Experimental json changes

dump1090.c

@@ -82,6 +82,7 @@ void modesInitConfig(void) {
     Modes.interactive_display_ttl = MODES_INTERACTIVE_DISPLAY_TTL;
     Modes.fUserLat                = MODES_USER_LATITUDE_DFLT;
     Modes.fUserLon                = MODES_USER_LONGITUDE_DFLT;
+    Modes.json_interval           = 1;
 }
 //
 //=========================================================================
@@ -436,6 +437,8 @@ void showHelp(void) {
 "--debug <flags>          Debug mode (verbose), see README for details\n"
 "--quiet                  Disable output to stdout. Use for daemon applications\n"
 "--ppm <error>            Set receiver error in parts per million (default 0)\n"
+"--write-json <dir>       Periodically write json output to <dir> (for serving by a separate webserver)\n"
+"--write-json-every <t>   Write json output every t seconds (default 1)\n"
 "--help                   Show this help\n"
 "\n"
 "Debug mode flags: d = Log frames decoded with errors\n"
@@ -571,6 +574,7 @@ static void display_stats(void) {
 //
 void backgroundTasks(void) {
     static time_t next_stats;
+    static time_t next_json;
 
     if (Modes.net) {
         modesReadFromClients();
@@ -594,6 +598,14 @@ void backgroundTasks(void) {
             next_stats = now + Modes.stats;
         }
     }
+
+    if (Modes.json_path && Modes.json_interval > 0) {
+        time_t now = time(NULL);
+        if (now > next_json) {
+            modesWriteJson(Modes.json_path);
+            next_json = now + Modes.json_interval;
+        }
+    }
 }
 //
 //=========================================================================
@@ -778,6 +790,15 @@ int main(int argc, char **argv) {
         } else if (!strcmp(argv[j],"--interactive-rtl1090")) {
             Modes.interactive = 1;
             Modes.interactive_rtl1090 = 1;
+#ifndef _WIN32
+        } else if (!strcmp(argv[j], "--write-json") && more) {
+            ++j;
+            Modes.json_path = malloc(strlen(argv[j]) + 11);
+            strcpy(Modes.json_path, argv[j]);
+            strcat(Modes.json_path, "/aircraft.json");
+        } else if (!strcmp(argv[j], "--write-json-every") && more) {
+            Modes.json_interval = atoi(argv[++j]);
+#endif
         } else {
             fprintf(stderr,
                 "Unknown or not enough arguments for option '%s'.\n\n",

dump1090.h

@@ -57,6 +57,7 @@
     #include <ctype.h>
     #include <sys/stat.h>
     #include <sys/ioctl.h>
+    #include <limits.h>
     #include "rtl-sdr.h"
     #include "anet.h"
 #else
@@ -318,6 +319,9 @@ struct {                             // Internal state
     int   metric;                    // Use metric units
     int   mlat;                      // Use Beast ascii format for raw data output, i.e. @...; iso *...;
     int   interactive_rtl1090;       // flight table in interactive mode is formatted like RTL1090
+    
+    char *json_path;                 // Path to json data file to write, or NULL not to.
+    int   json_interval;             // Interval between rewriting the json data file
 
     // User details
     double fUserLat;                // Users receiver/antenna lat/lon needed for initial surface location
@@ -458,6 +462,7 @@ void modesReadFromClients (void);
 void modesSendAllClients  (int service, void *msg, int len);
 void modesQueueOutput     (struct modesMessage *mm);
 void modesReadFromClient(struct client *c, char *sep, int(*handler)(struct client *, char *));
+void modesWriteJson       (const char *path);
 
 #ifdef __cplusplus
 }

net_io.c

@@ -694,6 +694,43 @@ char *aircraftsToJson(int *len) {
     *len = p-buf;
     return buf;
 }
+
+// Write JSON state to json_path
+void modesWriteJson(const char *path)
+{
+#ifndef _WIN32
+    char tmppath[PATH_MAX];
+    int fd;
+    int len = 0;
+    char *content;
+
+    snprintf(tmppath, PATH_MAX, "%s.XXXXXX", path);
+    tmppath[PATH_MAX-1] = 0;
+    fd = mkstemp(tmppath);
+    if (fd < 0)
+        return;
+    
+    content = aircraftsToJson(&len);
+    if (write(fd, content, len) != len)
+        goto error_1;
+
+    if (close(fd) < 0)
+        goto error_2;
+
+    free(content);
+    rename(tmppath, path);
+    return;
+
+ error_1:
+    close(fd);
+ error_2:
+    free(content);
+    unlink(tmppath);
+    return;
+
+#endif
+}
+
 //
 //=========================================================================
 //
@@ -754,8 +791,8 @@ int handleHTTPRequest(struct client *c, char *p) {
 
     // Select the content to send, we have just two so far:
     // "/" -> Our google map application.
-    // "/data.json" -> Our ajax request to update planes.
-    if (strstr(url, "/data.json")) {
+    // "/aircraft.json" -> Our ajax request to update planes.
+    if (strstr(url, "/data/aircraft.json")) {
         statuscode = 200;
         content = aircraftsToJson(&clen);
         //snprintf(ctype, sizeof ctype, MODES_CONTENT_TYPE_JSON);

public_html/script.js

@@ -18,7 +18,7 @@ CenterLon = Number(localStorage['CenterLon']) || CONST_CENTERLON;
 ZoomLvl   = Number(localStorage['ZoomLvl']) || CONST_ZOOMLVL;
 
 function fetchData() {
-	$.getJSON('/dump1090/data.json', function(data) {
+	$.getJSON('data/aircraft.json', function(data) {
 		PlanesOnMap = 0
 		SpecialSquawk = false;