From e4f280f17ffe80c6292d0d117262719b691082fb Mon Sep 17 00:00:00 2001
From: Justin Traglia <95511699+jtraglia@users.noreply.github.com>
Date: Fri, 27 Jan 2023 16:16:41 +0100
Subject: [PATCH] Add compute_kzg_proof to java bindings (#94)

---
 bindings/java/c_kzg_4844_jni.c                | 28 +++++++++++++++++++
 bindings/java/c_kzg_4844_jni.h                |  7 +++++
 .../java/ethereum/ckzg4844/CKZG4844JNI.java   | 10 +++++++
 .../ethereum/ckzg4844/CKZG4844JNITest.java    |  9 ++++++
 .../java/ethereum/ckzg4844/TestUtils.java     |  4 +++
 5 files changed, 58 insertions(+)

diff --git a/bindings/java/c_kzg_4844_jni.c b/bindings/java/c_kzg_4844_jni.c
index e9ba408..0b27f7f 100644
--- a/bindings/java/c_kzg_4844_jni.c
+++ b/bindings/java/c_kzg_4844_jni.c
@@ -125,6 +125,34 @@ JNIEXPORT void JNICALL Java_ethereum_ckzg4844_CKZG4844JNI_freeTrustedSetup(JNIEn
   reset_trusted_setup();
 }
 
+JNIEXPORT jbyteArray JNICALL Java_ethereum_ckzg4844_CKZG4844JNI_computeKzgProof(JNIEnv *env, jclass thisCls, jbyteArray blob, jbyteArray z_bytes)
+{
+  if (settings == NULL)
+  {
+    throw_exception(env, TRUSTED_SETUP_NOT_LOADED);
+    return NULL;
+  }
+
+  Blob *blob_native = (Blob *)(*env)->GetByteArrayElements(env, blob, NULL);
+  Bytes32 *z_native = (Bytes32 *)(*env)->GetByteArrayElements(env, z_bytes, NULL);
+
+  jbyteArray proof = (*env)->NewByteArray(env, BYTES_PER_PROOF);
+  KZGProof *proof_native = (KZGProof *)(uint8_t *)(*env)->GetByteArrayElements(env, proof, NULL);
+
+  C_KZG_RET ret = compute_kzg_proof(proof_native, blob_native, z_native, settings);
+
+  (*env)->ReleaseByteArrayElements(env, blob, (jbyte *)blob_native, JNI_ABORT);
+  (*env)->ReleaseByteArrayElements(env, proof, (jbyte *)proof_native, 0);
+
+  if (ret != C_KZG_OK)
+  {
+    throw_c_kzg_exception(env, ret, "There was an error while computing kzg proof.");
+    return NULL;
+  }
+
+  return proof;
+}
+
 JNIEXPORT jbyteArray JNICALL Java_ethereum_ckzg4844_CKZG4844JNI_computeAggregateKzgProof(JNIEnv *env, jclass thisCls, jbyteArray blobs, jlong count)
 {
   if (settings == NULL)
diff --git a/bindings/java/c_kzg_4844_jni.h b/bindings/java/c_kzg_4844_jni.h
index 91d15b0..27ed9f5 100644
--- a/bindings/java/c_kzg_4844_jni.h
+++ b/bindings/java/c_kzg_4844_jni.h
@@ -42,6 +42,13 @@ extern "C"
    */
   JNIEXPORT void JNICALL Java_ethereum_ckzg4844_CKZG4844JNI_freeTrustedSetup(JNIEnv *, jclass);
 
+  /*
+   * Class:     ethereum_ckzg4844_CKZG4844JNI
+   * Method:    computeKzgProof
+   * Signature: ([B[B)[B
+   */
+  JNIEXPORT jbyteArray JNICALL Java_ethereum_ckzg4844_CKZG4844JNI_computeKzgProof(JNIEnv *, jclass, jbyteArray, jbyteArray);
+
   /*
    * Class:     ethereum_ckzg4844_CKZG4844JNI
    * Method:    computeAggregateKzgProof
diff --git a/bindings/java/src/main/java/ethereum/ckzg4844/CKZG4844JNI.java b/bindings/java/src/main/java/ethereum/ckzg4844/CKZG4844JNI.java
index 2eb2337..4acd9de 100644
--- a/bindings/java/src/main/java/ethereum/ckzg4844/CKZG4844JNI.java
+++ b/bindings/java/src/main/java/ethereum/ckzg4844/CKZG4844JNI.java
@@ -113,6 +113,16 @@ public class CKZG4844JNI {
    */
   public static native void freeTrustedSetup();
 
+  /**
+   * Compute proof at point z for the polynomial represented by blob.
+   *
+   * @param blob blob bytes
+   * @param z_bytes a point
+   * @return the proof
+   * @throws CKZGException if there is a crypto error
+   */
+  public static native byte[] computeKzgProof(byte[] blob, byte[] z_bytes);
+
   /**
    * Calculates aggregated proof for the given blobs
    *
diff --git a/bindings/java/src/test/java/ethereum/ckzg4844/CKZG4844JNITest.java b/bindings/java/src/test/java/ethereum/ckzg4844/CKZG4844JNITest.java
index 3bfc298..f10de22 100644
--- a/bindings/java/src/test/java/ethereum/ckzg4844/CKZG4844JNITest.java
+++ b/bindings/java/src/test/java/ethereum/ckzg4844/CKZG4844JNITest.java
@@ -82,6 +82,15 @@ public class CKZG4844JNITest {
             parameters.getProof()));
   }
 
+  @Test
+  public void checkComputeKzgProof() {
+    loadTrustedSetup();
+    final byte[] blob = TestUtils.createRandomBlob();
+    final byte[] z_bytes = TestUtils.randomBLSFieldElementBytes();
+    CKZG4844JNI.computeKzgProof(blob, z_bytes);
+    CKZG4844JNI.freeTrustedSetup();
+  }
+
   @Test
   public void checkCustomExceptionIsThrownAsExpected() {
 
diff --git a/bindings/java/src/testFixtures/java/ethereum/ckzg4844/TestUtils.java b/bindings/java/src/testFixtures/java/ethereum/ckzg4844/TestUtils.java
index d0dd7e5..da63cf8 100644
--- a/bindings/java/src/testFixtures/java/ethereum/ckzg4844/TestUtils.java
+++ b/bindings/java/src/testFixtures/java/ethereum/ckzg4844/TestUtils.java
@@ -128,6 +128,10 @@ public class TestUtils {
     return randomBLSFieldElement();
   }
 
+  public static byte[] randomBLSFieldElementBytes() {
+    return randomBLSFieldElement().toArray(ByteOrder.LITTLE_ENDIAN);
+  }
+
   private static InputStream readResource(final String resource) {
     return Thread.currentThread().getContextClassLoader().getResourceAsStream(resource);
   }