[LEDE-DEV] [PATCH libubox] blobmsg_json: add new functions blobmsg_format_json_value*

[Matthias Schiffer]

The current blobmsg_format_json* functions will return invalid JSON when
the "list" argument is given as false (blobmsg_format_element() will
output the name of the blob_attr as if the value is printed as part of a
JSON object).

To avoid breaking software relying on this behaviour, introduce new
functions which will never print the blob_attr name and thus always
produce valid JSON.

Signed-off-by: Matthias Schiffer <mschiffer at universe-factory.net>
---
 blobmsg_json.c | 49 ++++++++++++++++++++++++++++++++++++-------------
 blobmsg_json.h | 14 ++++++++++++++
 2 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/blobmsg_json.c b/blobmsg_json.c
index 5713948..538c816 100644
--- a/blobmsg_json.c
+++ b/blobmsg_json.c
@@ -207,7 +207,7 @@ static void blobmsg_format_string(struct strbuf *s, const char *str)
 
 static void blobmsg_format_json_list(struct strbuf *s, struct blob_attr *attr, int len, bool array);
 
-static void blobmsg_format_element(struct strbuf *s, struct blob_attr *attr, bool array, bool head)
+static void blobmsg_format_element(struct strbuf *s, struct blob_attr *attr, bool without_name, bool head)
 {
 	const char *data_str;
 	char buf[32];
@@ -217,7 +217,7 @@ static void blobmsg_format_element(struct strbuf *s, struct blob_attr *attr, boo
 	if (!blobmsg_check_attr(attr, false))
 		return;
 
-	if (!array && blobmsg_name(attr)[0]) {
+	if (!without_name && blobmsg_name(attr)[0]) {
 		blobmsg_format_string(s, blobmsg_name(attr));
 		blobmsg_puts(s, ": ", s->indent ? 2 : 1);
 	}
@@ -286,22 +286,26 @@ static void blobmsg_format_json_list(struct strbuf *s, struct blob_attr *attr, i
 	blobmsg_puts(s, (array ? "]" : "}"), 1);
 }
 
+static void setup_strbuf(struct strbuf *s, struct blob_attr *attr, blobmsg_json_format_t cb, void *priv, int indent) {
+	s->len = blob_len(attr);
+	s->buf = malloc(s->len);
+	s->pos = 0;
+	s->custom_format = cb;
+	s->priv = priv;
+	s->indent = false;
+
+	if (indent >= 0) {
+		s->indent = true;
+		s->indent_level = indent;
+	}
+}
+
 char *blobmsg_format_json_with_cb(struct blob_attr *attr, bool list, blobmsg_json_format_t cb, void *priv, int indent)
 {
 	struct strbuf s;
 	bool array;
 
-	s.len = blob_len(attr);
-	s.buf = malloc(s.len);
-	s.pos = 0;
-	s.custom_format = cb;
-	s.priv = priv;
-	s.indent = false;
-
-	if (indent >= 0) {
-		s.indent = true;
-		s.indent_level = indent;
-	}
+	setup_strbuf(&s, attr, cb, priv, indent);
 
 	array = blob_is_extended(attr) &&
 		blobmsg_type(attr) == BLOBMSG_TYPE_ARRAY;
@@ -321,3 +325,22 @@ char *blobmsg_format_json_with_cb(struct blob_attr *attr, bool list, blobmsg_jso
 
 	return s.buf;
 }
+
+char *blobmsg_format_json_value_with_cb(struct blob_attr *attr, blobmsg_json_format_t cb, void *priv, int indent)
+{
+	struct strbuf s;
+
+	setup_strbuf(&s, attr, cb, priv, indent);
+
+	blobmsg_format_element(&s, attr, true, false);
+
+	if (!s.len) {
+		free(s.buf);
+		return NULL;
+	}
+
+	s.buf = realloc(s.buf, s.pos + 1);
+	s.buf[s.pos] = 0;
+
+	return s.buf;
+}
diff --git a/blobmsg_json.h b/blobmsg_json.h
index cd9ed33..9dfc02d 100644
--- a/blobmsg_json.h
+++ b/blobmsg_json.h
@@ -42,4 +42,18 @@ static inline char *blobmsg_format_json_indent(struct blob_attr *attr, bool list
 	return blobmsg_format_json_with_cb(attr, list, NULL, NULL, indent);
 }
 
+char *blobmsg_format_json_value_with_cb(struct blob_attr *attr,
+					blobmsg_json_format_t cb, void *priv,
+					int indent);
+
+static inline char *blobmsg_format_json_value(struct blob_attr *attr)
+{
+	return blobmsg_format_json_value_with_cb(attr, NULL, NULL, -1);
+}
+
+static inline char *blobmsg_format_json_value_indent(struct blob_attr *attr, int indent)
+{
+	return blobmsg_format_json_value_with_cb(attr, NULL, NULL, indent);
+}
+
 #endif
-- 
2.8.3