize;
+}
+
+int geonames_lookup(const char *place, struct coords *result) {
+	CURL *ch;
+	CURLcode res;
+
+	struct json_object *jobj;
+
+	/* setup curl */
+	ch = curl_easy_init();
+	if (!ch) return -1;
+
+	/* prepare url */
+	int len = strlen(place) + strlen(request_url_tpl) + 1;
+	char *request_url = malloc(len);
+	if (!request_url) {
+		return -2;
+	}
+
+	snprintf(request_url, len, request_url_tpl, place, username);
+
+#ifdef DEBUG
+	printf("request url: %s\r\n", request_url);
+#endif
+
+	curl_easy_setopt(ch, CURLOPT_URL, request_url);
+	curl_easy_setopt(ch, CURLOPT_WRITEFUNCTION, json_parse_callback);
+	curl_easy_setopt(ch, CURLOPT_WRITEDATA, (void *) &jobj);
+	curl_easy_setopt(ch, CURLOPT_USERAGENT, "libastro/1.0");
+
+	/* perform request */
+	res = curl_easy_perform(ch);
+
+	/* always cleanup */ 
+	curl_easy_cleanup(ch);
+
+	if (res != CURLE_OK) {
+		fprintf(stderr, "request failed: %s\n", curl_easy_strerror(res));
+		return EXIT_FAILURE;
+	}
+
+	if (jobj) {
+		return geonames_parse(jobj, result);;
+	}
+	else {
+		return EXIT_FAILURE;
+	}
+}
+
+int geonames_parse(struct json_object *jobj, struct coords *result) {
+	struct json_object *jobj_place = json_object_array_get_idx(json_object_object_get(jobj, "geonames"), 0);
+
+	result->lat = json_object_get_double(json_object_object_get(jobj_place, "lat"));
+	result->lon = json_object_get_double(json_object_object_get(jobj_place, "lng"));
+
+	/* cleanup */
+	json_object_put(jobj);
+
+	return EXIT_SUCCESS;
+}

src/geonames.h

@@ -0,0 +1,16 @@
+#ifndef _GEONAMES_H_
+#define _GEONAMES_H_
+
+//#define DEBUG 1
+
+#include <json/json.h>
+
+struct coords {
+	double lat;
+	double lon;
+};
+
+int geonames_lookup(const char *place, struct coords *coords);
+int geonames_parse(struct json_object *jobj, struct coords *result);
+
+#endif /* _GEONAMES_H_ */

src/geonames_test.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+
+#include "geonames.h"
+
+int main(int argc, char *argv[]) {
+	struct coords res;
+	char *name = "Aachen";
+
+	if (argc == 2) {
+		name = argv[1];
+	}
+
+	if (geonames_lookup(name, &res) == 0) {
+		printf("%s is at (%.4f, %.4f)\r\n", name, res.lat, res.lon);
+		return 0;
+	}
+
+	return 0;
+}