Function DownloadAndCacheFile

src/colmap/util/file.cc:470–515

}

std::string DownloadAndCacheFile(const std::string& uri) {
  const std::vector<std::string> parts = StringSplit(uri, ";");
  THROW_CHECK_EQ(parts.size(), 3)
      << "Invalid URI format. Expected: <url>;<name>;<sha256>";

  const std::string& url = parts[0];
  THROW_CHECK(!url.empty());
  const std::string& name = parts[1];
  THROW_CHECK(!name.empty());
  const std::string& sha256 = parts[2];
  THROW_CHECK_EQ(sha256.size(), 64);

  std::filesystem::path download_cache_dir;
  if (download_cache_dir_overwrite.has_value()) {
    download_cache_dir = *download_cache_dir_overwrite;
  } else {
    const std::optional<std::filesystem::path> home_dir = HomeDir();
    THROW_CHECK(home_dir.has_value());
    download_cache_dir = *home_dir / ".cache" / "colmap";
  }

  if (!std::filesystem::exists(download_cache_dir)) {
    VLOG(2) << "Creating download cache directory: " << download_cache_dir;
    THROW_CHECK(std::filesystem::create_directories(download_cache_dir));
  }

  const auto path = download_cache_dir / (sha256 + "-" + name);

  if (std::filesystem::exists(path)) {
    VLOG(2) << "File already downloaded. Skipping download.";
    std::vector<char> blob;
    ReadBinaryBlob(path.string(), &blob);
    THROW_CHECK_EQ(ComputeSHA256({blob.data(), blob.size()}), sha256)
        << "The cached file does not match the expected SHA256";
  } else {
    LOG(INFO) << "Downloading file from: " << url;
    const std::optional<std::string> blob = DownloadFile(url);
    THROW_CHECK(blob.has_value()) << "Failed to download file";
    THROW_CHECK_EQ(ComputeSHA256({blob->data(), blob->size()}), sha256)
        << "The downloaded file does not match the expected SHA256";
    LOG(INFO) << "Caching file at: " << path;
    WriteBinaryBlob(path.string(), {blob->data(), blob->size()});
  }

  return path.string();
}

void OverwriteDownloadCacheDir(std::filesystem::path path) {
  download_cache_dir_overwrite = std::move(path);