From 1a515475a69d42bd4a311a5e38a655631848647a Mon Sep 17 00:00:00 2001
From: at055612 <at055612@gmail.com>
Date: Thu, 12 Nov 2020 09:06:43 +0000
Subject: [PATCH] gh-169 Fix AbsatractByteBufferProxy.compareBuff, improve
 ComparatorTest

---
 .../java/org/lmdbjava/ByteBufferProxy.java    |  4 +--
 .../java/org/lmdbjava/ComparatorTest.java     | 36 +++++++++++++++++--
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/src/main/java/org/lmdbjava/ByteBufferProxy.java b/src/main/java/org/lmdbjava/ByteBufferProxy.java
index 9d1b0f8..5ded7b7 100644
--- a/src/main/java/org/lmdbjava/ByteBufferProxy.java
+++ b/src/main/java/org/lmdbjava/ByteBufferProxy.java
@@ -133,7 +133,7 @@ public static int compareBuff(final ByteBuffer o1, final ByteBuffer o2) {
       final int minWords = minLength / Long.BYTES;
 
       final boolean reverse1 = o1.order() == LITTLE_ENDIAN;
-      final boolean reverse2 = o1.order() == LITTLE_ENDIAN;
+      final boolean reverse2 = o2.order() == LITTLE_ENDIAN;
       for (int i = 0; i < minWords * Long.BYTES; i += Long.BYTES) {
         final long lw = reverse1 ? reverseBytes(o1.getLong(i)) : o1.getLong(i);
         final long rw = reverse2 ? reverseBytes(o2.getLong(i)) : o2.getLong(i);
@@ -152,7 +152,7 @@ public static int compareBuff(final ByteBuffer o1, final ByteBuffer o2) {
         }
       }
 
-      return o1.capacity() - o2.capacity();
+      return o1.remaining() - o2.remaining();
     }
 
     static Field findField(final Class<?> c, final String name) {
diff --git a/src/test/java/org/lmdbjava/ComparatorTest.java b/src/test/java/org/lmdbjava/ComparatorTest.java
index e849983..44d40cf 100644
--- a/src/test/java/org/lmdbjava/ComparatorTest.java
+++ b/src/test/java/org/lmdbjava/ComparatorTest.java
@@ -33,6 +33,7 @@
 import static org.lmdbjava.DirectBufferProxy.PROXY_DB;
 
 import java.nio.ByteBuffer;
+import java.util.Arrays;
 import java.util.Comparator;
 
 import com.google.common.primitives.SignedBytes;
@@ -156,9 +157,38 @@ private static class ByteBufferRunner implements ComparatorRunner {
 
     @Override
     public int compare(final byte[] o1, final byte[] o2) {
-      final ByteBuffer o1b = ByteBuffer.wrap(o1);
-      final ByteBuffer o2b = ByteBuffer.wrap(o2);
-      return PROXY_OPTIMAL.compare(o1b, o2b);
+      // Convert arrays to buffers that are larger than the array, with
+      // limit set at the array length. One buffer bigger than the other.
+      ByteBuffer o1b = arrayToBuffer(o1, o1.length * 3);
+      ByteBuffer o2b = arrayToBuffer(o2, o2.length * 2);
+      final int result = PROXY_OPTIMAL.compare(o1b, o2b);
+
+      // Now swap which buffer is bigger
+      o1b = arrayToBuffer(o1, o1.length * 2);
+      o2b = arrayToBuffer(o2, o2.length * 3);
+      final int result2 = PROXY_OPTIMAL.compare(o1b, o2b);
+
+      assertThat(result2, is(result));
+
+      // Now try with buffers sized to the array.
+      o1b = ByteBuffer.wrap(o1);
+      o2b = ByteBuffer.wrap(o2);
+      final int result3 = PROXY_OPTIMAL.compare(o1b, o2b);
+
+      assertThat(result3, is(result));
+
+      return result;
+    }
+
+    private ByteBuffer arrayToBuffer(final byte[] arr, final int bufferCapacity) {
+      if (bufferCapacity < arr.length) {
+        throw new IllegalArgumentException("bufferCapacity < arr.length");
+      }
+      final byte[] newArr = Arrays.copyOf(arr, bufferCapacity);
+      final ByteBuffer byteBuffer = ByteBuffer.wrap(newArr);
+      byteBuffer.limit(arr.length);
+      byteBuffer.position(0);
+      return byteBuffer;
     }
   }