Move CDiskBlockPos from chain to flatfile.

src/flatfile.h

@@ -1,12 +1,51 @@
-// Copyright (c) 2019 The Bitcoin Core developers
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_FLATFILE_H
 #define BITCOIN_FLATFILE_H
 
-#include <chain.h>
+#include <string>
+
 #include <fs.h>
+#include <serialize.h>
+
+struct CDiskBlockPos
+{
+    int nFile;
+    unsigned int nPos;
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action) {
+        READWRITE(VARINT(nFile, VarIntMode::NONNEGATIVE_SIGNED));
+        READWRITE(VARINT(nPos));
+    }
+
+    CDiskBlockPos() {
+        SetNull();
+    }
+
+    CDiskBlockPos(int nFileIn, unsigned int nPosIn) {
+        nFile = nFileIn;
+        nPos = nPosIn;
+    }
+
+    friend bool operator==(const CDiskBlockPos &a, const CDiskBlockPos &b) {
+        return (a.nFile == b.nFile && a.nPos == b.nPos);
+    }
+
+    friend bool operator!=(const CDiskBlockPos &a, const CDiskBlockPos &b) {
+        return !(a == b);
+    }
+
+    void SetNull() { nFile = -1; nPos = 0; }
+    bool IsNull() const { return (nFile == -1); }
+
+    std::string ToString() const;
+};
 
 /**
  * FlatFileSeq represents a sequence of numbered files storing raw data. This class facilitates