column.h

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/** @file storage/temptable/include/temptable/column.h
TempTable Column declaration. */
 
#ifndef TEMPTABLE_COLUMN_H
#define TEMPTABLE_COLUMN_H
 
#include <cstddef>
#include <vector>
 
#include "my_dbug.h"
#include "sql/field.h"
#include "storage/temptable/include/temptable/allocator.h"
#include "storage/temptable/include/temptable/misc.h"
 
namespace temptable {
 
/** A column class that describes the metadata of a column. */
class Column {
 public:
  /** Constructor. */
  Column(
      /** [in] A pointer to the row (user data). */
      const unsigned char *mysql_row,
      /** [in] MySQL table that contains the column. */
      const TABLE &mysql_table TEMPTABLE_UNUSED_NODBUG,
      /** [in] MySQL field (column/cell) that describes the columns. */
      const Field &mysql_field);
 
  /** Check if a particular cell is NULL. The cell is the intersection of this
   * column with the provided row (in MySQL write_row() format).
   * @return true if the cell is NULL */
  bool read_is_null(
      /** [in] MySQL row that contains the cell to be checked. */
      const unsigned char *mysql_row) const;
 
  /** Write the information that cell is NULL or not. */
  void write_is_null(
      /** [in] True if cell is NULL, false if it has value. */
      bool is_null,
      /** [out] MySQL row buffer to write data into. */
      unsigned char *mysql_row,
      /** [in] Length of the row buffer. */
      size_t mysql_row_length) const;
 
  /** In MySQL write_row() format - the length of the actual user data of a cell
   * in a given row.
   * @return user data length of the cell that corresponds to this column in the
   * given row */
  uint32_t read_user_data_length(
      /** [in] MySQL row buffer to read data from. */
      const unsigned char *mysql_row) const;
 
  /** Write the length of user data stored in a cell. */
  void write_user_data_length(
      /** [in] User data length. */
      uint32_t data_length,
      /** [out] MySQL row buffer to write data into. */
      unsigned char *mysql_row,
      /** [in] Length of the row buffer. */
      size_t mysql_row_length) const;
 
  /** Return pointer to user data in MySQL row.
   * @return Pointer to user data. */
  const unsigned char *get_user_data_ptr(const unsigned char *mysql_row) const;
 
  /** Reads user data stored in a cell.
   * Cannot be used for columns stored as BLOBs.
   * Performs a deep copy of the data. */
  void read_user_data(
      /** [out] Pointer to store user data. */
      unsigned char *data,
      /** [out] Length of the data to read. */
      uint32_t data_length,
      /** [in] MySQL row buffer to read data from. */
      const unsigned char *mysql_row,
      /** [in] Length of the row buffer. */
      size_t mysql_row_length) const;
 
  /** Write user data stored in a cell.
   * Cannot be used for columns stored as blobs. */
  void write_user_data(
      /** [in] True if cell is NULL, false if it has value. */
      bool is_null,
      /** [in] Pointer to used data. */
      const unsigned char *data,
      /** [in] Length of user data. */
      uint32_t data_length,
      /** [out] MySQL row buffer to write data into. */
      unsigned char *mysql_row,
      /** [in] Length of the row buffer. */
      size_t mysql_row_length) const;
 
 private:
  /** Check if the cells in this column can be NULL.
   * @return true if cells are allowed to be NULL. */
  bool is_nullable() const;
 
  /** Check this column stores blobs.
   * @return true if it is a blob column. */
  bool is_blob() const;
 
  /** Check if different cells that belong to this column can have different
   * size (eg VARCHAR).
   * @return true if all cells are the same size */
  bool is_fixed_size() const;
 
  /** Reads user data stored in a cell.
   * Cannot be used for columns stored as BLOBs.
   * Performs a deep copy of the data. */
  void read_std_user_data(
      /** [out] Pointer to store user data. */
      unsigned char *data,
      /** [out] Length of the data to read. */
      uint32_t data_length,
      /** [in] MySQL row buffer to read data from. */
      const unsigned char *mysql_row,
      /** [in] Length of the row buffer. */
      size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const;
 
  /** Write user data stored in a cell.
   * Cannot be used for columns stored as blobs. */
  void write_std_user_data(
      /** [in] Pointer to used data. */
      const unsigned char *data,
      /** [in] Length of user data. */
      uint32_t data_length,
      /** [out] MySQL row buffer to write data into. */
      unsigned char *mysql_row,
      /** [in] Length of the row buffer. */
      size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const;
 
  /** Reads user data stored in a cell for columns stored as BLOBs.
   * Performs a deep copy of the data. */
  void read_blob_user_data(
      /** [out] Pointer to store user data. */
      unsigned char *data,
      /** [out] Length of the data to read. */
      uint32_t data_length,
      /** [in] MySQL row buffer to read data from. */
      const unsigned char *mysql_row,
      /** [in] Length of the row buffer. */
      size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const;
 
  /** Write user data stored in a cell for columns stored as BLOBs.
   * NOTE: Currently only pointer is stored, no data is copied and the
   * length is ignored. */
  void write_blob_user_data(
      /** [in] Pointer to user data. Can be NULL for cells with NULL value. */
      const unsigned char *data,
      /** [in] Length of user data. */
      uint32_t data_length,
      /** [out] MySQL row buffer to write data into. */
      unsigned char *mysql_row,
      /** [in] Length of the row buffer. */
      size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const;
 
  /** Calculate pointer to user data in a MySQL row.
   * Cannot be used for columns stored as BLOBs.
   * @return Pointer to user data stored in a cell. */
  const unsigned char *calculate_user_data_ptr(
      /** [in] MySQL row buffer that stores the user data. */
      const unsigned char *mysql_row) const;
 
  /** Reads pointer to user data for a column stored as BLOB.
   * @return Pointer to user data stored in a BLOB field. */
  const unsigned char *read_blob_data_ptr(
      /** [in] MySQL row buffer that stores BLOB data pointer. */
      const unsigned char *mysql_row) const;
 
  /** True if can be NULL. */
  bool m_nullable;
 
  /** True if it is a blob. */
  bool m_is_blob;
 
  /** Bitmask to extract is is-NULL bit from the is-NULL byte. */
  uint8_t m_null_bitmask;
 
  /** The number of bytes that indicate the length of the user data in the
   * cell, for variable sized cells. If this is 0, then the cell is fixed
   * size. */
  uint8_t m_length_bytes_size;
 
  union {
    /** Length of the user data of a cell.
     * It is for fixed size cells (when `m_length_bytes_size == 0`). */
    uint32_t m_length;
 
    /** Offset of the bytes that indicate the user data length of a cell.
     * It is used for variable size cells (when `m_length_bytes_size > 0`). */
    uint32_t m_offset;
  };
 
  /** The offset of the is-NULL byte from the start of the mysql row. If
   * `m_null_bitmask` is set in this byte and `m_nullable` is true, then that
   * particular cell is NULL. */
  uint32_t m_null_byte_offset;
 
  /** The offset of the user data from the start of the mysql row in bytes. */
  uint32_t m_user_data_offset;
};
 
/** A type that designates all the columns of a table. */
typedef std::vector<Column, Allocator<Column>> Columns;
 
/* Implementation of inlined methods. */
 
inline bool Column::is_nullable() const { return m_nullable; }
 
inline bool Column::is_blob() const { return m_is_blob; }
 
inline bool Column::read_is_null(const unsigned char *mysql_row) const {
  return m_nullable && (m_null_bitmask & *(mysql_row + m_null_byte_offset));
}
 
inline void Column::write_is_null(bool is_null, unsigned char *mysql_row,
                                  size_t mysql_row_length
                                      TEMPTABLE_UNUSED_NODBUG) const {
  if (is_nullable()) {
    unsigned char *b = mysql_row + m_null_byte_offset;
 
    assert(buf_is_inside_another(b, 1, mysql_row, mysql_row_length));
 
    if (is_null) {
      *b |= m_null_bitmask;
    } else {
      *b &= ~m_null_bitmask;
    }
  } else {
    assert(!is_null);
  }
}
 
inline bool Column::is_fixed_size() const { return m_length_bytes_size == 0; }
 
inline uint32_t Column::read_user_data_length(
    const unsigned char *mysql_row) const {
  if (m_length_bytes_size == 0) {
    /* Fixed size cell. */
    return m_length;
  }
 
  // data_length may contain junk value while particular cell is NULL
  if (read_is_null(mysql_row)) {
    return 0;
  }
 
  const unsigned char *p = mysql_row + m_offset;
  switch (m_length_bytes_size) {
    case 1:
      return *p;
    case 2:
      return *p | (*(p + 1) << 8);
    case 3:
      return *p | (*(p + 1) << 8) | (*(p + 2) << 16);
    case 4:
      return *p | (*(p + 1) << 8) | (*(p + 2) << 16) | (*(p + 3) << 24);
  }
 
  my_abort();
  return 0;
}
 
inline void Column::write_user_data_length(
    uint32_t data_length, unsigned char *mysql_row,
    size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const {
  unsigned char *p = mysql_row + m_offset;
 
  assert((m_length_bytes_size == 0) ||
         (buf_is_inside_another(p, m_length_bytes_size, mysql_row,
                                mysql_row_length)));
 
  switch (m_length_bytes_size) {
    case 0:
      /* Fixed size cell. */
      break;
    case 1:
      assert(data_length <= 0xFF);
      p[0] = data_length;
      break;
    case 2:
      assert(data_length <= 0xFFFF);
      p[0] = (data_length & 0x000000FF);
      p[1] = (data_length & 0x0000FF00) >> 8;
      break;
    case 3:
      assert(data_length <= 0xFFFFFF);
      p[0] = (data_length & 0x000000FF);
      p[1] = (data_length & 0x0000FF00) >> 8;
      p[2] = (data_length & 0x00FF0000) >> 16;
      break;
    case 4:
      /* assert(data_length <= 0xFFFFFFFF). */
      p[0] = (data_length & 0x000000FF);
      p[1] = (data_length & 0x0000FF00) >> 8;
      p[2] = (data_length & 0x00FF0000) >> 16;
      p[3] = (data_length & 0xFF000000) >> 24;
      break;
    default:
      DBUG_ABORT();
  }
}
 
inline void Column::read_user_data(unsigned char *data, uint32_t data_length,
                                   const unsigned char *mysql_row,
                                   size_t mysql_row_length) const {
  if (is_blob()) {
    read_blob_user_data(data, data_length, mysql_row, mysql_row_length);
  } else {
    read_std_user_data(data, data_length, mysql_row, mysql_row_length);
  }
}
 
inline void Column::write_user_data(bool is_null, const unsigned char *data,
                                    uint32_t data_length,
                                    unsigned char *mysql_row,
                                    size_t mysql_row_length) const {
  if (is_blob()) {
    if (is_null) {
      write_blob_user_data(nullptr, 0, mysql_row, mysql_row_length);
    } else {
      assert(data);
      write_blob_user_data(data, data_length, mysql_row, mysql_row_length);
    }
  } else {
    write_std_user_data(data, data_length, mysql_row, mysql_row_length);
  }
}
 
inline void Column::read_std_user_data(
    unsigned char *data, uint32_t data_length, const unsigned char *mysql_row,
    size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const {
  assert(!is_blob());
 
  const unsigned char *p = mysql_row + m_user_data_offset;
 
  assert(buf_is_inside_another(p, data_length, mysql_row, mysql_row_length));
 
  memcpy(data, p, data_length);
}
 
inline void Column::write_std_user_data(
    const unsigned char *data, uint32_t data_length, unsigned char *mysql_row,
    size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const {
  assert(!is_blob());
 
  if (data_length > 0) {
    unsigned char *p = mysql_row + m_user_data_offset;
 
    assert(buf_is_inside_another(p, data_length, mysql_row, mysql_row_length));
 
    memcpy(p, data, data_length);
  }
}
 
inline void Column::read_blob_user_data(
    unsigned char *data, uint32_t data_length, const unsigned char *mysql_row,
    size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const {
  assert(is_blob());
 
  const unsigned char *p = mysql_row + m_user_data_offset;
 
  const unsigned char *ptr_to_data;
 
  assert(buf_is_inside_another(p, sizeof(ptr_to_data), mysql_row,
                               mysql_row_length));
 
  /* read the address */
  memcpy(&ptr_to_data, p, sizeof(ptr_to_data));
 
  assert((ptr_to_data) || (data_length == 0));
 
  memcpy(data, ptr_to_data, data_length);
}
 
inline void Column::write_blob_user_data(
    const unsigned char *data, uint32_t data_length TEMPTABLE_UNUSED,
    unsigned char *mysql_row,
    size_t mysql_row_length TEMPTABLE_UNUSED_NODBUG) const {
  assert(is_blob());
 
  unsigned char *p = mysql_row + m_user_data_offset;
 
  /* Note1: data could be NULL.
   * Note2: shallow copy - pointer to original data is stored. */
  const unsigned char *ptr_to_data = data;
 
  assert(buf_is_inside_another(p, sizeof(ptr_to_data), mysql_row,
                               mysql_row_length));
 
  memcpy(p, &ptr_to_data, sizeof(ptr_to_data));
}
 
inline const unsigned char *Column::get_user_data_ptr(
    const unsigned char *mysql_row) const {
  if (is_blob()) {
    return read_blob_data_ptr(mysql_row);
  } else {
    return calculate_user_data_ptr(mysql_row);
  }
}
 
inline const unsigned char *Column::calculate_user_data_ptr(
    const unsigned char *mysql_row) const {
  assert(!is_blob());
 
  return (mysql_row + m_user_data_offset);
}
 
inline const unsigned char *Column::read_blob_data_ptr(
    const unsigned char *mysql_row) const {
  assert(is_blob());
 
  const unsigned char *p = mysql_row + m_user_data_offset;
 
  const unsigned char *data_ptr;
 
  /* read the address */
  memcpy(&data_ptr, p, sizeof(data_ptr));
 
  return data_ptr;
}
 
} /* namespace temptable */
 
#endif /* TEMPTABLE_COLUMN_H */