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diff --git a/src/primitives/pureheader.h b/src/primitives/pureheader.h
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+++ b/src/primitives/pureheader.h
@@ -0,0 +1,157 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2013 The Bitcoin developers
+// Distributed under the MIT/X11 software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_PRIMITIVES_PUREHEADER_H
+#define BITCOIN_PRIMITIVES_PUREHEADER_H
+
+#include "serialize.h"
+#include "uint256.h"
+
+/**
+ * A block header without auxpow information.  This "intermediate step"
+ * in constructing the full header is useful, because it breaks the cyclic
+ * dependency between auxpow (referencing a parent block header) and
+ * the block header (referencing an auxpow).  The parent block header
+ * does not have auxpow itself, so it is a pure header.
+ */
+class CPureBlockHeader
+{
+public:
+
+    /* Modifiers to the version.  */
+    static const int32_t VERSION_AUXPOW = (1 << 8);
+
+    /** Bits above are reserved for the auxpow chain ID.  */
+    static const int32_t VERSION_CHAIN_START = (1 << 16);
+
+    // header
+    int32_t nVersion;
+    uint256 hashPrevBlock;
+    uint256 hashMerkleRoot;
+    uint32_t nTime;
+    uint32_t nBits;
+    uint32_t nNonce;
+
+    CPureBlockHeader()
+    {
+        SetNull();
+    }
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action) {
+        READWRITE(this->nVersion);
+        READWRITE(hashPrevBlock);
+        READWRITE(hashMerkleRoot);
+        READWRITE(nTime);
+        READWRITE(nBits);
+        READWRITE(nNonce);
+    }
+
+    void SetNull()
+    {
+        nVersion = 0;
+        hashPrevBlock.SetNull();
+        hashMerkleRoot.SetNull();
+        nTime = 0;
+        nBits = 0;
+        nNonce = 0;
+    }
+
+    bool IsNull() const
+    {
+        return (nBits == 0);
+    }
+
+    uint256 GetHash() const;
+    uint256 GetPoWHash() const;
+
+    int64_t GetBlockTime() const
+    {
+        return (int64_t)nTime;
+    }
+
+    /* Below are methods to interpret the version with respect to
+       auxpow data and chain ID.  This used to be in the CBlockVersion
+       class, but was moved here when we switched back to nVersion being
+       a pure int member as preparation to undoing the "abuse" and
+       allowing BIP9 to work.  */
+
+    /**
+     * Extract the base version (without modifiers and chain ID).
+     * @return The base version./
+     */
+    inline int32_t GetBaseVersion() const
+    {
+        return GetBaseVersion(nVersion);
+    }
+    static inline int32_t GetBaseVersion(int32_t ver)
+    {
+        return ver % VERSION_AUXPOW;
+    }
+
+    /**
+     * Set the base version (apart from chain ID and auxpow flag) to
+     * the one given.  This should only be called when auxpow is not yet
+     * set, to initialise a block!
+     * @param nBaseVersion The base version.
+     * @param nChainId The auxpow chain ID.
+     */
+    void SetBaseVersion(int32_t nBaseVersion, int32_t nChainId);
+
+    /**
+     * Extract the chain ID.
+     * @return The chain ID encoded in the version.
+     */
+    inline int32_t GetChainId() const
+    {
+        return nVersion >> 16;
+    }
+
+    /**
+     * Set the chain ID.  This is used for the test suite.
+     * @param ch The chain ID to set.
+     */
+    inline void SetChainId(int32_t chainId)
+    {
+        nVersion %= VERSION_CHAIN_START;
+        nVersion |= chainId * VERSION_CHAIN_START;
+    }
+
+    /**
+     * Check if the auxpow flag is set in the version.
+     * @return True iff this block version is marked as auxpow.
+     */
+    inline bool IsAuxpow() const
+    {
+        return nVersion & VERSION_AUXPOW;
+    }
+
+    /**
+     * Set the auxpow flag.  This is used for testing.
+     * @param auxpow Whether to mark auxpow as true.
+     */
+    inline void SetAuxpowFlag(bool auxpow)
+    {
+        if (auxpow)
+            nVersion |= VERSION_AUXPOW;
+        else
+            nVersion &= ~VERSION_AUXPOW;
+    }
+
+    /**
+     * Check whether this is a "legacy" block without chain ID.
+     * @return True iff it is.
+     */
+    inline bool IsLegacy() const
+    {
+        return nVersion == 1
+            // Dogecoin: We have a random v2 block with no AuxPoW, treat as legacy
+            || (nVersion == 2 && GetChainId() == 0);
+    }
+};
+
+#endif // BITCOIN_PRIMITIVES_PUREHEADER_H