largeobject.hxx

/* Large Objects interface.
 *
 * Allows access to large objects directly, or through I/O streams.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/largeobject instead.
 *
 * Copyright (c) 2000-2020, Jeroen T. Vermeulen.
 *
 * See COPYING for copyright license.  If you did not receive a file called
 * COPYING with this source code, please notify the distributor of this
 * mistake, or contact the author.
 */
#ifndef PQXX_H_LARGEOBJECT
#define PQXX_H_LARGEOBJECT

#include "pqxx/compiler-public.hxx"
#include "pqxx/internal/compiler-internal-pre.hxx"

#include <streambuf>

#include "pqxx/dbtransaction.hxx"


namespace pqxx
{

class PQXX_LIBEXPORT largeobject
{
public:
  using size_type = large_object_size_type;

  largeobject() noexcept = default;


  explicit largeobject(dbtransaction &t);


  explicit largeobject(oid o) noexcept : m_id{o} {}


  largeobject(dbtransaction &t, std::string_view file);


  largeobject(largeobjectaccess const &o) noexcept;


  [[nodiscard]] oid id() const noexcept { return m_id; }


  [[nodiscard]] bool operator==(largeobject const &other) const
  {
    return m_id == other.m_id;
  }

  [[nodiscard]] bool operator!=(largeobject const &other) const
  {
    return m_id != other.m_id;
  }

  [[nodiscard]] bool operator<=(largeobject const &other) const
  {
    return m_id <= other.m_id;
  }

  [[nodiscard]] bool operator>=(largeobject const &other) const
  {
    return m_id >= other.m_id;
  }

  [[nodiscard]] bool operator<(largeobject const &other) const
  {
    return m_id < other.m_id;
  }

  [[nodiscard]] bool operator>(largeobject const &other) const
  {
    return m_id > other.m_id;
  }


  void to_file(dbtransaction &t, std::string_view file) const;


  void remove(dbtransaction &t) const;

protected:
  PQXX_PURE static internal::pq::PGconn *
  raw_connection(dbtransaction const &T);

  PQXX_PRIVATE std::string reason(connection const &, int err) const;

private:
  oid m_id = oid_none;
};


class PQXX_LIBEXPORT largeobjectaccess : private largeobject
{
public:
  using largeobject::size_type;
  using off_type = size_type;
  using pos_type = size_type;


  using openmode = std::ios::openmode;

  static constexpr auto default_mode{std::ios::in | std::ios::out |
                                     std::ios::binary};

  using seekdir = std::ios::seekdir;


  explicit largeobjectaccess(dbtransaction &t, openmode mode = default_mode);


  largeobjectaccess(dbtransaction &t, oid o, openmode mode = default_mode);


  largeobjectaccess(
    dbtransaction &t, largeobject o, openmode mode = default_mode);


  largeobjectaccess(
    dbtransaction &t, std::string_view file, openmode mode = default_mode);

  ~largeobjectaccess() noexcept { close(); }


  using largeobject::id;


  void to_file(std::string_view file) const
  {
    largeobject::to_file(m_trans, file);
  }

  using largeobject::to_file;


  void write(char const buf[], size_t len);


  void write(std::string_view buf) { write(buf.data(), buf.size()); }


  size_type read(char buf[], size_t len);


  size_type seek(size_type dest, seekdir dir);


  [[nodiscard]] size_type tell() const;


  pos_type cseek(off_type dest, seekdir dir) noexcept;


  off_type cwrite(char const buf[], size_t len) noexcept;


  off_type cread(char buf[], size_t len) noexcept;


  [[nodiscard]] pos_type ctell() const noexcept;

  void process_notice(std::string const &) noexcept;

  using largeobject::remove;

  using largeobject::operator==;
  using largeobject::operator!=;
  using largeobject::operator<;
  using largeobject::operator<=;
  using largeobject::operator>;
  using largeobject::operator>=;

  largeobjectaccess() = delete;
  largeobjectaccess(largeobjectaccess const &) = delete;
  largeobjectaccess operator=(largeobjectaccess const &) = delete;

private:
  PQXX_PRIVATE std::string reason(int err) const;
  internal::pq::PGconn *raw_connection() const
  {
    return largeobject::raw_connection(m_trans);
  }

  PQXX_PRIVATE void open(openmode mode);
  void close() noexcept;

  dbtransaction &m_trans;
  int m_fd = -1;
};



template<typename CHAR = char, typename TRAITS = std::char_traits<CHAR>>
class largeobject_streambuf : public std::basic_streambuf<CHAR, TRAITS>
{
  using size_type = largeobject::size_type;

public:
  using char_type = CHAR;
  using traits_type = TRAITS;
  using int_type = typename traits_type::int_type;
  using pos_type = typename traits_type::pos_type;
  using off_type = typename traits_type::off_type;
  using openmode = largeobjectaccess::openmode;
  using seekdir = largeobjectaccess::seekdir;

  static constexpr auto default_mode{std::ios::in | std::ios::out |
                                     std::ios::binary};

  largeobject_streambuf(
    dbtransaction &t, largeobject o, openmode mode = default_mode,
    size_type buf_size = 512) :
          m_bufsize{buf_size},
          m_obj{t, o, mode},
          m_g{nullptr},
          m_p{nullptr}
  {
    initialize(mode);
  }

  largeobject_streambuf(
    dbtransaction &t, oid o, openmode mode = default_mode,
    size_type buf_size = 512) :
          m_bufsize{buf_size},
          m_obj{t, o, mode},
          m_g{nullptr},
          m_p{nullptr}
  {
    initialize(mode);
  }

  virtual ~largeobject_streambuf() noexcept
  {
    delete[] m_p;
    delete[] m_g;
  }

  void process_notice(std::string const &s) { m_obj.process_notice(s); }

protected:
  virtual int sync() override
  {
    // setg() sets eback, gptr, egptr.
    this->setg(this->eback(), this->eback(), this->egptr());
    return overflow(eof());
  }

  virtual pos_type seekoff(off_type offset, seekdir dir, openmode) override
  {
    return adjust_eof(m_obj.cseek(largeobjectaccess::off_type(offset), dir));
  }

  virtual pos_type seekpos(pos_type pos, openmode) override
  {
    largeobjectaccess::pos_type const newpos{
      m_obj.cseek(largeobjectaccess::off_type(pos), std::ios::beg)};
    return adjust_eof(newpos);
  }

  virtual int_type overflow(int_type ch) override
  {
    auto *const pp{this->pptr()};
    if (pp == nullptr)
      return eof();
    auto *const pb{this->pbase()};
    int_type res{0};

    if (pp > pb)
    {
      auto const out{
        adjust_eof(m_obj.cwrite(pb, static_cast<std::size_t>(pp - pb)))};
      if constexpr (std::is_arithmetic_v<decltype(out)>)
        res = check_cast<int_type>(out);
      else
        res = int_type(out);
    }
    this->setp(m_p, m_p + m_bufsize);

    // Write that one more character, if it's there.
    if (ch != eof())
    {
      *this->pptr() = static_cast<char_type>(ch);
      this->pbump(1);
    }
    return res;
  }

  virtual int_type overflow() { return overflow(eof()); }

  virtual int_type underflow() override
  {
    if (this->gptr() == nullptr)
      return eof();
    auto *const eb{this->eback()};
    auto const res{adjust_eof(
      m_obj.cread(this->eback(), static_cast<std::size_t>(m_bufsize)))};
    this->setg(
      eb, eb, eb + (res == eof() ? 0 : static_cast<std::size_t>(res)));
    return (res == eof() or res == 0) ? eof() : traits_type::to_int_type(*eb);
  }

private:
  static int_type eof() { return traits_type::eof(); }

  template<typename INTYPE> static std::streampos adjust_eof(INTYPE pos)
  {
    bool const at_eof{pos == -1};
    if constexpr (std::is_arithmetic_v<std::streampos>)
    {
      return check_cast<std::streampos>(
        (at_eof ? eof() : pos), "large object seek");
    }
    else
    {
      return std::streampos(at_eof ? eof() : pos);
    }
  }

  void initialize(openmode mode)
  {
    if ((mode & std::ios::in) != 0)
    {
      m_g = new char_type[unsigned(m_bufsize)];
      this->setg(m_g, m_g, m_g);
    }
    if ((mode & std::ios::out) != 0)
    {
      m_p = new char_type[unsigned(m_bufsize)];
      this->setp(m_p, m_p + m_bufsize);
    }
  }

  size_type const m_bufsize;
  largeobjectaccess m_obj;

  char_type *m_g, *m_p;
};



template<typename CHAR = char, typename TRAITS = std::char_traits<CHAR>>
class basic_ilostream : public std::basic_istream<CHAR, TRAITS>
{
  using super = std::basic_istream<CHAR, TRAITS>;

public:
  using char_type = CHAR;
  using traits_type = TRAITS;
  using int_type = typename traits_type::int_type;
  using pos_type = typename traits_type::pos_type;
  using off_type = typename traits_type::off_type;


  basic_ilostream(
    dbtransaction &t, largeobject o, largeobject::size_type buf_size = 512) :
          super{nullptr},
          m_buf{t, o, std::ios::in | std::ios::binary, buf_size}
  {
    super::init(&m_buf);
  }


  basic_ilostream(
    dbtransaction &t, oid o, largeobject::size_type buf_size = 512) :
          super{nullptr},
          m_buf{t, o, std::ios::in | std::ios::binary, buf_size}
  {
    super::init(&m_buf);
  }

private:
  largeobject_streambuf<CHAR, TRAITS> m_buf;
};

using ilostream = basic_ilostream<char>;



template<typename CHAR = char, typename TRAITS = std::char_traits<CHAR>>
class basic_olostream : public std::basic_ostream<CHAR, TRAITS>
{
  using super = std::basic_ostream<CHAR, TRAITS>;

public:
  using char_type = CHAR;
  using traits_type = TRAITS;
  using int_type = typename traits_type::int_type;
  using pos_type = typename traits_type::pos_type;
  using off_type = typename traits_type::off_type;


  basic_olostream(
    dbtransaction &t, largeobject o, largeobject::size_type buf_size = 512) :
          super{nullptr},
          m_buf{t, o, std::ios::out | std::ios::binary, buf_size}
  {
    super::init(&m_buf);
  }


  basic_olostream(
    dbtransaction &t, oid o, largeobject::size_type buf_size = 512) :
          super{nullptr},
          m_buf{t, o, std::ios::out | std::ios::binary, buf_size}
  {
    super::init(&m_buf);
  }

  ~basic_olostream()
  {
    try
    {
      m_buf.pubsync();
      m_buf.pubsync();
    }
    catch (std::exception const &e)
    {
      m_buf.process_notice(e.what());
    }
  }

private:
  largeobject_streambuf<CHAR, TRAITS> m_buf;
};

using olostream = basic_olostream<char>;



template<typename CHAR = char, typename TRAITS = std::char_traits<CHAR>>
class basic_lostream : public std::basic_iostream<CHAR, TRAITS>
{
  using super = std::basic_iostream<CHAR, TRAITS>;

public:
  using char_type = CHAR;
  using traits_type = TRAITS;
  using int_type = typename traits_type::int_type;
  using pos_type = typename traits_type::pos_type;
  using off_type = typename traits_type::off_type;


  basic_lostream(
    dbtransaction &t, largeobject o, largeobject::size_type buf_size = 512) :
          super{nullptr},
          m_buf{t, o, std::ios::in | std::ios::out | std::ios::binary,
                buf_size}
  {
    super::init(&m_buf);
  }


  basic_lostream(
    dbtransaction &t, oid o, largeobject::size_type buf_size = 512) :
          super{nullptr},
          m_buf{t, o, std::ios::in | std::ios::out | std::ios::binary,
                buf_size}
  {
    super::init(&m_buf);
  }

  ~basic_lostream()
  {
    try
    {
      m_buf.pubsync();
      m_buf.pubsync();
    }
    catch (std::exception const &e)
    {
      m_buf.process_notice(e.what());
    }
  }

private:
  largeobject_streambuf<CHAR, TRAITS> m_buf;
};

using lostream = basic_lostream<char>;
} // namespace pqxx

#include "pqxx/internal/compiler-internal-post.hxx"
#endif