lib/jsonwrt: introduce ul_jsonwrt_empty()

The new function optimizes the printing of empty objects and arrays in
a "pretty" way, instead of using the ul_jsonwrt_..._open() and
ul_jsonwrt_..._close() functions, which add extra line breaks to the
output.

Signed-off-by: Karel Zak <kzak@redhat.com>

2 files changed, 31 insertions, 12 deletions

diff --git a/include/jsonwrt.h b/include/jsonwrt.h
index 1944d993dc..31e180abe5 100644
--- a/include/jsonwrt.h
+++ b/include/jsonwrt.h
@@ -23,6 +23,7 @@ int ul_jsonwrt_is_ready(struct ul_jsonwrt *fmt);
 void ul_jsonwrt_indent(struct ul_jsonwrt *fmt);
 void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type);
 void ul_jsonwrt_close(struct ul_jsonwrt *fmt, int type);
+void ul_jsonwrt_empty(struct ul_jsonwrt *fmt, const char *name, int type);
 void ul_jsonwrt_flush(struct ul_jsonwrt *fmt);
 
 #define ul_jsonwrt_root_open(_f)	ul_jsonwrt_open(_f, NULL, UL_JSON_OBJECT)
@@ -30,14 +31,15 @@ void ul_jsonwrt_flush(struct ul_jsonwrt *fmt);
 
 #define ul_jsonwrt_array_open(_f, _n)	ul_jsonwrt_open(_f, _n, UL_JSON_ARRAY)
 #define ul_jsonwrt_array_close(_f)	ul_jsonwrt_close(_f, UL_JSON_ARRAY)
+#define ul_jsonwrt_array_empty(_f, _n)	ul_jsonwrt_empty(_f, _n, UL_JSON_ARRAY)
 
 #define ul_jsonwrt_object_open(_f, _n)	ul_jsonwrt_open(_f, _n, UL_JSON_OBJECT)
 #define ul_jsonwrt_object_close(_f)	ul_jsonwrt_close(_f, UL_JSON_OBJECT)
+#define ul_jsonwrt_object_empty(_f, _n)	ul_jsonwrt_empty(_f, _n, UL_JSON_OBJECT)
 
 #define ul_jsonwrt_value_open(_f, _n)	ul_jsonwrt_open(_f, _n, UL_JSON_VALUE)
 #define ul_jsonwrt_value_close(_f)	ul_jsonwrt_close(_f, UL_JSON_VALUE)
 
-
 void ul_jsonwrt_value_raw(struct ul_jsonwrt *fmt,
 			const char *name, const char *data);
 void ul_jsonwrt_value_s(struct ul_jsonwrt *fmt,
@@ -50,7 +52,7 @@ void ul_jsonwrt_value_double(struct ul_jsonwrt *fmt,
 			const char *name, long double data);
 void ul_jsonwrt_value_boolean(struct ul_jsonwrt *fmt,
 			const char *name, int data);
-void ul_jsonwrt_value_null(struct ul_jsonwrt *fmt,
-			const char *name);
+
+#define ul_jsonwrt_value_null(_f, _n)	ul_jsonwrt_empty(_f, _n, UL_JSON_VALUE)
 
 #endif /* UTIL_LINUX_JSONWRT_H */
diff --git a/lib/jsonwrt.c b/lib/jsonwrt.c
index e21368de2a..365d845ce9 100644
--- a/lib/jsonwrt.c
+++ b/lib/jsonwrt.c
@@ -122,7 +122,7 @@ void ul_jsonwrt_indent(struct ul_jsonwrt *fmt)
 		fputs("   ", fmt->out);
 }
 
-void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type)
+static void print_name(struct ul_jsonwrt *fmt, const char *name)
 {
 	if (name) {
 		if (fmt->after_close)
@@ -135,6 +135,11 @@ void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type)
 		else
 			ul_jsonwrt_indent(fmt);
 	}
+}
+
+void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type)
+{
+	print_name(fmt, name);
 
 	switch (type) {
 	case UL_JSON_OBJECT:
@@ -152,6 +157,25 @@ void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type)
 	fmt->after_close = 0;
 }
 
+void ul_jsonwrt_empty(struct ul_jsonwrt *fmt, const char *name, int type)
+{
+	print_name(fmt, name);
+
+	switch (type) {
+	case UL_JSON_OBJECT:
+		fputs(name ? ": {}" : "{}", fmt->out);
+		break;
+	case UL_JSON_ARRAY:
+		fputs(name ? ": []" : "[]", fmt->out);
+		break;
+	case UL_JSON_VALUE:
+		fputs(name ? ": null" : "null", fmt->out);
+		break;
+	}
+
+	fmt->after_close = 1;
+}
+
 void ul_jsonwrt_close(struct ul_jsonwrt *fmt, int type)
 {
 	assert(fmt->indent > 0);
@@ -178,6 +202,7 @@ void ul_jsonwrt_close(struct ul_jsonwrt *fmt, int type)
 	fmt->after_close = 1;
 }
 
+
 void ul_jsonwrt_flush(struct ul_jsonwrt *fmt)
 {
 	fflush(fmt->out);
@@ -239,11 +264,3 @@ void ul_jsonwrt_value_boolean(struct ul_jsonwrt *fmt,
 	fputs(data ? "true" : "false", fmt->out);
 	ul_jsonwrt_value_close(fmt);
 }
-
-void ul_jsonwrt_value_null(struct ul_jsonwrt *fmt,
-			const char *name)
-{
-	ul_jsonwrt_value_open(fmt, name);
-	fputs("null", fmt->out);
-	ul_jsonwrt_value_close(fmt);
-}