From 6d86b2cf16f0e316e52ec1293b5fcad391ad6bff Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@z.cash>
Date: Mon, 11 Feb 2019 16:20:11 +0000
Subject: [PATCH] Extract rust_vec_to_java() utility function

---
 src/main/rust/lib.rs   | 23 ++++++++++-------------
 src/main/rust/utils.rs | 34 +++++++++++++++++++++++++++++++++-
 2 files changed, 43 insertions(+), 14 deletions(-)

diff --git a/src/main/rust/lib.rs b/src/main/rust/lib.rs
index a2a34040..c3a574b4 100644
--- a/src/main/rust/lib.rs
+++ b/src/main/rust/lib.rs
@@ -9,7 +9,7 @@ const SAPLING_CONSENSUS_BRANCH_ID: u32 = 0x76b8_09bb;
 use android_logger::Filter;
 use jni::{
     objects::{JClass, JString},
-    sys::{jboolean, jbyteArray, jint, jlong, jobjectArray, jsize, jstring, JNI_FALSE, JNI_TRUE},
+    sys::{jboolean, jbyteArray, jint, jlong, jobjectArray, jstring, JNI_FALSE, JNI_TRUE},
     JNIEnv,
 };
 use log::Level;
@@ -97,21 +97,18 @@ pub unsafe extern "C" fn Java_cash_z_wallet_sdk_jni_JniConverter_initAccountsTab
         vec![]
     };
 
-    let jempty = env.new_string("").expect("Couldn't create Java string!");
-    let jret = env
-        .new_object_array(ret.len() as jsize, "java/lang/String", *jempty)
-        .expect("Couldn't create Java array!");
-    for (i, extsk) in ret.into_iter().enumerate() {
-        let jextsk = env
-            .new_string(encode_extended_spending_key(
+    utils::rust_vec_to_java(
+        &env,
+        ret,
+        "java/lang/String",
+        |env, extsk| {
+            env.new_string(encode_extended_spending_key(
                 HRP_SAPLING_EXTENDED_SPENDING_KEY_TEST,
                 &extsk,
             ))
-            .expect("Couldn't create Java string!");
-        env.set_object_array_element(jret, i as jsize, *jextsk)
-            .expect("Couldn't set Java array element!");
-    }
-    jret
+        },
+        |env| env.new_string(""),
+    )
 }
 
 #[no_mangle]
diff --git a/src/main/rust/utils.rs b/src/main/rust/utils.rs
index b519be74..6e4f7b91 100644
--- a/src/main/rust/utils.rs
+++ b/src/main/rust/utils.rs
@@ -1,7 +1,39 @@
-use jni::{objects::JString, JNIEnv};
+use jni::{
+    descriptors::Desc,
+    errors::Result as JNIResult,
+    objects::{JClass, JObject, JString},
+    sys::{jobjectArray, jsize},
+    JNIEnv,
+};
+use std::ops::Deref;
 
 pub(crate) fn java_string_to_rust(env: &JNIEnv<'_>, jstring: JString<'_>) -> String {
     env.get_string(jstring)
         .expect("Couldn't get Java string!")
         .into()
 }
+
+pub(crate) fn rust_vec_to_java<'a, T, U, V, F, G>(
+    env: &JNIEnv<'a>,
+    data: Vec<T>,
+    element_class: U,
+    element_map: F,
+    empty_element: G,
+) -> jobjectArray
+where
+    U: Desc<'a, JClass<'a>>,
+    V: Deref<Target = JObject<'a>>,
+    F: Fn(&JNIEnv<'a>, T) -> JNIResult<V>,
+    G: Fn(&JNIEnv<'a>) -> JNIResult<V>,
+{
+    let jempty = empty_element(env).expect("Couldn't create Java string!");
+    let jret = env
+        .new_object_array(data.len() as jsize, element_class, *jempty)
+        .expect("Couldn't create Java array!");
+    for (i, elem) in data.into_iter().enumerate() {
+        let jelem = element_map(env, elem).expect("Couldn't map element to Java!");
+        env.set_object_array_element(jret, i as jsize, *jelem)
+            .expect("Couldn't set Java array element!");
+    }
+    jret
+}