Add sim parsing for Steam2 sim/sid installers (#95)

* Add model for sim file

* Add sim parsing for steam2 installer set

* First round of fixes

SabreTools.Serialization.Readers/Steam2Installer.cs

@@ -0,0 +1,172 @@
+using System.IO;
+using System.Text;
+using SabreTools.Data.Models.Steam2Installer;
+using SabreTools.IO.Extensions;
+using SabreTools.Numerics.Extensions;
+using SabreTools.Text.Extensions;
+
+namespace SabreTools.Serialization.Readers
+{
+    public class Steam2Installer : BaseBinaryReader<Steam2InstallerSet>
+    {
+         /// <inheritdoc/>
+        public override Steam2InstallerSet? Deserialize(Stream? data)
+        {
+            // If the data is invalid
+            if (data is null || !data.CanRead)
+                return null;
+
+            try
+            {
+                // Cache the current offset
+                long initialOffset = data.Position;
+
+                // Create a new Steam2 Installer set to populate
+                var si = new Steam2InstallerSet();
+
+                // Try to parse the .sim file
+                var sim = ParseSim(data);
+
+                // Make sure the sim was parsed properly
+                if (sim == null)
+                    return null;
+
+                // Set the sim file
+                si.Sim = sim;
+
+                return si;
+            }
+            catch
+            {
+                // Ignore the actual error
+                return null;
+            }
+        }
+
+        /// <summary>
+        /// Parse a Sim file
+        /// </summary>
+        /// <param name="data">Stream to parse</param>
+        /// <returns>Filled Sim on success, null on error</returns>
+        public static SimFile? ParseSim(Stream data)
+        {
+            // Create a new Sim file to populate
+            var si = new SimFile();
+
+            // Try to parse the .sim file header
+            var header = ParseHeader(data);
+
+            // Make sure the magic is correct
+            if (header.Magic != Constants.SimSignatureUInt32)
+                return null;
+
+            // Make sure the version is correct
+            if (header.Version != 1)
+                return null;
+
+            // Make sure string bytes section doesn't go beyond EOF
+            if (header.StringsSize > data.Length - data.Position)
+                return null;
+
+            // Set the header
+            si.Header = header;
+
+            // Read the string section bytes
+            byte[] stringsBytes = data.ReadBytes((int)header.StringsSize);
+
+            // Read the size and number of file entries
+            uint fileEntriesSize = data.ReadUInt32LittleEndian();
+            uint fileEntriesCount = data.ReadUInt32LittleEndian();
+
+            // Make sure reading the file entries won't go beyond EOF
+            if (fileEntriesSize > data.Length - data.Position)
+                return null;
+
+            // Try to parse the entry table
+            var table = ParseTable(data, fileEntriesCount, stringsBytes);
+            if (table is null || table.Length != fileEntriesCount)
+                return null;
+
+            // Set the entry table
+            si.FileEntries = table;
+
+            return si;
+        }
+
+        /// <summary>
+        /// Parse a Stream into a Header
+        /// </summary>
+        /// <param name="data">Stream to parse</param>
+        /// <returns>Filled Header on success, null on error</returns>
+        public static Header ParseHeader(Stream data)
+        {
+            var obj = new Header();
+
+            obj.Magic = data.ReadUInt32LittleEndian();
+            obj.Version = data.ReadUInt32LittleEndian();
+            obj.Discs = data.ReadUInt32LittleEndian();
+            obj.StringsSize = data.ReadUInt32LittleEndian();
+
+            return obj;
+        }
+
+        /// <summary>
+        /// Parse a Stream into an entry table
+        /// </summary>
+        /// <param name="data">Stream to parse</param>
+        /// <param name="count">Number of entries to parse</param>
+        /// <returns>Filled entry table on success, null on error</returns>
+        public static FileEntry[]? ParseTable(Stream data, uint count, byte[] stringsBytes)
+        {
+            if (count == 0)
+                return [];
+
+            var obj = new FileEntry[count];
+            for (uint i = 0; i < count; i++)
+            {
+                var fileEntry = ParseFileEntry(data, stringsBytes);
+                if (fileEntry is null)
+                    return null;
+
+                obj[i] = fileEntry;
+            }
+
+            return obj;
+        }
+
+        /// <summary>
+        /// Parse a Stream into a FileEntry
+        /// </summary>
+        /// <param name="data">Stream to parse</param>
+        /// <returns>Filled FileEntry on success, null on error</returns>
+        public static FileEntry? ParseFileEntry(Stream data, byte[] stringsBytes)
+        {
+            var obj = new FileEntry();
+
+            obj.NameOffset = data.ReadUInt32LittleEndian();
+            obj.PathOffset = data.ReadUInt32LittleEndian();
+            obj.DepotId = data.ReadUInt32LittleEndian();
+            obj.Offset = data.ReadUInt64LittleEndian();
+            obj.Size = data.ReadUInt64LittleEndian();
+            obj.DiscNumber = data.ReadByteValue();
+            obj.VolumeNumber = data.ReadByteValue();
+            obj.Encrypted = data.ReadByte() != 0;
+            obj.Unknown = data.ReadByteValue();
+
+            // Read file path and name strings
+            int nameOffset = (int)obj.NameOffset;
+            string? name = stringsBytes.ReadNullTerminatedAnsiString(ref nameOffset); // Unsure on encoding, assumed ascii/ansi
+            if (name is null)
+                return null;
+
+            obj.Name = name;
+            int pathOffset = (int)obj.PathOffset;
+            string? path = stringsBytes.ReadNullTerminatedAnsiString(ref pathOffset); // Unsure on encoding, assumed ascii/ansi
+            if (path is null)
+                return null;
+
+            obj.Path = path;
+            return obj;
+        }
+    }
+}