251};
252
253std::unique_ptr<CCoinsViewCursor> CCoinsViewDB::Cursor() const
254{
255    auto i = std::make_unique<CCoinsViewDBCursor>(
256        const_cast<CDBWrapper&>(*m_db).NewIterator(), GetBestBlock());
257    /* It seems that there are no "const iterators" for LevelDB.  Since we
258       only need read operations on it, use a const-cast to get around
259       that restriction.  */
260    i->pcursor->Seek(DB_COIN);
261    // Cache key of first record
262    if (i->pcursor->Valid()) {
263        CoinEntry entry(&i->keyTmp.second);
264        i->pcursor->GetKey(entry);
265        i->keyTmp.first = entry.key;
266    } else {
267        i->keyTmp.first = 0; // Make sure Valid() and GetKey() return false
268    }
269    return i;
270}
271
272bool CCoinsViewDBCursor::GetKey(COutPoint &key) const
273{
274    // Return cached key
275    if (keyTmp.first == DB_COIN) {
276        key = keyTmp.second;
277        return true;
278    }
279    return false;
280}
281
282bool CCoinsViewDBCursor::GetValue(Coin &coin) const
283{
284    return pcursor->GetValue(coin);
285}
286
287bool CCoinsViewDBCursor::Valid() const
288{
289    return keyTmp.first == DB_COIN;
290}
291
292void CCoinsViewDBCursor::Next()
293{
294    pcursor->Next();
295    CoinEntry entry(&keyTmp.second);
296    if (!pcursor->Valid() || !pcursor->GetKey(entry)) {
297        keyTmp.first = 0; // Invalidate cached key after last record so that Valid() and GetKey() return false
298    } else {
299        keyTmp.first = entry.key;
300    }
301}
302