filter: make a few low level functions public

I think the friendly ones are not that ergonomic. Maybe we should
fix those.

Signed-off-by: William Casarin <[email protected]>

src/filter.rs

@@ -115,14 +115,14 @@ impl FilterBuilder {
         unsafe { bindings::ndb_filter_add_int_element(self.as_mut_ptr(), i) };
     }
 
-    fn add_str_element(&mut self, s: &str) {
+    pub fn add_str_element(&mut self, s: &str) {
         let c_str = CString::new(s).expect("string to cstring conversion failed");
         unsafe {
             bindings::ndb_filter_add_str_element(self.as_mut_ptr(), c_str.as_ptr());
         };
     }
 
-    fn add_id_element(&mut self, id: &[u8; 32]) {
+    pub fn add_id_element(&mut self, id: &[u8; 32]) {
         let ptr: *const ::std::os::raw::c_uchar = id.as_ptr() as *const ::std::os::raw::c_uchar;
         unsafe {
             bindings::ndb_filter_add_id_element(self.as_mut_ptr(), ptr);
@@ -133,7 +133,7 @@ impl FilterBuilder {
         unsafe { bindings::ndb_filter_start_field(self.as_mut_ptr(), field) };
     }
 
-    fn start_tags_field(&mut self, tag: char) {
+    pub fn start_tags_field(&mut self, tag: char) {
         unsafe { bindings::ndb_filter_start_tag_field(self.as_mut_ptr(), tag as u8 as c_char) };
     }
 
@@ -170,11 +170,11 @@ impl FilterBuilder {
         self.start_tags_field('p');
     }
 
-    fn start_tag_field(&mut self, tag: char) {
+    pub fn start_tag_field(&mut self, tag: char) {
         unsafe { bindings::ndb_filter_start_tag_field(self.as_mut_ptr(), tag as u8 as c_char) };
     }
 
-    fn end_field(&mut self) {
+    pub fn end_field(&mut self) {
         unsafe { bindings::ndb_filter_end_field(self.as_mut_ptr()) }
     }