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	diff --git a/src/coins.cpp b/src/coins.cpp
	index 723e114708..060d6b7c5d 100644
	--- a/src/coins.cpp
	+++ b/src/coins.cpp
	@@ -1,282 +1,291 @@
	// Copyright (c) 2012-2014 The Bitcoin Core developers
	// Distributed under the MIT software license, see the accompanying
	// file COPYING or http://www.opensource.org/licenses/mit-license.php.

	#include "coins.h"

	#include "memusage.h"
	#include "random.h"

	#include <assert.h>

	/**
	* calculate number of bytes for the bitmask, and its number of non-zero bytes
	* each bit in the bitmask represents the availability of one output, but the
	* availabilities of the first two outputs are encoded separately
	*/
	void CCoins::CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const {
	unsigned int nLastUsedByte = 0;
	for (unsigned int b = 0; 2+b*8 < vout.size(); b++) {
	bool fZero = true;
	for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++) {
	if (!vout[2+b*8+i].IsNull()) {
	fZero = false;
	continue;
	}
	}
	if (!fZero) {
	nLastUsedByte = b + 1;
	nNonzeroBytes++;
	}
	}
	nBytes += nLastUsedByte;
	}

	bool CCoins::Spend(uint32_t nPos)
	{
	if (nPos >= vout.size() \|\| vout[nPos].IsNull())
	return false;
	vout[nPos].SetNull();
	Cleanup();
	return true;
	}

	bool CCoinsView::GetCoins(const uint256 &txid, CCoins &coins) const { return false; }
	bool CCoinsView::HaveCoins(const uint256 &txid) const { return false; }
	uint256 CCoinsView::GetBestBlock() const { return uint256(); }
	bool CCoinsView::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return false; }
	bool CCoinsView::GetStats(CCoinsStats &stats) const { return false; }


	CCoinsViewBacked::CCoinsViewBacked(CCoinsView *viewIn) : base(viewIn) { }
	bool CCoinsViewBacked::GetCoins(const uint256 &txid, CCoins &coins) const { return base->GetCoins(txid, coins); }
	bool CCoinsViewBacked::HaveCoins(const uint256 &txid) const { return base->HaveCoins(txid); }
	uint256 CCoinsViewBacked::GetBestBlock() const { return base->GetBestBlock(); }
	void CCoinsViewBacked::SetBackend(CCoinsView &viewIn) { base = &viewIn; }
	bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return base->BatchWrite(mapCoins, hashBlock); }
	bool CCoinsViewBacked::GetStats(CCoinsStats &stats) const { return base->GetStats(stats); }

	CCoinsKeyHasher::CCoinsKeyHasher() : salt(GetRandHash()) {}

	CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), hasModifier(false), cachedCoinsUsage(0) { }

	CCoinsViewCache::~CCoinsViewCache()
	{
	assert(!hasModifier);
	}

	size_t CCoinsViewCache::DynamicMemoryUsage() const {
	return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
	}

	CCoinsMap::const_iterator CCoinsViewCache::FetchCoins(const uint256 &txid) const {
	CCoinsMap::iterator it = cacheCoins.find(txid);
	if (it != cacheCoins.end())
	return it;
	CCoins tmp;
	if (!base->GetCoins(txid, tmp))
	return cacheCoins.end();
	CCoinsMap::iterator ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry())).first;
	tmp.swap(ret->second.coins);
	if (ret->second.coins.IsPruned()) {
	// The parent only has an empty entry for this txid; we can consider our
	// version as fresh.
	ret->second.flags = CCoinsCacheEntry::FRESH;
	}
	cachedCoinsUsage += ret->second.coins.DynamicMemoryUsage();
	return ret;
	}

	bool CCoinsViewCache::GetCoins(const uint256 &txid, CCoins &coins) const {
	CCoinsMap::const_iterator it = FetchCoins(txid);
	if (it != cacheCoins.end()) {
	coins = it->second.coins;
	return true;
	}
	return false;
	}

	CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
	assert(!hasModifier);
	std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
	size_t cachedCoinUsage = 0;
	if (ret.second) {
	if (!base->GetCoins(txid, ret.first->second.coins)) {
	// The parent view does not have this entry; mark it as fresh.
	ret.first->second.coins.Clear();
	ret.first->second.flags = CCoinsCacheEntry::FRESH;
	} else if (ret.first->second.coins.IsPruned()) {
	// The parent view only has a pruned entry for this; mark it as fresh.
	ret.first->second.flags = CCoinsCacheEntry::FRESH;
	}
	} else {
	cachedCoinUsage = ret.first->second.coins.DynamicMemoryUsage();
	}
	// Assume that whenever ModifyCoins is called, the entry will be modified.
	ret.first->second.flags \|= CCoinsCacheEntry::DIRTY;
	return CCoinsModifier(*this, ret.first, cachedCoinUsage);
	}

	CCoinsModifier CCoinsViewCache::ModifyNewCoins(const uint256 &txid) {
	assert(!hasModifier);
	std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
	ret.first->second.coins.Clear();
	ret.first->second.flags = CCoinsCacheEntry::FRESH;
	ret.first->second.flags \|= CCoinsCacheEntry::DIRTY;
	return CCoinsModifier(*this, ret.first, 0);
	}

	const CCoins* CCoinsViewCache::AccessCoins(const uint256 &txid) const {
	CCoinsMap::const_iterator it = FetchCoins(txid);
	if (it == cacheCoins.end()) {
	return NULL;
	} else {
	return &it->second.coins;
	}
	}

	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,
	// as we only care about the case where a transaction was replaced entirely
	// in a reorganization (which wipes vout entirely, as opposed to spending
	// which just cleans individual outputs).
	return (it != cacheCoins.end() && !it->second.coins.vout.empty());
	}

	uint256 CCoinsViewCache::GetBestBlock() const {
	if (hashBlock.IsNull())
	hashBlock = base->GetBestBlock();
	return hashBlock;
	}

	void CCoinsViewCache::SetBestBlock(const uint256 &hashBlockIn) {
	hashBlock = hashBlockIn;
	}

	bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn) {
	assert(!hasModifier);
	for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
	if (it->second.flags & CCoinsCacheEntry::DIRTY) { // Ignore non-dirty entries (optimization).
	CCoinsMap::iterator itUs = cacheCoins.find(it->first);
	if (itUs == cacheCoins.end()) {
	// The parent cache does not have an entry, while the child does
	// We can ignore it if it's both FRESH and pruned in the child
	if (!(it->second.flags & CCoinsCacheEntry::FRESH && it->second.coins.IsPruned())) {
	// Otherwise we will need to create it in the parent
	// and move the data up and mark it as dirty
	CCoinsCacheEntry& entry = cacheCoins[it->first];
	entry.coins.swap(it->second.coins);
	cachedCoinsUsage += entry.coins.DynamicMemoryUsage();
	entry.flags = CCoinsCacheEntry::DIRTY;
	// We can mark it FRESH in the parent if it was FRESH in the child
	// Otherwise it might have just been flushed from the parent's cache
	// and already exist in the grandparent
	if (it->second.flags & CCoinsCacheEntry::FRESH)
	entry.flags \|= CCoinsCacheEntry::FRESH;
	}
	} else {
	// Found the entry in the parent cache
	if ((itUs->second.flags & CCoinsCacheEntry::FRESH) && it->second.coins.IsPruned()) {
	// The grandparent does not have an entry, and the child is
	// modified and being pruned. This means we can just delete
	// it from the parent.
	cachedCoinsUsage -= itUs->second.coins.DynamicMemoryUsage();
	cacheCoins.erase(itUs);
	} else {
	// A normal modification.
	cachedCoinsUsage -= itUs->second.coins.DynamicMemoryUsage();
	itUs->second.coins.swap(it->second.coins);
	cachedCoinsUsage += itUs->second.coins.DynamicMemoryUsage();
	itUs->second.flags \|= CCoinsCacheEntry::DIRTY;
	}
	}
	}
	CCoinsMap::iterator itOld = it++;
	mapCoins.erase(itOld);
	}
	hashBlock = hashBlockIn;
	return true;
	}

	bool CCoinsViewCache::Flush() {
	bool fOk = base->BatchWrite(cacheCoins, hashBlock);
	cacheCoins.clear();
	cachedCoinsUsage = 0;
	return fOk;
	}

	+void CCoinsViewCache::Uncache(const uint256& hash)
	+{
	+ CCoinsMap::iterator it = cacheCoins.find(hash);
	+ if (it != cacheCoins.end() && it->second.flags == 0) {
	+ cachedCoinsUsage -= it->second.coins.DynamicMemoryUsage();
	+ cacheCoins.erase(it);
	+ }
	+}
	+
	unsigned int CCoinsViewCache::GetCacheSize() const {
	return cacheCoins.size();
	}

	const CTxOut &CCoinsViewCache::GetOutputFor(const CTxIn& input) const
	{
	const CCoins* coins = AccessCoins(input.prevout.hash);
	assert(coins && coins->IsAvailable(input.prevout.n));
	return coins->vout[input.prevout.n];
	}

	CAmount CCoinsViewCache::GetValueIn(const CTransaction& tx) const
	{
	if (tx.IsCoinBase())
	return 0;

	CAmount nResult = 0;
	for (unsigned int i = 0; i < tx.vin.size(); i++)
	nResult += GetOutputFor(tx.vin[i]).nValue;

	return nResult;
	}

	bool CCoinsViewCache::HaveInputs(const CTransaction& tx) const
	{
	if (!tx.IsCoinBase()) {
	for (unsigned int i = 0; i < tx.vin.size(); i++) {
	const COutPoint &prevout = tx.vin[i].prevout;
	const CCoins* coins = AccessCoins(prevout.hash);
	if (!coins \|\| !coins->IsAvailable(prevout.n)) {
	return false;
	}
	}
	}
	return true;
	}

	double CCoinsViewCache::GetPriority(const CTransaction &tx, int nHeight, CAmount &inChainInputValue) const
	{
	inChainInputValue = 0;
	if (tx.IsCoinBase())
	return 0.0;
	double dResult = 0.0;
	BOOST_FOREACH(const CTxIn& txin, tx.vin)
	{
	const CCoins* coins = AccessCoins(txin.prevout.hash);
	assert(coins);
	if (!coins->IsAvailable(txin.prevout.n)) continue;
	if (coins->nHeight <= nHeight) {
	dResult += coins->vout[txin.prevout.n].nValue * (nHeight-coins->nHeight);
	inChainInputValue += coins->vout[txin.prevout.n].nValue;
	}
	}
	return tx.ComputePriority(dResult);
	}

	CCoinsModifier::CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage) : cache(cache_), it(it_), cachedCoinUsage(usage) {
	assert(!cache.hasModifier);
	cache.hasModifier = true;
	}

	CCoinsModifier::~CCoinsModifier()
	{
	assert(cache.hasModifier);
	cache.hasModifier = false;
	it->second.coins.Cleanup();
	cache.cachedCoinsUsage -= cachedCoinUsage; // Subtract the old usage
	if ((it->second.flags & CCoinsCacheEntry::FRESH) && it->second.coins.IsPruned()) {
	cache.cacheCoins.erase(it);
	} else {
	// If the coin still exists after the modification, add the new usage
	cache.cachedCoinsUsage += it->second.coins.DynamicMemoryUsage();
	}
	}
	diff --git a/src/coins.h b/src/coins.h
	index d174422100..5beea711b2 100644
	--- a/src/coins.h
	+++ b/src/coins.h
	@@ -1,480 +1,486 @@
	// Copyright (c) 2009-2010 Satoshi Nakamoto
	// Copyright (c) 2009-2014 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 "compressor.h"
	#include "core_memusage.h"
	#include "memusage.h"
	#include "serialize.h"
	#include "uint256.h"

	#include <assert.h>
	#include <stdint.h>

	#include <boost/foreach.hpp>
	#include <boost/unordered_map.hpp>

	/**
	* Pruned version of CTransaction: only retains metadata and unspent transaction outputs
	*
	* Serialized format:
	* - VARINT(nVersion)
	* - VARINT(nCode)
	* - unspentness bitvector, for vout[2] and further; least significant byte first
	* - the non-spent CTxOuts (via CTxOutCompressor)
	* - VARINT(nHeight)
	*
	* The nCode value consists of:
	* - bit 0: IsCoinBase()
	* - bit 1: vout[0] is not spent
	* - bit 2: vout[1] is not spent
	* - The higher bits encode N, the number of non-zero bytes in the following bitvector.
	* - In case both bit 1 and bit 2 are unset, they encode N-1, as there must be at
	* least one non-spent output).
	*
	* Example: 0104835800816115944e077fe7c803cfa57f29b36bf87c1d358bb85e
	* <><><--------------------------------------------><---->
	* \| \ \| /
	* version code vout[1] height
	*
	* - version = 1
	* - code = 4 (vout[1] is not spent, and 0 non-zero bytes of bitvector follow)
	* - unspentness bitvector: as 0 non-zero bytes follow, it has length 0
	* - vout[1]: 835800816115944e077fe7c803cfa57f29b36bf87c1d35
	* * 8358: compact amount representation for 60000000000 (600 BTC)
	* * 00: special txout type pay-to-pubkey-hash
	* * 816115944e077fe7c803cfa57f29b36bf87c1d35: address uint160
	* - height = 203998
	*
	*
	* Example: 0109044086ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4eebbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa486af3b
	* <><><--><--------------------------------------------------><----------------------------------------------><---->
	* / \ \ \| \| /
	* version code unspentness vout[4] vout[16] height
	*
	* - version = 1
	* - code = 9 (coinbase, neither vout[0] or vout[1] are unspent,
	* 2 (1, +1 because both bit 1 and bit 2 are unset) non-zero bitvector bytes follow)
	* - unspentness bitvector: bits 2 (0x04) and 14 (0x4000) are set, so vout[2+2] and vout[14+2] are unspent
	* - vout[4]: 86ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4ee
	* * 86ef97d579: compact amount representation for 234925952 (2.35 BTC)
	* * 00: special txout type pay-to-pubkey-hash
	* * 61b01caab50f1b8e9c50a5057eb43c2d9563a4ee: address uint160
	* - vout[16]: bbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa4
	* * bbd123: compact amount representation for 110397 (0.001 BTC)
	* * 00: special txout type pay-to-pubkey-hash
	* * 8c988f1a4a4de2161e0f50aac7f17e7f9555caa4: address uint160
	* - height = 120891
	*/
	class CCoins
	{
	public:
	//! whether transaction is a coinbase
	bool fCoinBase;

	//! unspent transaction outputs; spent outputs are .IsNull(); spent outputs at the end of the array are dropped
	std::vector<CTxOut> vout;

	//! at which height this transaction was included in the active block chain
	int nHeight;

	//! version of the CTransaction; accesses to this value should probably check for nHeight as well,
	//! as new tx version will probably only be introduced at certain heights
	int nVersion;

	void FromTx(const CTransaction &tx, int nHeightIn) {
	fCoinBase = tx.IsCoinBase();
	vout = tx.vout;
	nHeight = nHeightIn;
	nVersion = tx.nVersion;
	ClearUnspendable();
	}

	//! construct a CCoins from a CTransaction, at a given height
	CCoins(const CTransaction &tx, int nHeightIn) {
	FromTx(tx, nHeightIn);
	}

	void Clear() {
	fCoinBase = false;
	std::vector<CTxOut>().swap(vout);
	nHeight = 0;
	nVersion = 0;
	}

	//! empty constructor
	CCoins() : fCoinBase(false), vout(0), nHeight(0), nVersion(0) { }

	//!remove spent outputs at the end of vout
	void Cleanup() {
	while (vout.size() > 0 && vout.back().IsNull())
	vout.pop_back();
	if (vout.empty())
	std::vector<CTxOut>().swap(vout);
	}

	void ClearUnspendable() {
	BOOST_FOREACH(CTxOut &txout, vout) {
	if (txout.scriptPubKey.IsUnspendable())
	txout.SetNull();
	}
	Cleanup();
	}

	void swap(CCoins &to) {
	std::swap(to.fCoinBase, fCoinBase);
	to.vout.swap(vout);
	std::swap(to.nHeight, nHeight);
	std::swap(to.nVersion, nVersion);
	}

	//! equality test
	friend bool operator==(const CCoins &a, const CCoins &b) {
	// Empty CCoins objects are always equal.
	if (a.IsPruned() && b.IsPruned())
	return true;
	return a.fCoinBase == b.fCoinBase &&
	a.nHeight == b.nHeight &&
	a.nVersion == b.nVersion &&
	a.vout == b.vout;
	}
	friend bool operator!=(const CCoins &a, const CCoins &b) {
	return !(a == b);
	}

	void CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const;

	bool IsCoinBase() const {
	return fCoinBase;
	}

	unsigned int GetSerializeSize(int nType, int nVersion) const {
	unsigned int nSize = 0;
	unsigned int nMaskSize = 0, nMaskCode = 0;
	CalcMaskSize(nMaskSize, nMaskCode);
	bool fFirst = vout.size() > 0 && !vout[0].IsNull();
	bool fSecond = vout.size() > 1 && !vout[1].IsNull();
	assert(fFirst \|\| fSecond \|\| nMaskCode);
	unsigned int nCode = 8*(nMaskCode - (fFirst \|\| fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
	// version
	nSize += ::GetSerializeSize(VARINT(this->nVersion), nType, nVersion);
	// size of header code
	nSize += ::GetSerializeSize(VARINT(nCode), nType, nVersion);
	// spentness bitmask
	nSize += nMaskSize;
	// txouts themself
	for (unsigned int i = 0; i < vout.size(); i++)
	if (!vout[i].IsNull())
	nSize += ::GetSerializeSize(CTxOutCompressor(REF(vout[i])), nType, nVersion);
	// height
	nSize += ::GetSerializeSize(VARINT(nHeight), nType, nVersion);
	return nSize;
	}

	template<typename Stream>
	void Serialize(Stream &s, int nType, int nVersion) const {
	unsigned int nMaskSize = 0, nMaskCode = 0;
	CalcMaskSize(nMaskSize, nMaskCode);
	bool fFirst = vout.size() > 0 && !vout[0].IsNull();
	bool fSecond = vout.size() > 1 && !vout[1].IsNull();
	assert(fFirst \|\| fSecond \|\| nMaskCode);
	unsigned int nCode = 8*(nMaskCode - (fFirst \|\| fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
	// version
	::Serialize(s, VARINT(this->nVersion), nType, nVersion);
	// header code
	::Serialize(s, VARINT(nCode), nType, nVersion);
	// spentness bitmask
	for (unsigned int b = 0; b<nMaskSize; b++) {
	unsigned char chAvail = 0;
	for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++)
	if (!vout[2+b*8+i].IsNull())
	chAvail \|= (1 << i);
	::Serialize(s, chAvail, nType, nVersion);
	}
	// txouts themself
	for (unsigned int i = 0; i < vout.size(); i++) {
	if (!vout[i].IsNull())
	::Serialize(s, CTxOutCompressor(REF(vout[i])), nType, nVersion);
	}
	// coinbase height
	::Serialize(s, VARINT(nHeight), nType, nVersion);
	}

	template<typename Stream>
	void Unserialize(Stream &s, int nType, int nVersion) {
	unsigned int nCode = 0;
	// version
	::Unserialize(s, VARINT(this->nVersion), nType, nVersion);
	// header code
	::Unserialize(s, VARINT(nCode), nType, nVersion);
	fCoinBase = nCode & 1;
	std::vector<bool> vAvail(2, false);
	vAvail[0] = (nCode & 2) != 0;
	vAvail[1] = (nCode & 4) != 0;
	unsigned int nMaskCode = (nCode / 8) + ((nCode & 6) != 0 ? 0 : 1);
	// spentness bitmask
	while (nMaskCode > 0) {
	unsigned char chAvail = 0;
	::Unserialize(s, chAvail, nType, nVersion);
	for (unsigned int p = 0; p < 8; p++) {
	bool f = (chAvail & (1 << p)) != 0;
	vAvail.push_back(f);
	}
	if (chAvail != 0)
	nMaskCode--;
	}
	// txouts themself
	vout.assign(vAvail.size(), CTxOut());
	for (unsigned int i = 0; i < vAvail.size(); i++) {
	if (vAvail[i])
	::Unserialize(s, REF(CTxOutCompressor(vout[i])), nType, nVersion);
	}
	// coinbase height
	::Unserialize(s, VARINT(nHeight), nType, nVersion);
	Cleanup();
	}

	//! mark a vout spent
	bool Spend(uint32_t nPos);

	//! check whether a particular output is still available
	bool IsAvailable(unsigned int nPos) const {
	return (nPos < vout.size() && !vout[nPos].IsNull());
	}

	//! check whether the entire CCoins is spent
	//! note that only !IsPruned() CCoins can be serialized
	bool IsPruned() const {
	BOOST_FOREACH(const CTxOut &out, vout)
	if (!out.IsNull())
	return false;
	return true;
	}

	size_t DynamicMemoryUsage() const {
	size_t ret = memusage::DynamicUsage(vout);
	BOOST_FOREACH(const CTxOut &out, vout) {
	ret += RecursiveDynamicUsage(out.scriptPubKey);
	}
	return ret;
	}
	};

	class CCoinsKeyHasher
	{
	private:
	uint256 salt;

	public:
	CCoinsKeyHasher();

	/**
	* 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 uint256& key) const {
	return key.GetHash(salt);
	}
	};

	struct CCoinsCacheEntry
	{
	CCoins coins; // 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).
	};

	CCoinsCacheEntry() : coins(), flags(0) {}
	};

	typedef boost::unordered_map<uint256, CCoinsCacheEntry, CCoinsKeyHasher> CCoinsMap;

	struct CCoinsStats
	{
	int nHeight;
	uint256 hashBlock;
	uint64_t nTransactions;
	uint64_t nTransactionOutputs;
	uint64_t nSerializedSize;
	uint256 hashSerialized;
	CAmount nTotalAmount;

	CCoinsStats() : nHeight(0), nTransactions(0), nTransactionOutputs(0), nSerializedSize(0), nTotalAmount(0) {}
	};


	/** Abstract view on the open txout dataset. */
	class CCoinsView
	{
	public:
	//! Retrieve the CCoins (unspent transaction outputs) for a given txid
	virtual bool GetCoins(const uint256 &txid, CCoins &coins) const;

	//! Just check whether we have data for a given txid.
	//! This may (but cannot always) return true for fully spent transactions
	virtual bool HaveCoins(const uint256 &txid) const;

	//! Retrieve the block hash whose state this CCoinsView currently represents
	virtual uint256 GetBestBlock() const;

	//! Do a bulk modification (multiple CCoins changes + BestBlock change).
	//! The passed mapCoins can be modified.
	virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);

	//! Calculate statistics about the unspent transaction output set
	virtual bool GetStats(CCoinsStats &stats) const;

	//! As we use CCoinsViews polymorphically, have a virtual destructor
	virtual ~CCoinsView() {}
	};


	/** CCoinsView backed by another CCoinsView */
	class CCoinsViewBacked : public CCoinsView
	{
	protected:
	CCoinsView *base;

	public:
	CCoinsViewBacked(CCoinsView *viewIn);
	bool GetCoins(const uint256 &txid, CCoins &coins) const;
	bool HaveCoins(const uint256 &txid) const;
	uint256 GetBestBlock() const;
	void SetBackend(CCoinsView &viewIn);
	bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
	bool GetStats(CCoinsStats &stats) const;
	};


	class CCoinsViewCache;

	/**
	* A reference to a mutable cache entry. Encapsulating it allows us to run
	* cleanup code after the modification is finished, and keeping track of
	* concurrent modifications.
	*/
	class CCoinsModifier
	{
	private:
	CCoinsViewCache& cache;
	CCoinsMap::iterator it;
	size_t cachedCoinUsage; // Cached memory usage of the CCoins object before modification
	CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage);

	public:
	CCoins* operator->() { return &it->second.coins; }
	CCoins& operator*() { return it->second.coins; }
	~CCoinsModifier();
	friend class CCoinsViewCache;
	};

	/** CCoinsView that adds a memory cache for transactions to another CCoinsView */
	class CCoinsViewCache : public CCoinsViewBacked
	{
	protected:
	/* Whether this cache has an active modifier. */
	bool hasModifier;


	/**
	* 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 CCoins objects. */
	mutable size_t cachedCoinsUsage;

	public:
	CCoinsViewCache(CCoinsView *baseIn);
	~CCoinsViewCache();

	// Standard CCoinsView methods
	bool GetCoins(const uint256 &txid, CCoins &coins) const;
	bool HaveCoins(const uint256 &txid) const;
	uint256 GetBestBlock() const;
	void SetBestBlock(const uint256 &hashBlock);
	bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);

	/**
	* Return a pointer to CCoins in the cache, or NULL if not found. This is
	* more efficient than GetCoins. Modifications to other cache entries are
	* allowed while accessing the returned pointer.
	*/
	const CCoins* AccessCoins(const uint256 &txid) 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
	* allowed.
	*/
	CCoinsModifier ModifyCoins(const uint256 &txid);

	/**
	* Return a modifiable reference to a CCoins. Assumes that no entry with the given
	* txid exists and creates a new one. This saves a database access in the case where
	* the coins were to be wiped out by FromTx anyway. This should not be called with
	* the 2 historical coinbase duplicate pairs because the new coins are marked fresh, and
	* in the event the duplicate coinbase was spent before a flush, the now pruned coins
	* would not properly overwrite the first coinbase of the pair. Simultaneous modifications
	* are not allowed.
	*/
	CCoinsModifier ModifyNewCoins(const uint256 &txid);

	/**
	* 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 transaction with the given hash from the cache, if it is
	+ * not modified.
	+ */
	+ void Uncache(const uint256 &txid);
	+
	//! Calculate the size of the cache (in number of transactions)
	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;

	/**
	* Return priority of tx at height nHeight. Also calculate the sum of the values of the inputs
	* that are already in the chain. These are the inputs that will age and increase priority as
	* new blocks are added to the chain.
	*/
	double GetPriority(const CTransaction &tx, int nHeight, CAmount &inChainInputValue) const;

	const CTxOut &GetOutputFor(const CTxIn& input) const;

	friend class CCoinsModifier;

	private:
	CCoinsMap::iterator FetchCoins(const uint256 &txid);
	CCoinsMap::const_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.
	*/
	CCoinsViewCache(const CCoinsViewCache &);
	};

	#endif // BITCOIN_COINS_H

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