Reduce minimum required GLib version to 2.58

Makes the life of backporters easier. This is the version used by latest
Debian stable (buster) so it's a reasonable target.

meson.build

@@ -60,10 +60,10 @@ add_global_arguments('-DAS_COMPILATION', language : 'c')
 #
 # Dependencies
 #
-glib_dep = dependency('glib-2.0', version: '>=2.62')
-gobject_dep = dependency('gobject-2.0', version: '>=2.62')
-gio_dep = dependency('gio-2.0', version: '>=2.62')
-gio_unix_dep = dependency('gio-unix-2.0', version: '>=2.62')
+glib_dep = dependency('glib-2.0', version: '>=2.58')
+gobject_dep = dependency('gobject-2.0', version: '>=2.58')
+gio_dep = dependency('gio-2.0', version: '>=2.58')
+gio_unix_dep = dependency('gio-unix-2.0', version: '>=2.58')
 soup_dep = dependency('libsoup-2.4', version: '>= 2.56')
 xml2_dep = dependency('libxml-2.0')
 yaml_dep = dependency('yaml-0.1')

src/as-release.c

@@ -303,7 +303,7 @@ as_release_set_timestamp (AsRelease *release, guint64 timestamp)
 
 	priv->timestamp = timestamp;
 	g_free (priv->date);
-	priv->date = g_date_time_format_iso8601 (time);
+	priv->date = as_date_time_format_iso8601 (time);
 }
 
 /**
@@ -434,7 +434,7 @@ as_release_set_timestamp_eol (AsRelease *release, guint64 timestamp)
 
 	time = g_date_time_new_from_unix_utc (timestamp);
 	g_free (priv->date_eol);
-	priv->date_eol = g_date_time_format_iso8601 (time);
+	priv->date_eol = as_date_time_format_iso8601 (time);
 }
 
 /**
@@ -1021,7 +1021,7 @@ as_release_to_xml_node (AsRelease *release, AsContext *ctx, xmlNode *root)
 					(xmlChar*) time_str);
 		} else {
 			g_autoptr(GDateTime) time = g_date_time_new_from_unix_utc (priv->timestamp);
-			time_str = g_date_time_format_iso8601 (time);
+			time_str = as_date_time_format_iso8601 (time);
 			xmlNewProp (subnode, (xmlChar*) "date",
 					(xmlChar*) time_str);
 		}
@@ -1168,7 +1168,7 @@ as_release_emit_yaml (AsRelease *release, AsContext *ctx, yaml_emitter_t *emitte
 						      priv->timestamp);
 		} else {
 			g_autoptr(GDateTime) time = g_date_time_new_from_unix_utc (priv->timestamp);
-			time_str = g_date_time_format_iso8601 (time);
+			time_str = as_date_time_format_iso8601 (time);
 			as_yaml_emit_entry (emitter, "date", time_str);
 		}
 	}

src/as-utils-private.h

@@ -128,6 +128,8 @@ gchar			*as_ptr_array_to_str (GPtrArray *array,
 AS_INTERNAL_VISIBLE
 gchar			*as_filebasename_from_uri (const gchar *uri);
 
+gchar			*as_date_time_format_iso8601 (GDateTime *datetime);
+
 #pragma GCC visibility pop
 G_END_DECLS
 

src/as-utils.c

@@ -1391,3 +1391,43 @@ as_filebasename_from_uri (const gchar *uri)
 
 	return bname;
 }
+
+/**
+ * as_date_time_format_iso8601:
+ * @datetime: A #GDateTime
+ *
+ * Format datetime in ISO 8601 format.
+ *
+ * Compatibility wrapper to support GLib < 2.62.
+ * This function can go away if we bump the GLib minimal version.
+ */
+gchar*
+as_date_time_format_iso8601 (GDateTime *datetime)
+{
+#if GLIB_CHECK_VERSION(2,62,0)
+	return g_date_time_format_iso8601 (datetime);
+#else
+	GString *outstr = NULL;
+	gchar *main_date = NULL;
+	gint64 offset;
+
+	/* Main date and time. */
+	main_date = g_date_time_format (datetime, "%Y-%m-%dT%H:%M:%S");
+	outstr = g_string_new (main_date);
+	g_free (main_date);
+
+	/* Timezone. Format it as `%:::z` unless the offset is zero, in which case
+	 * we can simply use `Z`. */
+	offset = g_date_time_get_utc_offset (datetime);
+
+	if (offset == 0) {
+		g_string_append_c (outstr, 'Z');
+	} else {
+		gchar *time_zone = g_date_time_format (datetime, "%:::z");
+		g_string_append (outstr, time_zone);
+		g_free (time_zone);
+	}
+
+	return g_string_free (outstr, FALSE);
+#endif
+}