From 7ae77904b349729d469a529b15b892157dd2ce29 Mon Sep 17 00:00:00 2001
From: Matthew Swift <matthew.swift@forgerock.com>
Date: Thu, 02 Apr 2015 10:16:45 +0000
Subject: [PATCH] OPENDJ-1711 - re-implement VLV support for pluggable backends

---
 opendj-sdk/opendj-server-legacy/src/test/java/org/opends/server/backends/pluggable/ControlsTestCase.java |   71 +++++++++++++++++++++++
 opendj-sdk/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/VLVIndex.java         |   50 ++++++++++++----
 2 files changed, 108 insertions(+), 13 deletions(-)

diff --git a/opendj-sdk/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/VLVIndex.java b/opendj-sdk/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/VLVIndex.java
index 0c865cc..b8f037c 100644
--- a/opendj-sdk/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/VLVIndex.java
+++ b/opendj-sdk/opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/VLVIndex.java
@@ -607,7 +607,7 @@
       final ByteStringBuilder encodedPrimaryKey = new ByteStringBuilder(assertion.length() + 10);
       final MatchingRule matchingRule = primarySortKey.getAttributeType().getOrderingMatchingRule();
       final ByteString normalizedAttributeValue = matchingRule.normalizeAttributeValue(assertion);
-      encodeVLVKeyValue(primarySortKey, normalizedAttributeValue, encodedPrimaryKey);
+      encodeVLVKeyValue(normalizedAttributeValue, encodedPrimaryKey, primarySortKey.ascending());
       return encodedPrimaryKey;
     }
     catch (final DecodeException e)
@@ -803,37 +803,61 @@
           }
         }
       }
-      encodeVLVKeyValue(sortKey, sortValue, builder);
+      encodeVLVKeyValue(sortValue, builder, sortKey.ascending());
     }
   }
 
-  private static void encodeVLVKeyValue(final SortKey sortKey, final ByteString normalizedAttributeValue,
-      final ByteStringBuilder builder)
+  /**
+   * Package private for testing.
+   * <p>
+   * Keys are logically encoded as follows:
+   * <ul>
+   * <li>if the key is {@code null} then append {@code 0xff} in order to ensure that all
+   * {@code null} keys sort after non-{@code null} keys in ascending order
+   * <li>else
+   * <ul>
+   * <li>escape any bytes that look like a separator byte ({@code 0x00}) or a separator escape byte
+   * ({@code 0x01}) by prefixing the byte with a separator escape byte ({@code 0x01})
+   * <li>escape the first byte if it looks like a null key byte ({@code 0xff}) or a null key escape
+   * byte ({@code 0xfe}) by prefixing the byte with a null key escape byte ({@code 0xfe})
+   * </ul>
+   * <li>append a separator byte ({@code 0x00}) which will be used for distinguishing between the
+   * end of the key and the start of the next key
+   * <li>invert all the bytes if the sort order is descending.
+   * </ul>
+   */
+  static void encodeVLVKeyValue(final ByteString keyBytes, final ByteStringBuilder builder,
+      final boolean ascending)
   {
-    final boolean ascending = sortKey.ascending();
     final byte separator = ascending ? (byte) 0x00 : (byte) 0xff;
-    if (normalizedAttributeValue != null)
+    if (keyBytes != null)
     {
-      // Ensure that all keys sort before (ascending) or after (descending) missing keys.
-      builder.append(separator);
-
       final byte escape = ascending ? (byte) 0x01 : (byte) 0xfe;
       final byte sortOrderMask = separator;
-      final int length = normalizedAttributeValue.length();
+      final int length = keyBytes.length();
       for (int i = 0; i < length; i++)
       {
-        final byte b = normalizedAttributeValue.byteAt(i);
-        if (b == separator || b == escape)
+        final byte b = keyBytes.byteAt(i);
+        if ((b & (byte) 0x01) == b)
         {
+          // Escape bytes that look like a separator.
           builder.append(escape);
         }
+        else if (i == 0 && (b & (byte) 0xfe) == (byte) 0xfe)
+        {
+          /*
+           * Ensure that all keys sort before (ascending) or after (descending) null keys, by
+           * escaping the first byte if it looks like a null key.
+           */
+          builder.append((byte) ~escape);
+        }
         // Invert the bits if this key is in descending order.
         builder.append((byte) (b ^ sortOrderMask));
       }
     }
     else
     {
-      // Ensure that missing keys sort after (ascending) or before (descending) all other keys.
+      // Ensure that null keys sort after (ascending) or before (descending) all other keys.
       builder.append(ascending ? (byte) 0xff : (byte) 0x00);
     }
     builder.append(separator);
diff --git a/opendj-sdk/opendj-server-legacy/src/test/java/org/opends/server/backends/pluggable/ControlsTestCase.java b/opendj-sdk/opendj-server-legacy/src/test/java/org/opends/server/backends/pluggable/ControlsTestCase.java
index 85060d2..061a550 100644
--- a/opendj-sdk/opendj-server-legacy/src/test/java/org/opends/server/backends/pluggable/ControlsTestCase.java
+++ b/opendj-sdk/opendj-server-legacy/src/test/java/org/opends/server/backends/pluggable/ControlsTestCase.java
@@ -43,6 +43,7 @@
 
 import org.forgerock.opendj.config.server.ConfigException;
 import org.forgerock.opendj.ldap.ByteString;
+import org.forgerock.opendj.ldap.ByteStringBuilder;
 import org.forgerock.opendj.ldap.ResultCode;
 import org.forgerock.opendj.ldap.SearchScope;
 import org.opends.server.DirectoryServerTestCase;
@@ -169,6 +170,76 @@
   }
 
   @DataProvider
+  private Object[][] encodedKeyDataProvider()
+  {
+    // @formatter:off
+    return new Object[][] {
+      // Null keys sort after everything else.
+      { null,           null,           0 },
+      { "",             null,          -1 },
+      { null,           "",             1 },
+      { "00",           null,          -1 },
+      { null,           "00",           1 },
+      { "ff",           null,          -1 },
+      { null,           "ff",           1 },
+
+      // Empty keys sort before everything else.
+      { "",             "",             0 },
+      { "00",           "",             1 },
+      { "",             "00",          -1 },
+      { "ff",           "",             1 },
+      { "",             "ff",          -1 },
+
+      // Bytes comparisons are unsigned.
+      { "00",           "00",           0 },
+      { "00",           "ff",          -1 },
+      { "ff",           "00",           1 },
+      { "ff",           "ff",           0 },
+
+      // Short keys sort before long keys.
+      { "0000",         "00",           1 },
+      { "00",           "0000",        -1 },
+      { "ffff",         "ff",           1 },
+      { "ff",           "ffff",        -1 },
+      { "0000",         "0000",         0 },
+      { "ffff",         "ffff",         0 },
+      { "0000",         "ffff",        -1 },
+      { "ffff",         "0000",         1 },
+    };
+    // @formatter:on
+  }
+
+  @Test(dataProvider = "encodedKeyDataProvider")
+  public void vlvKeyEncodingGenerateCorrectAscendingSortOrder(String key1, String key2, int expectedCompareResult)
+  {
+    ByteString bytes1 = key1 != null ? ByteString.valueOfHex(key1) : null;
+    ByteStringBuilder encodedBytes1 = new ByteStringBuilder();
+    VLVIndex.encodeVLVKeyValue(bytes1, encodedBytes1, true);
+
+    ByteString bytes2 = key2 != null ? ByteString.valueOfHex(key2) : null;
+    ByteStringBuilder encodedBytes2 = new ByteStringBuilder();
+    VLVIndex.encodeVLVKeyValue(bytes2, encodedBytes2, true);
+
+    int actualResult = Math.min(Math.max(encodedBytes1.compareTo(encodedBytes2), -1), 1);
+    assertThat(actualResult).isEqualTo(expectedCompareResult);
+  }
+
+  @Test(dataProvider = "encodedKeyDataProvider")
+  public void vlvKeyEncodingGenerateCorrectDescendingSortOrder(String key1, String key2, int expectedCompareResult)
+  {
+    ByteString bytes1 = key1 != null ? ByteString.valueOfHex(key1) : null;
+    ByteStringBuilder encodedBytes1 = new ByteStringBuilder();
+    VLVIndex.encodeVLVKeyValue(bytes1, encodedBytes1, false);
+
+    ByteString bytes2 = key2 != null ? ByteString.valueOfHex(key2) : null;
+    ByteStringBuilder encodedBytes2 = new ByteStringBuilder();
+    VLVIndex.encodeVLVKeyValue(bytes2, encodedBytes2, false);
+
+    int actualResult = Math.min(Math.max(encodedBytes1.compareTo(encodedBytes2), -1), 1);
+    assertThat(actualResult).isEqualTo(-expectedCompareResult);
+  }
+
+  @DataProvider
   private Object[][] indexedVlvByAssertionDataProvider()
   {
     // @formatter:off

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