From 3891fe57d4a67c4b85dd2064d4bd26aa535d2374 Mon Sep 17 00:00:00 2001
From: Marco Stronati <marco@stronati.org>
Date: Tue, 6 Aug 2019 23:41:33 +0200
Subject: [PATCH 1/2] Make initialization of sprout validation key optional

This makes the C interface behave like `zcash_proofs` and allows to
init the library without downloading the heavy sprout parameters.
In the special case where `librustzcash_init_zksnark_params` is called
with the sprout arguments path set to NULL and length set to 0, the
arguments are passed as None to `load_parameters`.
---
 librustzcash/src/rustzcash.rs | 41 ++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/librustzcash/src/rustzcash.rs b/librustzcash/src/rustzcash.rs
index 1db70ac..0f47d8f 100644
--- a/librustzcash/src/rustzcash.rs
+++ b/librustzcash/src/rustzcash.rs
@@ -143,9 +143,13 @@ pub extern "system" fn librustzcash_init_zksnark_params(
     let output_path = Path::new(OsStr::from_bytes(unsafe {
         slice::from_raw_parts(output_path, output_path_len)
     }));
-    let sprout_path = Path::new(OsStr::from_bytes(unsafe {
-        slice::from_raw_parts(sprout_path, sprout_path_len)
-    }));
+    let sprout_path = if sprout_path.is_null() && sprout_path_len == 0 {
+        None
+    } else {
+        Some(Path::new(OsStr::from_bytes(unsafe {
+            slice::from_raw_parts(sprout_path, sprout_path_len)
+        })))
+    };
 
     init_zksnark_params(
         spend_path,
@@ -174,8 +178,13 @@ pub extern "system" fn librustzcash_init_zksnark_params(
         OsString::from_wide(unsafe { slice::from_raw_parts(spend_path, spend_path_len) });
     let output_path =
         OsString::from_wide(unsafe { slice::from_raw_parts(output_path, output_path_len) });
-    let sprout_path =
-        OsString::from_wide(unsafe { slice::from_raw_parts(sprout_path, sprout_path_len) });
+    let sprout_path = if sprout_path.is_null() && sprout_path_len == 0 {
+        None
+    } else {
+        Some(OsStr::from_wide(unsafe {
+            slice::from_raw_parts(sprout_path, sprout_path_len)
+        }))
+    };
 
     init_zksnark_params(
         Path::new(&spend_path),
@@ -192,7 +201,7 @@ fn init_zksnark_params(
     spend_hash: *const c_char,
     output_path: &Path,
     output_hash: *const c_char,
-    sprout_path: &Path,
+    sprout_path: Option<&Path>,
     sprout_hash: *const c_char,
 ) {
     // Initialize jubjub parameters here
@@ -206,9 +215,15 @@ fn init_zksnark_params(
         .to_str()
         .expect("hash should be a valid string");
 
-    let sprout_hash = unsafe { CStr::from_ptr(sprout_hash) }
-        .to_str()
-        .expect("hash should be a valid string");
+    let sprout_hash_option = if sprout_path.is_none() {
+        None
+    } else {
+        Some(
+            unsafe { CStr::from_ptr(sprout_hash) }
+                .to_str()
+                .expect("hash should be a valid string"),
+        )
+    };
 
     // Load params
     let (spend_params, spend_vk, output_params, output_vk, sprout_vk) = load_parameters(
@@ -216,8 +231,8 @@ fn init_zksnark_params(
         spend_hash,
         output_path,
         output_hash,
-        Some(sprout_path),
-        Some(sprout_hash),
+        sprout_path,
+        sprout_hash_option,
     );
 
     // Caller is responsible for calling this function once, so
@@ -225,11 +240,11 @@ fn init_zksnark_params(
     unsafe {
         SAPLING_SPEND_PARAMS = Some(spend_params);
         SAPLING_OUTPUT_PARAMS = Some(output_params);
-        SPROUT_GROTH16_PARAMS_PATH = Some(sprout_path.to_owned());
+        SPROUT_GROTH16_PARAMS_PATH = sprout_path.map(|p| p.to_owned());
 
         SAPLING_SPEND_VK = Some(spend_vk);
         SAPLING_OUTPUT_VK = Some(output_vk);
-        SPROUT_GROTH16_VK = Some(sprout_vk.unwrap());
+        SPROUT_GROTH16_VK = sprout_vk;
     }
 }
 

From 37531ed7479755a944317c6e2699d125036d7aa2 Mon Sep 17 00:00:00 2001
From: Marco Stronati <marco@stronati.org>
Date: Wed, 21 Aug 2019 08:28:44 +0200
Subject: [PATCH 2/2] Fixes after feedback

---
 librustzcash/src/rustzcash.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/librustzcash/src/rustzcash.rs b/librustzcash/src/rustzcash.rs
index 0f47d8f..dca6617 100644
--- a/librustzcash/src/rustzcash.rs
+++ b/librustzcash/src/rustzcash.rs
@@ -143,7 +143,7 @@ pub extern "system" fn librustzcash_init_zksnark_params(
     let output_path = Path::new(OsStr::from_bytes(unsafe {
         slice::from_raw_parts(output_path, output_path_len)
     }));
-    let sprout_path = if sprout_path.is_null() && sprout_path_len == 0 {
+    let sprout_path = if sprout_path.is_null() {
         None
     } else {
         Some(Path::new(OsStr::from_bytes(unsafe {
@@ -178,7 +178,7 @@ pub extern "system" fn librustzcash_init_zksnark_params(
         OsString::from_wide(unsafe { slice::from_raw_parts(spend_path, spend_path_len) });
     let output_path =
         OsString::from_wide(unsafe { slice::from_raw_parts(output_path, output_path_len) });
-    let sprout_path = if sprout_path.is_null() && sprout_path_len == 0 {
+    let sprout_path = if sprout_path.is_null() {
         None
     } else {
         Some(OsStr::from_wide(unsafe {
@@ -215,7 +215,7 @@ fn init_zksnark_params(
         .to_str()
         .expect("hash should be a valid string");
 
-    let sprout_hash_option = if sprout_path.is_none() {
+    let sprout_hash = if sprout_path.is_none() {
         None
     } else {
         Some(
@@ -232,7 +232,7 @@ fn init_zksnark_params(
         output_path,
         output_hash,
         sprout_path,
-        sprout_hash_option,
+        sprout_hash,
     );
 
     // Caller is responsible for calling this function once, so