HBASE-22504 Optimize the MultiByteBuff#get(ByteBuffer, offset, len)

hbase-common/src/main/java/org/apache/hadoop/hbase/nio/MultiByteBuff.java

@@ -598,8 +598,7 @@ public class MultiByteBuff extends ByteBuff {
     sourceOffset = sourceOffset - this.itemBeginPos[itemIndex];
     while (length > 0) {
       int toRead = Math.min((item.limit() - sourceOffset), length);
-      ByteBufferUtils.copyFromBufferToArray(dst, item, sourceOffset, offset,
-          toRead);
+      ByteBufferUtils.copyFromBufferToArray(dst, item, sourceOffset, offset, toRead);
       length -= toRead;
       if (length == 0) break;
       itemIndex++;
@@ -1020,24 +1019,30 @@ public class MultiByteBuff extends ByteBuff {
     }
     pair.setFirst(ByteBuffer.wrap(dst));
     pair.setSecond(0);
-    return;
   }
 
   /**
    * Copies the content from an this MBB to a ByteBuffer
-   * @param out the ByteBuffer to which the copy has to happen
-   * @param sourceOffset the offset in the MBB from which the elements has
-   * to be copied
+   * @param out the ByteBuffer to which the copy has to happen, its position will be advanced.
+   * @param sourceOffset the offset in the MBB from which the elements has to be copied
    * @param length the length in the MBB upto which the elements has to be copied
    */
   @Override
-  public void get(ByteBuffer out, int sourceOffset,
-      int length) {
+  public void get(ByteBuffer out, int sourceOffset, int length) {
     checkRefCount();
-      // Not used from real read path actually. So not going with
-      // optimization
-    for (int i = 0; i < length; ++i) {
-      out.put(this.get(sourceOffset + i));
+    int itemIndex = getItemIndex(sourceOffset);
+    ByteBuffer in = this.items[itemIndex];
+    sourceOffset = sourceOffset - this.itemBeginPos[itemIndex];
+    while (length > 0) {
+      int toRead = Math.min(in.limit() - sourceOffset, length);
+      ByteBufferUtils.copyFromBufferToBuffer(in, out, sourceOffset, toRead);
+      length -= toRead;
+      if (length == 0) {
+        break;
+      }
+      itemIndex++;
+      in = this.items[itemIndex];
+      sourceOffset = 0;
     }
   }
 

hbase-common/src/main/java/org/apache/hadoop/hbase/util/ByteBufferUtils.java

@@ -721,8 +721,8 @@ public final class ByteBufferUtils {
    * @param sourceOffset offset in the source buffer
    * @param length how many bytes to copy
    */
-  public static void copyFromBufferToBuffer(ByteBuffer in,
-      ByteBuffer out, int sourceOffset, int length) {
+  public static void copyFromBufferToBuffer(ByteBuffer in, ByteBuffer out, int sourceOffset,
+      int length) {
     if (in.hasArray() && out.hasArray()) {
       System.arraycopy(in.array(), sourceOffset + in.arrayOffset(), out.array(), out.position()
           + out.arrayOffset(), length);
@@ -737,27 +737,6 @@ public final class ByteBufferUtils {
     }
   }
 
-  /**
-   * Find length of common prefix of two parts in the buffer
-   * @param buffer Where parts are located.
-   * @param offsetLeft Offset of the first part.
-   * @param offsetRight Offset of the second part.
-   * @param limit Maximal length of common prefix.
-   * @return Length of prefix.
-   */
-  public static int findCommonPrefix(ByteBuffer buffer, int offsetLeft,
-      int offsetRight, int limit) {
-    int prefix = 0;
-
-    for (; prefix < limit; ++prefix) {
-      if (buffer.get(offsetLeft + prefix) != buffer.get(offsetRight + prefix)) {
-        break;
-      }
-    }
-
-    return prefix;
-  }
-
   /**
    * Find length of common prefix in two arrays.
    * @param left Array to be compared.

hbase-common/src/test/java/org/apache/hadoop/hbase/nio/TestMultiByteBuff.java

@@ -457,4 +457,29 @@ public class TestMultiByteBuff {
     assertEquals(i, mbb.getInt());
     assertEquals(l, mbb.getLong());
   }
+
+  @Test
+  public void testGetByteBufferWithOffsetAndPos() {
+    byte[] a = Bytes.toBytes("abcd");
+    byte[] b = Bytes.toBytes("efghijkl");
+    ByteBuffer aa = ByteBuffer.wrap(a);
+    ByteBuffer bb = ByteBuffer.wrap(b);
+    MultiByteBuff mbb = new MultiByteBuff(aa, bb);
+    ByteBuffer out = ByteBuffer.allocate(12);
+    mbb.get(out, 0, 1);
+    assertEquals(out.position(), 1);
+    assertTrue(Bytes.equals(Bytes.toBytes("a"), 0, 1, out.array(), 0, 1));
+
+    mbb.get(out, 1, 4);
+    assertEquals(out.position(), 5);
+    assertTrue(Bytes.equals(Bytes.toBytes("abcde"), 0, 5, out.array(), 0, 5));
+
+    mbb.get(out, 10, 1);
+    assertEquals(out.position(), 6);
+    assertTrue(Bytes.equals(Bytes.toBytes("abcdek"), 0, 6, out.array(), 0, 6));
+
+    mbb.get(out, 0, 6);
+    assertEquals(out.position(), 12);
+    assertTrue(Bytes.equals(Bytes.toBytes("abcdekabcdef"), 0, 12, out.array(), 0, 12));
+  }
 }