blob.hxx

/* Binary Large Objects interface.
 *
 * Read or write large objects, stored in their own storage on the server.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/largeobject instead.
 *
 * Copyright (c) 2000-2025, 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_BLOB
#define PQXX_H_BLOB

#if !defined(PQXX_HEADER_PRE)
#  error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
#endif

#include <cstdint>

#if defined(PQXX_HAVE_PATH)
#  include <filesystem>
#endif

// C++20: Assume support.
#if defined(PQXX_HAVE_RANGES)
#  include <ranges>
#endif

// C++20: Assume support.
#if __has_include(<span>)
#  include <span>
#endif

#include "pqxx/dbtransaction.hxx"


namespace pqxx
{
class PQXX_LIBEXPORT blob
{
public:

  [[nodiscard]] static oid create(dbtransaction &, oid = 0);

  static void remove(dbtransaction &, oid);

  [[nodiscard]] static blob open_r(dbtransaction &, oid);
  // Open blob for writing.  Any attempt to read from it will fail.
  [[nodiscard]] static blob open_w(dbtransaction &, oid);
  // Open blob for reading and/or writing.
  [[nodiscard]] static blob open_rw(dbtransaction &, oid);


  blob() = default;

  blob(blob &&);
  blob &operator=(blob &&);

  blob(blob const &) = delete;
  blob &operator=(blob const &) = delete;
  ~blob();


  static constexpr std::size_t chunk_limit = 0x7fffffff;


  std::size_t read(bytes &buf, std::size_t size);

#if defined(PQXX_HAVE_SPAN)

  template<std::size_t extent = std::dynamic_extent>
  std::span<std::byte> read(std::span<std::byte, extent> buf)
  {
    return buf.subspan(0, raw_read(std::data(buf), std::size(buf)));
  }
#endif // PQXX_HAVE_SPAN

#if defined(PQXX_HAVE_CONCEPTS) && defined(PQXX_HAVE_RANGES) &&               \
  defined(PQXX_HAVE_SPAN)

  template<binary DATA> std::span<std::byte> read(DATA &buf)
  {
    return {std::data(buf), raw_read(std::data(buf), std::size(buf))};
  }
#else  // PQXX_HAVE_CONCEPTS && PQXX_HAVE_SPAN

  template<typename ALLOC> bytes_view read(std::vector<std::byte, ALLOC> &buf)
  {
    return {std::data(buf), raw_read(std::data(buf), std::size(buf))};
  }
#endif // PQXX_HAVE_CONCEPTS && PQXX_HAVE_SPAN

#if defined(PQXX_HAVE_CONCEPTS) && defined(PQXX_HAVE_RANGES)

  template<binary DATA> void write(DATA const &data)
  {
    raw_write(std::data(data), std::size(data));
  }
#else

  template<typename DATA> void write(DATA const &data)
  {
    raw_write(std::data(data), std::size(data));
  }
#endif


  void resize(std::int64_t size);

  [[nodiscard]] std::int64_t tell() const;


  std::int64_t seek_abs(std::int64_t offset = 0);

  std::int64_t seek_rel(std::int64_t offset = 0);

  std::int64_t seek_end(std::int64_t offset = 0);


  static oid from_buf(dbtransaction &tx, bytes_view data, oid id = 0);


  static void append_from_buf(dbtransaction &tx, bytes_view data, oid id);

  [[nodiscard]] static oid from_file(dbtransaction &, char const path[]);

#if defined(PQXX_HAVE_PATH) && !defined(_WIN32)

  [[nodiscard]] static oid
  from_file(dbtransaction &tx, std::filesystem::path const &path)
  {
    return from_file(tx, path.c_str());
  }
#endif


  static oid from_file(dbtransaction &, char const path[], oid);

#if defined(PQXX_HAVE_PATH) && !defined(_WIN32)

  static oid
  from_file(dbtransaction &tx, std::filesystem::path const &path, oid id)
  {
    return from_file(tx, path.c_str(), id);
  }
#endif


  static void to_buf(dbtransaction &, oid, bytes &, std::size_t max_size);


  static std::size_t append_to_buf(
    dbtransaction &tx, oid id, std::int64_t offset, bytes &buf,
    std::size_t append_max);

  static void to_file(dbtransaction &, oid, char const path[]);

#if defined(PQXX_HAVE_PATH) && !defined(_WIN32)

  static void
  to_file(dbtransaction &tx, oid id, std::filesystem::path const &path)
  {
    to_file(tx, id, path.c_str());
  }
#endif


  void close();

private:
  PQXX_PRIVATE blob(connection &cx, int fd) noexcept : m_conn{&cx}, m_fd{fd} {}
  static PQXX_PRIVATE blob open_internal(dbtransaction &, oid, int);
  static PQXX_PRIVATE pqxx::internal::pq::PGconn *
  raw_conn(pqxx::connection *) noexcept;
  static PQXX_PRIVATE pqxx::internal::pq::PGconn *
  raw_conn(pqxx::dbtransaction const &) noexcept;
  static PQXX_PRIVATE std::string errmsg(connection const *);
  static PQXX_PRIVATE std::string errmsg(dbtransaction const &tx)
  {
    return errmsg(&tx.conn());
  }
  PQXX_PRIVATE std::string errmsg() const { return errmsg(m_conn); }
  PQXX_PRIVATE std::int64_t seek(std::int64_t offset, int whence);
  std::size_t raw_read(std::byte buf[], std::size_t size);
  void raw_write(std::byte const buf[], std::size_t size);

  connection *m_conn = nullptr;
  int m_fd = -1;
};
} // namespace pqxx
#endif