fix signature and generate h

bindings.h

@@ -0,0 +1,59 @@
+#include <cstdarg>
+#include <cstdint>
+#include <cstdlib>
+#include <new>
+
+template<typename T>
+struct Option;
+
+struct NodeLink {
+  enum class Tag {
+    Stored,
+    Generated,
+  };
+
+  struct Stored_Body {
+    uint32_t _0;
+  };
+
+  struct Generated_Body {
+    uint32_t _0;
+  };
+
+  Tag tag;
+  union {
+    Stored_Body stored;
+    Generated_Body generated;
+  };
+};
+
+struct NodeData {
+  uint8_t subtree_commitment[32];
+  uint32_t start_time;
+  uint32_t end_time;
+  uint32_t start_target;
+  uint32_t end_target;
+  uint8_t start_sapling_root[32];
+  uint8_t end_sapling_root[32];
+  uint64_t subtree_total_work;
+  uint32_t start_height;
+  uint32_t end_height;
+  uint64_t shielded_tx;
+};
+
+struct MMRNode {
+  Option<NodeLink> left;
+  Option<NodeLink> right;
+  NodeData data;
+};
+
+extern "C" {
+
+void append(const MMRNode *stored,
+            uint32_t stored_count,
+            const MMRNode *generated,
+            uint32_t generated_count,
+            uint32_t *append_count,
+            MMRNode *append_buffer);
+
+} // extern "C"

src/lib.rs

@@ -58,7 +58,7 @@ pub extern fn append(
     generated_count: u32,
     append_count: *mut u32,
     append_buffer: *mut MMRNode,
-) -> MMRNode {
+) {
 
     // TODO: construct tree and write to (append_count, append_buffer)
     // TODO: also return generated??