From fb350e788bed62a945cc93f98071db9788fe3397 Mon Sep 17 00:00:00 2001
From: Carles Fernandez <carles.fernandez@gmail.com>
Date: Wed, 29 May 2019 15:56:12 +0200
Subject: [PATCH] Search for system-wide volk_gnsssdr_config file

---
 .../volk_gnsssdr/lib/volk_gnsssdr_prefs.c     | 51 +++++++++++++++----
 1 file changed, 42 insertions(+), 9 deletions(-)

diff --git a/src/algorithms/libs/volk_gnsssdr_module/volk_gnsssdr/lib/volk_gnsssdr_prefs.c b/src/algorithms/libs/volk_gnsssdr_module/volk_gnsssdr/lib/volk_gnsssdr_prefs.c
index 87a51732d..7045ee2aa 100644
--- a/src/algorithms/libs/volk_gnsssdr_module/volk_gnsssdr/lib/volk_gnsssdr_prefs.c
+++ b/src/algorithms/libs/volk_gnsssdr_module/volk_gnsssdr/lib/volk_gnsssdr_prefs.c
@@ -19,6 +19,13 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#if defined(_MSC_VER)
+#include <io.h>
+#define access _access
+#define F_OK 0
+#else
+#include <unistd.h>
+#endif
 #include <volk_gnsssdr/volk_gnsssdr_prefs.h>
 
 
@@ -29,7 +36,7 @@ void volk_gnsssdr_get_config_path(char *path)
     const char *suffix2 = "/volk_gnsssdr/volk_gnsssdr_config";  // non-hidden
     char *home = NULL;
 
-    //allows config redirection via env variable
+    // allows config redirection via env variable
     home = getenv("VOLK_CONFIGPATH");
     if (home != NULL)
         {
@@ -38,17 +45,43 @@ void volk_gnsssdr_get_config_path(char *path)
             return;
         }
 
-    if (home == NULL) home = getenv("HOME");
-    if (home == NULL) home = getenv("APPDATA");
-    if (home == NULL)
+    // check for user-local config file
+    home = getenv("HOME");
+    if (home != NULL)
         {
-            path[0] = 0;
+            strncpy(path, home, 512);
+            strcat(path, suffix);
+            if (access(path, F_OK) != -1)
+                {
+                    return;
+                }
+        }
+
+    // check for config file in APPDATA (Windows)
+    home = getenv("APPDATA");
+    if (home != NULL)
+        {
+            strncpy(path, home, 512);
+            strcat(path, suffix);
+            if (access(path, F_OK) != -1)
+                {
+                    return;
+                }
+        }
+
+    // check for system-wide config file
+    if (access("/etc/volk_gnsssdr/volk_gnsssdr_config", F_OK) != -1)
+        {
+            strncpy(path, "/etc", 512);
+            strcat(path, suffix2);
             return;
         }
-    strncpy(path, home, 512);
-    strcat(path, suffix);
+
+    path[0] = 0;
+    return;
 }
 
+
 size_t volk_gnsssdr_load_preferences(volk_gnsssdr_arch_pref_t **prefs_res)
 {
     FILE *config_file;
@@ -56,13 +89,13 @@ size_t volk_gnsssdr_load_preferences(volk_gnsssdr_arch_pref_t **prefs_res)
     size_t n_arch_prefs = 0;
     volk_gnsssdr_arch_pref_t *prefs = NULL;
 
-    //get the config path
+    // get the config path
     volk_gnsssdr_get_config_path(path);
     if (!path[0]) return n_arch_prefs;  //no prefs found
     config_file = fopen(path, "r");
     if (!config_file) return n_arch_prefs;  //no prefs found
 
-    //reset the file pointer and write the prefs into volk_gnsssdr_arch_prefs
+    // reset the file pointer and write the prefs into volk_gnsssdr_arch_prefs
     while (fgets(line, sizeof(line), config_file) != NULL)
         {
             prefs = (volk_gnsssdr_arch_pref_t *)realloc(prefs, (n_arch_prefs + 1) * sizeof(*prefs));