1 files changed, 103 insertions, 0 deletions
diff --git a/src/inc/bitmask.h b/src/inc/bitmask.h
new file mode 100644
index 0000000000..a59d2e252d
--- /dev/null
+++ b/src/inc/bitmask.h
@@ -0,0 +1,103 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+// --------------------------------------------------------------------------------
+// BitMask.h
+// --------------------------------------------------------------------------------
+
+// --------------------------------------------------------------------------------
+// BitMask is an arbitrarily large sized bitfield which has optimal storage 
+// for 32 bits or less.  
+// Storage is proportional to the highest index which is set. 
+// --------------------------------------------------------------------------------
+
+
+#include <clrtypes.h>
+
+#ifndef _BITMASK_H_
+#define _BITMASK_H_
+
+class BitMask
+{
+ public:
+
+    BitMask();
+    ~BitMask();
+
+    BOOL TestBit(int bit);
+    void SetBit(int bit);
+    void ClearBit(int bit);
+
+    // returns true if any bit is set
+    BOOL TestAnyBit();
+
+    void ClearAllBits();
+
+    // Allocation exposed for ngen save/fixup
+    size_t GetAllocatedBlockOffset();
+    void *GetAllocatedBlock();
+    COUNT_T GetAllocatedBlockSize();
+
+ private:
+
+    static const int BIT_SIZE_SHIFT = 5;
+    static const int BIT_SIZE = (1<<BIT_SIZE_SHIFT);
+    static const int BIT_SIZE_MASK = BIT_SIZE-1;
+
+    static const COUNT_T MIN_ARRAY_ALLOCATION = 3;
+
+    // The first bit is used to indicate whether we've got a flat mask or
+    // an array of mask elements
+    BOOL IsArray();
+
+    // Indexing computations
+    COUNT_T BitToIndex(int bit);
+    COUNT_T BitToShift(int bit);
+
+    // Generic mask array access.  Works for either case (array or non-array).
+    COUNT_T *GetMaskArray();
+    COUNT_T GetMaskArraySize();
+
+    // Need more bits...
+    void GrowArray(COUNT_T newSize);
+    
+    union
+    {
+        COUNT_T     m_mask;
+        COUNT_T     *m_maskArray; // first array element is size of rest of array
+    };
+};
+
+// provides a wrapper around the BitMask class providing synchronized reads/writes safe for multithreaded access.
+// I've only added the public methods that were required by Module which needs a thread-safe BitMask.  add others as required.
+class SynchronizedBitMask
+{
+ public:
+    // Allow Module access so we can use Offsetof on this class's private members during native image creation (determinism)
+    friend class Module;
+    SynchronizedBitMask();
+    ~SynchronizedBitMask() {}
+
+    BOOL TestBit(int bit);
+    void SetBit(int bit);
+    void ClearBit(int bit);
+
+    BOOL TestAnyBit();
+
+    void ClearAllBits();
+
+ private:
+
+    BitMask m_bitMask;
+
+    // note that this lock (at present) doesn't support promotion from reader->writer so be very careful
+    // when taking this lock else you might deadlock your own thread!
+    SimpleRWLock m_bitMaskLock;
+};
+
+#include <bitmask.inl>
+
+#endif // _BITMASK_H_