add JSON_C_TO_STRING_COLOR option

This option enable color in json_object_to_json_string_ext.
I've try to made something similar to jq output,
but I've color true/false and null in purple,
as it's what is common color scheme used in programing language in emacs.

also add a '-c' option into json_parser to test it.

note: that I could have done a color() function similar to
what is done with indent(), but as the code is pretty small
I've keep it as it. so if you want  me to use a subfunction
tell me and I'll do it.

Signed-off-by: Matthias Gatto <matthias.gatto@protonmail.com>

apps/json_parse.c

@@ -38,6 +38,7 @@
 static int formatted_output = JSON_C_TO_STRING_SPACED;
 static int show_output = 1;
 static int strict_mode = 0;
+static int color = 0;
 static const char *fname = NULL;
 
 #ifndef HAVE_JSON_TOKENER_GET_PARSE_END
@@ -141,7 +142,7 @@ static int showobj(struct json_object *new_obj)
 	if (show_output)
 	{
 		const char *output;
-		output = json_object_to_json_string_ext(new_obj, formatted_output);
+		output = json_object_to_json_string_ext(new_obj, formatted_output | color);
 		printf("%s\n", output);
 	}
 
@@ -160,6 +161,7 @@ static void usage(const char *argv0, int exitval, const char *errmsg)
 	fprintf(fp, "  -f - Format the output to stdout with JSON_C_TO_STRING_PRETTY (default is JSON_C_TO_STRING_SPACED)\n");
 	fprintf(fp, "  -F - Format the output to stdout with <arg>, e.g. 0 for JSON_C_TO_STRING_PLAIN\n");
 	fprintf(fp, "  -n - No output\n");
+	fprintf(fp, "  -c - color\n");
 	fprintf(fp, "  -s - Parse in strict mode, flags:\n");
 	fprintf(fp, "       JSON_TOKENER_STRICT|JSON_TOKENER_ALLOW_TRAILING_CHARS\n");
 	fprintf(fp, " Diagnostic information will be emitted to stderr\n");
@@ -173,7 +175,7 @@ int main(int argc, char **argv)
 {
 	int opt;
 
-	while ((opt = getopt(argc, argv, "fF:hns")) != -1)
+	while ((opt = getopt(argc, argv, "fF:hnsc")) != -1)
 	{
 		switch (opt)
 		{
@@ -181,6 +183,7 @@ int main(int argc, char **argv)
 		case 'F': formatted_output = atoi(optarg); break;
 		case 'n': show_output = 0; break;
 		case 's': strict_mode = 1; break;
+		case 'c': color = JSON_C_TO_STRING_COLOR; break;
 		case 'h': usage(argv[0], 0, NULL);
 		default: /* '?' */ usage(argv[0], EXIT_FAILURE, "Unknown arguments");
 		}

json_object.c

@@ -64,6 +64,12 @@ static void json_object_generic_delete(struct json_object *jso);
 #define inline
 #endif
 
+/* define colors */
+#define ANSI_COLOR_RESET "\033[0m"
+#define ANSI_COLOR_FG_GREEN "\033[0;32m"
+#define ANSI_COLOR_FG_BLUE "\033[0;34m"
+#define ANSI_COLOR_FG_MAGENTA "\033[0;35m"
+
 /*
  * Helper functions to more safely cast to a particular type of json_object
  */
@@ -472,15 +478,28 @@ static int json_object_object_to_json_string(struct json_object *jso, struct pri
 		if (flags & JSON_C_TO_STRING_SPACED && !(flags & JSON_C_TO_STRING_PRETTY))
 			printbuf_strappend(pb, " ");
 		indent(pb, level + 1, flags);
+		if (flags & JSON_C_TO_STRING_COLOR)
+			printbuf_strappend(pb, ANSI_COLOR_FG_BLUE);
+
 		printbuf_strappend(pb, "\"");
 		json_escape_str(pb, iter.key, strlen(iter.key), flags);
+		printbuf_strappend(pb, "\"");
+
+		if (flags & JSON_C_TO_STRING_COLOR)
+			printbuf_strappend(pb, ANSI_COLOR_RESET);
+
 		if (flags & JSON_C_TO_STRING_SPACED)
-			printbuf_strappend(pb, "\": ");
+			printbuf_strappend(pb, ": ");
 		else
-			printbuf_strappend(pb, "\":");
-		if (iter.val == NULL)
+			printbuf_strappend(pb, ":");
+
+		if (iter.val == NULL) {
+			if (flags & JSON_C_TO_STRING_COLOR)
+				printbuf_strappend(pb, ANSI_COLOR_FG_MAGENTA);
 			printbuf_strappend(pb, "null");
-		else if (iter.val->_to_json_string(iter.val, pb, level + 1, flags) < 0)
+			if (flags & JSON_C_TO_STRING_COLOR)
+				printbuf_strappend(pb, ANSI_COLOR_RESET);
+		} else if (iter.val->_to_json_string(iter.val, pb, level + 1, flags) < 0)
 			return -1;
 	}
 	if ((flags & JSON_C_TO_STRING_PRETTY) && had_children)
@@ -626,9 +645,18 @@ void json_object_object_del(struct json_object *jso, const char *key)
 static int json_object_boolean_to_json_string(struct json_object *jso, struct printbuf *pb,
                                               int level, int flags)
 {
+	int ret;
+
+	if (flags & JSON_C_TO_STRING_COLOR)
+		printbuf_strappend(pb, ANSI_COLOR_FG_MAGENTA);
+
 	if (JC_BOOL(jso)->c_boolean)
-		return printbuf_strappend(pb, "true");
-	return printbuf_strappend(pb, "false");
+		ret = printbuf_strappend(pb, "true");
+	else
+		ret = printbuf_strappend(pb, "false");
+	if (ret > -1 && flags & JSON_C_TO_STRING_COLOR)
+		return printbuf_strappend(pb, ANSI_COLOR_RESET);
+	return ret;
 }
 
 struct json_object *json_object_new_boolean(json_bool b)
@@ -1217,9 +1245,13 @@ static int json_object_string_to_json_string(struct json_object *jso, struct pri
                                              int level, int flags)
 {
 	ssize_t len = JC_STRING(jso)->len;
+	if (flags & JSON_C_TO_STRING_COLOR)
+		printbuf_strappend(pb, ANSI_COLOR_FG_GREEN);
 	printbuf_strappend(pb, "\"");
 	json_escape_str(pb, get_string_component(jso), len < 0 ? -(ssize_t)len : len, flags);
 	printbuf_strappend(pb, "\"");
+	if (flags & JSON_C_TO_STRING_COLOR)
+		printbuf_strappend(pb, ANSI_COLOR_RESET);
 	return 0;
 }
 
@@ -1392,9 +1424,15 @@ static int json_object_array_to_json_string(struct json_object *jso, struct prin
 			printbuf_strappend(pb, " ");
 		indent(pb, level + 1, flags);
 		val = json_object_array_get_idx(jso, ii);
-		if (val == NULL)
+		if (val == NULL) {
+
+			if (flags & JSON_C_TO_STRING_COLOR)
+				printbuf_strappend(pb, ANSI_COLOR_FG_MAGENTA);
 			printbuf_strappend(pb, "null");
-		else if (val->_to_json_string(val, pb, level + 1, flags) < 0)
+			if (flags & JSON_C_TO_STRING_COLOR)
+				printbuf_strappend(pb, ANSI_COLOR_RESET);
+
+		} else if (val->_to_json_string(val, pb, level + 1, flags) < 0)
 			return -1;
 	}
 	if ((flags & JSON_C_TO_STRING_PRETTY) && had_children)

json_object.h

@@ -74,6 +74,15 @@ extern "C" {
  */
 #define JSON_C_TO_STRING_NOSLASHESCAPE (1 << 4)
 
+/**
+ * A flag for the json_object_to_json_string_ext() and
+ * json_object_to_file_ext() functions which causes
+ * the output to be formatted.
+ *
+ * Use color for printing json.
+ */
+#define JSON_C_TO_STRING_COLOR (1 << 5)
+
 /**
  * A flag for the json_object_object_add_ex function which
  * causes the value to be added without a check if it already exists.