@Override
      public int compareTo(byte[] buffer1, int offset1, int length1, byte[] buffer2, int offset2,
        int length2) {

        // Short circuit equal case
        if (buffer1 == buffer2 && offset1 == offset2 && length1 == length2) {
          return 0;
        }
        final int stride = 8;
        final int minLength = Math.min(length1, length2);
        int strideLimit = minLength & ~(stride - 1);
        final long offset1Adj = offset1 + UnsafeAccess.BYTE_ARRAY_BASE_OFFSET;
        final long offset2Adj = offset2 + UnsafeAccess.BYTE_ARRAY_BASE_OFFSET;
        int i;

        /*
         * Compare 8 bytes at a time. Benchmarking on x86 shows a stride of 8 bytes is no slower
         * than 4 bytes even on 32-bit. On the other hand, it is substantially faster on 64-bit.
         */
        for (i = 0; i < strideLimit; i += stride) {
          long lw = HBasePlatformDependent.getLong(buffer1, offset1Adj + i);
          long rw = HBasePlatformDependent.getLong(buffer2, offset2Adj + i);
          if (lw != rw) {
            if (!UnsafeAccess.LITTLE_ENDIAN) {
              return ((lw + Long.MIN_VALUE) < (rw + Long.MIN_VALUE)) ? -1 : 1;
            }

            /*
             * We want to compare only the first index where left[index] != right[index]. This
             * corresponds to the least significant nonzero byte in lw ^ rw, since lw and rw are
             * little-endian. Long.numberOfTrailingZeros(diff) tells us the least significant
             * nonzero bit, and zeroing out the first three bits of L.nTZ gives us the shift to get
             * that least significant nonzero byte. This comparison logic is based on UnsignedBytes
             * comparator from guava v21
             */
            int n = Long.numberOfTrailingZeros(lw ^ rw) & ~0x7;
            return ((int) ((lw >>> n) & 0xFF)) - ((int) ((rw >>> n) & 0xFF));
          }
        }

        // The epilogue to cover the last (minLength % stride) elements.
        for (; i < minLength; i++) {
          int a = (buffer1[offset1 + i] & 0xFF);
          int b = (buffer2[offset2 + i] & 0xFF);
          if (a != b) {
            return a - b;
          }
        }
        return length1 - length2;
      }
Lexicographically compare two arrays.
@param buffer1 left operand
@param buffer2 right operand
@param offset1 Where to start comparing in the left buffer
@param offset2 Where to start comparing in the right buffer
@param length1 How much to compare from the left buffer
@param length2 How much to compare from the right buffer
@return 0 if equal, < 0 if left is less than right, etc.
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Bytes.java