From 4635d9b36bfc6528d4e64386f73ca605c80cc83f Mon Sep 17 00:00:00 2001
From: Ahmed Yasin Koculu <koculu@gmail.com>
Date: Mon, 8 Aug 2022 04:18:35 +0200
Subject: [PATCH] Fix multi segment incorrect key meta data issue.

---
 .../Segments/Disk/MultiSectorDiskSegment.cs   | 47 ++++++++++++-------
 .../Disk/MultiSectorDiskSegmentCreator.cs     | 12 ++---
 2 files changed, 37 insertions(+), 22 deletions(-)

diff --git a/src/ZoneTree/Segments/Disk/MultiSectorDiskSegment.cs b/src/ZoneTree/Segments/Disk/MultiSectorDiskSegment.cs
index 3152c0a..bf8356b 100644
--- a/src/ZoneTree/Segments/Disk/MultiSectorDiskSegment.cs
+++ b/src/ZoneTree/Segments/Disk/MultiSectorDiskSegment.cs
@@ -308,19 +308,47 @@ public sealed class MultiSectorDiskSegment<TKey, TValue> : IDiskSegment<TKey, TV
     {
         var off = 0;
         var sectorIndex = 0;
-        while (off + Sectors[sectorIndex].Length <= index)
+        var len = Sectors[sectorIndex].Length;
+        while (off + len <= index)
         {
-            off += Sectors[sectorIndex].Length;
+            off += len;
             ++sectorIndex;
+            len = Sectors[sectorIndex].Length;
         }
         var localIndex = index - off;
+
+        if (localIndex == 0)
+            return SectorKeys[sectorIndex*2];
+        if (localIndex == len - 1)
+            return SectorKeys[sectorIndex * 2 + 1];
+
         var key = Sectors[sectorIndex].GetKey(localIndex);
         return key;
     }
 
+    public TValue GetValue(int index)
+    {
+        var off = 0;
+        var sectorIndex = 0;
+        var len = Sectors[sectorIndex].Length;
+        while (off + len <= index)
+        {
+            off += len;
+            ++sectorIndex;
+            len = Sectors[sectorIndex].Length;
+        }
+        var localIndex = index - off;
+
+        if (localIndex == 0)
+            return SectorValues[sectorIndex * 2];
+        if (localIndex == len - 1)
+            return SectorValues[sectorIndex * 2 + 1];
+
+        return Sectors[sectorIndex].GetValue(localIndex);
+    }
+
     public int GetLastSmallerOrEqualPosition(in TKey key)
     {
-        var sparseArrayLength = SectorKeys.Length;
         (var left, var found) = SearchLastSmallerOrEqualPositionInSparseArray(in key);
         var sectorIndex = left / 2;
         var isStartOfSector = left % 2 == 0 ? 1 : 0;
@@ -359,19 +387,6 @@ public sealed class MultiSectorDiskSegment<TKey, TValue> : IDiskSegment<TKey, TV
         return new SeekableIterator<TKey, TValue>(this);
     }
 
-    public TValue GetValue(int index)
-    {
-        var off = 0;
-        var sectorIndex = 0;
-        while (off + Sectors[sectorIndex].Length <= index)
-        {
-            off += Sectors[sectorIndex].Length;
-            ++sectorIndex;
-        }
-        var localIndex = index - off;
-        return Sectors[sectorIndex].GetValue(localIndex);
-    }
-
     public void InitSparseArray(int size)
     {
     }
diff --git a/src/ZoneTree/Segments/Disk/MultiSectorDiskSegmentCreator.cs b/src/ZoneTree/Segments/Disk/MultiSectorDiskSegmentCreator.cs
index 89ce0da..d0e5aee 100644
--- a/src/ZoneTree/Segments/Disk/MultiSectorDiskSegmentCreator.cs
+++ b/src/ZoneTree/Segments/Disk/MultiSectorDiskSegmentCreator.cs
@@ -155,10 +155,10 @@ public sealed class MultiSectorDiskSegmentCreator<TKey, TValue> : IDiskSegmentCr
     {
         var len = Sectors.Count * 2;
         bw.Write(len);
-        for (var i = 0; i < len; i += 2)
+        for (var i = 0; i < len; ++i)
         {
-            var a = i / 2;
-            var b = a + 1;
+            var a = i++;
+            var b = i;
             var k1 = SectorKeys[a];
             var bytes = KeySerializer.Serialize(k1);
             bw.Write(bytes.Length);
@@ -175,10 +175,10 @@ public sealed class MultiSectorDiskSegmentCreator<TKey, TValue> : IDiskSegmentCr
     {
         var len = Sectors.Count * 2;
         bw.Write(len);
-        for (var i = 0; i < len; i += 2)
+        for (var i = 0; i < len; ++i)
         {
-            var a = i / 2;
-            var b = a + 1;
+            var a = i++;
+            var b = i;
             var v1 = SectorValues[a];
             var bytes = ValueSerializer.Serialize(v1);
             bw.Write(bytes.Length);