Make a fmt::Write impl for pointer writes

src/dumper.rs

@@ -1,4 +1,5 @@
 use crate::externs::{memset, strcmp};
+use crate::fmt::WriteToPtr;
 use crate::yaml::{
     yaml_anchors_t, yaml_char_t, yaml_document_t, yaml_emitter_t, yaml_event_t, yaml_mark_t,
     yaml_node_item_t, yaml_node_pair_t, yaml_node_t, YAML_ALIAS_EVENT, YAML_ANY_ENCODING,
@@ -9,7 +10,6 @@ use crate::yaml::{
 use crate::{libc, yaml_document_delete, yaml_emitter_emit, yaml_free, yaml_malloc, PointerExt};
 use core::mem::{size_of, MaybeUninit};
 use core::ptr::{self, addr_of_mut};
-use core::slice;
 pub unsafe fn yaml_emitter_open(mut emitter: *mut yaml_emitter_t) -> libc::c_int {
     let mut event = MaybeUninit::<yaml_event_t>::uninit();
     let event = event.as_mut_ptr();
@@ -241,8 +241,7 @@ unsafe fn yaml_emitter_generate_anchor(
     if anchor.is_null() {
         return ptr::null_mut::<yaml_char_t>();
     }
-    let mut buffer = slice::from_raw_parts_mut(anchor.cast(), 16);
-    let _ = write!(buffer, "id{:03}\0", anchor_id);
+    write!(WriteToPtr::new(anchor), "id{:03}\0", anchor_id);
     anchor
 }
 unsafe fn yaml_emitter_dump_node(emitter: *mut yaml_emitter_t, index: libc::c_int) -> libc::c_int {

src/lib.rs

@@ -182,6 +182,36 @@ pub mod externs {
     }
 }
 
+mod fmt {
+    use crate::yaml_char_t;
+    use core::fmt::{self, Write};
+    use core::ptr;
+
+    pub struct WriteToPtr {
+        ptr: *mut yaml_char_t,
+    }
+
+    impl WriteToPtr {
+        pub unsafe fn new(ptr: *mut yaml_char_t) -> Self {
+            WriteToPtr { ptr }
+        }
+
+        pub fn write_fmt(&mut self, args: fmt::Arguments) {
+            let _ = Write::write_fmt(self, args);
+        }
+    }
+
+    impl Write for WriteToPtr {
+        fn write_str(&mut self, s: &str) -> fmt::Result {
+            unsafe {
+                ptr::copy_nonoverlapping(s.as_ptr(), self.ptr, s.len());
+                self.ptr = self.ptr.add(s.len());
+            }
+            Ok(())
+        }
+    }
+}
+
 trait PointerExt: Sized {
     fn c_offset_from(self, origin: Self) -> isize;
 }