java: introduce proper types and minimise reliance on ByteBuffer/byte[]

bindings/java/CMakeLists.txt

@@ -15,6 +15,13 @@ add_jar(evmc-jar
     java/src/main/java/org/ethereum/evmc/EvmcVm.java
     java/src/main/java/org/ethereum/evmc/Host.java
     java/src/main/java/org/ethereum/evmc/HostContext.java
+    java/src/main/java/org/ethereum/evmc/StorageStatus.java
+    java/src/main/java/org/ethereum/evmc/types/Address.java
+    java/src/main/java/org/ethereum/evmc/types/Bytes32.java
+    java/src/main/java/org/ethereum/evmc/types/FixedLengthType.java
+    java/src/main/java/org/ethereum/evmc/types/Message.java
+    java/src/main/java/org/ethereum/evmc/types/TxContext.java
+    java/src/main/java/org/ethereum/evmc/types/Uint256.java
     GENERATE_NATIVE_HEADERS evmc-java-native-headers)
 
 add_library(evmc-java SHARED)

bindings/java/java/src/main/java/org/ethereum/evmc/EvmcVm.java

@@ -8,6 +8,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
+import org.ethereum.evmc.types.*;
 
 /**
  * The Java interface to the evm instance.
@@ -143,17 +144,19 @@ public String version() {
    *
    * <p>This is a mandatory method and MUST NOT be set to NULL.
    */
-  private static native ByteBuffer execute(
-      ByteBuffer nativeVm, HostContext context, int rev, ByteBuffer msg, ByteBuffer code);
+  private static native void execute(
+      ByteBuffer nativeVm, HostContext context, int rev, Message msg, ByteBuffer code, Result result);
 
   /**
    * Function is a wrapper around native execute.
    *
    * <p>This allows the context to managed in one method
    */
-  public synchronized ByteBuffer execute(
-      HostContext context, int rev, ByteBuffer msg, ByteBuffer code) {
-    return execute(nativeVm, context, rev, msg, code);
+  public synchronized Result execute(
+      HostContext context, int rev, Message msg, ByteBuffer code) {
+    Result result;
+    execute(nativeVm, context, rev, msg, code, result);
+    return result;
   }
 
   /**

bindings/java/java/src/main/java/org/ethereum/evmc/Host.java

@@ -4,6 +4,10 @@
 package org.ethereum.evmc;
 
 import java.nio.ByteBuffer;
+import java.util.Arrays;
+import org.ethereum.evmc.types.*;
+import org.ethereum.evmc.types.Address;
+import org.ethereum.evmc.types.Bytes32;
 
 /**
  * The Host interface.
@@ -21,56 +25,59 @@ private static ByteBuffer ensureDirectBuffer(ByteBuffer input) {
 
   /** Check account existence callback function. */
   static boolean account_exists(HostContext context, byte[] address) {
-    return context.accountExists(address);
+    return context.accountExists(new Address(address));
   }
 
   /** Get storage callback function. */
   static ByteBuffer get_storage(HostContext context, byte[] address, byte[] key) {
-    return ensureDirectBuffer(context.getStorage(address, key));
+    return context.getStorage(new Address(address), new Bytes32(key)).getByteBuffer();
   }
 
   /** Set storage callback function. */
   static int set_storage(HostContext context, byte[] address, byte[] key, byte[] value) {
-    return context.setStorage(address, key, value);
+    StorageStatus status =
+        context.setStorage(new Address(address), new Bytes32(key), new Bytes32(value));
+    return status.code;
   }
+
   /** Get balance callback function. */
   static ByteBuffer get_balance(HostContext context, byte[] address) {
-    return ensureDirectBuffer(context.getBalance(address));
+    return context.getBalance(new Address(address)).getByteBuffer();
   }
 
   /** Get code size callback function. */
   static int get_code_size(HostContext context, byte[] address) {
-    return context.getCodeSize(address);
+    return context.getCodeSize(new Address(address));
   }
 
   /** Get code hash callback function. */
   static ByteBuffer get_code_hash(HostContext context, byte[] address) {
-    return ensureDirectBuffer(context.getCodeHash(address));
+    return context.getCodeHash(new Address(address)).getByteBuffer();
   }
 
   /** Copy code callback function. */
   static ByteBuffer copy_code(HostContext context, byte[] address) {
-    return ensureDirectBuffer(context.getCode(address));
+    return ensureDirectBuffer(context.getCode(new Address(address)));
   }
 
   /** Selfdestruct callback function. */
   static void selfdestruct(HostContext context, byte[] address, byte[] beneficiary) {
-    context.selfdestruct(address, beneficiary);
+    context.selfdestruct(new Address(address), new Address(beneficiary));
   }
 
   /** Call callback function. */
-  static ByteBuffer call(HostContext context, ByteBuffer msg) {
-    return ensureDirectBuffer(context.call(msg));
+  static Result call(HostContext context, Message msg) {
+    return context.call(msg);
   }
 
   /** Get transaction context callback function. */
   static ByteBuffer get_tx_context(HostContext context) {
-    return ensureDirectBuffer(context.getTxContext());
+    return context.getTxContext().getByteBuffer();
   }
 
   /** Get block hash callback function. */
   static ByteBuffer get_block_hash_fn(HostContext context, long number) {
-    return ensureDirectBuffer(context.getBlockHash(number));
+    return context.getBlockHash(number).getByteBuffer();
   }
 
   /** Emit log callback function. */
@@ -81,7 +88,10 @@ static void emit_log(
       int data_size,
       byte[][] topics,
       int topic_count) {
-    context.emitLog(address, data, data_size, topics, topic_count);
+    context.emitLog(
+        new Address(address),
+        data,
+        Arrays.stream(topics).map(Bytes32::new).toArray(Bytes32[]::new));
   }
 
   /** Access account callback function. */

bindings/java/java/src/main/java/org/ethereum/evmc/HostContext.java

@@ -4,6 +4,7 @@
 package org.ethereum.evmc;
 
 import java.nio.ByteBuffer;
+import org.ethereum.evmc.types.*;
 
 /**
  * This interface represents the callback functions must be implemented in order to interface with
@@ -18,7 +19,7 @@ public interface HostContext {
    * @param address The address of the account the query is about.
    * @return true if exists, false otherwise.
    */
-  boolean accountExists(byte[] address);
+  boolean accountExists(Address address);
 
   /**
    * Access account function.
@@ -54,7 +55,7 @@ public interface HostContext {
    * @param key The index of the account's storage entry.
    * @return The storage value at the given storage key or null bytes if the account does not exist.
    */
-  ByteBuffer getStorage(byte[] address, byte[] key);
+  Bytes32 getStorage(Address address, Bytes32 key);
 
   /**
    * Set storage function.
@@ -69,7 +70,7 @@ public interface HostContext {
    * @param value The value to be stored.
    * @return The effect on the storage item.
    */
-  int setStorage(byte[] address, byte[] key, byte[] value);
+  StorageStatus setStorage(Address address, Bytes32 key, Bytes32 value);
 
   /**
    * Get balance function.
@@ -79,7 +80,7 @@ public interface HostContext {
    * @param address The address of the account.
    * @return The balance of the given account or 0 if the account does not exist.
    */
-  ByteBuffer getBalance(byte[] address);
+  Uint256 getBalance(Address address);
 
   /**
    * Get code size function.
@@ -90,7 +91,7 @@ public interface HostContext {
    * @param address The address of the account.
    * @return The size of the code in the account or 0 if the account does not exist.
    */
-  int getCodeSize(byte[] address);
+  int getCodeSize(Address address);
 
   /**
    * Get code hash function.
@@ -102,7 +103,7 @@ public interface HostContext {
    * @param address The address of the account.
    * @return The hash of the code in the account or null bytes if the account does not exist.
    */
-  ByteBuffer getCodeHash(byte[] address);
+  Bytes32 getCodeHash(Address address);
 
   /**
    * Copy code function.
@@ -115,7 +116,7 @@ public interface HostContext {
    * @param address The address of the account.
    * @return A copy of the requested code.
    */
-  ByteBuffer getCode(byte[] address);
+  ByteBuffer getCode(Address address);
 
   /**
    * Selfdestruct function.
@@ -126,15 +127,15 @@ public interface HostContext {
    * @param address The address of the contract to be selfdestructed.
    * @param beneficiary The address where the remaining ETH is going to be transferred.
    */
-  void selfdestruct(byte[] address, byte[] beneficiary);
+  void selfdestruct(Address address, Address beneficiary);
 
   /**
    * This function supports EVM calls.
    *
    * @param msg The call parameters.
    * @return The result of the call.
    */
-  ByteBuffer call(ByteBuffer msg);
+  Result call(Message msg);
 
   /**
    * Get transaction context function.
@@ -143,7 +144,7 @@ public interface HostContext {
    *
    * @return The transaction context.
    */
-  ByteBuffer getTxContext();
+  TxContext getTxContext();
 
   /**
    * Get block hash function.
@@ -155,7 +156,7 @@ public interface HostContext {
    * @param number The block number.
    * @return The block hash or null bytes if the information about the block is not available.
    */
-  ByteBuffer getBlockHash(long number);
+  Bytes32 getBlockHash(long number);
 
   /**
    * Log function.
@@ -165,9 +166,7 @@ public interface HostContext {
    *
    * @param address The address of the contract that generated the log.
    * @param data The unindexed data attached to the log.
-   * @param dataSize The length of the data.
    * @param topics The the array of topics attached to the log.
-   * @param topicCount The number of the topics. Valid values are between 0 and 4 inclusively.
    */
-  void emitLog(byte[] address, byte[] data, int dataSize, byte[][] topics, int topicCount);
+  void emitLog(Address address, byte[] data, Bytes32[] topics);
 }

bindings/java/java/src/main/java/org/ethereum/evmc/StorageStatus.java

@@ -0,0 +1,24 @@
+package org.ethereum.evmc;
+
+public enum StorageStatus {
+  /** The value of a storage item has been left unchanged: 0 -> 0 and X -> X. */
+  EVMC_STORAGE_UNCHANGED(0),
+
+  /** The value of a storage item has been modified: X -> Y. */
+  EVMC_STORAGE_MODIFIED(1),
+
+  /** A storage item has been modified after being modified before: X -> Y -> Z. */
+  EVMC_STORAGE_MODIFIED_AGAIN(2),
+
+  /** A new storage item has been added: 0 -> X. */
+  EVMC_STORAGE_ADDED(3),
+
+  /** A storage item has been deleted: X -> 0. */
+  EVMC_STORAGE_DELETED(4);
+
+  public final int code;
+
+  StorageStatus(int code) {
+    this.code = code;
+  }
+}

bindings/java/java/src/main/java/org/ethereum/evmc/types/Address.java

@@ -0,0 +1,21 @@
+// EVMC: Ethereum Client-VM Connector API.
+// Copyright 2019-2020 The EVMC Authors.
+// Licensed under the Apache License, Version 2.0.
+package org.ethereum.evmc.types;
+
+import java.nio.ByteBuffer;
+
+public class Address extends FixedLengthType {
+  @Override
+  protected int expectedLength() {
+    return 20;
+  }
+
+  public Address(byte[] data) {
+    super(data);
+  }
+
+  public Address(ByteBuffer data) {
+    super(data);
+  }
+}

bindings/java/java/src/main/java/org/ethereum/evmc/types/Bytes32.java

@@ -0,0 +1,18 @@
+// EVMC: Ethereum Client-VM Connector API.
+// Copyright 2019-2020 The EVMC Authors.
+// Licensed under the Apache License, Version 2.0.
+package org.ethereum.evmc.types;
+
+public class Bytes32 extends FixedLengthType {
+
+  public static final Bytes32 EMPTY = new Bytes32(new byte[32]);
+
+  @Override
+  protected int expectedLength() {
+    return 32;
+  }
+
+  public Bytes32(byte[] data) {
+    super(data);
+  }
+}

bindings/java/java/src/main/java/org/ethereum/evmc/types/FixedLengthType.java

@@ -0,0 +1,60 @@
+// EVMC: Ethereum Client-VM Connector API.
+// Copyright 2019-2020 The EVMC Authors.
+// Licensed under the Apache License, Version 2.0.
+package org.ethereum.evmc.types;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.Arrays;
+
+public abstract class FixedLengthType {
+  protected abstract int expectedLength();
+
+  private final byte[] data;
+
+  public byte[] get() {
+    return this.data;
+  }
+
+  public ByteBuffer getByteBuffer() {
+    // This is big endian by default, which is what we want.
+    return ByteBuffer.allocateDirect(this.data.length).put(this.data);
+  }
+
+  public FixedLengthType(byte[] data) {
+    if (data == null) {
+      throw new IllegalArgumentException("data cannot be null");
+    }
+    if (data.length != expectedLength()) {
+      throw new IllegalArgumentException(
+          "data length expected to be " + expectedLength() + ", was " + data.length);
+    }
+    this.data = data;
+  }
+
+  public FixedLengthType(ByteBuffer data) {
+    if (data == null) {
+      throw new IllegalArgumentException("data cannot be null");
+    }
+    int length = data.remaining();
+    if (length != expectedLength()) {
+      throw new IllegalArgumentException(
+          "data length expected to be " + expectedLength() + ", was " + length);
+    }
+    this.data = new byte[length];
+    data.order(ByteOrder.BIG_ENDIAN).get(this.data, 0, length);
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) return true;
+    if (o == null || getClass() != o.getClass()) return false;
+    FixedLengthType that = (FixedLengthType) o;
+    return Arrays.equals(data, that.data);
+  }
+
+  @Override
+  public int hashCode() {
+    return Arrays.hashCode(data);
+  }
+}