~drizzle-trunk/drizzle/development

/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-

 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:

 *

 *  Copyright (C) 2008 Sun Microsystems

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; version 2 of the License.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, write to the Free Software

 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 */

#ifndef RPL_UTILITY_H

#define RPL_UTILITY_H

#ifndef __cplusplus

#error "Don't include this C++ header file from a non-C++ file!"

#endif

#include <drizzled/server_includes.h>

class Relay_log_info;

/**

  A table definition from the master.

  The responsibilities of this class is:

  - Extract and decode table definition data from the table map event

  - Check if table definition in table map is compatible with table

    definition on slave

  Currently, the only field type data available is an array of the

  type operators that are present in the table map event.

  @todo Add type operands to this structure to allow detection of

     difference between, e.g., BIT(5) and BIT(10).

 */

class table_def

{

public:

  /**

    Convenience declaration of the type of the field type data in a

    table map event.

  */

  typedef unsigned char field_type;

  /**

    Constructor.

    @param types Array of types

    @param size  Number of elements in array 'types'

    @param field_metadata Array of extra information about fields

    @param metadata_size Size of the field_metadata array

    @param null_bitmap The bitmap of fields that can be null

   */

  table_def(field_type *types, uint32_t size, unsigned char *field_metadata, 

      int metadata_size, unsigned char *null_bitmap)

    : m_size(size), m_type(0), m_field_metadata_size(metadata_size),

      m_field_metadata(0), m_null_bits(0), m_memory(NULL)

  {

    m_memory= (unsigned char *)my_multi_malloc(MYF(MY_WME),

                                       &m_type, size,

                                       &m_field_metadata,

                                       size * sizeof(uint16_t),

                                       &m_null_bits, (size + 7) / 8,

                                       NULL);

    memset(m_field_metadata, 0, size * sizeof(uint16_t));

    if (m_type)

      memcpy(m_type, types, size);

    else

      m_size= 0;

    /*

      Extract the data from the table map into the field metadata array

      iff there is field metadata. The variable metadata_size will be

      0 if we are replicating from an older version server since no field

      metadata was written to the table map. This can also happen if 

      there were no fields in the master that needed extra metadata.

    */

    if (m_size && metadata_size)

    { 

      int index= 0;

      for (unsigned int i= 0; i < m_size; i++)

      {

        switch (m_type[i]) {

        case DRIZZLE_TYPE_BLOB:

        case DRIZZLE_TYPE_DOUBLE:

        {

          /*

            These types store a single byte.

          */

          m_field_metadata[i]= field_metadata[index];

          index++;

          break;

        }

        case DRIZZLE_TYPE_ENUM:

        {

          uint16_t x= field_metadata[index++] << 8U; // real_type

          x+= field_metadata[index++];            // pack or field length

          m_field_metadata[i]= x;

          break;

        }

        case DRIZZLE_TYPE_VARCHAR:

        {

          /*

            These types store two bytes.

          */

          char *ptr= (char *)&field_metadata[index];

          m_field_metadata[i]= uint2korr(ptr);

          index= index + 2;

          break;

        }

        case DRIZZLE_TYPE_NEWDECIMAL:

        {

          uint16_t x= field_metadata[index++] << 8U; // precision

          x+= field_metadata[index++];            // decimals

          m_field_metadata[i]= x;

          break;

        }

        default:

          m_field_metadata[i]= 0;

          break;

        }

      }

    }

    if (m_size && null_bitmap)

       memcpy(m_null_bits, null_bitmap, (m_size + 7) / 8);

  }

  ~table_def() {

    my_free(m_memory, MYF(0));

    m_type= 0;

    m_size= 0;

  }

  /**

    Return the number of fields there is type data for.

    @return The number of fields that there is type data for.

   */

  uint32_t size() const { return m_size; }

  /*

    Return a representation of the type data for one field.

    @param index Field index to return data for

    @return Will return a representation of the type data for field

    <code>index</code>. Currently, only the type identifier is

    returned.

   */

  field_type type(uint32_t index) const

  {

    assert(index < m_size);

    return m_type[index];

  }

  /*

    This function allows callers to get the extra field data from the

    table map for a given field. If there is no metadata for that field

    or there is no extra metadata at all, the function returns 0.

    The function returns the value for the field metadata for column at 

    position indicated by index. As mentioned, if the field was a type 

    that stores field metadata, that value is returned else zero (0) is 

    returned. This method is used in the unpack() methods of the 

    corresponding fields to properly extract the data from the binary log 

    in the event that the master's field is smaller than the slave.

  */

  uint16_t field_metadata(uint32_t index) const

  {

    assert(index < m_size);

    if (m_field_metadata_size)

      return m_field_metadata[index];

    else

      return 0;

  }

  /*

    This function returns whether the field on the master can be null.

    This value is derived from field->maybe_null().

  */

  bool maybe_null(uint32_t index) const

  {

    assert(index < m_size);

    return ((m_null_bits[(index / 8)] & 

            (1 << (index % 8))) == (1 << (index %8)));

  }

  /*

    This function returns the field size in raw bytes based on the type

    and the encoded field data from the master's raw data. This method can 

    be used for situations where the slave needs to skip a column (e.g., 

    WL#3915) or needs to advance the pointer for the fields in the raw 

    data from the master to a specific column.

  */

  uint32_t calc_field_size(uint32_t col, unsigned char *master_data) const;

  /**

    Decide if the table definition is compatible with a table.

    Compare the definition with a table to see if it is compatible

    with it.

    A table definition is compatible with a table if:

      - the columns types of the table definition is a (not

        necessarily proper) prefix of the column type of the table, or

      - the other way around

    @param rli   Pointer to relay log info

    @param table Pointer to table to compare with.

    @retval 1  if the table definition is not compatible with @c table

    @retval 0  if the table definition is compatible with @c table

  */

  int compatible_with(Relay_log_info const *rli, Table *table) const;

private:

  uint32_t m_size;           // Number of elements in the types array

  field_type *m_type;                     // Array of type descriptors

  uint32_t m_field_metadata_size;

  uint16_t *m_field_metadata;

  unsigned char *m_null_bits;

  unsigned char *m_memory;

};

/**

   Extend the normal table list with a few new fields needed by the

   slave thread, but nowhere else.

 */

struct RPL_TableList

  : public TableList

{

  bool m_tabledef_valid;

  table_def m_tabledef;

};

/* Anonymous namespace for template functions/classes */

namespace {

  /*

    Smart pointer that will automatically call my_afree (a macro) when

    the pointer goes out of scope.  This is used so that I do not have

    to remember to call my_afree() before each return.  There is no

    overhead associated with this, since all functions are inline.

    I (Matz) would prefer to use the free function as a template

    parameter, but that is not possible when the "function" is a

    macro.

  */

  template <class Obj>

  class auto_afree_ptr

  {

    Obj* m_ptr;

  public:

    auto_afree_ptr(Obj* ptr) : m_ptr(ptr) { }

    ~auto_afree_ptr() { if (m_ptr) my_afree(m_ptr); }

    void assign(Obj* ptr) {

      /* Only to be called if it hasn't been given a value before. */

      assert(m_ptr == NULL);

      m_ptr= ptr;

    }

    Obj* get() { return m_ptr; }

  };

}

#endif /* RPL_UTILITY_H */