## 【比特币】Merkle树

2019年05月15日 ⁄ 综合 ⁄ 共 1628字 ⁄ 字号 评论关闭

In cryptography and computer
science
a hash tree or Merkle
tree
is a tree in which every non-leaf node is labelled with the hash of
the labels of its children nodes.

uint256 CBlock::BuildMerkleTree() const
{
vMerkleTree.clear();
BOOST_FOREACH(const CTransaction& tx, vtx)
vMerkleTree.push_back(tx.GetHash());
int j = 0;
for (int nSize = vtx.size(); nSize > 1; nSize = (nSize + 1) / 2)
{
for (int i = 0; i < nSize; i += 2)
{
int i2 = std::min(i+1, nSize-1);
vMerkleTree.push_back(Hash(BEGIN(vMerkleTree[j+i]),  END(vMerkleTree[j+i]),
BEGIN(vMerkleTree[j+i2]), END(vMerkleTree[j+i2])));
}
j += nSize;
}
return (vMerkleTree.empty() ? 0 : vMerkleTree.back());
}

/** Compute the 256-bit hash of the concatenation of two objects. */
template<typename T1, typename T2>
inline uint256 Hash(const T1 p1begin, const T1 p1end,
const T2 p2begin, const T2 p2end) {
static const unsigned char pblank[1] = {};
uint256 result;
CHash256().Write(p1begin == p1end ? pblank : (const unsigned char*)&p1begin[0], (p1end - p1begin) * sizeof(p1begin[0]))
.Write(p2begin == p2end ? pblank : (const unsigned char*)&p2begin[0], (p2end - p2begin) * sizeof(p2begin[0]))
.Finalize((unsigned char*)&result);
return result;
}

/** A hasher class for Bitcoin's 256-bit hash (double SHA-256). */
class CHash256 {
private:
CSHA256 sha;
public:
static const size_t OUTPUT_SIZE = CSHA256::OUTPUT_SIZE;

void Finalize(unsigned char hash[OUTPUT_SIZE]) {
unsigned char buf[sha.OUTPUT_SIZE];
sha.Finalize(buf);
sha.Reset().Write(buf, sha.OUTPUT_SIZE).Finalize(hash);
}

CHash256& Write(const unsigned char *data, size_t len) {
sha.Write(data, len);
return *this;
}

CHash256& Reset() {
sha.Reset();
return *this;
}
};