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Merkle.cpp
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Merkle.cpp
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//
// Fulcrum - A fast & nimble SPV Server for Bitcoin Cash
// Copyright (C) 2019-2020 Calin A. Culianu <calin.culianu@gmail.com>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program (see LICENSE.txt). If not, see
// <https://www.gnu.org/licenses/>.
//
#include "Merkle.h"
#include "Util.h"
#include <algorithm>
#include <list>
namespace Merkle {
BranchAndRootPair branchAndRoot(const HashVec &hashVec, unsigned index, const std::optional<unsigned> & optLen)
{
BranchAndRootPair ret;
const unsigned hvsz = unsigned(hashVec.size());
if (!hvsz || index >= hvsz) {
Error() << __PRETTY_FUNCTION__ << ": Misused. Please specify a non-empty hash vector as well as an in-range index. FIXME!";
throw BadArgs(QString("Bad args to %1").arg(__FUNCTION__));
}
const unsigned natLen = branchLength(unsigned(hvsz));
const unsigned length = optLen.value_or(natLen);
if (length < natLen) {
Error() << __PRETTY_FUNCTION__ << ": Misused. Must specify a length argument that is >= " << natLen << " for a vector of size " << hvsz << ". FIXME!";
throw BadArgs(QString("Bad length arg to %1").arg(__FUNCTION__));
}
HashVec branch;
branch.reserve(length);
HashVec hashes;
hashes.reserve(hvsz+1);
// Copy all hashVec to our working vector, to start. This vector mutates as we iterate below.
hashes.insert(hashes.end(), hashVec.begin(), hashVec.end());
for (unsigned i = 0; i < length; ++i) {
if (hashes.size() & 0x1) // is odd, add the end twice
hashes.emplace_back(hashes.back());
branch.push_back(hashes[index ^ 1]);
index >>= 1;
constexpr auto recomputeHashes = [](HashVec & hashes) {
HashVec hv;
const unsigned sz = unsigned(hashes.size());
hv.reserve( (sz / 2) + 1 );
for (unsigned i = 0; i < sz; i+=2) {
hv.emplace_back(BTC::Hash(hashes[i] + hashes[i+1]));
}
hashes.swap(hv);
};
recomputeHashes(hashes); // makes hashes be 1/2 the size each time
}
if (UNLIKELY(hashes.empty())) {
Error() << __PRETTY_FUNCTION__ << ": INTERNAL ERROR. Output vector is empty! FIXME!";
throw InternalError(QString("%1: Output hash vector is empty").arg(__FUNCTION__));
}
ret = { std::move(branch), hashes.front() };
return ret;
}
Hash rootFromProof(const Hash & hashIn, const HashVec &branch, unsigned index)
{
Hash hash = hashIn; // shallow copy, working hash
for (const auto & h : branch) {
if (index & 1) // odd
hash = BTC::Hash(h + hash);
else
hash = BTC::Hash(hash + h);
index >>= 1;
}
if (index) {
Error() << __PRETTY_FUNCTION__ << ": INTERNAL ERROR. Passed-in index is out of range! FIXME!";
throw BadArgs(QString("%1: Index argument out of range").arg(__FUNCTION__));
}
return hash;
}
HashVec level(const HashVec &hashes, unsigned depthHigher)
{
HashVec ret;
if (depthHigher > MaxDepth) {
Error() << __PRETTY_FUNCTION__ << ": INTERNAL ERROR. depthHigher is too large " << depthHigher << " > " << MaxDepth << ". FIXME!";
throw BadArgs("Argument depthHigher is too large");
}
if (hashes.empty()) {
Error() << __PRETTY_FUNCTION__ << ": INTERNAL ERROR. empty hashes vector! FIXME!";
throw BadArgs("Argument hashes cannot be empty");
}
const unsigned hsz = unsigned(hashes.size());
const unsigned size = 1 << depthHigher;
ret.reserve(hsz/size + 1);
for (unsigned i = 0; i < hsz; i += size) {
const auto endIndex = std::min(i+size, hsz); // ensure we don't go past end of array
ret.emplace_back(
root(HashVec(hashes.begin()+i, hashes.begin()+endIndex), depthHigher) );
}
return ret;
}
BranchAndRootPair branchAndRootFromLevel(const HashVec & level, const HashVec & leafHashes, unsigned index, unsigned depthHigher)
{
BranchAndRootPair ret;
if (level.empty() || leafHashes.empty() || depthHigher > MaxDepth) {
Error() << __PRETTY_FUNCTION__ << ": Invalid args";
throw BadArgs(QString("Invalid arguments to %1").arg(__FUNCTION__));
}
const unsigned leafIndex = (index >> depthHigher) << depthHigher; // funny way to make 0's on the right.
auto leafPair = branchAndRoot(leafHashes, index - leafIndex, depthHigher);
auto & [leafBranch, leafRoot] = leafPair;
index >>= depthHigher;
const auto levelPair = branchAndRoot(level, index);
const auto & [levelBranch, root] = levelPair;
if (index >= level.size() || leafRoot != level[index]) {
Error() << __PRETTY_FUNCTION__ << ": leaf hashes inconsistent with level. FIXME!";
throw InternalError(QString("%1: leaf hashes inconsistent with level").arg(__FUNCTION__));
}
auto & outVec (leafBranch); // we concatenate to the end of this vector
outVec.reserve(outVec.size() + levelBranch.size()); // make room
// concatenate leaf hash vector and level hash vector together (back into our leafBranch vector to save on redundant copies)
std::move(levelBranch.begin(), levelBranch.end(), std::back_inserter(outVec));
ret = { std::move(outVec), root };
return ret;
}
void test() {
Merkle::HashVec txs = {
"5b357a2f1f18955e8fd08dc2d8443b0806cbbe6d60b29a7370844e4815ff0efb",
"001dd1663f777a646190959122bcfd69ad6160c28bc3e99e3df65b1cb26bcc6d",
"036ec76bdcd873d70f31c95637624c9ec975622cd2a7f34ff0130b36f51f87bb",
"9e7ea0aa7df987ebafa2d392bee9bd5076a7b787bd450295cbcfc029224ed5e7",
"e92c4f0a7e04ef1e65141c59343006f384a91b79605ca98dfe5caef7404481d5",
"fdc2657742610dbc3dbea05f3e072b33811248b01a1b8de397fb68b0d67af4be",
"768df8f9ef6226f3dddb2f532c28565b5d4f4d3e575d88f0cf7df8e3bf76a9b3",
"590b32aaefb8ddf113ad6be70934381b951931a3076fa82ab199416eb01dcb48",
"00000000f8bf61018ddd77d23c112e874682704a290252f635e7df06c8a317b8",
};
for (auto & tx : txs) tx = QByteArray::fromHex(tx);
auto pair = Merkle::branchAndRoot(txs, 0);
static const auto ba2quoted = [](const auto &b){return QString("'%1'").arg(QString::fromUtf8(b.toHex()));};
Log() << "Txs: [ " << Util::Stringify(txs, ba2quoted) << " ]";
Log() << "Branch: [ " << Util::Stringify(pair.first, ba2quoted) << " ]";
Log() << "Root: '" << pair.second.toHex() << "'";
Log() << "Level1: [ " << Util::Stringify(Merkle::level(txs, 1), ba2quoted) << " ]";
const size_t num = 64000;
Log() << "Testing performance, filling " << num << " hashes and computing merkle...";
// next, test perfromance -- by
Merkle::HashVec txs2(num);
for (size_t i = 0; i < txs2.size(); ++i) {
QByteArray & ba = txs2[i];
ba.resize(HashLen);
QRandomGenerator::securelySeeded().fillRange(reinterpret_cast<uint32_t *>(ba.data()), HashLen/sizeof(uint32_t));
}
const auto t0 = Util::getTimeNS();
auto pair2 = Merkle::branchAndRoot(txs2, 0);
Log() << "Merkle took: " << QString::number((Util::getTimeNS() - t0)/1e6, 'f', 4) << " msec";
}
Cache::Cache(const GetHashesFunc & f)
: getHashesFunc(f)
{
if (!getHashesFunc)
throw BadArgs("Merkle::Cache requires a valid getHashes function");
}
HashVec Cache::getHashes(unsigned int from, unsigned int count) const
{
QString err;
auto ret = getHashesFunc(from, count, &err);
if (ret.size() != count) {
throw InternalError(QString("In getHashes, expected %1 hashes, instead got %2%3")
.arg(count).arg(ret.size()).arg(err.isEmpty() ? "" : QString(": %1").arg(err)));
} else if (!err.isEmpty())
throw InternalError(err);
return ret;
}
void Cache::initialize(unsigned l)
{
ExclusiveLockGuard g(lock);
Log() << "Initializing header merkle cache ...";
const auto hashes = getHashes(0, l);
initialize_nolock(hashes);
}
void Cache::initialize(const HashVec &hashes)
{
ExclusiveLockGuard g(lock);
Log() << "Initializing header merkle cache ...";
initialize_nolock(hashes);
}
void Cache::initialize_nolock(const HashVec &hashes)
{
length = unsigned(hashes.size());
if (!length)
throw BadArgs("Merkle cache was initialized with an empty vector");
depthHigher = Merkle::treeDepth(length) / 2;
level = getLevel(hashes);
initialized = true;
Debug() << "Merkle cache initialized to length " << length;
}
HashVec Cache::getLevel(const HashVec &hashes) const {
return Merkle::level(hashes, depthHigher);
}
void Cache::extendTo(unsigned l) {
if (l <= length)
return;
auto start = leafStart(length);
// Note this may throw here if a reorg happened and not enough headers now exist. Caller will just send error
// to the client, which is what we want.
auto hashes = getHashes(start, l-start);
const auto limit = (start >> depthHigher);
if (limit > level.size())
throw InternalError("limit > levelSize in extendTo");
level.erase(level.begin() + limit, level.end());
auto vec = getLevel(hashes);
level.reserve(level.size() + vec.size());
level.insert(level.end(), vec.begin(), vec.end());
length = l;
Debug() << "Merkle cache extended to length " << length;
}
HashVec Cache::levelFor(unsigned l) const
{
HashVec ret;
if (l == length) {
ret = level;
return ret;
}
unsigned limit = l >> depthHigher;
if (limit >= level.size())
// should we throw do this instead?
//limit = unsigned(level.size());
throw InternalError("limit >= levelSize");
ret.reserve(limit);
ret.insert(ret.end(), level.begin(), level.begin() + limit);
const auto leafstart = leafStart(l);
const auto count = std::min(segmentLength(), l - leafstart);
const auto hashes = getHashes(leafstart, count);
const auto vec = getLevel(hashes);
ret.reserve(ret.size() + vec.size());
ret.insert(ret.end(), vec.begin(), vec.end());
return ret;
}
BranchAndRootPair Cache::branchAndRoot(unsigned length, unsigned index)
{
if (!length)
throw BadArgs(QString("%1: length must not be 0").arg(__FUNCTION__));
if (index >= length)
throw BadArgs(QString("%1: index must be less than length").arg(__FUNCTION__));
if (!initialized)
throw InternalError(QString("%1: Merkle cache is not initialized").arg(__FUNCTION__));
BranchAndRootPair ret;
ExclusiveLockGuard g(lock);
extendTo(length);
if (length > this->length) {
// ruh-roh.. what to do here?
throw InternalError(QString("%1: extendTo failed to extend length to %2").arg(__FUNCTION__).arg(length));
}
auto ls = leafStart(index);
auto count = std::min(segmentLength(), length - ls);
auto leafHashes = getHashes(ls, count);
if (length < segmentLength()) {
ret = Merkle::branchAndRoot(leafHashes, index);
return ret;
}
auto level = levelFor(length);
ret = Merkle::branchAndRootFromLevel(level, leafHashes, index, depthHigher);
return ret;
}
void Cache::truncate(unsigned length)
{
if (!initialized)
return;
if (!length)
throw BadArgs(QString("%1: length cannot be 0").arg(__FUNCTION__));
ExclusiveLockGuard g(lock);
if (this->length <= length)
// we are already smaller than length, so it's fine.
return;
length = leafStart(length);
this->length = length;
auto limit = length >> depthHigher;
if (limit > level.size()) {
limit = unsigned(level.size());
Warning() << "limit > levelSize in merkle cache truncate. FIXME!";
}
level.erase(level.begin()+limit, level.end());
Debug() << "Merkle cache truncated to length " << length;
}
} // end namespace Merkle