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Includes the following functions: metaphon() - an enhanced soundex function, myfunc_double() - an example of a function that uses double vaules, myfunc_int() - an example of a function that uses integer values.
====================
/* Copyright Abandoned 1998 TCX DataKonsult AB & Monty Program KB & Detron HB &
Alexis Mikhailov <root@medinf.chuvashia.su>
This file is public domain and comes with NO WARRANTY of any kind */
/*
** 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, 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.
**
**
** 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.
**
** On the end is a couple of functions that converts hostnames to ip and
** vice versa.
**
** A dynamicly loadable file should be compiled sharable
** (something like: gcc -shared -o udf_example.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 -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 ?)
**
** 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";
**
** 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;
**
** 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)
**
*/
#ifdef STANDARD
#include <stdio.h>
#include <string.h>
#else
#include <global.h>
#include <my_sys.h>
#endif
#include <mysql.h>
#include <m_ctype.h>
#include <m_string.h> // To get strmov()
#ifdef HAVE_DLOPEN
/* These must be right or mysqld will not find the symbol! */
extern "C" {
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);
longlong myfunc_int(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
char *error);
}
/*************************************************************************
** 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
**
** 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
** error Points to error marker.
****************************************************************************/
void metaphon_deinit(UDF_INIT *initid)
{
}
/***************************************************************************
** 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, UDF_ARGS *args, char *result,
unsigned long *length, char *is_null, char *error)
{
const char *word=args->args[0];
if (!word) // Null argument
{
*is_null=1;
return 0;
}
const char *w_end=word+args->lengths[0];
char *org_result=result;
char *n, *n_start, *n_end; /* pointers to string */
char *metaph, *metaph_end; /* pointers to metaph */
char ntrans[32]; /* word with uppercase letters */
char newm[8]; /* new metaph for comparison */
int KSflag; /* state flag for X to KS */
/*--------------------------------------------------------
* 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' ) ?
(char)'K' : (char)'X';
else
*result++ = 'K';
}
break;
case 'D': /* J before DGE, DGI, DGY, else T */
*result++ =
( n[1] == 'G' &&
MAKESOFT ( n[2])) ?
(char)'J' : (char)'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' ) ?
(char)'J' : (char)'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'
? (char)'F' : (char)'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'))) ?
(char)'X' : (char)'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= (ulong) (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)
{
if (!args->arg_count)
{
strcpy(message,"myfunc_double must have at least on argument");
return 1;
}
/*
** As this function wants to have everything as strings, force all arguments
** to strings.
*/
for (uint 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=8; // 3 digits + . + 2 decimals
return 0;
}
double myfunc_double(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
char *error)
{
unsigned long val = 0;
unsigned long v = 0;
for (uint i = 0; i < args->arg_count; i++)
{
if (args->args[i] == NULL)
continue;
val += args->lengths[i];
for (uint 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
***************************************************************************/
long long myfunc_int(UDF_INIT *initid, UDF_ARGS *args, char *is_null,
char *error)
{
long long val = 0;
for (uint 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 += *((long long*) args->args[i]);
break;
case REAL_RESULT: // Add numers as long long
val += (long long) *((double*) args->args[i]);
break;
}
}
return val;
}
#endif /* HAVE_DLOPEN */
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