BlobBuilder.LinkSuffix/LinkPrefix need to Free zero length chunks (#1…

…00039) * BlobBuilder.LinkSuffix/LinkPrefix need to Free zero length chunks * free child blob list * fix remarks 1 * add unit tests
dotnet · Apr 5, 2024 · fc9ab41 · fc9ab41
1 parent 3e98877
commit fc9ab41
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Showing 2 changed files with 36 additions and 3 deletions.
diff --git a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/BlobBuilder.cs b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/BlobBuilder.cs
@@ -47,7 +47,7 @@ public partial class BlobBuilder
         private uint _length;
 
         private const uint IsFrozenMask = 0x80000000;
-        private bool IsHead => (_length & IsFrozenMask) == 0;
+        internal bool IsHead => (_length & IsFrozenMask) == 0;
         private int Length => (int)(_length & ~IsFrozenMask);
         private uint FrozenLength => _length | IsFrozenMask;
         private Span<byte> Span => _buffer.AsSpan(0, Length);
@@ -97,8 +97,7 @@ public void Clear()
             {
                 if (chunk != this)
                 {
-                    chunk.ClearChunk();
-                    chunk.FreeChunk();
+                    chunk.ClearAndFreeChunk();
                 }
             }
 
@@ -396,6 +395,7 @@ public void LinkPrefix(BlobBuilder prefix)
             // avoid chaining empty chunks:
             if (prefix.Count == 0)
             {
+                prefix.ClearAndFreeChunk();
                 return;
             }
 
@@ -456,6 +456,7 @@ public void LinkSuffix(BlobBuilder suffix)
             // avoid chaining empty chunks:
             if (suffix.Count == 0)
             {
+                suffix.ClearAndFreeChunk();
                 return;
             }
 
@@ -1177,5 +1178,11 @@ private static string Display(byte[] bytes, int length)
                 BitConverter.ToString(bytes, 0, length) :
                 BitConverter.ToString(bytes, 0, MaxDisplaySize / 2) + "-...-" + BitConverter.ToString(bytes, length - MaxDisplaySize / 2, MaxDisplaySize / 2);
         }
+
+        private void ClearAndFreeChunk()
+        {
+            ClearChunk();
+            FreeChunk();
+        }
     }
 }
diff --git a/src/libraries/System.Reflection.Metadata/tests/Metadata/BlobTests.cs b/src/libraries/System.Reflection.Metadata/tests/Metadata/BlobTests.cs
@@ -1090,5 +1090,31 @@ public void PrematureEndOfStream()
 
             AssertEx.Equal(sourceArray, builder.ToArray());
         }
+
+        [Fact]
+        public void LinkEmptySuffixAndPrefixShouldFreeThem()
+        {
+            var b1 = PooledBlobBuilder.GetInstance();
+            var b2 = PooledBlobBuilder.GetInstance();
+            var b3 = PooledBlobBuilder.GetInstance();
+            var b4 = PooledBlobBuilder.GetInstance();
+            var b5 = PooledBlobBuilder.GetInstance();
+
+            b1.WriteBytes(1, 1);
+            b2.WriteBytes(1, 1);
+            b3.WriteBytes(1, 1);
+
+            b1.LinkSuffix(b2);
+            Assert.False(b2.IsHead);
+
+            b1.LinkPrefix(b3);
+            Assert.False(b3.IsHead);
+
+            b1.LinkSuffix(b4);
+            Assert.True(b4.IsHead);
+
+            b1.LinkPrefix(b5);
+            Assert.True(b4.IsHead);
+        }
     }
 }