Use lazy_static to initialize the Jubjub parameters, to avoid passing parameters around.

include/librustzcash.h

@@ -3,37 +3,26 @@
 
 #include <stdint.h>
 
-struct librustzcash_params {
-};
-
 extern "C" {
     uint64_t librustzcash_xor(uint64_t a, uint64_t b);
 
-    /// Initializes some parameters for sapling-crypto,
-    /// returning a pointer to the parameters. You should
-    /// free this when you're done with 
-    /// `librustzcash_free_params()`.
-    librustzcash_params* librustzcash_init_params();
-
-    /// Frees some parameters that were previously returned
-    /// from `librustzcash_init_params()`. Only call this
-    /// once.
-    void librustzcash_free_params(librustzcash_params* params);
+    /// Writes the "uncommitted" note value for empty leaves
+    /// of the merkle tree. `result` must be a valid pointer
+    /// to 32 bytes which will be written.
+    void librustzcash_tree_uncommitted(
+        unsigned char *result
+    );
 
     /// Computes a merkle tree hash for a given depth.
     /// The `depth` parameter should not be larger than
     /// 62.
     ///
-    /// Params must be a valid pointer that was returned
-    /// from `librustzcash_init_params()`.
-    ///
     /// `a` and `b` each must be of length 32, and must each
     /// be scalars of BLS12-381.
     ///
     /// The result of the merkle tree hash is placed in
     /// `result`, which must also be of length 32.
     void librustzcash_merkle_hash(
-        const librustzcash_params* params,
         size_t depth,
         const unsigned char *a,
         const unsigned char *b,