libutil/util_fmt: Add util_fmt_type_to_name()

Add a function to get the textual name of an enum util_fmt_t value. To
make this robust to changes in the order of elements in the format array
initialize this using named indices.

Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

include/lib/util_fmt.h

@@ -157,6 +157,16 @@ void util_fmt_exit(void);
  */
 bool util_fmt_name_to_type(const char *name, enum util_fmt_t *type);
 
+/**
+ * util_fmt_type_to_name() - Get name of given format type identifier.
+ * @type: Format type identifier
+ *
+ * Get the name corresponding to the given format type identifier.
+ *
+ * Return: name of the format type
+ */
+const char *util_fmt_type_to_name(enum util_fmt_t type);
+
 /**
  * util_fmt_set_indent() - Set indentation parameters.
  * @base    : Base indentation level to apply to all output lines (default 0)

libutil/util_fmt.c

@@ -89,11 +89,26 @@ static const struct {
 	const char *name;
 	enum util_fmt_t fmt;
 } formats[] = {
-	{ "json", FMT_JSON },
-	{ "json-seq", FMT_JSONSEQ },
-	{ "jsonl", FMT_JSONL },
-	{ "pairs", FMT_PAIRS },
-	{ "csv",  FMT_CSV },
+	[FMT_JSON] = {
+		.name = "json",
+		.fmt = FMT_JSON
+	},
+	[FMT_JSONSEQ] = {
+		.name = "json-seq",
+		.fmt = FMT_JSONSEQ
+	},
+	[FMT_JSONL] = {
+		.name = "jsonl",
+		.fmt = FMT_JSONL
+	},
+	[FMT_PAIRS] = {
+		.name = "pairs",
+		.fmt = FMT_PAIRS
+	},
+	[FMT_CSV] = {
+		.name = "csv",
+		.fmt = FMT_CSV
+	},
 };
 
 /* Signal mask for blocking INT and TERM signals. */
@@ -112,6 +127,11 @@ bool util_fmt_name_to_type(const char *name, enum util_fmt_t *type)
 	return false;
 }
 
+const char *util_fmt_type_to_name(enum util_fmt_t type)
+{
+	return formats[type].name;
+}
+
 bool util_fmt_is_json(enum util_fmt_t type)
 {
 	switch (type) {