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lbrycrd/src/coins.h
Wladimir J. van der Laan 509cb006d5 txdb: Add Cursor() method to CCoinsView to iterate over UTXO set 
Add a method Cursor() to CCoinsView that returns a cursor which can be
used to iterate over the whole UTXO set.

- rpc: Change gettxoutsetinfo to use new Cursor method

- txdb: Remove GetStats method - Now that GetStats is implemented in
  terms of Cursor, remove it.
2016-04-15 16:33:05 +02:00

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2015 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;
/** Cursor for iterating over CoinsView state */
class CCoinsViewCursor
{
public:
CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
virtual ~CCoinsViewCursor();
virtual bool GetKey(uint256 &key) const = 0;
virtual bool GetValue(CCoins &coins) const = 0;
/* Don't care about GetKeySize here */
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 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);
//! Get a cursor to iterate over the whole state
virtual CCoinsViewCursor *Cursor() 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);
CCoinsViewCursor *Cursor() 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);
/**
* Check if we have the given tx already loaded in this cache.
* The semantics are the same as HaveCoins(), but no calls to
* the backing CCoinsView are made.
*/
bool HaveCoinsInCache(const uint256 &txid) const;
/**
* 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, bool coinbase);
/**
* 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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