file: handle return output of b64_decode

Solve this compile warning:

file.c:300:16: error: comparison of unsigned expression < 0 is always false [-Werror,-Wtautological-compare]
                if (data_len < 0)

Signed-off-by: Luka Perkov <luka@openwrt.org>

diff --git a/file.c b/file.c
index 91a55a1..b17692a 100644 (file)
--- a/file.c
+++ b/file.c
@@ -271,7 +271,7 @@ rpc_file_write(struct ubus_context *ctx, struct ubus_object *obj,
        mode_t prev_mode, mode = 0666;
        int fd, rv = 0;
        void *data = NULL;
-       size_t data_len = 0;
+       ssize_t data_len = 0;
 
        blobmsg_parse(rpc_file_rw_policy, __RPC_F_RW_MAX, tb,
                      blob_data(msg), blob_len(msg));