From cd6f8f3db37619d2fe95bc9a44a3a10bd37a5f15 Mon Sep 17 00:00:00 2001
From: Matt Nadareski <mnadareski@outlook.com>
Date: Fri, 4 Nov 2022 13:48:30 -0700
Subject: [PATCH] Add LE/LX object page table

---
 BurnOutSharp.Models/LinearExecutable/Enums.cs | 29 +++++++++
 .../LinearExecutable/Executable.cs            |  6 +-
 .../LinearExecutable/ObjectPageTableEntry.cs  | 60 +++++++++++++++++++
 3 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 BurnOutSharp.Models/LinearExecutable/ObjectPageTableEntry.cs

diff --git a/BurnOutSharp.Models/LinearExecutable/Enums.cs b/BurnOutSharp.Models/LinearExecutable/Enums.cs
index 0b9a4c4d..e83194d8 100644
--- a/BurnOutSharp.Models/LinearExecutable/Enums.cs
+++ b/BurnOutSharp.Models/LinearExecutable/Enums.cs
@@ -313,6 +313,35 @@ namespace BurnOutSharp.Models.LinearExecutable
         PrivilegeLevel = 0x8000,
     }
 
+    [Flags]
+    public enum ObjectPageFlags : ushort
+    {
+        /// <summary>
+        /// Legal Physical Page in the module (Offset from Preload Page Section).
+        /// </summary>
+        LegalPhysicalPage = 0x0000,
+
+        /// <summary>
+        /// Iterated Data Page (Offset from Iterated Data Pages Section).
+        /// </summary>
+        IteratedDataPage = 0x0001,
+
+        /// <summary>
+        /// Invalid Page (zero).
+        /// </summary>
+        InvalidPage = 0x0002,
+
+        /// <summary>
+        /// Zero Filled Page (zero).
+        /// </summary>
+        ZeroFilledPage = 0x0003,
+
+        /// <summary>
+        /// Range of Pages.
+        /// </summary>
+        RangeOfPages = 0x0004,
+    }
+
     public enum OperatingSystem : ushort
     {
         /// <summary>
diff --git a/BurnOutSharp.Models/LinearExecutable/Executable.cs b/BurnOutSharp.Models/LinearExecutable/Executable.cs
index 0ca8b39c..643c6a1c 100644
--- a/BurnOutSharp.Models/LinearExecutable/Executable.cs
+++ b/BurnOutSharp.Models/LinearExecutable/Executable.cs
@@ -25,7 +25,11 @@ namespace BurnOutSharp.Models.LinearExecutable
         /// </summary>
         public ObjectTableEntry[] ObjectTable { get; set; }
 
-        // TODO: Object page map table
+        /// <summary>
+        /// Object page table
+        /// </summary>
+        public ObjectPageTableEntry[] ObjectPageTable { get; set; }
+
         // TODO: Object iterate data map table
         // TODO: Resource table
         // TODO: Resident-names table
diff --git a/BurnOutSharp.Models/LinearExecutable/ObjectPageTableEntry.cs b/BurnOutSharp.Models/LinearExecutable/ObjectPageTableEntry.cs
new file mode 100644
index 00000000..6681a173
--- /dev/null
+++ b/BurnOutSharp.Models/LinearExecutable/ObjectPageTableEntry.cs
@@ -0,0 +1,60 @@
+using System.Runtime.InteropServices;
+
+namespace BurnOutSharp.Models.LinearExecutable
+{
+    /// <summary>
+    /// The Object page table provides information about a logical page in an object.
+    /// A logical page may be an enumerated page, a pseudo page or an iterated page.
+    /// The structure of the object page table in conjunction with the structure of
+    /// the object table allows for efficient access of a page when a page fault occurs,
+    /// while still allowing the physical page data to be located in the preload page,
+    /// demand load page or iterated data page sections in the linear EXE module. The
+    /// logical page entries in the Object Page Table are numbered starting from one.
+    /// The Object Page Table is parallel to the Fixup Page Table as they are both
+    /// indexed by the logical page number. 
+    /// </summary>
+    /// <see href="https://faydoc.tripod.com/formats/exe-LE.htm"/>
+    /// <see href="http://www.edm2.com/index.php/LX_-_Linear_eXecutable_Module_Format_Description"/>
+    [StructLayout(LayoutKind.Sequential)]
+    public class ObjectPageTableEntry
+    {
+        /// <summary>
+        /// Offset to the page data in the EXE file.
+        /// </summary>
+        /// <remarks>
+        /// This field, when bit shifted left by the PAGE OFFSET SHIFT from the module
+        /// header, specifies the offset from the beginning of the Preload Page section
+        /// of the physical page data in the EXE file that corresponds to this logical
+        /// page entry. The page data may reside in the Preload Pages, Demand Load Pages
+        /// or the Iterated Data Pages sections.
+        /// 
+        /// If the FLAGS field specifies that this is a zero-Filled page then the PAGE
+        /// DATA OFFSET field will contain a 0.
+        /// 
+        /// If the logical page is specified as an iterated data page, as indicated by
+        /// the FLAGS field, then this field specifies the offset into the Iterated Data
+        /// Pages section.
+        /// 
+        /// The logical page number (Object Page Table index), is used to index the Fixup
+        /// Page Table to find any fixups associated with the logical page. 
+        /// </remarks>
+        public uint PageDataOffset;
+
+        /// <summary>
+        /// Number of bytes of data for this page.
+        /// </summary>
+        /// <remarks>
+        /// This field specifies the actual number of bytes that represent the page in the
+        /// file. If the PAGE SIZE field from the module header is greater than the value
+        /// of this field and the FLAGS field indicates a Legal Physical Page, the remaining
+        /// bytes are to be filled with zeros. If the FLAGS field indicates an Iterated Data
+        /// Page, the iterated data records will completely fill out the remainder. 
+        /// </remarks>
+        public ushort DataSize;
+
+        /// <summary>
+        /// Attributes specifying characteristics of this logical page.
+        /// </summary>
+        public ObjectPageFlags Flags;
+    }
+}