osrm-backend/include/storage/io.hpp

#ifndef OSRM_STORAGE_IO_HPP_
#define OSRM_STORAGE_IO_HPP_

#include "util/exception.hpp"
#include "util/fingerprint.hpp"
#include "util/simple_logger.hpp"

#include <boost/filesystem/fstream.hpp>
#include <boost/iostreams/seek.hpp>

#include <cerrno>
#include <cstring>
#include <tuple>
#include <type_traits>

namespace osrm
{
namespace storage
{
namespace io
{

class FileReader
{
  private:
    const std::string filename;
    boost::filesystem::ifstream input_stream;

  public:
    class LineWrapper : public std::string
    {
        friend std::istream &operator>>(std::istream &is, LineWrapper &line)
        {
            return std::getline(is, line);
        }
    };
    auto GetLineIteratorBegin() { return std::istream_iterator<LineWrapper>(input_stream); }
    auto GetLineIteratorEnd() { return std::istream_iterator<LineWrapper>(); }

    enum FingerprintFlag
    {
        VerifyFingerprint,
        HasNoFingerprint
    };
    FileReader(const std::string &filename, const FingerprintFlag flag)
        : FileReader(boost::filesystem::path(filename), flag)
    {
    }

    FileReader(const boost::filesystem::path &filename_, const FingerprintFlag flag)
        : filename(filename_.string())
    {
        input_stream.open(filename_, std::ios::binary);
        if (!input_stream)
            throw util::exception("Error opening " + filename + ":" + std::strerror(errno));

        if (flag == VerifyFingerprint && !ReadAndCheckFingerprint())
        {
            throw util::exception("Fingerprint mismatch in " + filename);
        }
    }

    /* Read count objects of type T into pointer dest */
    template <typename T> void ReadInto(T *dest, const std::size_t count)
    {
#if not defined __GNUC__ or __GNUC__ > 4
        static_assert(std::is_trivially_copyable<T>::value,
                      "bytewise reading requires trivially copyable type");
#endif

        if (count == 0)
            return;

        const auto &result = input_stream.read(reinterpret_cast<char *>(dest), count * sizeof(T));

        if (!result)
        {
            if (result.eof())
            {
                throw util::exception("Error reading from " + filename +
                                      ": Unexpected end of file");
            }
            throw util::exception("Error reading from " + filename + ": " + std::strerror(errno));
        }
    }

    template <typename T> void ReadInto(std::vector<T> &target)
    {
        ReadInto(target.data(), target.size());
    }

    template <typename T> void ReadInto(T &target) { ReadInto(&target, 1); }

    template <typename T> T ReadOne()
    {
        T tmp;
        ReadInto(tmp);
        return tmp;
    }

    template <typename T> void Skip(const std::size_t element_count)
    {
        boost::iostreams::seek(input_stream, element_count * sizeof(T), BOOST_IOS::cur);
    }

    /*******************************************/

    std::uint32_t ReadElementCount32() { return ReadOne<std::uint32_t>(); }
    std::uint64_t ReadElementCount64() { return ReadOne<std::uint64_t>(); }

    template <typename T> void DeserializeVector(std::vector<T> &data)
    {
        const auto count = ReadElementCount64();
        data.resize(count);
        ReadInto(data.data(), count);
    }

    bool ReadAndCheckFingerprint()
    {
        auto fingerprint = ReadOne<util::FingerPrint>();
        const auto valid = util::FingerPrint::GetValid();
        // compare the compilation state stored in the fingerprint
        return valid.IsMagicNumberOK(fingerprint) && valid.TestContractor(fingerprint) &&
               valid.TestGraphUtil(fingerprint) && valid.TestRTree(fingerprint) &&
               valid.TestQueryObjects(fingerprint);
    }

    std::size_t Size()
    {
        auto current_pos = input_stream.tellg();
        input_stream.seekg(0, input_stream.end);
        auto length = input_stream.tellg();
        input_stream.seekg(current_pos, input_stream.beg);
        return length;
    }

    std::vector<std::string> ReadLines()
    {
        std::vector<std::string> result;
        std::string thisline;
        try
        {
            while (std::getline(input_stream, thisline))
            {
                result.push_back(thisline);
            }
        }
        catch (const std::ios_base::failure &e)
        {
            // EOF is OK here, everything else, re-throw
            if (!input_stream.eof())
                throw;
        }
        return result;
    }

    std::string ReadLine()
    {
        std::string thisline;
        try
        {
            std::getline(input_stream, thisline);
        }
        catch (const std::ios_base::failure &e)
        {
            // EOF is OK here, everything else, re-throw
            if (!input_stream.eof())
                throw;
        }
        return thisline;
    }
};
}
}
}

#endif