SQLite

  int argc, 
  sqlite3_value **argv
){
  ReCompiled *pRe;          /* Compiled regular expression */
  const char *zPattern;     /* The regular expression */
  const unsigned char *zStr;/* String being searched */
  const char *zErr;         /* Compile error message */
  int setAux = 0;           /* True to invoke sqlite3_set_auxdata() */

  pRe = sqlite3_get_auxdata(context, 0);
  if( pRe==0 ){
    zPattern = (const char*)sqlite3_value_text(argv[0]);
    if( zPattern==0 ) return;
    zErr = re_compile(&pRe, zPattern, 0);
    if( zErr ){
      re_free(pRe);
      sqlite3_result_error(context, zErr, -1);
      return;
    }
    if( pRe==0 ){
      sqlite3_result_error_nomem(context);
      return;
    }
    sqlite3_set_auxdata(context, 0, pRe, (void(*)(void*))re_free);
    setAux = 1;
  }
  zStr = (const unsigned char*)sqlite3_value_text(argv[1]);
  if( zStr!=0 ){
    sqlite3_result_int(context, re_match(pRe, zStr, -1));
  }
  if( setAux ){
    sqlite3_set_auxdata(context, 0, pRe, (void(*)(void*))re_free);
  }
}

/*
** Invoke this routine to register the regexp() function with the
** SQLite database connection.
*/
#ifdef _WIN32

/*
** CAPI3REF: Function Auxiliary Data
**
** The following two functions may be used by scalar SQL functions to
** associate metadata with argument values. If the same value is passed to
** multiple invocations of the same SQL function during query execution, under
** some circumstances the associated metadata may be preserved. This may
** be used, for example, to add a regular-expression matching scalar
** some circumstances the associated metadata may be preserved. This might
** be used, for example, in a regular-expression matching
** function. The compiled version of the regular expression is stored as
** metadata associated with the SQL value passed as the regular expression
** pattern.  The compiled regular expression can be reused on multiple
** invocations of the same function so that the original pattern string
** does not need to be recompiled on each invocation.
**
** ^The sqlite3_get_auxdata() interface returns a pointer to the metadata
** associated by the sqlite3_set_auxdata() function with the Nth argument
** value to the application-defined function. ^If no metadata has been ever
** been set for the Nth argument of the function, or if the corresponding
** function parameter has changed since the meta-data was set,
** then sqlite3_get_auxdata() returns a NULL pointer.
**
** ^The sqlite3_set_auxdata() interface saves the metadata
** ^The sqlite3_set_auxdata(C,N,P,X) interface saves P as metadata for the N-th
** pointed to by its 3rd parameter as the metadata for the N-th
** argument of the application-defined function.  Subsequent
** calls to sqlite3_get_auxdata() might return this data, if it has
** not been destroyed.
** ^If it is not NULL, SQLite will invoke the destructor
** function given by the 4th parameter to sqlite3_set_auxdata() on
** the metadata when the corresponding function parameter changes
** or when the SQL statement completes, whichever comes first.
** argument of the application-defined function.  ^Subsequent
** calls to sqlite3_get_auxdata(C,N) return P from the most recent
** sqlite3_set_auxdata(C,N,P,X) call if the data has not been dropped, or
** NULL if the data has been dropped.
** ^(If it is not NULL, SQLite will invoke the destructor
** function X passed to sqlite3_set_auxdata(C,N,P,X) when <ul>
** <li> the corresponding function parameter changes,
** <li> [sqlite3_reset()] or [sqlite3_finalize()] is called for the
**      SQL statement,
** <li> sqlite3_set_auxdata() is invoked again on the same parameter, or
** <li> a memory allocation error occurs. </ul>)^
**
** SQLite is free to call the destructor and drop metadata on any
** parameter of any function at any time.  ^The only guarantee is that
** the destructor will be called before the metadata is dropped.
** the destructor will be called when the [prepared statement] is destroyed.
** Note in particular that the destructor X in the call to
** sqlite3_set_auxdata(C,N,P,X) might be called immediately, before
** the sqlite3_set_auxdata() call even returns.  Hence sqlite3_set_auxdata()
** should be called near the end of the function implementation and the
** implementation should not make any use of P after sqlite3_set_auxdata()
** has been called.
**
** ^(In practice, metadata is preserved between function calls for
** expressions that are constant at compile time. This includes literal
** values and [parameters].)^
** function parameters that are compile-time constants, including literal
** values and [parameters] and expressions composed from the same.)^
**
** These routines must be called from the same thread in which
** the SQL function is running.
*/
void *sqlite3_get_auxdata(sqlite3_context*, int N);
void sqlite3_set_auxdata(sqlite3_context*, int N, void*, void (*)(void*));