[VirtualPC disk image] Implement support for writing sparse (dynamica…

…lly allocated) images. Fixes #645
aaru-dps · Jan 2, 2024 · 64c4c88 · 64c4c88
1 parent 75d9d0e
commit 64c4c88
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Showing 4 changed files with 274 additions and 21 deletions.
diff --git a/Aaru.Images/VHD/Properties.cs b/Aaru.Images/VHD/Properties.cs
@@ -85,10 +85,13 @@ public sealed partial class Vhd
         MediaType.PCCardTypeIV
     };
 
-    // TODO: Support dynamic images
     /// <inheritdoc />
-    public IEnumerable<(string name, Type type, string description, object @default)> SupportedOptions =>
-        Array.Empty<(string name, Type type, string description, object @default)>();
+    public IEnumerable<(string name, Type type, string description, object @default)> SupportedOptions => new[]
+    {
+        ("dynamic", typeof(bool), "Create a dynamic image, empty sectors are ignored", (object)true),
+        ("block_size", typeof(uint),
+         "Block size. Must be a power of 2. Only 2MiB and 512KiB are supported by VirtualPC", 2097152)
+    };
 
     /// <inheritdoc />
     public IEnumerable<string> KnownExtensions => new[]

diff --git a/Aaru.Images/VHD/Read.cs b/Aaru.Images/VHD/Read.cs
@@ -379,8 +379,7 @@ public ErrorNumber Open(IFilter imageFilter)
 
             _thisDynamic = new DynamicDiskHeader
             {
-                LocatorEntries = new ParentLocatorEntry[8],
-                Reserved2      = new byte[256]
+                LocatorEntries = new ParentLocatorEntry[8], Reserved2 = new byte[256]
             };
 
             for(var i = 0; i < 8; i++)
@@ -475,8 +474,6 @@ public ErrorNumber Open(IFilter imageFilter)
             var batStopwatch = new Stopwatch();
             batStopwatch.Start();
 
-            _blockAllocationTable = new uint[_thisDynamic.MaxTableEntries];
-
             var bat = new byte[_thisDynamic.MaxTableEntries * 4];
             imageStream.Seek((long)_thisDynamic.TableOffset, SeekOrigin.Begin);
             imageStream.EnsureRead(bat, 0, bat.Length);
@@ -485,9 +482,6 @@ public ErrorNumber Open(IFilter imageFilter)
 
             _blockAllocationTable = MemoryMarshal.Cast<byte, uint>(span)[..(int)_thisDynamic.MaxTableEntries].ToArray();
 
-            for(var i = 0; i < _blockAllocationTable.Length; i++)
-                _blockAllocationTable[i] = Swapping.Swap(_blockAllocationTable[i]);
-
             batStopwatch.Stop();
 
             AaruConsole.DebugWriteLine(MODULE_NAME, Localization.Filling_the_BAT_took_0_seconds,
@@ -704,7 +698,9 @@ public ErrorNumber ReadSector(ulong sectorAddress, out byte[] buffer)
                 // Sector number inside of block
                 var sectorInBlock = (uint)(sectorAddress % (_thisDynamic.BlockSize / 512));
 
-                if(_blockAllocationTable[blockNumber] == 0xFFFFFFFF)
+                uint blockPosition = Swapping.Swap(_blockAllocationTable[blockNumber]);
+
+                if(blockPosition == 0xFFFFFFFF)
                 {
                     buffer = new byte[512];
 
@@ -714,7 +710,7 @@ public ErrorNumber ReadSector(ulong sectorAddress, out byte[] buffer)
                 var bitmap = new byte[_bitmapSize * 512];
 
                 // Offset of block in file
-                long blockOffset = _blockAllocationTable[blockNumber] * 512L;
+                long blockOffset = blockPosition * 512L;
 
                 var bitmapByte = (int)Math.Floor((double)sectorInBlock / 8);
                 var bitmapBit  = (int)(sectorInBlock % 8);
@@ -748,7 +744,7 @@ public ErrorNumber ReadSector(ulong sectorAddress, out byte[] buffer)
                     */
 
                 buffer = new byte[512];
-                uint sectorOffset = _blockAllocationTable[blockNumber] + _bitmapSize + sectorInBlock;
+                uint sectorOffset = blockPosition + _bitmapSize + sectorInBlock;
                 thisStream = _thisFilter.GetDataForkStream();
 
                 thisStream.Seek(sectorOffset * 512, SeekOrigin.Begin);
@@ -821,14 +817,17 @@ public ErrorNumber ReadSectors(ulong sectorAddress, uint length, out byte[] buff
                 else
                     sectorsToReadHere = length;
 
+                // Keep the BAT in memory in big endian
+                uint blockPosition = Swapping.Swap(_blockAllocationTable[blockNumber]);
+
                 // Offset of sector in file
-                uint sectorOffset = _blockAllocationTable[blockNumber] + _bitmapSize + sectorInBlock;
+                uint sectorOffset = blockPosition + _bitmapSize + sectorInBlock;
 
                 // Data that can be read in this block
                 var prefix = new byte[sectorsToReadHere * 512];
 
                 // 0xFFFFFFFF means unallocated
-                if(_blockAllocationTable[blockNumber] != 0xFFFFFFFF)
+                if(blockPosition != 0xFFFFFFFF)
                 {
                     Stream thisStream = _thisFilter.GetDataForkStream();
                     thisStream.Seek(sectorOffset * 512, SeekOrigin.Begin);

diff --git a/Aaru.Images/VHD/VHD.cs b/Aaru.Images/VHD/VHD.cs
@@ -50,6 +50,13 @@ public sealed partial class Vhd : IWritableImage
     const string      MODULE_NAME = "Virtual PC plugin";
     uint              _bitmapSize;
     uint[]            _blockAllocationTable;
+    bool              _blockInCache;
+    uint              _blockSize;
+    byte[]            _cachedBlock;
+    uint              _cachedBlockNumber;
+    long              _cachedBlockPosition;
+    long              _currentFooterPosition;
+    bool              _dynamic;
     ImageInfo         _imageInfo;
     byte[][]          _locatorEntriesData;
     DateTime          _parentDateTime;