~drizzle-trunk/drizzle/development

/* Copyright (C) 2000-2006 MySQL AB

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/*

  Because of the function new_field() all field classes that have static

  variables must declare the size_of() member function.

*/

#ifdef USE_PRAGMA_INTERFACE

#pragma interface			/* gcc class implementation */

#endif

#define DATETIME_DEC                     6

#define DOUBLE_TO_STRING_CONVERSION_BUFFER_SIZE FLOATING_POINT_BUFFER

const uint32_t max_field_size= (uint32_t) 4294967295U;

class Send_field;

class Protocol;

class Create_field;

struct st_cache_field;

int field_conv(Field *to,Field *from);

inline uint get_enum_pack_length(int elements)

{

  return elements < 256 ? 1 : 2;

}

inline uint get_set_pack_length(int elements)

{

  uint len= (elements + 7) / 8;

  return len > 4 ? 8 : len;

}

class Field

{

  Field(const Item &);				/* Prevent use of these */

  void operator=(Field &);

public:

  static void *operator new(size_t size) {return sql_alloc(size); }

  static void operator delete(void *ptr_arg __attribute__((unused)),

                              size_t size __attribute__((unused)))

  { TRASH(ptr_arg, size); }

  uchar		*ptr;			// Position to field in record

  uchar		*null_ptr;		// Byte where null_bit is

  /*

    Note that you can use table->in_use as replacement for current_thd member 

    only inside of val_*() and store() members (e.g. you can't use it in cons)

  */

  Table *table;		// Pointer for table

  Table *orig_table;		// Pointer to original table

  const char	**table_name, *field_name;

  LEX_STRING	comment;

  /* Field is part of the following keys */

  key_map	key_start, part_of_key, part_of_key_not_clustered;

  key_map       part_of_sortkey;

  /* 

    We use three additional unireg types for TIMESTAMP to overcome limitation 

    of current binary format of .frm file. We'd like to be able to support 

    NOW() as default and on update value for such fields but unable to hold 

    this info anywhere except unireg_check field. This issue will be resolved

    in more clean way with transition to new text based .frm format.

    See also comment for Field_timestamp::Field_timestamp().

  */

  enum utype  { NONE,DATE,SHIELD,NOEMPTY,CASEUP,PNR,BGNR,PGNR,YES,NO,REL,

		CHECK,EMPTY,UNKNOWN_FIELD,CASEDN,NEXT_NUMBER,INTERVAL_FIELD,

                BIT_FIELD, TIMESTAMP_OLD_FIELD, CAPITALIZE, BLOB_FIELD,

                TIMESTAMP_DN_FIELD, TIMESTAMP_UN_FIELD, TIMESTAMP_DNUN_FIELD};

  enum imagetype { itRAW, itMBR};

  utype		unireg_check;

  uint32_t	field_length;		// Length of field

  uint32_t	flags;

  uint16_t        field_index;            // field number in fields array

  uchar		null_bit;		// Bit used to test null bit

  /**

     If true, this field was created in create_tmp_field_from_item from a NULL

     value. This means that the type of the field is just a guess, and the type

     may be freely coerced to another type.

     @see create_tmp_field_from_item

     @see Item_type_holder::get_real_type

   */

  bool is_created_from_null_item;

  Field(uchar *ptr_arg,uint32_t length_arg,uchar *null_ptr_arg,

        uchar null_bit_arg, utype unireg_check_arg,

        const char *field_name_arg);

  virtual ~Field() {}

  /* Store functions returns 1 on overflow and -1 on fatal error */

  virtual int  store(const char *to, uint length, const CHARSET_INFO * const cs)=0;

  virtual int  store(double nr)=0;

  virtual int  store(int64_t nr, bool unsigned_val)=0;

  virtual int  store_decimal(const my_decimal *d)=0;

  virtual int store_time(DRIZZLE_TIME *ltime, timestamp_type t_type);

  int store(const char *to, uint length, const CHARSET_INFO * const cs,

            enum_check_fields check_level);

  virtual double val_real(void)=0;

  virtual int64_t val_int(void)=0;

  virtual my_decimal *val_decimal(my_decimal *);

  inline String *val_str(String *str) { return val_str(str, str); }

  /*

     val_str(buf1, buf2) gets two buffers and should use them as follows:

     if it needs a temp buffer to convert result to string - use buf1

       example Field_tiny::val_str()

     if the value exists as a string already - use buf2

       example Field_varstring::val_str() (???)

     consequently, buf2 may be created as 'String buf;' - no memory

     will be allocated for it. buf1 will be allocated to hold a

     value if it's too small. Using allocated buffer for buf2 may result in

     an unnecessary free (and later, may be an alloc).

     This trickery is used to decrease a number of malloc calls.

  */

  virtual String *val_str(String*,String *)=0;

  String *val_int_as_str(String *val_buffer, bool unsigned_flag);

  /*

   str_needs_quotes() returns true if the value returned by val_str() needs

   to be quoted when used in constructing an SQL query.

  */

  virtual bool str_needs_quotes() { return false; }

  virtual Item_result result_type () const=0;

  virtual Item_result cmp_type () const { return result_type(); }

  virtual Item_result cast_to_int_type () const { return result_type(); }

  static bool type_can_have_key_part(enum_field_types);

  static enum_field_types field_type_merge(enum_field_types, enum_field_types);

  static Item_result result_merge_type(enum_field_types);

  virtual bool eq(Field *field)

  {

    return (ptr == field->ptr && null_ptr == field->null_ptr &&

            null_bit == field->null_bit);

  }

  virtual bool eq_def(Field *field);

  /*

    pack_length() returns size (in bytes) used to store field data in memory

    (i.e. it returns the maximum size of the field in a row of the table,

    which is located in RAM).

  */

  virtual uint32_t pack_length() const { return (uint32_t) field_length; }

  /*

    pack_length_in_rec() returns size (in bytes) used to store field data on

    storage (i.e. it returns the maximal size of the field in a row of the

    table, which is located on disk).

  */

  virtual uint32_t pack_length_in_rec() const { return pack_length(); }

  virtual int compatible_field_size(uint field_metadata);

  virtual uint pack_length_from_metadata(uint field_metadata)

  { return field_metadata; }

  /*

    This method is used to return the size of the data in a row-based

    replication row record. The default implementation of returning 0 is

    designed to allow fields that do not use metadata to return true (1)

    from compatible_field_size() which uses this function in the comparison.

    The default value for field metadata for fields that do not have 

    metadata is 0. Thus, 0 == 0 means the fields are compatible in size.

    Note: While most classes that override this method return pack_length(),

    the classes Field_varstring, and Field_blob return 

    field_length + 1, field_length, and pack_length_no_ptr() respectfully.

  */

  virtual uint row_pack_length() { return 0; }

  virtual int save_field_metadata(uchar *first_byte)

  { return do_save_field_metadata(first_byte); }

  /*

    data_length() return the "real size" of the data in memory.

    For varstrings, this does _not_ include the length bytes.

  */

  virtual uint32_t data_length() { return pack_length(); }

  /*

    used_length() returns the number of bytes actually used to store the data

    of the field. So for a varstring it includes both lenght byte(s) and

    string data, and anything after data_length() bytes are unused.

  */

  virtual uint32_t used_length() { return pack_length(); }

  virtual uint32_t sort_length() const { return pack_length(); }

  /**

     Get the maximum size of the data in packed format.

     @return Maximum data length of the field when packed using the

     Field::pack() function.

   */

  virtual uint32_t max_data_length() const {

    return pack_length();

  };

  virtual int reset(void) { memset(ptr, 0, pack_length()); return 0; }

  virtual void reset_fields() {}

  virtual void set_default()

  {

    my_ptrdiff_t l_offset= (my_ptrdiff_t) (table->getDefaultValues() - table->record[0]);

    memcpy(ptr, ptr + l_offset, pack_length());

    if (null_ptr)

      *null_ptr= ((*null_ptr & (uchar) ~null_bit) | (null_ptr[l_offset] & null_bit));

  }

  virtual bool binary() const { return 1; }

  virtual bool zero_pack() const { return 1; }

  virtual enum ha_base_keytype key_type() const { return HA_KEYTYPE_BINARY; }

  virtual uint32_t key_length() const { return pack_length(); }

  virtual enum_field_types type() const =0;

  virtual enum_field_types real_type() const { return type(); }

  inline  int cmp(const uchar *str) { return cmp(ptr,str); }

  virtual int cmp_max(const uchar *a, const uchar *b,

                      uint max_len __attribute__((unused)))

    { return cmp(a, b); }

  virtual int cmp(const uchar *,const uchar *)=0;

  virtual int cmp_binary(const uchar *a,const uchar *b,

                         uint32_t  __attribute__((unused)) max_length=UINT32_MAX)

  { return memcmp(a,b,pack_length()); }

  virtual int cmp_offset(uint row_offset)

  { return cmp(ptr,ptr+row_offset); }

  virtual int cmp_binary_offset(uint row_offset)

  { return cmp_binary(ptr, ptr+row_offset); };

  virtual int key_cmp(const uchar *a,const uchar *b)

  { return cmp(a, b); }

  virtual int key_cmp(const uchar *str, uint length __attribute__((unused)))

  { return cmp(ptr,str); }

  virtual uint decimals() const { return 0; }

  /*

    Caller beware: sql_type can change str.Ptr, so check

    ptr() to see if it changed if you are using your own buffer

    in str and restore it with set() if needed

  */

  virtual void sql_type(String &str) const =0;

  virtual uint size_of() const =0;		// For new field

  inline bool is_null(my_ptrdiff_t row_offset= 0)

  { return null_ptr ? (null_ptr[row_offset] & null_bit ? 1 : 0) : table->null_row; }

  inline bool is_real_null(my_ptrdiff_t row_offset= 0)

    { return null_ptr ? (null_ptr[row_offset] & null_bit ? 1 : 0) : 0; }

  inline bool is_null_in_record(const uchar *record)

  {

    if (!null_ptr)

      return 0;

    return test(record[(uint) (null_ptr -table->record[0])] &

		null_bit);

  }

  inline bool is_null_in_record_with_offset(my_ptrdiff_t offset)

  {

    if (!null_ptr)

      return 0;

    return test(null_ptr[offset] & null_bit);

  }

  inline void set_null(my_ptrdiff_t row_offset= 0)

    { if (null_ptr) null_ptr[row_offset]|= null_bit; }

  inline void set_notnull(my_ptrdiff_t row_offset= 0)

    { if (null_ptr) null_ptr[row_offset]&= (uchar) ~null_bit; }

  inline bool maybe_null(void) { return null_ptr != 0 || table->maybe_null; }

  inline bool real_maybe_null(void) { return null_ptr != 0; }

  enum {

    LAST_NULL_BYTE_UNDEF= 0

  };

  /*

    Find the position of the last null byte for the field.

    SYNOPSIS

      last_null_byte()

    DESCRIPTION

      Return a pointer to the last byte of the null bytes where the

      field conceptually is placed.

    RETURN VALUE

      The position of the last null byte relative to the beginning of

      the record. If the field does not use any bits of the null

      bytes, the value 0 (LAST_NULL_BYTE_UNDEF) is returned.

   */

  size_t last_null_byte() const {

    size_t bytes= do_last_null_byte();

    assert(bytes <= table->getNullBytes());

    return bytes;

  }

  virtual void make_field(Send_field *);

  virtual void sort_string(uchar *buff,uint length)=0;

  virtual bool optimize_range(uint idx, uint part);

  /*

    This should be true for fields which, when compared with constant

    items, can be casted to int64_t. In this case we will at 'fix_fields'

    stage cast the constant items to int64_ts and at the execution stage

    use field->val_int() for comparison.  Used to optimize clauses like

    'a_column BETWEEN date_const, date_const'.

  */

  virtual bool can_be_compared_as_int64_t() const { return false; }

  virtual void free() {}

  virtual Field *new_field(MEM_ROOT *root, Table *new_table,

                           bool keep_type);

  virtual Field *new_key_field(MEM_ROOT *root, Table *new_table,

                               uchar *new_ptr, uchar *new_null_ptr,

                               uint new_null_bit);

  Field *clone(MEM_ROOT *mem_root, Table *new_table);

  inline void move_field(uchar *ptr_arg,uchar *null_ptr_arg,uchar null_bit_arg)

  {

    ptr=ptr_arg; null_ptr=null_ptr_arg; null_bit=null_bit_arg;

  }

  inline void move_field(uchar *ptr_arg) { ptr=ptr_arg; }

  virtual void move_field_offset(my_ptrdiff_t ptr_diff)

  {

    ptr=ADD_TO_PTR(ptr,ptr_diff, uchar*);

    if (null_ptr)

      null_ptr=ADD_TO_PTR(null_ptr,ptr_diff,uchar*);

  }

  virtual void get_image(uchar *buff, uint length,

                         const CHARSET_INFO * const cs __attribute__((unused)))

    { memcpy(buff,ptr,length); }

  virtual void set_image(const uchar *buff,uint length,

                         const CHARSET_INFO * const cs __attribute__((unused)))

    { memcpy(ptr,buff,length); }

  /*

    Copy a field part into an output buffer.

    SYNOPSIS

      Field::get_key_image()

      buff   [out] output buffer

      length       output buffer size

      type         itMBR for geometry blobs, otherwise itRAW

    DESCRIPTION

      This function makes a copy of field part of size equal to or

      less than "length" parameter value.

      For fields of string types (CHAR, VARCHAR, TEXT) the rest of buffer

      is padded by zero byte.

    NOTES

      For variable length character fields (i.e. UTF-8) the "length"

      parameter means a number of output buffer bytes as if all field

      characters have maximal possible size (mbmaxlen). In the other words,

      "length" parameter is a number of characters multiplied by

      field_charset->mbmaxlen.

    RETURN

      Number of copied bytes (excluding padded zero bytes -- see above).

  */

  virtual uint get_key_image(uchar *buff, uint length,

                             imagetype type __attribute__((unused)))

  {

    get_image(buff, length, &my_charset_bin);

    return length;

  }

  virtual void set_key_image(const uchar *buff,uint length)

    { set_image(buff,length, &my_charset_bin); }

  inline int64_t val_int_offset(uint row_offset)

    {

      ptr+=row_offset;

      int64_t tmp=val_int();

      ptr-=row_offset;

      return tmp;

    }

  inline int64_t val_int(const uchar *new_ptr)

  {

    uchar *old_ptr= ptr;

    int64_t return_value;

    ptr= (uchar*) new_ptr;

    return_value= val_int();

    ptr= old_ptr;

    return return_value;

  }

  inline String *val_str(String *str, const uchar *new_ptr)

  {

    uchar *old_ptr= ptr;

    ptr= (uchar*) new_ptr;

    val_str(str);

    ptr= old_ptr;

    return str;

  }

  virtual bool send_binary(Protocol *protocol);

  virtual uchar *pack(uchar *to, const uchar *from,

                      uint max_length, bool low_byte_first);

  /**

     @overload Field::pack(uchar*, const uchar*, uint, bool)

  */

  uchar *pack(uchar *to, const uchar *from)

  {

    uchar *result= this->pack(to, from, UINT_MAX, table->s->db_low_byte_first);

    return(result);

  }

  virtual const uchar *unpack(uchar* to, const uchar *from,

                              uint param_data, bool low_byte_first);

  /**

     @overload Field::unpack(uchar*, const uchar*, uint, bool)

  */

  const uchar *unpack(uchar* to, const uchar *from)

  {

    const uchar *result= unpack(to, from, 0U, table->s->db_low_byte_first);

    return(result);

  }

  virtual uchar *pack_key(uchar* to, const uchar *from,

                          uint max_length, bool low_byte_first)

  {

    return pack(to, from, max_length, low_byte_first);

  }

  virtual uchar *pack_key_from_key_image(uchar* to, const uchar *from,

					uint max_length, bool low_byte_first)

  {

    return pack(to, from, max_length, low_byte_first);

  }

  virtual const uchar *unpack_key(uchar* to, const uchar *from,

                                  uint max_length, bool low_byte_first)

  {

    return unpack(to, from, max_length, low_byte_first);

  }

  virtual uint packed_col_length(const uchar *to __attribute__((unused)),

                                 uint length)

  { return length;}

  virtual uint max_packed_col_length(uint max_length)

  { return max_length;}

  virtual int pack_cmp(const uchar *a,const uchar *b,

                       uint key_length_arg __attribute__((unused)),

                       bool insert_or_update __attribute__((unused)))

  { return cmp(a,b); }

  virtual int pack_cmp(const uchar *b,

                       uint key_length_arg __attribute__((unused)),

                       bool insert_or_update __attribute__((unused)))

  { return cmp(ptr,b); }

  uint offset(uchar *record)

  {

    return (uint) (ptr - record);

  }

  void copy_from_tmp(int offset);

  uint fill_cache_field(struct st_cache_field *copy);

  virtual bool get_date(DRIZZLE_TIME *ltime,uint fuzzydate);

  virtual bool get_time(DRIZZLE_TIME *ltime);

  virtual const CHARSET_INFO *charset(void) const { return &my_charset_bin; }

  virtual const CHARSET_INFO *sort_charset(void) const { return charset(); }

  virtual bool has_charset(void) const { return false; }

  virtual void set_charset(const CHARSET_INFO * const charset_arg __attribute__((unused)))

  { }

  virtual enum Derivation derivation(void) const

  { return DERIVATION_IMPLICIT; }

  virtual void set_derivation(enum Derivation derivation_arg __attribute__((unused)))

  { }

  bool set_warning(DRIZZLE_ERROR::enum_warning_level, unsigned int code,

                   int cuted_increment);

  void set_datetime_warning(DRIZZLE_ERROR::enum_warning_level, uint code, 

                            const char *str, uint str_len,

                            timestamp_type ts_type, int cuted_increment);

  void set_datetime_warning(DRIZZLE_ERROR::enum_warning_level, uint code, 

                            int64_t nr, timestamp_type ts_type,

                            int cuted_increment);

  void set_datetime_warning(DRIZZLE_ERROR::enum_warning_level, const uint code, 

                            double nr, timestamp_type ts_type);

  inline bool check_overflow(int op_result)

  {

    return (op_result == E_DEC_OVERFLOW);

  }

  int warn_if_overflow(int op_result);

  void init(Table *table_arg)

  {

    orig_table= table= table_arg;

    table_name= &table_arg->alias;

  }

  /* maximum possible display length */

  virtual uint32_t max_display_length()= 0;

  virtual uint is_equal(Create_field *new_field);

  /* convert decimal to int64_t with overflow check */

  int64_t convert_decimal2int64_t(const my_decimal *val, bool unsigned_flag,

                                    int *err);

  /* The max. number of characters */

  inline uint32_t char_length() const

  {

    return field_length / charset()->mbmaxlen;

  }

  inline enum column_format_type column_format() const

  {

    return (enum column_format_type)

      ((flags >> COLUMN_FORMAT_FLAGS) & COLUMN_FORMAT_MASK);

  }

  /* Hash value */

  virtual void hash(uint32_t *nr, uint32_t *nr2);

  friend bool reopen_table(THD *,Table *,bool);

  friend int cre_myisam(char * name, register Table *form, uint options,

			uint64_t auto_increment_value);

  friend class Copy_field;

  friend class Item_avg_field;

  friend class Item_std_field;

  friend class Item_sum_num;

  friend class Item_sum_sum;

  friend class Item_sum_str;

  friend class Item_sum_count;

  friend class Item_sum_avg;

  friend class Item_sum_std;

  friend class Item_sum_min;

  friend class Item_sum_max;

  friend class Item_func_group_concat;

private:

  /*

    Primitive for implementing last_null_byte().

    SYNOPSIS

      do_last_null_byte()

    DESCRIPTION

      Primitive for the implementation of the last_null_byte()

      function. This represents the inheritance interface and can be

      overridden by subclasses.

   */

  virtual size_t do_last_null_byte() const;

/**

   Retrieve the field metadata for fields.

   This default implementation returns 0 and saves 0 in the metadata_ptr

   value.

   @param   metadata_ptr   First byte of field metadata

   @returns 0 no bytes written.

*/

  virtual int do_save_field_metadata(uchar *metadata_ptr __attribute__((unused)))

  { return 0; }

};

class Field_num :public Field {

public:

  const uint8_t dec;

  bool decimal_precision;	// Purify cannot handle bit fields & only for decimal type

  bool unsigned_flag;	// Purify cannot handle bit fields

  Field_num(uchar *ptr_arg,uint32_t len_arg, uchar *null_ptr_arg,

	    uchar null_bit_arg, utype unireg_check_arg,

	    const char *field_name_arg,

            uint8_t dec_arg, bool zero_arg, bool unsigned_arg);

  Item_result result_type () const { return REAL_RESULT; }

  void add_unsigned(String &res) const;

  friend class Create_field;

  void make_field(Send_field *);

  uint decimals() const { return (uint) dec; }

  uint size_of() const { return sizeof(*this); }

  bool eq_def(Field *field);

  int store_decimal(const my_decimal *);

  my_decimal *val_decimal(my_decimal *);

  uint is_equal(Create_field *new_field);

  int check_int(const CHARSET_INFO * const cs, const char *str, int length,

                const char *int_end, int error);

  bool get_int(const CHARSET_INFO * const cs, const char *from, uint len, 

               int64_t *rnd, uint64_t unsigned_max, 

               int64_t signed_min, int64_t signed_max);

};

/* base class for all string related classes */

class Field_str :public Field {

protected:

  const CHARSET_INFO *field_charset;

  enum Derivation field_derivation;

public:

  Field_str(uchar *ptr_arg,uint32_t len_arg, uchar *null_ptr_arg,

	    uchar null_bit_arg, utype unireg_check_arg,

	    const char *field_name_arg, const CHARSET_INFO * const charset);

  Item_result result_type () const { return STRING_RESULT; }

  uint decimals() const { return NOT_FIXED_DEC; }

  int  store(double nr);

  int  store(int64_t nr, bool unsigned_val)=0;

  int  store_decimal(const my_decimal *);

  int  store(const char *to,uint length, const CHARSET_INFO * const cs)=0;

  uint size_of() const { return sizeof(*this); }

  const CHARSET_INFO *charset(void) const { return field_charset; }

  void set_charset(const CHARSET_INFO * const charset_arg) { field_charset= charset_arg; }

  enum Derivation derivation(void) const { return field_derivation; }

  virtual void set_derivation(enum Derivation derivation_arg)

  { field_derivation= derivation_arg; }

  bool binary() const { return field_charset == &my_charset_bin; }

  uint32_t max_display_length() { return field_length; }

  friend class Create_field;

  my_decimal *val_decimal(my_decimal *);

  virtual bool str_needs_quotes() { return true; }

  bool compare_str_field_flags(Create_field *new_field, uint32_t flags);

  uint is_equal(Create_field *new_field);

};

/* base class for Field_varstring and Field_blob */

class Field_longstr :public Field_str

{

protected:

  int report_if_important_data(const char *ptr, const char *end);

public:

  Field_longstr(uchar *ptr_arg, uint32_t len_arg, uchar *null_ptr_arg,

                uchar null_bit_arg, utype unireg_check_arg,

                const char *field_name_arg, const CHARSET_INFO * const charset_arg)

    :Field_str(ptr_arg, len_arg, null_ptr_arg, null_bit_arg, unireg_check_arg,

               field_name_arg, charset_arg)

    {}

  int store_decimal(const my_decimal *d);

  uint32_t max_data_length() const;

};

/* base class for float and double and decimal (old one) */

class Field_real :public Field_num {

public:

  bool not_fixed;

  Field_real(uchar *ptr_arg, uint32_t len_arg, uchar *null_ptr_arg,

             uchar null_bit_arg, utype unireg_check_arg,

             const char *field_name_arg,

             uint8_t dec_arg, bool zero_arg, bool unsigned_arg)

    :Field_num(ptr_arg, len_arg, null_ptr_arg, null_bit_arg, unireg_check_arg,

               field_name_arg, dec_arg, zero_arg, unsigned_arg),

    not_fixed(dec_arg >= NOT_FIXED_DEC)

    {}

  int store_decimal(const my_decimal *);

  my_decimal *val_decimal(my_decimal *);

  int truncate(double *nr, double max_length);

  uint32_t max_display_length() { return field_length; }

  uint size_of() const { return sizeof(*this); }

  virtual const uchar *unpack(uchar* to, const uchar *from,

                              uint param_data, bool low_byte_first);

  virtual uchar *pack(uchar* to, const uchar *from,

                      uint max_length, bool low_byte_first);