0.6.5: Prevent context release during compression/decompression if Di…

…spose is not called
oleg-st · Nov 14, 2022 · d1bcfea · d1bcfea
1 parent 6c6ee89
commit d1bcfea
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Showing 3 changed files with 38 additions and 6 deletions.
diff --git a/src/ZstdSharp/Compressor.cs b/src/ZstdSharp/Compressor.cs
@@ -11,6 +11,12 @@ public unsafe class Compressor : IDisposable
 
         private int level = DefaultCompressionLevel;
 
+        /*
+         * We have a finalizer that releases cctx (to prevent memory leaks if Disposed is not called),
+         * so we need to delay running the object's finalizer when dealing with cctx inside our methods.
+         * For this purpose we use GC.KeepAlive(this)
+         * For reference: https://devblogs.microsoft.com/oldnewthing/20100813-00/?p=13153
+         */
         private ZSTD_CCtx_s* cctx;
 
         public int Level
@@ -30,20 +36,22 @@ public void SetParameter(ZSTD_cParameter parameter, int value)
         {
             EnsureNotDisposed();
             Methods.ZSTD_CCtx_setParameter(cctx, parameter, value).EnsureZstdSuccess();
+            GC.KeepAlive(this);
         }
 
         public int GetParameter(ZSTD_cParameter parameter)
         {
             EnsureNotDisposed();
             int value;
             Methods.ZSTD_CCtx_getParameter(cctx, parameter, &value).EnsureZstdSuccess();
+            GC.KeepAlive(this);
             return value;
         }
 
         public void LoadDictionary(byte[] dict)
         {
             var dictReadOnlySpan = new ReadOnlySpan<byte>(dict);
-            this.LoadDictionary(dictReadOnlySpan);
+            LoadDictionary(dictReadOnlySpan);
         }
 
         public void LoadDictionary(ReadOnlySpan<byte> dict)
@@ -59,6 +67,7 @@ public void LoadDictionary(ReadOnlySpan<byte> dict)
                 fixed (byte* dictPtr = dict)
                     Methods.ZSTD_CCtx_loadDictionary(cctx, dictPtr, (nuint) dict.Length).EnsureZstdSuccess();
             }
+            GC.KeepAlive(this);
         }
 
         public Compressor(int level = DefaultCompressionLevel)
@@ -96,9 +105,13 @@ public int Wrap(ReadOnlySpan<byte> src, Span<byte> dest)
             EnsureNotDisposed();
             fixed (byte* srcPtr = src)
             fixed (byte* destPtr = dest)
-                return (int) Methods
+            {
+                var returnValue = (int) Methods
                     .ZSTD_compress2(cctx, destPtr, (nuint) dest.Length, srcPtr, (nuint) src.Length)
                     .EnsureZstdSuccess();
+                GC.KeepAlive(this);
+                return returnValue;
+            }
         }
 
         public int Wrap(ArraySegment<byte> src, ArraySegment<byte> dest) 
@@ -118,6 +131,7 @@ public bool TryWrap(ReadOnlySpan<byte> src, Span<byte> dest, out int written)
             {
                 var returnValue =
                     Methods.ZSTD_compress2(cctx, destPtr, (nuint) dest.Length, srcPtr, (nuint) src.Length);
+                GC.KeepAlive(this);
 
                 if (returnValue == unchecked(0 - (nuint)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall))
                 {
@@ -163,7 +177,9 @@ internal nuint CompressStream(ref ZSTD_inBuffer_s input, ref ZSTD_outBuffer_s ou
             fixed (ZSTD_inBuffer_s* inputPtr = &input)
             fixed (ZSTD_outBuffer_s* outputPtr = &output)
             {
-                return Methods.ZSTD_compressStream2(cctx, outputPtr, inputPtr, directive).EnsureZstdSuccess();
+                var returnValue = Methods.ZSTD_compressStream2(cctx, outputPtr, inputPtr, directive).EnsureZstdSuccess();
+                GC.KeepAlive(this);
+                return returnValue;
             }
         }
     }

diff --git a/src/ZstdSharp/Decompressor.cs b/src/ZstdSharp/Decompressor.cs
@@ -5,6 +5,12 @@ namespace ZstdSharp
 {
     public unsafe class Decompressor : IDisposable
     {
+        /*
+         * We have a finalizer that releases dctx (to prevent memory leaks if Disposed is not called),
+         * so we need to delay running the object's finalizer when dealing with dctx inside our methods.
+         * For this purpose we use GC.KeepAlive(this)
+         * For reference: https://devblogs.microsoft.com/oldnewthing/20100813-00/?p=13153
+         */
         private ZSTD_DCtx_s* dctx;
 
         public Decompressor()
@@ -23,13 +29,15 @@ public void SetParameter(ZSTD_dParameter parameter, int value)
         {
             EnsureNotDisposed();
             Methods.ZSTD_DCtx_setParameter(dctx, parameter, value).EnsureZstdSuccess();
+            GC.KeepAlive(this);
         }
 
         public int GetParameter(ZSTD_dParameter parameter)
         {
             EnsureNotDisposed();
             int value;
             Methods.ZSTD_DCtx_getParameter(dctx, parameter, &value).EnsureZstdSuccess();
+            GC.KeepAlive(this);
             return value;
         }
 
@@ -51,6 +59,7 @@ public void LoadDictionary(ReadOnlySpan<byte> dict)
                 fixed (byte* dictPtr = dict)
                     Methods.ZSTD_DCtx_loadDictionary(dctx, dictPtr, (nuint) dict.Length).EnsureZstdSuccess();
             }
+            GC.KeepAlive(this);
         }
 
         public static ulong GetDecompressedSize(ReadOnlySpan<byte> src)
@@ -88,9 +97,13 @@ public int Unwrap(ReadOnlySpan<byte> src, Span<byte> dest)
             EnsureNotDisposed();
             fixed (byte* srcPtr = src)
             fixed (byte* destPtr = dest)
-                return (int) Methods
+            {
+                var returnValue = (int) Methods
                     .ZSTD_decompressDCtx(dctx, destPtr, (nuint) dest.Length, srcPtr, (nuint) src.Length)
                     .EnsureZstdSuccess();
+                GC.KeepAlive(this);
+                return returnValue;
+            }
         }
 
         public int Unwrap(byte[] src, int srcOffset, int srcLength, byte[] dst, int dstOffset, int dstLength)
@@ -107,6 +120,7 @@ public bool TryUnwrap(ReadOnlySpan<byte> src, Span<byte> dest, out int written)
             {
                 var returnValue =
                     Methods.ZSTD_decompressDCtx(dctx, destPtr, (nuint) dest.Length, srcPtr, (nuint) src.Length);
+                GC.KeepAlive(this);
 
                 if (returnValue == unchecked(0 - (nuint)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall))
                 {
@@ -148,7 +162,9 @@ internal nuint DecompressStream(ref ZSTD_inBuffer_s input, ref ZSTD_outBuffer_s
             fixed (ZSTD_inBuffer_s* inputPtr = &input)
             fixed (ZSTD_outBuffer_s* outputPtr = &output)
             {
-                return Methods.ZSTD_decompressStream(dctx, outputPtr, inputPtr).EnsureZstdSuccess();
+                var returnValue = Methods.ZSTD_decompressStream(dctx, outputPtr, inputPtr).EnsureZstdSuccess();
+                GC.KeepAlive(this);
+                return returnValue;
             }
         }
     }

diff --git a/src/ZstdSharp/ZstdSharp.csproj b/src/ZstdSharp/ZstdSharp.csproj
@@ -14,7 +14,7 @@
     <PackageProjectUrl>https://github.com/oleg-st/ZstdSharp</PackageProjectUrl>
     <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
     <PackageTags>zstd zstandard port compression</PackageTags>
-    <Version>0.6.4</Version>
+    <Version>0.6.5</Version>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">