source2/Kernel/System/Cosmos.System/Filesystem/FAT.cs

@@ -5,5 +5,72 @@ using System.Text;
 
 namespace Cosmos.System.Filesystem {
   public class FAT : Filesystem {
+    readonly public int BytesPerSector;
+    readonly public int SectorsPerCluster;
+    readonly public int ReservedSectorCount;
+    readonly public int NumberOfFATs;
+    readonly public int FatSectorCount;
+    readonly public int TotalSectorCount;
+    readonly public int DataSectorCount;
+    readonly public int ClusterCount;
+    readonly public int RootSector; // FAT12/16
+    readonly public int RootCluster; // FAT32
+    readonly public int RootEntryCount;
+
+    public enum FatTypeEnum {Unknown, Fat12, Fat16, Fat32}
+    readonly public FatTypeEnum FatType = FatTypeEnum.Unknown;
+
+    Cosmos.Hardware.BlockDevice.BlockDevice mDevice;
+
+    public FAT(Cosmos.Hardware.BlockDevice.BlockDevice aDevice) {
+      mDevice = aDevice;
+
+      // 0xAA55
+      // [510] == 0x55
+      // [511] == 0xAA
+      // This is the FAT signature. We need to check it in the future.
+
+      var xBPB = new byte[512];
+      mDevice.ReadBlock(0, xBPB);
+      BytesPerSector = xBPB[12] << 8 | xBPB[11];
+      SectorsPerCluster = xBPB[13];
+      ReservedSectorCount = xBPB[15] << 8 | xBPB[14];
+      NumberOfFATs = xBPB[16];
+      RootEntryCount = xBPB[18] << 8 | xBPB[17];
+
+      TotalSectorCount = xBPB[20] << 8 | xBPB[19];
+      if (TotalSectorCount == 0) {
+        TotalSectorCount = xBPB[35] << 24 | xBPB[34] << 16 | xBPB[33] << 8 | xBPB[32];
+      }
+
+      FatSectorCount = xBPB[23] << 8 | xBPB[22];
+      if (FatSectorCount == 0) {
+        FatSectorCount = xBPB[39] << 24 | xBPB[38] << 16 | xBPB[37] << 8 | xBPB[36];
+      }
+
+      DataSectorCount = TotalSectorCount - (ReservedSectorCount + (NumberOfFATs * FatSectorCount) + ReservedSectorCount);
+ 
+      // Computation rounds down. 
+      ClusterCount = DataSectorCount / SectorsPerCluster;
+      // Determine the FAT type. Do not use another method - this IS the official and
+      // proper way to determine FAT type.
+      // Comparisons are purposefully < and not <=
+      // FAT16 starts at 4085
+      // FAT32 starts at 65525 
+      if (ClusterCount < 4085) {
+        FatType = FatTypeEnum.Fat12;
+      } else if(ClusterCount < 65525) {
+        FatType = FatTypeEnum.Fat16;
+      } else {
+        FatType = FatTypeEnum.Fat32;
+      }
+
+      if (FatType == FatTypeEnum.Fat32) {
+        RootCluster = xBPB[47] << 24 | xBPB[46] << 16 | xBPB[45] << 8 | xBPB[44];
+      } else {
+        RootSector = ReservedSectorCount + (NumberOfFATs * FatSectorCount);
+      }
+    }
+
   }
 }

source2/Kernel/System/Hardware/Cosmos.Hardware/BlockDevice/Partition.cs

@@ -20,12 +20,14 @@ namespace Cosmos.Hardware.BlockDevice {
       // TODO:UInt64
       UInt32 xHostBlockNo = mStartingSector + aBlockNo;
       CheckBlockNo(xHostBlockNo);
+      mHost.ReadBlock(xHostBlockNo, aData);
     }
 
     public override void WriteBlock(UInt32 aBlockNo, byte[] aData) {
       // TODO:UInt64
       UInt32 xHostBlockNo = mStartingSector + aBlockNo;
       CheckBlockNo(xHostBlockNo);
+      mHost.WriteBlock(xHostBlockNo, aData);
     }
 
   }

source2/Users/Kudzu/Breakpoints/BreakpointsKernel.csproj

@@ -59,7 +59,6 @@
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="Cosmos.Debug.Kernel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=5ae71220097cb983, processorArchitecture=MSIL" />
-    <Reference Include="Cosmos.System, Version=1.0.0.0, Culture=neutral, PublicKeyToken=5ae71220097cb983, processorArchitecture=MSIL" />
     <Reference Include="System" />
     <Reference Include="System.Core">
       <RequiredTargetFramework>3.5</RequiredTargetFramework>
@@ -74,6 +73,14 @@
       <Project>{1FAC100C-D732-4EA4-B518-5AF4BAF64F2E}</Project>
       <Name>Cosmos.Common.Extensions</Name>
     </ProjectReference>
+    <ProjectReference Include="..\..\..\Kernel\Common\Cosmos.Common\Cosmos.Common.csproj">
+      <Project>{04602B68-B877-4CA0-B17B-09C309732943}</Project>
+      <Name>Cosmos.Common</Name>
+    </ProjectReference>
+    <ProjectReference Include="..\..\..\Kernel\System\Cosmos.System\Cosmos.System.csproj">
+      <Project>{DA50B9B2-0E95-4F0D-A3C8-79FC549301B5}</Project>
+      <Name>Cosmos.System</Name>
+    </ProjectReference>
     <ProjectReference Include="..\..\..\Kernel\System\Hardware\Core\Cosmos.Core\Cosmos.Core.csproj">
       <Project>{5AC4773C-CB4E-4CD9-8D50-02E10A07DEE6}</Project>
       <Name>Cosmos.Core</Name>

source2/Users/Kudzu/Breakpoints/BreakpointsOS.cs

@@ -47,6 +47,8 @@ namespace BreakpointsKernel {
       Console.WriteLine("Model No: " + xATA.ModelNo);
       Console.WriteLine("Size: " + xATA.BlockCount * xATA.BlockSize / 1024 / 1024 + " MB");
 
+      var xFS = new Cosmos.System.Filesystem.FAT(BlockDevice.Devices[1]);
+
       //var xWrite = new byte[512];
       //for (int i = 0; i < 512; i++) {
       //  xWrite[i] = (byte)i;