ndbapi-examples/common/array_adapter.hpp

/*
   Copyright (c) 2014, 2021, Oracle and/or its affiliates.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   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, version 2.0, 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 ARRAY_ADAPTER_HPP
#define ARRAY_ADAPTER_HPP

#include <algorithm>
#include <assert.h>

/*
 Utility classes to convert between C++ strings/byte arrays and the
 internal format used for [VAR]CHAR/BINARY types.

 Base class that can be used for read operations. The column type is
 taken from the NdbRecAttr object, so only one object is needed to
 convert from different [VAR]CHAR/BINARY types. No additional memory
 is allocated.
 */
class ReadOnlyArrayAdapter {
public:
  ReadOnlyArrayAdapter() {}

  enum ErrorType {Success,
                  InvalidColumnType,
                  InvalidArrayType,
                  InvalidNullColumn,
                  InvalidNullAttribute,
                  InvalidNullaRef,
                  BytesOutOfRange,
                  UnknownError};

  /*
    Return a C++ string from the aRef() value of attr. This value
    will use the column and column type from attr. The advantage is
    for reading; the same ArrayAdapter can be used for multiple
    columns. The disadvantage is; passing an attribute not of
    [VAR]CHAR/BINARY type will result in a traditional exit(-1)
    */
  std::string get_string(const NdbRecAttr* attr,
                         ErrorType& error) const;

  /* Calculate the first_byte and number of bytes in aRef for attr */
  void get_byte_array(const NdbRecAttr* attr,
                      const char*& first_byte,
                      size_t& bytes,
                      ErrorType& error) const;

  /* Check if a column is of type [VAR]BINARY */
  bool is_binary_array_type(const NdbDictionary::Column::Type t) const;

  /* Check if a column is of type [VAR]BINARY or [VAR]CHAR */
  bool is_array_type(const NdbDictionary::Column::Type t) const;
private:
  /* Disable copy constructor */
  ReadOnlyArrayAdapter(const ReadOnlyArrayAdapter& a) {}
};


 /*
  Extension to ReadOnlyArrayAdapter to be used together with
  insert/write/update operations. Memory is allocated for each
  call to make_aRef or allocate_in_bytes. The memory allocated will
  be deallocated by the destructor. To save memory, the scope of an
  instance of this class should not be longer than the life time of
  the transaction. On the other hand, it must be long enough for the
  usage of all references created
  */
class ReadWriteArrayAdapter : public ReadOnlyArrayAdapter {
public:
  ReadWriteArrayAdapter() {}

  /* Destructor, the only place where memory is deallocated */
  ~ReadWriteArrayAdapter();

  /*
   Create a binary representation of the string 's' and return a
   pointer to it. This pointer can later be used as argument to for
   example setValue
   */
  char* make_aRef(const NdbDictionary::Column* column,
                  std::string s,
                  ErrorType& error);

  /*
   Allocate a number of bytes suitable for this column type. aRef
   can later be used as argument to for example setValue. first_byte
   is the first byte to store data to. bytes is the number of bytes
   to allocate
   */
  void allocate_in_bytes(const NdbDictionary::Column* column,
                         char*& aRef,
                         char*& first_byte,
                         size_t bytes,
                         ErrorType& error);

private:
  /* Disable copy constructor */
  ReadWriteArrayAdapter(const ReadWriteArrayAdapter& a)
    :ReadOnlyArrayAdapter() {}

  /* Record of allocated char arrays to delete by the destructor */
  std::vector<char*> aRef_created;
};


inline ReadWriteArrayAdapter::~ReadWriteArrayAdapter()
{
  for (std::vector<char*>::iterator i = aRef_created.begin();
       i != aRef_created.end();
       ++i) {
    delete [] *i;
  }
}


char*
ReadWriteArrayAdapter::
make_aRef(const NdbDictionary::Column* column,
          std::string input,
          ErrorType& error)
{
  char* new_ref;
  char* data_start;

  /*
   Allocate bytes and push them into the aRef_created vector.
   After this operation, new_ref has a complete aRef to use in insertion
   and data_start has ptr from which data is to be written.
   The new_aref returned is padded completely with blank spaces.
   */
  allocate_in_bytes(column, new_ref, data_start, input.length(), error);

  if(error != Success)
  {
    return NULL;
  }

  /*
   Copy the input string into aRef's data pointer
   without affecting remaining blank spaces at end.
   */
  strncpy(data_start, input.c_str(), input.length());

  return new_ref;
}


void
ReadWriteArrayAdapter::
allocate_in_bytes(const NdbDictionary::Column* column,
                  char*& aRef,
                  char*& first_byte,
                  size_t bytes,
                  ErrorType& error)
{
  bool is_binary;
  char zero_char;
  NdbDictionary::Column::ArrayType array_type;
  size_t max_length;

  /* unless there is going to be any problem */
  error = Success;

  if (column == NULL)
  {
    error = InvalidNullColumn;
    aRef = NULL;
    first_byte = NULL;
    return;
  }

  if (!is_array_type(column->getType()))
  {
    error = InvalidColumnType;
    aRef = NULL;
    first_byte = NULL;
    return;
  }

  is_binary = is_binary_array_type(column->getType());
  zero_char = (is_binary ? 0 : ' ');
  array_type = column->getArrayType();
  max_length = column->getLength();

  if (bytes > max_length)
  {
    error = BytesOutOfRange;
    aRef = NULL;
    first_byte = NULL;
    return;
  }

  switch (array_type) {
  case NdbDictionary::Column::ArrayTypeFixed:
    /* no need to store length bytes */
    aRef = new char[max_length];
    first_byte = aRef;
    /* pad the complete string with blank space (or) null bytes */
    for (size_t i=0; i < max_length; i++) {
      aRef[i] = zero_char;
    }
    break;
  case NdbDictionary::Column::ArrayTypeShortVar:
    /* byte length stored over first byte. no padding required */
    aRef = new char[1 + bytes];
    first_byte = aRef + 1;
    aRef[0] = (char)bytes;
    break;
  case NdbDictionary::Column::ArrayTypeMediumVar:
    /* byte length stored over first two bytes. no padding required */
    aRef = new char[2 + bytes];
    first_byte = aRef + 2;
    aRef[0] = (char)(bytes % 256);
    aRef[1] = (char)(bytes / 256);
    break;
  }
  aRef_created.push_back(aRef);
}


std::string ReadOnlyArrayAdapter::get_string(const NdbRecAttr* attr,
                                             ErrorType& error) const
{
  size_t attr_bytes= 0;
  const char* data_ptr= NULL;
  std::string result= "";

  /* get the beginning of data and its size.. */
  get_byte_array(attr, data_ptr, attr_bytes, error);

  if(error != Success)
  {
    return result;
  }

  /* ..and copy the  value into result */
  result = string(data_ptr, attr_bytes);

  /* special treatment for FixedArrayType to eliminate padding characters */
  if(attr->getColumn()->getArrayType() == NdbDictionary::Column::ArrayTypeFixed)
  {
    char padding_char = ' ';
    std::size_t last = result.find_last_not_of(padding_char);
    result = result.substr(0, last+1);
  }

  return result;
}


void
ReadOnlyArrayAdapter::
get_byte_array(const NdbRecAttr* attr,
               const char*& data_ptr,
               size_t& bytes,
               ErrorType& error) const
{
  /* unless there is a problem */
  error= Success;

  if (attr == NULL)
  {
    error = InvalidNullAttribute;
    return;
  }

  if (!is_array_type(attr->getType()))
  {
    error = InvalidColumnType;
    return;
  }

  const NdbDictionary::Column::ArrayType array_type =
      attr->getColumn()->getArrayType();
  const size_t attr_bytes = attr->get_size_in_bytes();
  const char* aRef = attr->aRef();

  if(aRef == NULL)
  {
    error= InvalidNullaRef;
    return;
  }

  switch (array_type) {
  case NdbDictionary::Column::ArrayTypeFixed:
    /* no length bytes stored with aRef */
    data_ptr = aRef;
    bytes = attr_bytes;
    break;
  case NdbDictionary::Column::ArrayTypeShortVar:
    /* first byte of aRef has length of the data */
    data_ptr = aRef + 1;
    bytes = (size_t)(aRef[0]);
    break;
  case NdbDictionary::Column::ArrayTypeMediumVar:
    /* first two bytes of aRef has length of the data */
    data_ptr = aRef + 2;
    bytes = (size_t)(aRef[1]) * 256 + (size_t)(aRef[0]);
    break;
  default:
    /* should never reach here */
    data_ptr = NULL;
    bytes = 0;
    error = InvalidArrayType;
    break;
  }
}


bool
ReadOnlyArrayAdapter::
is_binary_array_type(const NdbDictionary::Column::Type t) const
{
  bool is_binary;

  switch (t)
  {
  case NdbDictionary::Column::Binary:
  case NdbDictionary::Column::Varbinary:
  case NdbDictionary::Column::Longvarbinary:
    is_binary = true;
    break;
  default:
    is_binary = false;
  }
  return is_binary;
}


bool
ReadOnlyArrayAdapter::
is_array_type(const NdbDictionary::Column::Type t) const
{
  bool is_array;

  switch (t)
  {
  case NdbDictionary::Column::Binary:
  case NdbDictionary::Column::Varbinary:
  case NdbDictionary::Column::Longvarbinary:
  case NdbDictionary::Column::Char:
  case NdbDictionary::Column::Varchar:
  case NdbDictionary::Column::Longvarchar:
    is_array = true;
    break;
  default:
    is_array = false;
  }
  return is_array;
}

#endif // #ifndef ARRAY_ADAPTER_HPP