Fixed crash when reading DWARF V2.

Fix _mapKeyToItem when on duplicate key exist.
Remove _items list. It is useless with __mapItems.Values.
Rename _mapItems to _mapUlongToItems.
Add TryFindByKey to be symmetric with TryFindByCode. Good reason to keep mapKeyToItem.

Author: dupont-al-videotron-ca

src/LibObjectFile/Dwarf/DwarfAbbreviation.cs

@@ -6,77 +6,53 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using LibObjectFile.Diagnostics;
 
 namespace LibObjectFile.Dwarf;
 
 [DebuggerDisplay("{" + nameof(DebuggerDisplay) + ",nq}")]
 public sealed class DwarfAbbreviation : DwarfObject<DwarfAbbreviationTable>
 {
-    private readonly List<DwarfAbbreviationItem> _items;
-    private readonly Dictionary<ulong, DwarfAbbreviationItem> _mapItems; // Only used if code are non contiguous
+    private readonly Dictionary<ulong, DwarfAbbreviationItem> _mapUlongToItems;
+
     private readonly Dictionary<DwarfAbbreviationItemKey, DwarfAbbreviationItem> _mapKeyToItem;
     private ulong _nextCode;
 
     public DwarfAbbreviation()
     {
-        _items = new List<DwarfAbbreviationItem>();
-        _mapItems = new Dictionary<ulong, DwarfAbbreviationItem>();
+        _mapUlongToItems = new Dictionary<ulong, DwarfAbbreviationItem>();
         _mapKeyToItem = new Dictionary<DwarfAbbreviationItemKey, DwarfAbbreviationItem>();
         _nextCode = 1;
     }
 
     public void Reset()
     {
         // Reset parent dependency
-        foreach (var dwarfAbbreviationItem in _items)
-        {
-            dwarfAbbreviationItem.Parent = null;
-        }
-
-        if (_mapItems.Count > 0)
+        foreach (var keyPair in _mapUlongToItems.Values)
         {
-            foreach (var keyPair in _mapItems)
-            {
-                keyPair.Value.Parent = null;
-            }
+            keyPair.Parent = null;
         }
-
-        _items.Clear();
-        _mapItems.Clear();
+        _mapUlongToItems.Clear();
         _mapKeyToItem.Clear();
         _nextCode = 1;
     }
 
-    public IEnumerable<DwarfAbbreviationItem> Items => _mapItems.Count > 0 ? GetMapItems() : _items;
+    public IEnumerable<DwarfAbbreviationItem> Items => _mapUlongToItems.Values;
 
-    private IEnumerable<DwarfAbbreviationItem> GetMapItems()
-    {
-        foreach (var item in _mapItems.Values)
-        {
-            yield return item;
-        }
-    }
-        
     public DwarfAbbreviationItem GetOrCreate(DwarfAbbreviationItemKey itemKey)
     {
-        if (!_mapKeyToItem.TryGetValue(itemKey, out var item))
+        if (!TryFindByKey(itemKey, out var item))
         {
             item = new DwarfAbbreviationItem(_nextCode, itemKey.Tag, itemKey.HasChildren, itemKey.Descriptors)
             {
                 Parent = this
             };
 
-            if (_mapItems.Count > 0)
-            {
-
-                _mapItems[_nextCode] = item;
-            }
-            else
-            {
-                _items.Add(item);
-            }
+            // insert or update new item
+            _mapUlongToItems[_nextCode] = item;
 
+            // not found insert new item
             _mapKeyToItem[itemKey] = item;
 
             _nextCode++;
@@ -93,24 +69,16 @@ public bool TryFindByCode(ulong code, [NotNullWhen(true)] out DwarfAbbreviationI
             return false;
         }
 
-        code--;
-
-        if (_mapItems.Count > 0)
-        {
-            return _mapItems.TryGetValue(code, out item);
-        }
-
-        if (code < int.MaxValue && (int)code < _items.Count)
-        {
-            item = _items[(int) code];
-            return true;
-        }
+        return _mapUlongToItems.TryGetValue(code, out item);
+    }
 
+    public bool TryFindByKey(DwarfAbbreviationItemKey key, [NotNullWhen(true)] out DwarfAbbreviationItem? item)
+    {
         item = null;
-        return false;
+        return _mapKeyToItem.TryGetValue(key, out item);
     }
 
-    private string DebuggerDisplay => $"Count = {(_mapItems.Count > 0 ? _mapItems.Count : _items.Count)}";
+    private string DebuggerDisplay => $"Count = {_mapUlongToItems.Count}";
 
     private bool TryReadNext(DwarfReader reader)
     {
@@ -123,45 +91,27 @@ private bool TryReadNext(DwarfReader reader)
 
         var item = new DwarfAbbreviationItem
         {
-            Position = startOffset, 
+            Position = startOffset,
             Code = code
         };
 
-        var index = code - 1;
-        bool canAddToList = _mapItems.Count == 0 && index < int.MaxValue && _items.Count == (int)index;
-
         item.Read(reader);
 
-        if (canAddToList)
+        if (_mapUlongToItems.ContainsKey(code))
         {
-            _items.Add(item);
-            _nextCode++;
+            reader.Diagnostics.Error(DiagnosticId.DWARF_ERR_InvalidData, $"Invalid code {code} found while another code already exists in this abbreviation.");
+            return false;
         }
-        else
-        {
-            if (_mapItems.Count == 0)
-            {
-                for (var i = 0; i < _items.Count; i++)
-                {
-                    var previousItem = _items[i];
-                    _mapItems.Add((ulong)i + 1, previousItem);
-                }
-                _items.Clear();
-            }
-
-            // TODO: check collisions
-            if (_mapItems.ContainsKey(code))
-            {
-                reader.Diagnostics.Error(DiagnosticId.DWARF_ERR_InvalidData, $"Invalid code {code} found while another code already exists in this abbreviation.");
-                return false;
-            }
-            _mapItems.Add(code, item);
 
-            _nextCode = Math.Max(code, _nextCode) + 1;
-        }
+        _mapUlongToItems.Add(code, item);
+        _nextCode = Math.Max(code, _nextCode) + 1;
 
         var key = new DwarfAbbreviationItemKey(item.Tag, item.HasChildren, item.Descriptors);
-        _mapKeyToItem.Add(key, item);
+
+        if (!_mapKeyToItem.ContainsKey(key))
+        {
+            _mapKeyToItem.Add(key, item);
+        }
 
         return true;
     }
@@ -180,24 +130,9 @@ public override void Write(DwarfWriter writer)
     {
         var startOffset = writer.Position;
         Debug.Assert(startOffset == Position);
-        if (_mapItems.Count > 0)
+        foreach (var item in _mapUlongToItems.Values)
         {
-            foreach (var itemPair in _mapItems)
-            {
-                var item = itemPair.Value;
-                item.Write(writer);
-            }
-
-        }
-        else
-        {
-            if (_items.Count > 0)
-            {
-                foreach (var item in _items)
-                {
-                    item.Write(writer);
-                }
-            }
+            item.Write(writer);
         }
 
         // End of abbreviation item
@@ -210,28 +145,11 @@ protected override void UpdateLayoutCore(DwarfLayoutContext context)
     {
         var endOffset = Position;
 
-        if (_mapItems.Count > 0)
+        foreach (var item in _mapUlongToItems.Values)
         {
-            foreach (var itemPair in _mapItems)
-            {
-                var item = itemPair.Value;
-                item.Position = endOffset;
-                item.UpdateLayout(context);
-                endOffset += item.Size;
-            }
-
-        }
-        else
-        {
-            if (_items.Count > 0)
-            {
-                foreach (var item in _items)
-                {
-                    item.Position = endOffset;
-                    item.UpdateLayout(context);
-                    endOffset += item.Size;
-                }
-            }
+            item.Position = endOffset;
+            item.UpdateLayout(context);
+            endOffset += item.Size;
         }
 
         endOffset += DwarfHelper.SizeOfULEB128(0);