Merge branch '3.0-poc' into 3.0-poc-draft

Author: jeremy-visionaid

OpenMcdf3/CfbBinaryReader.cs

@@ -7,23 +7,34 @@ namespace OpenMcdf3;
 /// </summary>
 internal sealed class CfbBinaryReader : BinaryReader
 {
+    readonly byte[] guidBuffer = new byte[16];
     readonly byte[] buffer = new byte[DirectoryEntry.NameFieldLength];
 
     public CfbBinaryReader(Stream input)
         : base(input, Encoding.Unicode, true)
     {
     }
 
-    public Guid ReadGuid() => new(ReadBytes(16));
+    public Guid ReadGuid()
+    {
+        int bytesRead = 0;
+        do
+        {
+            int n = Read(guidBuffer, bytesRead, guidBuffer.Length - bytesRead);
+            if (n == 0)
+                throw new EndOfStreamException();
+            bytesRead += n;
+        } while (bytesRead < guidBuffer.Length);
+
+        return new Guid(guidBuffer);
+    }
 
     public DateTime ReadFileTime()
     {
         long fileTime = ReadInt64();
         return DateTime.FromFileTimeUtc(fileTime);
     }
 
-    private void ReadBytes(byte[] buffer) => Read(buffer, 0, buffer.Length);
-
     public Header ReadHeader()
     {
         Header header = new();
@@ -90,8 +101,9 @@ public DirectoryEntry ReadDirectoryEntry(Version version)
 
         DirectoryEntry entry = new();
         Read(buffer, 0, DirectoryEntry.NameFieldLength);
-        int nameLength = Math.Max(0, ReadUInt16() - 2);
-        entry.Name = Encoding.Unicode.GetString(buffer, 0, nameLength);
+        ushort nameLength = ReadUInt16();
+        int clampedNameLength = Math.Max(0, Math.Min(ushort.MaxValue, nameLength - 2));
+        entry.Name = Encoding.Unicode.GetString(buffer, 0, clampedNameLength);
         entry.Type = ReadStorageType();
         entry.Color = ReadColor();
         entry.LeftSiblingId = ReadUInt32();

OpenMcdf3/FatSectorChainEnumerator.cs

@@ -56,7 +56,7 @@ public bool MoveNext()
         }
         else if (!current.IsEndOfChain)
         {
-            uint sectorId = fatEnumerator.GetNextFatSectorId(current.Id);
+            uint sectorId = GetNextFatSectorId(current.Id);
             current = new(sectorId, ioContext.Header.SectorSize);
             Index++;
         }
@@ -98,4 +98,23 @@ public void Reset()
         current = Sector.EndOfChain;
         Index = uint.MaxValue;
     }
+
+    /// <summary>
+    /// Gets the next sector ID in the FAT chain.
+    /// </summary>
+    uint GetNextFatSectorId(uint id)
+    {
+        if (id > SectorType.Maximum)
+            throw new ArgumentException("Invalid sector ID", nameof(id));
+
+        int elementCount = ioContext.Header.SectorSize / sizeof(uint);
+        uint sectorId = (uint)Math.DivRem(id, elementCount, out long sectorOffset);
+        if (!fatEnumerator.MoveTo(sectorId))
+            throw new ArgumentException("Invalid sector ID", nameof(id));
+
+        long position = fatEnumerator.Current.Position + sectorOffset * sizeof(uint);
+        ioContext.Reader.Seek(position);
+        uint nextId = ioContext.Reader.ReadUInt32();
+        return nextId;
+    }
 }

OpenMcdf3/FatSectorEnumerator.cs

@@ -83,7 +83,9 @@ public bool MoveNext()
         return true;
     }
 
-    /// <inheritdoc/>
+    /// <summary>
+    /// Moves the enumerator to the specified sector.
+    /// </summary>
     public bool MoveTo(uint sectorId)
     {
         if (sectorId < id)
@@ -107,21 +109,4 @@ public void Reset()
         difatSectorElementIndex = 0;
         current = Sector.EndOfChain;
     }
-
-    /// <inheritdoc/>
-    public uint GetNextFatSectorId(uint id)
-    {
-        if (id > SectorType.Maximum)
-            throw new ArgumentException("Invalid sector ID", nameof(id));
-
-        int elementCount = ioContext.Header.SectorSize / sizeof(uint);
-        uint sectorId = (uint)Math.DivRem(id, elementCount, out long sectorOffset);
-        if (!MoveTo(sectorId))
-            throw new ArgumentException("Invalid sector ID", nameof(id));
-
-        long position = Current.Position + sectorOffset * sizeof(uint);
-        ioContext.Reader.Seek(position);
-        uint nextId = ioContext.Reader.ReadUInt32();
-        return nextId;
-    }
 }

OpenMcdf3/FatStream.cs

@@ -73,14 +73,14 @@ public override int Read(byte[] buffer, int offset, int count)
         if (count == 0)
             return 0;
 
-        uint chainIndex = (uint)Math.DivRem(position, ioContext.Header.SectorSize, out long sectorOffset);
-        if (!chain.MoveTo(chainIndex))
-            return 0;
-
         int maxCount = (int)Math.Min(Math.Max(length - position, 0), int.MaxValue);
         if (maxCount == 0)
             return 0;
 
+        uint chainIndex = (uint)Math.DivRem(position, ioContext.Header.SectorSize, out long sectorOffset);
+        if (!chain.MoveTo(chainIndex))
+            return 0;
+
         int realCount = Math.Min(count, maxCount);
         int readCount = 0;
         do

OpenMcdf3/MiniFatStream.cs

@@ -71,14 +71,14 @@ public override int Read(byte[] buffer, int offset, int count)
         if (count == 0)
             return 0;
 
-        uint chainIndex = (uint)Math.DivRem(position, ioContext.Header.SectorSize, out long sectorOffset);
-        if (!chain.MoveTo(chainIndex))
-            return 0;
-
         int maxCount = (int)Math.Min(Math.Max(length - position, 0), int.MaxValue);
         if (maxCount == 0)
             return 0;
 
+        uint chainIndex = (uint)Math.DivRem(position, ioContext.Header.SectorSize, out long sectorOffset);
+        if (!chain.MoveTo(chainIndex))
+            return 0;
+
         int realCount = Math.Min(count, maxCount);
         int readCount = 0;
         do