Introduce new per-txout CCoinsViewCache functions

The new functions are:
* CCoinsViewCache::AddCoin: Add a single COutPoint/Coin pair.
* CCoinsViewCache::SpendCoin: Remove a single COutPoint.
* AddCoins: utility function that invokes CCoinsViewCache::AddCoin for
  each output in a CTransaction.
* AccessByTxid: utility function that searches for any output with
  a given txid.
* CCoinsViewCache::AccessCoin: retrieve the Coin for a COutPoint.
* CCoinsViewCache::HaveCoins: check whether a non-empty Coin exists
  for a given COutPoint.

The AddCoin and SpendCoin methods will eventually replace ModifyCoins
and ModifyNewCoins, AddCoins will replace CCoins::FromTx, and the new
AccessCoins and HaveCoins functions will replace their per-txid
counterparts.

Note that AccessCoin for now returns a copy of the Coin object. In a
later commit it will be change to returning a const reference (which
keeps working in all call sites).
This commit is contained in:
Pieter Wuille 2017-04-25 11:29:29 -07:00
parent bd83111a0f
commit 0003911326
2 changed files with 116 additions and 2 deletions

View file

@ -4,6 +4,7 @@
#include "coins.h"
#include "consensus/consensus.h"
#include "memusage.h"
#include "random.h"
@ -70,7 +71,7 @@ size_t CCoinsViewCache::DynamicMemoryUsage() const {
return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
}
CCoinsMap::const_iterator CCoinsViewCache::FetchCoins(const uint256 &txid) const {
CCoinsMap::iterator CCoinsViewCache::FetchCoins(const uint256 &txid) const {
CCoinsMap::iterator it = cacheCoins.find(txid);
if (it != cacheCoins.end())
return it;
@ -153,6 +154,58 @@ CCoinsModifier CCoinsViewCache::ModifyNewCoins(const uint256 &txid, bool coinbas
return CCoinsModifier(*this, ret.first, 0);
}
void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possible_overwrite) {
assert(!coin.IsPruned());
if (coin.out.scriptPubKey.IsUnspendable()) return;
CCoinsMap::iterator it;
bool inserted;
std::tie(it, inserted) = cacheCoins.emplace(std::piecewise_construct, std::forward_as_tuple(outpoint.hash), std::tuple<>());
bool fresh = false;
if (!inserted) {
cachedCoinsUsage -= it->second.coins.DynamicMemoryUsage();
}
if (!possible_overwrite) {
if (it->second.coins.IsAvailable(outpoint.n)) {
throw std::logic_error("Adding new coin that replaces non-pruned entry");
}
fresh = it->second.coins.IsPruned() && !(it->second.flags & CCoinsCacheEntry::DIRTY);
}
if (it->second.coins.vout.size() <= outpoint.n) {
it->second.coins.vout.resize(outpoint.n + 1);
}
it->second.coins.vout[outpoint.n] = std::move(coin.out);
it->second.coins.nHeight = coin.nHeight;
it->second.coins.fCoinBase = coin.fCoinBase;
it->second.flags |= CCoinsCacheEntry::DIRTY | (fresh ? CCoinsCacheEntry::FRESH : 0);
cachedCoinsUsage += it->second.coins.DynamicMemoryUsage();
}
void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight) {
bool fCoinbase = tx.IsCoinBase();
const uint256& txid = tx.GetHash();
for (size_t i = 0; i < tx.vout.size(); ++i) {
// Pass fCoinbase as the possible_overwrite flag to AddCoin, in order to correctly
// deal with the pre-BIP30 occurrances of duplicate coinbase transactions.
cache.AddCoin(COutPoint(txid, i), Coin(tx.vout[i], nHeight, fCoinbase), fCoinbase);
}
}
void CCoinsViewCache::SpendCoin(const COutPoint &outpoint, Coin* moveout) {
CCoinsMap::iterator it = FetchCoins(outpoint.hash);
if (it == cacheCoins.end()) return;
cachedCoinsUsage -= it->second.coins.DynamicMemoryUsage();
if (moveout && it->second.coins.IsAvailable(outpoint.n)) {
*moveout = Coin(it->second.coins.vout[outpoint.n], it->second.coins.nHeight, it->second.coins.fCoinBase);
}
it->second.coins.Spend(outpoint.n); // Ignore return value: SpendCoin has no effect if no UTXO found.
if (it->second.coins.IsPruned() && it->second.flags & CCoinsCacheEntry::FRESH) {
cacheCoins.erase(it);
} else {
cachedCoinsUsage += it->second.coins.DynamicMemoryUsage();
it->second.flags |= CCoinsCacheEntry::DIRTY;
}
}
const CCoins* CCoinsViewCache::AccessCoins(const uint256 &txid) const {
CCoinsMap::const_iterator it = FetchCoins(txid);
if (it == cacheCoins.end()) {
@ -162,6 +215,18 @@ const CCoins* CCoinsViewCache::AccessCoins(const uint256 &txid) const {
}
}
static const Coin coinEmpty;
const Coin CCoinsViewCache::AccessCoin(const COutPoint &outpoint) const {
CCoinsMap::const_iterator it = FetchCoins(outpoint.hash);
if (it == cacheCoins.end() || !it->second.coins.IsAvailable(outpoint.n)) {
return coinEmpty;
} else {
return Coin(it->second.coins.vout[outpoint.n], it->second.coins.nHeight, it->second.coins.fCoinBase);
}
}
bool CCoinsViewCache::HaveCoins(const uint256 &txid) const {
CCoinsMap::const_iterator it = FetchCoins(txid);
// We're using vtx.empty() instead of IsPruned here for performance reasons,
@ -171,6 +236,11 @@ bool CCoinsViewCache::HaveCoins(const uint256 &txid) const {
return (it != cacheCoins.end() && !it->second.coins.vout.empty());
}
bool CCoinsViewCache::HaveCoins(const COutPoint &outpoint) const {
CCoinsMap::const_iterator it = FetchCoins(outpoint.hash);
return (it != cacheCoins.end() && it->second.coins.IsAvailable(outpoint.n));
}
bool CCoinsViewCache::HaveCoinsInCache(const uint256 &txid) const {
CCoinsMap::const_iterator it = cacheCoins.find(txid);
return it != cacheCoins.end();
@ -318,3 +388,16 @@ CCoinsModifier::~CCoinsModifier()
CCoinsViewCursor::~CCoinsViewCursor()
{
}
static const size_t MAX_OUTPUTS_PER_BLOCK = MAX_BLOCK_BASE_SIZE / ::GetSerializeSize(CTxOut(), SER_NETWORK, PROTOCOL_VERSION); // TODO: merge with similar definition in undo.h.
const Coin AccessByTxid(const CCoinsViewCache& view, const uint256& txid)
{
COutPoint iter(txid, 0);
while (iter.n < MAX_OUTPUTS_PER_BLOCK) {
const Coin& alternate = view.AccessCoin(iter);
if (!alternate.IsPruned()) return alternate;
++iter.n;
}
return coinEmpty;
}

View file

@ -452,6 +452,7 @@ public:
// Standard CCoinsView methods
bool GetCoins(const uint256 &txid, CCoins &coins) const;
bool HaveCoins(const uint256 &txid) const;
bool HaveCoins(const COutPoint &outpoint) const;
uint256 GetBestBlock() const;
void SetBestBlock(const uint256 &hashBlock);
bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
@ -470,6 +471,14 @@ public:
*/
const CCoins* AccessCoins(const uint256 &txid) const;
/**
* Return a copy of a Coin in the cache, or a pruned one if not found. This is
* more efficient than GetCoins. Modifications to other cache entries are
* allowed while accessing the returned pointer.
* TODO: return a reference to a Coin after changing CCoinsViewCache storage.
*/
const Coin AccessCoin(const COutPoint &output) const;
/**
* Return a modifiable reference to a CCoins. If no entry with the given
* txid exists, a new one is created. Simultaneous modifications are not
@ -488,6 +497,19 @@ public:
*/
CCoinsModifier ModifyNewCoins(const uint256 &txid, bool coinbase);
/**
* 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.
*/
void 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.
@ -525,7 +547,7 @@ public:
friend class CCoinsModifier;
private:
CCoinsMap::const_iterator FetchCoins(const uint256 &txid) const;
CCoinsMap::iterator FetchCoins(const uint256 &txid) const;
/**
* By making the copy constructor private, we prevent accidentally using it when one intends to create a cache on top of a base cache.
@ -533,4 +555,13 @@ private:
CCoinsViewCache(const CCoinsViewCache &);
};
//! Utility function to add all of a transaction's outputs to a cache.
// It assumes that overwrites are only possible for coinbase transactions,
// TODO: pass in a boolean to limit these possible overwrites to known
// (pre-BIP34) cases.
void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight);
//! Utility function to find any unspent output with a given txid.
const Coin AccessByTxid(const CCoinsViewCache& cache, const uint256& txid);
#endif // BITCOIN_COINS_H