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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2017 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_COINS_H
#define BITCOIN_COINS_H
#include <primitives/transaction.h>
#include <compressor.h>
#include <core_memusage.h>
#include <hash.h>
#include <memusage.h>
#include <serialize.h>
#include <uint256.h>
#include <assert.h>
#include <stdint.h>
#include <unordered_map>
/**
* A UTXO entry.
*
* Serialized format:
* - VARINT((coinbase ? 1 : 0) | (height << 1))
* - the non-spent CTxOut (via CTxOutCompressor)
*/
class Coin
{
public:
//! unspent transaction output
CTxOut out;
//! whether containing transaction was a coinbase
unsigned int fCoinBase : 1;
//! at which height this containing transaction was included in the active block chain
uint32_t nHeight : 31;
//! construct a Coin from a CTxOut and height/coinbase information.
Coin(CTxOut&& outIn, int nHeightIn, bool fCoinBaseIn) : out(std::move(outIn)), fCoinBase(fCoinBaseIn), nHeight(nHeightIn) {}
Coin(const CTxOut& outIn, int nHeightIn, bool fCoinBaseIn) : out(outIn), fCoinBase(fCoinBaseIn),nHeight(nHeightIn) {}
void Clear() {
out.SetNull();
fCoinBase = false;
nHeight = 0;
}
//! empty constructor
Coin() : fCoinBase(false), nHeight(0) { }
bool IsCoinBase() const {
return fCoinBase;
}
template<typename Stream>
void Serialize(Stream &s) const {
assert(!IsSpent());
uint32_t code = nHeight * 2 + fCoinBase;
::Serialize(s, VARINT(code));
::Serialize(s, CTxOutCompressor(REF(out)));
}
template<typename Stream>
void Unserialize(Stream &s) {
uint32_t code = 0;
::Unserialize(s, VARINT(code));
nHeight = code >> 1;
fCoinBase = code & 1;
::Unserialize(s, REF(CTxOutCompressor(out)));
}
bool IsSpent() const {
return out.IsNull();
}
size_t DynamicMemoryUsage() const {
return memusage::DynamicUsage(out.scriptPubKey);
}
};
class SaltedOutpointHasher
{
private:
/** Salt */
const uint64_t k0, k1;
public:
SaltedOutpointHasher();
/**
* This *must* return size_t. With Boost 1.46 on 32-bit systems the
* unordered_map will behave unpredictably if the custom hasher returns a
* uint64_t, resulting in failures when syncing the chain (#4634).
*/
size_t operator()(const COutPoint& id) const {
return SipHashUint256Extra(k0, k1, id.hash, id.n);
}
};
struct CCoinsCacheEntry
{
Coin coin; // The actual cached data.
unsigned char flags;
enum Flags {
DIRTY = (1 << 0), // This cache entry is potentially different from the version in the parent view.
FRESH = (1 << 1), // The parent view does not have this entry (or it is pruned).
/* Note that FRESH is a performance optimization with which we can
* erase coins that are fully spent if we know we do not need to
* flush the changes to the parent cache. It is always safe to
* not mark FRESH if that condition is not guaranteed.
*/
};
CCoinsCacheEntry() : flags(0) {}
explicit CCoinsCacheEntry(Coin&& coin_) : coin(std::move(coin_)), flags(0) {}
};
typedef std::unordered_map<COutPoint, CCoinsCacheEntry, SaltedOutpointHasher> CCoinsMap;
/** Cursor for iterating over CoinsView state */
class CCoinsViewCursor
{
public:
CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
virtual ~CCoinsViewCursor() {}
virtual bool GetKey(COutPoint &key) const = 0;
virtual bool GetValue(Coin &coin) const = 0;
virtual unsigned int GetValueSize() const = 0;
virtual bool Valid() const = 0;
virtual void Next() = 0;
//! Get best block at the time this cursor was created
const uint256 &GetBestBlock() const { return hashBlock; }
private:
uint256 hashBlock;
};
/** Abstract view on the open txout dataset. */
class CCoinsView
{
public:
/** Retrieve the Coin (unspent transaction output) for a given outpoint.
* Returns true only when an unspent coin was found, which is returned in coin.
* When false is returned, coin's value is unspecified.
*/
virtual bool GetCoin(const COutPoint &outpoint, Coin &coin) const;
//! Just check whether a given outpoint is unspent.
virtual bool HaveCoin(const COutPoint &outpoint) const;
//! Retrieve the block hash whose state this CCoinsView currently represents
virtual uint256 GetBestBlock() const;
//! Retrieve the range of blocks that may have been only partially written.
//! If the database is in a consistent state, the result is the empty vector.
//! Otherwise, a two-element vector is returned consisting of the new and
//! the old block hash, in that order.
virtual std::vector<uint256> GetHeadBlocks() const;
//! Do a bulk modification (multiple Coin changes + BestBlock change).
//! The passed mapCoins can be modified.
virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
//! Get a cursor to iterate over the whole state
virtual CCoinsViewCursor *Cursor() const;
//! As we use CCoinsViews polymorphically, have a virtual destructor
virtual ~CCoinsView() {}
//! Estimate database size (0 if not implemented)
virtual size_t EstimateSize() const { return 0; }
};
/** CCoinsView backed by another CCoinsView */
class CCoinsViewBacked : public CCoinsView
{
protected:
CCoinsView *base;
public:
CCoinsViewBacked(CCoinsView *viewIn);
bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
bool HaveCoin(const COutPoint &outpoint) const override;
uint256 GetBestBlock() const override;
std::vector<uint256> GetHeadBlocks() const override;
void SetBackend(CCoinsView &viewIn);
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
CCoinsViewCursor *Cursor() const override;
size_t EstimateSize() const override;
};
/** CCoinsView that adds a memory cache for transactions to another CCoinsView */
class CCoinsViewCache : public CCoinsViewBacked
{
protected:
/**
* Make mutable so that we can "fill the cache" even from Get-methods
* declared as "const".
*/
mutable uint256 hashBlock;
mutable CCoinsMap cacheCoins;
/* Cached dynamic memory usage for the inner Coin objects. */
mutable size_t cachedCoinsUsage;
public:
CCoinsViewCache(CCoinsView *baseIn);
/**
* By deleting the copy constructor, we prevent accidentally using it when one intends to create a cache on top of a base cache.
*/
CCoinsViewCache(const CCoinsViewCache &) = delete;
// Standard CCoinsView methods
bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
bool HaveCoin(const COutPoint &outpoint) const override;
uint256 GetBestBlock() const override;
void SetBestBlock(const uint256 &hashBlock);
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
CCoinsViewCursor* Cursor() const override {
throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
}
/**
* Check if we have the given utxo already loaded in this cache.
* The semantics are the same as HaveCoin(), but no calls to
* the backing CCoinsView are made.
*/
bool HaveCoinInCache(const COutPoint &outpoint) const;
/**
* Return a reference to Coin in the cache, or a pruned one if not found. This is
* more efficient than GetCoin.
*
* Generally, do not hold the reference returned for more than a short scope.
* While the current implementation allows for modifications to the contents
* of the cache while holding the reference, this behavior should not be relied
* on! To be safe, best to not hold the returned reference through any other
* calls to this cache.
*/
const Coin& AccessCoin(const COutPoint &output) const;
/**
* Add a coin. Set potential_overwrite to true if a non-pruned version may
* already exist.
*/
void AddCoin(const COutPoint& outpoint, Coin&& coin, bool potential_overwrite);
/**
* Spend a coin. Pass moveto in order to get the deleted data.
* If no unspent output exists for the passed outpoint, this call
* has no effect.
*/
bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr);
/**
* Push the modifications applied to this cache to its base.
* Failure to call this method before destruction will cause the changes to be forgotten.
* If false is returned, the state of this cache (and its backing view) will be undefined.
*/
bool Flush();
/**
* Removes the UTXO with the given outpoint from the cache, if it is
* not modified.
*/
void Uncache(const COutPoint &outpoint);
//! Calculate the size of the cache (in number of transaction outputs)
unsigned int GetCacheSize() const;
//! Calculate the size of the cache (in bytes)
size_t DynamicMemoryUsage() const;
/**
* Amount of bitcoins coming in to a transaction
* Note that lightweight clients may not know anything besides the hash of previous transactions,
* so may not be able to calculate this.
*
* @param[in] tx transaction for which we are checking input total
* @return Sum of value of all inputs (scriptSigs)
*/
CAmount GetValueIn(const CTransaction& tx) const;
//! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
bool HaveInputs(const CTransaction& tx) const;
private:
CCoinsMap::iterator FetchCoin(const COutPoint &outpoint) const;
};
//! Utility function to add all of a transaction's outputs to a cache.
// When check is false, this assumes that overwrites are only possible for coinbase transactions.
// When check is true, the underlying view may be queried to determine whether an addition is
// an overwrite.
// TODO: pass in a boolean to limit these possible overwrites to known
// (pre-BIP34) cases.
void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false);
//! Utility function to find any unspent output with a given txid.
// This function can be quite expensive because in the event of a transaction
// which is not found in the cache, it can cause up to MAX_OUTPUTS_PER_BLOCK
// lookups to database, so it should be used with care.
const Coin& AccessByTxid(const CCoinsViewCache& cache, const uint256& txid);
#endif // BITCOIN_COINS_H