solidity/libsolutil/IpfsHash.cpp
2020-04-09 17:01:26 +02:00

203 lines
5.0 KiB
C++

/*
This file is part of solidity.
solidity 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.
solidity 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 solidity. If not, see <http://www.gnu.org/licenses/>.
*/
#include <libsolutil/IpfsHash.h>
#include <libsolutil/Assertions.h>
#include <libsolutil/Exceptions.h>
#include <libsolutil/picosha2.h>
#include <libsolutil/CommonData.h>
using namespace std;
using namespace solidity;
using namespace solidity::util;
namespace
{
bytes varintEncoding(size_t _n)
{
bytes encoded;
while (_n > 0x7f)
{
encoded.emplace_back(uint8_t(0x80 | (_n & 0x7f)));
_n >>= 7;
}
encoded.emplace_back(_n);
return encoded;
}
bytes encodeByteArray(bytes const& _data)
{
return bytes{0x0a} + varintEncoding(_data.size()) + _data;
}
bytes encodeHash(bytes const& _data)
{
return bytes{0x12, 0x20} + picosha2::hash256(_data);
}
bytes encodeLinkData(bytes const& _data)
{
return bytes{0x12} + varintEncoding(_data.size()) + _data;
}
string base58Encode(bytes const& _data)
{
static string const alphabet{"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"};
bigint data(toHex(_data, HexPrefix::Add));
string output;
while (data)
{
output += alphabet[size_t(data % alphabet.size())];
data /= alphabet.size();
}
reverse(output.begin(), output.end());
return output;
}
struct Chunk
{
Chunk() = default;
Chunk(bytes _hash, size_t _size, size_t _blockSize):
hash(std::move(_hash)),
size(_size),
blockSize(_blockSize)
{}
bytes hash = {};
size_t size = 0;
size_t blockSize = 0;
};
using Chunks = vector<Chunk>;
Chunk combineLinks(Chunks& _links)
{
bytes data = {};
bytes lengths = {};
Chunk chunk = {};
for (Chunk& link: _links)
{
chunk.size += link.size;
chunk.blockSize += link.blockSize;
data += encodeLinkData(
bytes {0x0a} +
varintEncoding(link.hash.size()) +
std::move(link.hash) +
bytes{0x12, 0x00, 0x18} +
varintEncoding(link.blockSize)
);
lengths += bytes{0x20} + varintEncoding(link.size);
}
bytes blockData = data + encodeByteArray(bytes{0x08, 0x02, 0x18} + varintEncoding(chunk.size) + lengths);
chunk.blockSize += blockData.size();
chunk.hash = encodeHash(blockData);
return chunk;
}
Chunks buildNextLevel(Chunks& _currentLevel)
{
size_t const maxChildNum = 174;
Chunks nextLevel;
Chunks links;
for (Chunk& chunk: _currentLevel)
{
links.emplace_back(std::move(chunk.hash), chunk.size, chunk.blockSize);
if (links.size() == maxChildNum)
{
nextLevel.emplace_back(combineLinks(links));
links = {};
}
}
if (!links.empty())
nextLevel.emplace_back(combineLinks(links));
return nextLevel;
}
/// Builds a tree starting from the bottom level where nodes are data nodes.
/// Data nodes should be calculated and passed as the only level in chunk levels
/// Each next level is calculated as following:
/// - Pick up to maxChildNum (174) nodes until a whole level is added, group them and pass to the node in the next level
/// - Do this until the current level has only one node, return the hash in that node
bytes groupChunksBottomUp(Chunks _currentLevel)
{
// when we reach root it will be the only node in that level
while (_currentLevel.size() != 1)
_currentLevel = buildNextLevel(_currentLevel);
// top level's only node stores the hash for file
return _currentLevel.front().hash;
}
}
bytes solidity::util::ipfsHash(string _data)
{
size_t const maxChunkSize = 1024 * 256;
size_t chunkCount = _data.length() / maxChunkSize + (_data.length() % maxChunkSize > 0 ? 1 : 0);
chunkCount = chunkCount == 0 ? 1 : chunkCount;
Chunks allChunks;
for (size_t chunkIndex = 0; chunkIndex < chunkCount; chunkIndex++)
{
bytes chunkBytes = asBytes(
_data.substr(chunkIndex * maxChunkSize, min(maxChunkSize, _data.length() - chunkIndex * maxChunkSize))
);
bytes lengthAsVarint = varintEncoding(chunkBytes.size());
bytes protobufEncodedData;
// Type: File
protobufEncodedData += bytes{0x08, 0x02};
if (!chunkBytes.empty())
{
// Data (length delimited bytes)
protobufEncodedData += bytes{0x12};
protobufEncodedData += lengthAsVarint;
protobufEncodedData += chunkBytes;
}
// filesize: length as varint
protobufEncodedData += bytes{0x18} + lengthAsVarint;
// PBDag:
// Data: (length delimited bytes)
bytes blockData = encodeByteArray(protobufEncodedData);
// Multihash: sha2-256, 256 bits
allChunks.emplace_back(
encodeHash(blockData),
chunkBytes.size(),
blockData.size()
);
}
return groupChunksBottomUp(std::move(allChunks));
}
string solidity::util::ipfsHashBase58(string _data)
{
return base58Encode(ipfsHash(std::move(_data)));
}