xref: /dports/databases/xtrabackup/percona-xtrabackup-2.4.21/sql/udf_example.cc

/* Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

   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 */

/*
** example file of UDF (user definable functions) that are dynamicly loaded
** into the standard mysqld core.
**
** The functions name, type and shared library is saved in the new system
** table 'func'.  To be able to create new functions one must have write
** privilege for the database 'mysql'.	If one starts MySQL with
** --skip-grant-tables, then UDF initialization will also be skipped.
**
** Syntax for the new commands are:
** create function <function_name> returns {string|real|integer}
**		  soname <name_of_shared_library>
** drop function <function_name>
**
** Each defined function may have a xxxx_init function and a xxxx_deinit
** function.  The init function should alloc memory for the function
** and tell the main function about the max length of the result
** (for string functions), number of decimals (for double functions) and
** if the result may be a null value.
**
** If a function sets the 'error' argument to 1 the function will not be
** called anymore and mysqld will return NULL for all calls to this copy
** of the function.
**
** All strings arguments to functions are given as string pointer + length
** to allow handling of binary data.
** Remember that all functions must be thread safe. This means that one is not
** allowed to alloc any global or static variables that changes!
** If one needs memory one should alloc this in the init function and free
** this on the __deinit function.
**
** Note that the init and __deinit functions are only called once per
** SQL statement while the value function may be called many times
**
** Function 'metaphon' returns a metaphon string of the string argument.
** This is something like a soundex string, but it's more tuned for English.
**
** Function 'myfunc_double' returns summary of codes of all letters
** of arguments divided by summary length of all its arguments.
**
** Function 'myfunc_int' returns summary length of all its arguments.
**
** Function 'sequence' returns an sequence starting from a certain number.
**
** Function 'myfunc_argument_name' returns name of argument.
**
** On the end is a couple of functions that converts hostnames to ip and
** vice versa.
**
** A dynamicly loadable file should be compiled shared.
** (something like: gcc -shared -o my_func.so myfunc.cc).
** You can easily get all switches right by doing:
** cd sql ; make udf_example.o
** Take the compile line that make writes, remove the '-c' near the end of
** the line and add -shared -o udf_example.so to the end of the compile line.
** The resulting library (udf_example.so) should be copied to some dir
** searched by ld. (/usr/lib ?)
** If you are using gcc, then you should be able to create the udf_example.so
** by simply doing 'make udf_example.so'.
**
** After the library is made one must notify mysqld about the new
** functions with the commands:
**
** CREATE FUNCTION metaphon RETURNS STRING SONAME "udf_example.so";
** CREATE FUNCTION myfunc_double RETURNS REAL SONAME "udf_example.so";
** CREATE FUNCTION myfunc_int RETURNS INTEGER SONAME "udf_example.so";
** CREATE FUNCTION sequence RETURNS INTEGER SONAME "udf_example.so";
** CREATE FUNCTION lookup RETURNS STRING SONAME "udf_example.so";
** CREATE FUNCTION reverse_lookup RETURNS STRING SONAME "udf_example.so";
** CREATE AGGREGATE FUNCTION avgcost RETURNS REAL SONAME "udf_example.so";
** CREATE FUNCTION myfunc_argument_name RETURNS STRING SONAME "udf_example.so";
**
** After this the functions will work exactly like native MySQL functions.
** Functions should be created only once.
**
** The functions can be deleted by:
**
** DROP FUNCTION metaphon;
** DROP FUNCTION myfunc_double;
** DROP FUNCTION myfunc_int;
** DROP FUNCTION lookup;
** DROP FUNCTION reverse_lookup;
** DROP FUNCTION avgcost;
** DROP FUNCTION myfunc_argument_name;
**
** The CREATE FUNCTION and DROP FUNCTION update the func@mysql table. All
** Active function will be reloaded on every restart of server
** (if --skip-grant-tables is not given)
**
** If you ge problems with undefined symbols when loading the shared
** library, you should verify that mysqld is compiled with the -rdynamic
** option.
**
** If you can't get AGGREGATES to work, check that you have the column
** 'type' in the mysql.func table.  If not, run 'mysql_upgrade'.
**
*/

#include <my_global.h>
#include <my_sys.h>

#include <new>
#include <vector>
#include <algorithm>

#if defined(MYSQL_SERVER)
#include <m_string.h>		/* To get my_stpcpy() */
#else
/* when compiled as standalone */
#include <string.h>
#define my_stpcpy(a,b) stpcpy(a,b)
#endif

#include <mysql.h>
#include <ctype.h>

#ifdef _WIN32
/* inet_aton needs winsock library */
#pragma comment(lib, "ws2_32")
#endif

#ifdef HAVE_DLOPEN

#if !defined(HAVE_GETHOSTBYADDR_R) || !defined(HAVE_SOLARIS_STYLE_GETHOST)
static native_mutex_t LOCK_hostname;
#endif

/* These must be right or mysqld will not find the symbol! */

C_MODE_START;
my_bool metaphon_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
void metaphon_deinit(UDF_INIT *initid);
char *metaphon(UDF_INIT *initid, UDF_ARGS *args, char *result,
	       unsigned long *length, char *is_null, char *error);
my_bool myfunc_double_init(UDF_INIT *, UDF_ARGS *args, char *message);
double myfunc_double(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
		     char *error);
my_bool myfunc_int_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
longlong myfunc_int(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
		    char *error);
my_bool sequence_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
 void sequence_deinit(UDF_INIT *initid);
longlong sequence(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
		   char *error);
my_bool avgcost_init( UDF_INIT* initid, UDF_ARGS* args, char* message );
void avgcost_deinit( UDF_INIT* initid );
void avgcost_reset( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error );
void avgcost_clear( UDF_INIT* initid, char* is_null, char *error );
void avgcost_add( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error );
double avgcost( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error );
my_bool is_const_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
char *is_const(UDF_INIT *initid, UDF_ARGS *args, char *result, unsigned long
               *length, char *is_null, char *error);
C_MODE_END;

/*************************************************************************
** Example of init function
** Arguments:
** initid	Points to a structure that the init function should fill.
**		This argument is given to all other functions.
**	my_bool maybe_null	1 if function can return NULL
**				Default value is 1 if any of the arguments
**				is declared maybe_null.
**	unsigned int decimals	Number of decimals.
**				Default value is max decimals in any of the
**				arguments.
**	unsigned int max_length  Length of string result.
**				The default value for integer functions is 21
**				The default value for real functions is 13+
**				default number of decimals.
**				The default value for string functions is
**				the longest string argument.
**	char *ptr;		A pointer that the function can use.
**
** args		Points to a structure which contains:
**	unsigned int arg_count		Number of arguments
**	enum Item_result *arg_type	Types for each argument.
**					Types are STRING_RESULT, REAL_RESULT
**					and INT_RESULT.
**	char **args			Pointer to constant arguments.
**					Contains 0 for not constant argument.
**	unsigned long *lengths;		max string length for each argument
**	char *maybe_null		Information of which arguments
**					may be NULL
**
** message	Error message that should be passed to the user on fail.
**		The message buffer is MYSQL_ERRMSG_SIZE big, but one should
**		try to keep the error message less than 80 bytes long!
**
** This function should return 1 if something goes wrong. In this case
** message should contain something usefull!
**************************************************************************/

#define MAXMETAPH 8

my_bool metaphon_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  if (args->arg_count != 1 || args->arg_type[0] != STRING_RESULT)
  {
    strcpy(message,"Wrong arguments to metaphon;  Use the source");
    return 1;
  }
  initid->max_length=MAXMETAPH;
  return 0;
}

/****************************************************************************
** Deinit function. This should free all resources allocated by
** this function.
** Arguments:
** initid	Return value from xxxx_init
****************************************************************************/


void metaphon_deinit(UDF_INIT *initid MY_ATTRIBUTE((unused)))
{
}

/***************************************************************************
** UDF string function.
** Arguments:
** initid	Structure filled by xxx_init
** args		The same structure as to xxx_init. This structure
**		contains values for all parameters.
**		Note that the functions MUST check and convert all
**		to the type it wants!  Null values are represented by
**		a NULL pointer
** result	Possible buffer to save result. At least 255 byte long.
** length	Pointer to length of the above buffer.	In this the function
**		should save the result length
** is_null	If the result is null, one should store 1 here.
** error	If something goes fatally wrong one should store 1 here.
**
** This function should return a pointer to the result string.
** Normally this is 'result' but may also be an alloced string.
***************************************************************************/

/* Character coding array */
static char codes[26] =  {
    1,16,4,16,9,2,4,16,9,2,0,2,2,2,1,4,0,2,4,4,1,0,0,0,8,0
 /* A  B C  D E F G  H I J K L M N O P Q R S T U V W X Y Z*/
    };

/*--- Macros to access character coding array -------------*/

#define ISVOWEL(x)  (codes[(x) - 'A'] & 1)	/* AEIOU */

    /* Following letters are not changed */
#define NOCHANGE(x) (codes[(x) - 'A'] & 2)	/* FJLMNR */

    /* These form diphthongs when preceding H */
#define AFFECTH(x) (codes[(x) - 'A'] & 4)	/* CGPST */

    /* These make C and G soft */
#define MAKESOFT(x) (codes[(x) - 'A'] & 8)	/* EIY */

    /* These prevent GH from becoming F */
#define NOGHTOF(x)  (codes[(x) - 'A'] & 16)	/* BDH */


char *metaphon(UDF_INIT *initid MY_ATTRIBUTE((unused)),
               UDF_ARGS *args, char *result, unsigned long *length,
               char *is_null, char *error MY_ATTRIBUTE((unused)))
{
  const char *word=args->args[0];
  const char *w_end;
  char *org_result;
  char *n, *n_start, *n_end; /* pointers to string */
  char *metaph_end;	     /* pointers to end of metaph */
  char ntrans[32];	     /* word with uppercase letters */
  int  KSflag;		     /* state flag for X to KS */

  if (!word)					/* Null argument */
  {
    /* The length is expected to be zero when the argument is NULL. */
    assert(args->lengths[0] == 0);
    *is_null=1;
    return 0;
  }

  w_end=word+args->lengths[0];
  org_result=result;

  /*--------------------------------------------------------
   *  Copy word to internal buffer, dropping non-alphabetic
   *  characters and converting to uppercase.
   *-------------------------------------------------------*/

  for (n = ntrans + 1, n_end = ntrans + sizeof(ntrans)-2;
	word != w_end && n < n_end; word++ )
    if ( isalpha ( *word ))
      *n++ = toupper ( *word );

  if ( n == ntrans + 1 )	/* return empty string if 0 bytes */
  {
    *length=0;
    return result;
  }
  n_end = n;			/* set n_end to end of string */
  ntrans[0] = 'Z';		/* ntrans[0] should be a neutral char */
  n[0]=n[1]=0;			/* pad with nulls */
  n = ntrans + 1;		/* assign pointer to start */

  /*------------------------------------------------------------
   *  check for all prefixes:
   *		PN KN GN AE WR WH and X at start.
   *----------------------------------------------------------*/

  switch ( *n ) {
  case 'P':
  case 'K':
  case 'G':
    if ( n[1] == 'N')
      *n++ = 0;
    break;
  case 'A':
    if ( n[1] == 'E')
      *n++ = 0;
    break;
  case 'W':
    if ( n[1] == 'R' )
      *n++ = 0;
    else
      if ( *(n + 1) == 'H')
      {
	n[1] = *n;
	*n++ = 0;
      }
    break;
  case 'X':
    *n = 'S';
    break;
  }

  /*------------------------------------------------------------
   *  Now, loop step through string, stopping at end of string
   *  or when the computed metaph is MAXMETAPH characters long
   *----------------------------------------------------------*/

  KSflag = 0; /* state flag for KS translation */

  for (metaph_end = result + MAXMETAPH, n_start = n;
	n < n_end && result < metaph_end; n++ )
  {

    if ( KSflag )
    {
      KSflag = 0;
      *result++ = *n;
    }
    else
    {
      /* drop duplicates except for CC */
      if ( *( n - 1 ) == *n && *n != 'C' )
	continue;

      /* check for F J L M N R or first letter vowel */
      if ( NOCHANGE ( *n ) ||
	   ( n == n_start && ISVOWEL ( *n )))
	*result++ = *n;
      else
	switch ( *n ) {
	case 'B':	 /* check for -MB */
	  if ( n < n_end || *( n - 1 ) != 'M' )
	    *result++ = *n;
	  break;

	case 'C': /* C = X ("sh" sound) in CH and CIA */
	  /*   = S in CE CI and CY	      */
	  /*	 dropped in SCI SCE SCY       */
	  /* else K			      */
	  if ( *( n - 1 ) != 'S' ||
	       !MAKESOFT ( n[1]))
	  {
	    if ( n[1] == 'I' && n[2] == 'A' )
	      *result++ = 'X';
	    else
	      if ( MAKESOFT ( n[1]))
		*result++ = 'S';
	      else
		if ( n[1] == 'H' )
		  *result++ = (( n == n_start &&
				 !ISVOWEL ( n[2])) ||
			       *( n - 1 ) == 'S' ) ?
		    'K' : 'X';
		else
		  *result++ = 'K';
	  }
	  break;

	case 'D':  /* J before DGE, DGI, DGY, else T */
	  *result++ =
	    ( n[1] == 'G' &&
	      MAKESOFT ( n[2])) ?
	    'J' : 'T';
	  break;

	case 'G':   /* complicated, see table in text */
	  if (( n[1] != 'H' || ISVOWEL ( n[2]))
	      && (
		  n[1] != 'N' ||
		  (
		   (n + 1) < n_end  &&
		   (
		    n[2] != 'E' ||
		    *( n + 3 ) != 'D'
		    )
		   )
		  )
	      && (
		  *( n - 1 ) != 'D' ||
		  !MAKESOFT ( n[1])
		  )
	      )
	    *result++ =
	      ( MAKESOFT ( *( n  + 1 )) &&
		n[2] != 'G' ) ?
	      'J' : 'K';
	  else
	    if ( n[1] == 'H'   &&
		!NOGHTOF( *( n - 3 )) &&
		*( n - 4 ) != 'H')
	      *result++ = 'F';
	  break;

	case 'H':   /* H if before a vowel and not after */
	  /* C, G, P, S, T */

	  if ( !AFFECTH ( *( n - 1 )) &&
	       ( !ISVOWEL ( *( n - 1 )) ||
		 ISVOWEL ( n[1])))
	    *result++ = 'H';
	  break;

	case 'K':    /* K = K, except dropped after C */
	  if ( *( n - 1 ) != 'C')
	    *result++ = 'K';
	  break;

	case 'P':    /* PH = F, else P = P */
	  *result++ = *( n +  1 ) == 'H'
	    ? 'F' : 'P';
	  break;
	case 'Q':   /* Q = K (U after Q is already gone */
	  *result++ = 'K';
	  break;

	case 'S':   /* SH, SIO, SIA = X ("sh" sound) */
	  *result++ = ( n[1] == 'H' ||
			( *(n  + 1) == 'I' &&
			  ( n[2] == 'O' ||
			    n[2] == 'A')))  ?
	    'X' : 'S';
	  break;

	case 'T':  /* TIO, TIA = X ("sh" sound) */
	  /* TH = 0, ("th" sound ) */
	  if ( *( n  + 1 ) == 'I' && ( n[2] == 'O'
				      || n[2] == 'A') )
	    *result++ = 'X';
	  else
	    if ( n[1] == 'H' )
	      *result++ = '0';
	    else
	      if ( *( n + 1) != 'C' || n[2] != 'H')
		*result++ = 'T';
	  break;

	case 'V':     /* V = F */
	  *result++ = 'F';
	  break;

	case 'W':     /* only exist if a vowel follows */
	case 'Y':
	  if ( ISVOWEL ( n[1]))
	    *result++ = *n;
	  break;

	case 'X':     /* X = KS, except at start */
	  if ( n == n_start )
	    *result++ = 'S';
	  else
	  {
	    *result++ = 'K'; /* insert K, then S */
	    KSflag = 1; /* this flag will cause S to be
			   inserted on next pass thru loop */
	  }
	  break;

	case 'Z':
	  *result++ = 'S';
	  break;
	}
    }
  }
  *length= (unsigned long) (result - org_result);
  return org_result;
}


/***************************************************************************
** UDF double function.
** Arguments:
** initid	Structure filled by xxx_init
** args		The same structure as to xxx_init. This structure
**		contains values for all parameters.
**		Note that the functions MUST check and convert all
**		to the type it wants!  Null values are represented by
**		a NULL pointer
** is_null	If the result is null, one should store 1 here.
** error	If something goes fatally wrong one should store 1 here.
**
** This function should return the result.
***************************************************************************/

my_bool myfunc_double_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  uint i;

  if (!args->arg_count)
  {
    strcpy(message,"myfunc_double must have at least one argument");
    return 1;
  }
  /*
  ** As this function wants to have everything as strings, force all arguments
  ** to strings.
  */
  for (i=0 ; i < args->arg_count; i++)
    args->arg_type[i]=STRING_RESULT;
  initid->maybe_null=1;		/* The result may be null */
  initid->decimals=2;		/* We want 2 decimals in the result */
  initid->max_length=6;		/* 3 digits + . + 2 decimals */
  return 0;
}


double myfunc_double(UDF_INIT *initid MY_ATTRIBUTE((unused)), UDF_ARGS *args,
                     char *is_null, char *error MY_ATTRIBUTE((unused)))
{
  unsigned long val = 0;
  unsigned long v = 0;
  uint i, j;

  for (i = 0; i < args->arg_count; i++)
  {
    if (args->args[i] == NULL)
      continue;
    val += args->lengths[i];
    for (j=args->lengths[i] ; j-- > 0 ;)
      v += args->args[i][j];
  }
  if (val)
    return (double) v/ (double) val;
  *is_null=1;
  return 0.0;
}


/***************************************************************************
** UDF long long function.
** Arguments:
** initid	Return value from xxxx_init
** args		The same structure as to xxx_init. This structure
**		contains values for all parameters.
**		Note that the functions MUST check and convert all
**		to the type it wants!  Null values are represented by
**		a NULL pointer
** is_null	If the result is null, one should store 1 here.
** error	If something goes fatally wrong one should store 1 here.
**
** This function should return the result as a long long
***************************************************************************/

/* This function returns the sum of all arguments */

longlong myfunc_int(UDF_INIT *initid MY_ATTRIBUTE((unused)), UDF_ARGS *args,
                    char *is_null MY_ATTRIBUTE((unused)),
                    char *error MY_ATTRIBUTE((unused)))
{
  longlong val = 0;
  uint i;

  for (i = 0; i < args->arg_count; i++)
  {
    if (args->args[i] == NULL)
      continue;
    switch (args->arg_type[i]) {
    case STRING_RESULT:			/* Add string lengths */
      val += args->lengths[i];
      break;
    case INT_RESULT:			/* Add numbers */
      val += *((longlong*) args->args[i]);
      break;
    case REAL_RESULT:			/* Add numers as longlong */
      val += (longlong) *((double*) args->args[i]);
      break;
    default:
      break;
    }
  }
  return val;
}

/*
  At least one of _init/_deinit is needed unless the server is started
  with --allow_suspicious_udfs.
*/
my_bool myfunc_int_init(UDF_INIT *initid MY_ATTRIBUTE((unused)),
                        UDF_ARGS *args MY_ATTRIBUTE((unused)),
                        char *message MY_ATTRIBUTE((unused)))
{
  return 0;
}

/*
  Simple example of how to get a sequences starting from the first argument
  or 1 if no arguments have been given
*/

my_bool sequence_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  if (args->arg_count > 1)
  {
    my_stpcpy(message,"This function takes none or 1 argument");
    return 1;
  }
  if (args->arg_count)
    args->arg_type[0]= INT_RESULT;		/* Force argument to int */

  if (!(initid->ptr=(char*) malloc(sizeof(longlong))))
  {
    my_stpcpy(message,"Couldn't allocate memory");
    return 1;
  }
  memset(initid->ptr, 0, sizeof(longlong));
  /*
    sequence() is a non-deterministic function : it has different value
    even if called with the same arguments.
  */
  initid->const_item=0;
  return 0;
}

void sequence_deinit(UDF_INIT *initid)
{
  if (initid->ptr)
    free(initid->ptr);
}

longlong sequence(UDF_INIT *initid MY_ATTRIBUTE((unused)), UDF_ARGS *args,
                  char *is_null MY_ATTRIBUTE((unused)),
                  char *error MY_ATTRIBUTE((unused)))
{
  ulonglong val=0;
  if (args->arg_count)
    val= *((longlong*) args->args[0]);
  return ++*((longlong*) initid->ptr) + val;
}


/****************************************************************************
** Some functions that handles IP and hostname conversions
** The orignal function was from Zeev Suraski.
**
** CREATE FUNCTION lookup RETURNS STRING SONAME "udf_example.so";
** CREATE FUNCTION reverse_lookup RETURNS STRING SONAME "udf_example.so";
**
****************************************************************************/

#ifndef _WIN32
#include <netdb.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif

C_MODE_START;
my_bool lookup_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
void lookup_deinit(UDF_INIT *initid);
char *lookup(UDF_INIT *initid, UDF_ARGS *args, char *result,
	     unsigned long *length, char *null_value, char *error);
my_bool reverse_lookup_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
void reverse_lookup_deinit(UDF_INIT *initid);
char *reverse_lookup(UDF_INIT *initid, UDF_ARGS *args, char *result,
		     unsigned long *length, char *null_value, char *error);
C_MODE_END;


/****************************************************************************
** lookup IP for an hostname.
**
** This code assumes that gethostbyname_r exists and inet_ntoa() is thread
** safe (As it is in Solaris)
****************************************************************************/


my_bool lookup_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  if (args->arg_count != 1 || args->arg_type[0] != STRING_RESULT)
  {
    my_stpcpy(message,"Wrong arguments to lookup;  Use the source");
    return 1;
  }
  initid->max_length=11;
  initid->maybe_null=1;
#if !defined(HAVE_GETHOSTBYADDR_R) || !defined(HAVE_SOLARIS_STYLE_GETHOST)
  (void) native_mutex_init(&LOCK_hostname,MY_MUTEX_INIT_SLOW);
#endif
  return 0;
}

void lookup_deinit(UDF_INIT *initid MY_ATTRIBUTE((unused)))
{
#if !defined(HAVE_GETHOSTBYADDR_R) || !defined(HAVE_SOLARIS_STYLE_GETHOST)
  (void) native_mutex_destroy(&LOCK_hostname);
#endif
}

char *lookup(UDF_INIT *initid MY_ATTRIBUTE((unused)), UDF_ARGS *args,
             char *result, unsigned long *res_length, char *null_value,
             char *error MY_ATTRIBUTE((unused)))
{
  uint length;
  char name_buff[256];
  struct hostent *hostent;
#if defined(HAVE_GETHOSTBYADDR_R) && defined(HAVE_SOLARIS_STYLE_GETHOST)
  int tmp_errno;
  char hostname_buff[2048];
  struct hostent tmp_hostent;
#endif
  struct in_addr in;

  if (!args->args[0] || !(length=args->lengths[0]))
  {
    *null_value=1;
    return 0;
  }
  if (length >= sizeof(name_buff))
    length=sizeof(name_buff)-1;
  memcpy(name_buff,args->args[0],length);
  name_buff[length]=0;
#if defined(HAVE_GETHOSTBYADDR_R) && defined(HAVE_SOLARIS_STYLE_GETHOST)
  if (!(hostent=gethostbyname_r(name_buff,&tmp_hostent,hostname_buff,
				sizeof(hostname_buff), &tmp_errno)))
  {
    *null_value=1;
    return 0;
  }
#else
  native_mutex_lock(&LOCK_hostname);
  if (!(hostent= gethostbyname((char*) name_buff)))
  {
    native_mutex_unlock(&LOCK_hostname);
    *null_value= 1;
    return 0;
  }
  native_mutex_unlock(&LOCK_hostname);
#endif
  memcpy(&in, *hostent->h_addr_list, sizeof(in.s_addr));
  *res_length= (ulong) (my_stpcpy(result, inet_ntoa(in)) - result);
  return result;
}


/****************************************************************************
** return hostname for an IP number.
** The functions can take as arguments a string "xxx.xxx.xxx.xxx" or
** four numbers.
****************************************************************************/

my_bool reverse_lookup_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  if (args->arg_count == 1)
    args->arg_type[0]= STRING_RESULT;
  else if (args->arg_count == 4)
    args->arg_type[0]=args->arg_type[1]=args->arg_type[2]=args->arg_type[3]=
      INT_RESULT;
  else
  {
    my_stpcpy(message,
	   "Wrong number of arguments to reverse_lookup;  Use the source");
    return 1;
  }
  initid->max_length=32;
  initid->maybe_null=1;
#if !defined(HAVE_GETHOSTBYADDR_R) || !defined(HAVE_SOLARIS_STYLE_GETHOST)
  (void) native_mutex_init(&LOCK_hostname,MY_MUTEX_INIT_SLOW);
#endif
  return 0;
}

void reverse_lookup_deinit(UDF_INIT *initid MY_ATTRIBUTE((unused)))
{
#if !defined(HAVE_GETHOSTBYADDR_R) || !defined(HAVE_SOLARIS_STYLE_GETHOST)
  (void) native_mutex_destroy(&LOCK_hostname);
#endif
}

char *reverse_lookup(UDF_INIT *initid MY_ATTRIBUTE((unused)), UDF_ARGS *args,
                     char *result, unsigned long *res_length,
                     char *null_value, char *error MY_ATTRIBUTE((unused)))
{
#if defined(HAVE_GETHOSTBYADDR_R) && defined(HAVE_SOLARIS_STYLE_GETHOST)
  char name_buff[256];
  struct hostent tmp_hostent;
  int tmp_errno;
#endif
  struct hostent *hp;
  unsigned long taddr;
  uint length;

  if (args->arg_count == 4)
  {
    if (!args->args[0] || !args->args[1] ||!args->args[2] ||!args->args[3])
    {
      *null_value=1;
      return 0;
    }
    sprintf(result,"%d.%d.%d.%d",
	    (int) *((longlong*) args->args[0]),
	    (int) *((longlong*) args->args[1]),
	    (int) *((longlong*) args->args[2]),
	    (int) *((longlong*) args->args[3]));
  }
  else
  {					/* string argument */
    if (!args->args[0])			/* Return NULL for NULL values */
    {
      *null_value=1;
      return 0;
    }
    length=args->lengths[0];
    if (length >= (uint) *res_length-1)
      length=(uint) *res_length;
    memcpy(result,args->args[0],length);
    result[length]=0;
  }

  taddr = inet_addr(result);
  if (taddr == (unsigned long) -1L)
  {
    *null_value=1;
    return 0;
  }
#if defined(HAVE_GETHOSTBYADDR_R) && defined(HAVE_SOLARIS_STYLE_GETHOST)
  if (!(hp=gethostbyaddr_r((char*) &taddr,sizeof(taddr), AF_INET,
			   &tmp_hostent, name_buff,sizeof(name_buff),
			   &tmp_errno)))
  {
    *null_value=1;
    return 0;
  }
#else
  native_mutex_lock(&LOCK_hostname);
  if (!(hp= gethostbyaddr((char*) &taddr, sizeof(taddr), AF_INET)))
  {
    native_mutex_unlock(&LOCK_hostname);
    *null_value= 1;
    return 0;
  }
  native_mutex_unlock(&LOCK_hostname);
#endif
  *res_length=(ulong) (my_stpcpy(result,hp->h_name) - result);
  return result;
}

/*
** Syntax for the new aggregate commands are:
** create aggregate function <function_name> returns {string|real|integer}
**		  soname <name_of_shared_library>
**
** Syntax for avgcost: avgcost( t.quantity, t.price )
**	with t.quantity=integer, t.price=double
** (this example is provided by Andreas F. Bobak <bobak@relog.ch>)
*/


struct avgcost_data
{
  ulonglong	count;
  longlong	totalquantity;
  double	totalprice;
};


/*
** Average Cost Aggregate Function.
*/
my_bool
avgcost_init( UDF_INIT* initid, UDF_ARGS* args, char* message )
{
  struct avgcost_data*	data;

  if (args->arg_count != 2)
  {
    strcpy(
	   message,
	   "wrong number of arguments: AVGCOST() requires two arguments"
	   );
    return 1;
  }

  if ((args->arg_type[0] != INT_RESULT) || (args->arg_type[1] != REAL_RESULT) )
  {
    strcpy(
	   message,
	   "wrong argument type: AVGCOST() requires an INT and a REAL"
	   );
    return 1;
  }

  /*
  **	force arguments to double.
  */
  /*args->arg_type[0]	= REAL_RESULT;
    args->arg_type[1]	= REAL_RESULT;*/

  initid->maybe_null	= 0;		/* The result may be null */
  initid->decimals	= 4;		/* We want 4 decimals in the result */
  initid->max_length	= 20;		/* 6 digits + . + 10 decimals */

  if (!(data = new (std::nothrow) avgcost_data))
  {
    my_stpcpy(message,"Couldn't allocate memory");
    return 1;
  }
  data->totalquantity	= 0;
  data->totalprice	= 0.0;

  initid->ptr = (char*)data;

  return 0;
}

void
avgcost_deinit( UDF_INIT* initid )
{
  void *void_ptr= initid->ptr;
  avgcost_data *data= static_cast<avgcost_data*>(void_ptr);
  delete data;
}


/* This is only for MySQL 4.0 compability */
void
avgcost_reset(UDF_INIT* initid, UDF_ARGS* args, char* is_null, char* message)
{
  avgcost_clear(initid, is_null, message);
  avgcost_add(initid, args, is_null, message);
}

/* This is needed to get things to work in MySQL 4.1.1 and above */

void
avgcost_clear(UDF_INIT* initid, char* is_null MY_ATTRIBUTE((unused)),
              char* message MY_ATTRIBUTE((unused)))
{
  struct avgcost_data* data = (struct avgcost_data*)initid->ptr;
  data->totalprice=	0.0;
  data->totalquantity=	0;
  data->count=		0;
}


void
avgcost_add(UDF_INIT* initid, UDF_ARGS* args,
            char* is_null MY_ATTRIBUTE((unused)),
            char* message MY_ATTRIBUTE((unused)))
{
  if (args->args[0] && args->args[1])
  {
    struct avgcost_data* data	= (struct avgcost_data*)initid->ptr;
    longlong quantity		= *((longlong*)args->args[0]);
    longlong newquantity	= data->totalquantity + quantity;
    double price		= *((double*)args->args[1]);

    data->count++;

    if (   ((data->totalquantity >= 0) && (quantity < 0))
	   || ((data->totalquantity <  0) && (quantity > 0)) )
    {
      /*
      **	passing from + to - or from - to +
      */
      if (   ((quantity < 0) && (newquantity < 0))
	     || ((quantity > 0) && (newquantity > 0)) )
      {
	data->totalprice	= price * (double)newquantity;
      }
      /*
      **	sub q if totalq > 0
      **	add q if totalq < 0
      */
      else
      {
	price		  = data->totalprice / (double)data->totalquantity;
	data->totalprice  = price * (double)newquantity;
      }
      data->totalquantity = newquantity;
    }
    else
    {
      data->totalquantity	+= quantity;
      data->totalprice		+= price * (double)quantity;
    }

    if (data->totalquantity == 0)
      data->totalprice = 0.0;
  }
}


double
avgcost( UDF_INIT* initid, UDF_ARGS* args MY_ATTRIBUTE((unused)),
         char* is_null, char* error MY_ATTRIBUTE((unused)))
{
  struct avgcost_data* data = (struct avgcost_data*)initid->ptr;
  if (!data->count || !data->totalquantity)
  {
    *is_null = 1;
    return 0.0;
  }

  *is_null = 0;
  return data->totalprice/(double)data->totalquantity;
}

my_bool myfunc_argument_name_init(UDF_INIT *initid, UDF_ARGS *args,
				  char *message);
char *myfunc_argument_name(UDF_INIT *initid, UDF_ARGS *args, char *result,
			   unsigned long *length, char *null_value,
			   char *error);

my_bool myfunc_argument_name_init(UDF_INIT *initid, UDF_ARGS *args,
				  char *message)
{
  if (args->arg_count != 1)
  {
    my_stpcpy(message,"myfunc_argument_name_init accepts only one argument");
    return 1;
  }
  initid->max_length= args->attribute_lengths[0];
  initid->maybe_null= 1;
  initid->const_item= 1;
  return 0;
}

char *myfunc_argument_name(UDF_INIT *initid MY_ATTRIBUTE((unused)),
                           UDF_ARGS *args, char *result,
                           unsigned long *length, char *null_value,
                           char *error MY_ATTRIBUTE((unused)))
{
  if (!args->attributes[0])
  {
    *null_value= 1;
    return 0;
  }
  (*length)--; /* space for ending \0 (for debugging purposes) */
  if (*length > args->attribute_lengths[0])
    *length= args->attribute_lengths[0];
  memcpy(result, args->attributes[0], *length);
  result[*length]= 0;
  return result;
}



my_bool is_const_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  if (args->arg_count != 1)
  {
    my_stpcpy(message, "IS_CONST accepts only one argument");
    return 1;
  }
  initid->ptr= (char*)((args->args[0] != NULL) ? 1UL : 0);
  return 0;
}

char * is_const(UDF_INIT *initid, UDF_ARGS *args MY_ATTRIBUTE((unused)),
                char *result, unsigned long *length,
                char *is_null, char *error MY_ATTRIBUTE((unused)))
{
  if (initid->ptr != 0) {
    sprintf(result, "const");
  } else {
    sprintf(result, "not const");
  }
  *is_null= 0;
  *length= (uint) strlen(result);
  return result;
}



extern "C"
my_bool check_const_len_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  if (args->arg_count != 1)
  {
    my_stpcpy(message, "CHECK_CONST_LEN accepts only one argument");
    return 1;
  }
  if (args->args[0] == 0)
  {
    initid->ptr= (char*)"Not constant";
  }
  else if(strlen(args->args[0]) == args->lengths[0])
  {
    initid->ptr= (char*)"Correct length";
  }
  else
  {
    initid->ptr= (char*)"Wrong length";
  }
  initid->max_length = 100;
  return 0;
}

extern "C"
char * check_const_len(UDF_INIT *initid, UDF_ARGS *args MY_ATTRIBUTE((unused)),
                char *result, unsigned long *length,
                char *is_null, char *error MY_ATTRIBUTE((unused)))
{
  my_stpcpy(result, initid->ptr);
  *length= (uint) strlen(result);
  *is_null= 0;
  return result;
}


C_MODE_START;
my_bool  my_median_init  (UDF_INIT *initid, UDF_ARGS *args, char *message);
void     my_median_deinit(UDF_INIT* initid);
void     my_median_add   (UDF_INIT* initid, UDF_ARGS* args,
                          char* is_null, char *error);
void     my_median_clear (UDF_INIT* initid, UDF_ARGS* args,
                          char* is_null, char *error);
longlong my_median       (UDF_INIT* initid, UDF_ARGS* args,
                          char* is_null, char *error);
C_MODE_END;

struct My_median_data
{
  std::vector<longlong> vec;
};


my_bool  my_median_init  (UDF_INIT *initid, UDF_ARGS *args, char *message)
{
  My_median_data *data= new (std::nothrow) My_median_data;
  if (!data)
  {
    my_stpcpy(message,"Could not allocate memory");
    return true;
  }
  initid->ptr= static_cast<char*>(static_cast<void*>(data));
  return false;
}

void my_median_deinit(UDF_INIT* initid)
{
  My_median_data *data=
    static_cast<My_median_data*>(static_cast<void*>(initid->ptr));
  delete data;
}

void my_median_add(UDF_INIT* initid, UDF_ARGS* args,
                   char* is_null MY_ATTRIBUTE((unused)),
                   char* message MY_ATTRIBUTE((unused)))
{
  My_median_data *data=
    static_cast<My_median_data*>(static_cast<void*>(initid->ptr));
  if (args->args[0])
  {
    void *arg0= args->args[0];
    longlong number= *(static_cast<longlong*>(arg0));
    data->vec.push_back(number);
  }
}

void my_median_clear(UDF_INIT* initid, UDF_ARGS* args,
                     char* is_null MY_ATTRIBUTE((unused)),
                     char* message MY_ATTRIBUTE((unused)))
{
  My_median_data *data=
    static_cast<My_median_data*>(static_cast<void*>(initid->ptr));
  data->vec.clear();
}

longlong my_median(UDF_INIT* initid, UDF_ARGS* args,
                   char* is_null,
                   char* message MY_ATTRIBUTE((unused)))
{
  My_median_data *data=
    static_cast<My_median_data*>(static_cast<void*>(initid->ptr));
  if (data->vec.size() == 0)
  {
    *is_null= 1;
    return 0;
  }
  const size_t ix= data->vec.size() / 2;
  std::nth_element(data->vec.begin(), data->vec.begin() + ix, data->vec.end());
  return data->vec[ix];
}

#endif /* HAVE_DLOPEN */