mem_db.cpp

#include "mem_db.hpp"
#include <array>
#include <fstream>

MemDb &MemDb::instance()
{
  static MemDb db;
  return db;
}

static auto ToStr(uint32_t v) -> std::string
{
  auto dig = std::array{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
  auto ret = std::string{};
  for (auto i = 0U; i < sizeof(v) * 2; ++i)
  {
    ret = dig[v % 16] + ret;
    v /= 16;
  }
  return ret;
}

std::optional<std::string> MemDb::lookup(uint32_t hash)
{
  std::unique_lock<std::mutex> lock(mutex);
  for (;;)
  {
    const auto iter = cache.find(hash);
    if (iter != std::end(cache))
      return iter->second;
    std::ifstream strm(".coddle/" + ToStr(hash) + ".artifact", std::ios::binary);
    if (!strm)
    {
      if (wip.find(hash) != std::end(wip))
      {
        cv.wait(lock);
        continue;
      }
      wip.insert(hash);
      return std::nullopt;
    }
    std::ostringstream out;
    out << strm.rdbuf();
    cache.emplace(hash, out.str());
    return out.str();
  }
}

void MemDb::insert(uint32_t hash, const std::string &serOut)
{
  const std::lock_guard<std::mutex> lock(mutex);
  cache.emplace(hash, serOut);
  {
    std::ofstream strm(".coddle/" + ToStr(hash) + ".artifact", std::ios::binary);
    strm << serOut;
  }
  wip.erase(hash);
  cv.notify_all();
}