libnm: add function nm_utils_file_search_in_paths()

We now also use a similar function in VPN plugins. It makes
sense to provide a generic implementation in libnm.

Signed-off-by: Thomas Haller <thaller@redhat.com>

https://bugzilla.gnome.org/show_bug.cgi?id=740783

3 files changed, 88 insertions, 0 deletions

diff --git a/libnm-core/nm-utils.c b/libnm-core/nm-utils.c
index f1f5a9e8ca..621b9bb2c0 100644
--- a/libnm-core/nm-utils.c
+++ b/libnm-core/nm-utils.c
@@ -2322,6 +2322,83 @@ nm_utils_file_is_pkcs12 (const char *filename)
 	return crypto_is_pkcs12_file (filename, NULL);
 }
 
+/**********************************************************************************************/
+
+/**
+ * nm_utils_file_search_in_paths:
+ * @progname: the helper program name, like "iptables"
+ *   Must be a non-empty string, without path separator (/).
+ * @try_first: (allow-none): a custom path to try first before searching.
+ *   It is silently ignored it it is empty or not an absolute path.
+ * @paths: (allow-none): a %NULL terminated list of search paths.
+ *   Can be empty or %NULL, in which case only @try_first is checked.
+ * @file_test_flags: the flags passed to g_file_test() when searching
+ *   for @progname. Set it to 0 to skip the g_file_test().
+ * @predicate: if given, pass the file name to this function
+ *   for additional checks. This check is performed after the check for
+ *   @file_test_flags. You cannot omit both @file_test_flags and @predicate.
+ * @user_data: (allow-none): user data for @predicate function.
+ * @error: on failure, a "not found" error using @error_domain and @error_code
+ *
+ * Searches for the @progname in common system paths.
+ *
+ * Returns: (transfer none): the full path to the helper, if found, or %NULL if not found.
+ *   The returned string is not owned by the caller, but later
+ *   invocations of the function might overwrite it.
+ */
+const char *
+nm_utils_file_search_in_paths (const char *progname,
+                               const char *try_first,
+                               const char *const *paths,
+                               GFileTest file_test_flags,
+                               NMUtilsFileSearchInPathsPredicate predicate,
+                               gpointer user_data,
+                               GError **error)
+{
+	GString *tmp;
+	const char *ret;
+
+	g_return_val_if_fail (!error || !*error, NULL);
+	g_return_val_if_fail (progname && progname[0] && !strchr (progname, '/'), NULL);
+	g_return_val_if_fail (!file_test_flags || predicate, NULL);
+
+	if (   try_first
+	    && try_first[0] == '/'
+	    && (file_test_flags == 0 && g_file_test (try_first, file_test_flags))
+	    && (!predicate || predicate (try_first, user_data)))
+		return g_intern_string (try_first);
+
+	if (!paths || !*paths)
+		goto NOT_FOUND;
+
+	tmp = g_string_sized_new (50);
+	for (; *paths; paths++) {
+		if (!*paths)
+			continue;
+		g_string_append (tmp, *paths);
+		if (tmp->str[tmp->len - 1] != '/')
+			g_string_append_c (tmp, '/');
+		g_string_append (tmp, progname);
+		if (   (file_test_flags == 0 || g_file_test (tmp->str, file_test_flags))
+		    && (!predicate || predicate (tmp->str, user_data))) {
+			/* For now, just intern the returned string. The API documentation leaves it
+			 * open to cache the value in a static (per-thread?) variable to avoid
+			 * memory-leaks when calling excessively often with different file names. */
+			ret = g_intern_string (tmp->str);
+			g_string_free (tmp, TRUE);
+			return ret;
+		}
+		g_string_set_size (tmp, 0);
+	}
+	g_string_free (tmp, TRUE);
+
+NOT_FOUND:
+	g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND, "Could not find %s binary", progname);
+	return NULL;
+}
+
+/**********************************************************************************************/
+
 /* Band, channel/frequency stuff for wireless */
 struct cf_pair {
 	guint32 chan;
diff --git a/libnm-core/nm-utils.h b/libnm-core/nm-utils.h
index dcfae00e09..4aad28b216 100644
--- a/libnm-core/nm-utils.h
+++ b/libnm-core/nm-utils.h
@@ -141,6 +141,16 @@ gboolean nm_utils_file_is_certificate (const char *filename);
 gboolean nm_utils_file_is_private_key (const char *filename, gboolean *out_encrypted);
 gboolean nm_utils_file_is_pkcs12 (const char *filename);
 
+typedef gboolean (*NMUtilsFileSearchInPathsPredicate) (const char *filename, gpointer user_data);
+
+const char *nm_utils_file_search_in_paths (const char *progname,
+                                           const char *try_first,
+                                           const char *const *paths,
+                                           GFileTest file_test_flags,
+                                           NMUtilsFileSearchInPathsPredicate predicate,
+                                           gpointer user_data,
+                                           GError **error);
+
 guint32 nm_utils_wifi_freq_to_channel (guint32 freq);
 guint32 nm_utils_wifi_channel_to_freq (guint32 channel, const char *band);
 guint32 nm_utils_wifi_find_next_channel (guint32 channel, int direction, char *band);
diff --git a/libnm/libnm.ver b/libnm/libnm.ver
index d81a24c7eb..1ef71a38d4 100644
--- a/libnm/libnm.ver
+++ b/libnm/libnm.ver
@@ -760,6 +760,7 @@ global:
 	nm_utils_file_is_certificate;
 	nm_utils_file_is_pkcs12;
 	nm_utils_file_is_private_key;
+	nm_utils_file_search_in_paths;
 	nm_utils_hexstr2bin;
 	nm_utils_hwaddr_atoba;
 	nm_utils_hwaddr_aton;