ddl0impl-file-reader.h

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/** @file include/ddl0impl-file-reader.h
 For scanning the temporary file.
 Created 2020-11-01 by Sunny Bains. */
 
#ifndef ddl0impl_file_reader_h
#define ddl0impl_file_reader_h
 
#include "ddl0impl-buffer.h"
 
namespace ddl {
 
// Forward declaration
struct File_cursor;
 
/** Read rows from the temporary file. */
struct File_reader : private ut::Non_copyable {
  /** Constructor.
  @param[in] file               Opened file.
  @param[in,out] index          Index that the rows belong to.
  @param[in] buffer_size        Size of file buffer for reading.
  @param[in] size               File size in bytes. */
  File_reader(const Unique_os_file_descriptor &file, dict_index_t *index,
              size_t buffer_size, os_offset_t size) noexcept
      : m_index(index), m_file(file), m_size(size), m_buffer_size(buffer_size) {
    ut_a(size > 0);
    ut_a(m_buffer_size > 0);
    ut_a(m_index != nullptr);
    ut_a(m_file.is_open());
  }
 
  /** Destructor. */
  ~File_reader() noexcept {
    if (m_aux_buf != nullptr) {
      ut::delete_arr(m_aux_buf);
    }
  }
 
  /** Prepare the file for reading.
  @return DB_SUCCESS or error code. */
  [[nodiscard]] dberr_t prepare() noexcept;
 
  /** The current row as a tuple. Note: the tuple only does a shallow copy.
  @param[in,out] builder        Index builder instance.
  @param[in,out] heap           Heap to use for allocation.
  @param[out] dtuple            Row converted to a tuple.
  @return DB_SUCCESS or error code. */
  [[nodiscard]] dberr_t get_tuple(Builder *builder, mem_heap_t *heap,
                                  dtuple_t *&dtuple) noexcept;
 
  /** Seek to the offset and read the page in.
  @param[in] offset              Offset to read in.
  @return DB_SUCCESS or error code. */
  dberr_t read(os_offset_t offset) noexcept;
 
  /** Set the range or rows to traverse.
  @param[in] offset              New offset to read from. */
  void set_offset(os_offset_t offset) noexcept { m_offset = offset; }
 
  /** @return true if the range first == second. */
  [[nodiscard]] bool eof() const noexcept { return m_offset == m_size; }
 
  /** @return the number of rows read from the file. */
  [[nodiscard]] uint64_t get_n_rows_read() const noexcept {
    return m_n_rows_read;
  }
 
 private:
  /** Seek to the start of the range and load load the page.
  @param[in] offset              Offset to read in.
  @return DB_SUCCESS or error code. */
  [[nodiscard]] dberr_t seek(os_offset_t offset) noexcept;
 
  /** Advance page number to the next and read in.
  @return DB_SUCCESS or error code. */
  [[nodiscard]] dberr_t read_next() noexcept;
 
  /** Advance the "cursor".
  @return DB_SUCCESS or error code. */
  [[nodiscard]] dberr_t next() noexcept;
 
 public:
  using Offsets = std::vector<ulint, ut::allocator<ulint>>;
 
  /** Index that the records belong to. */
  dict_index_t *m_index{};
 
  /** Pointer to current row. */
  const mrec_t *m_mrec{};
 
  /** Columns offsets. */
  Offsets m_offsets{};
 
  /** File handle to read from. */
  const Unique_os_file_descriptor &m_file;
 
 private:
  using Bounds = std::pair<const byte *, const byte *>;
 
  /** Size of the file in bytes. */
  os_offset_t m_size{};
 
  /** Offset to read. */
  os_offset_t m_offset{};
 
  /** Pointer current offset within file buffer. */
  const byte *m_ptr{};
 
  /** File buffer bounds. */
  Bounds m_bounds{};
 
  /** Auxiliary buffer for records that span across pages. */
  byte *m_aux_buf{};
 
  /** IO buffer size in bytes. */
  size_t m_buffer_size{};
 
  /** Aligned IO buffer. */
  Aligned_buffer m_aligned_buffer{};
 
  /** File buffer for reading. */
  IO_buffer m_io_buffer{};
 
  /** Number of rows read from the file. */
  uint64_t m_n_rows_read{};
 
  friend File_cursor;
};
 
}  // namespace ddl
 
#endif /* ddl0impl_file_reader_h */