I would rather add these functions directly to the core SQLite DLL in C in
and compile them directly into the code (using a conditional).
For example on the web I found an example of adding a sign() function:
/*
** Implementation of the sign() function
*/
static void signFunc(sqlite3_context *context, int argc, sqlite3_value
**argv){
assert( argc==1 );
switch( sqlite3_value_type(argv[0]) ){
case SQLITE_INTEGER: {
i64 iVal = sqlite3_value_int64(argv[0]);
/* 1st change below. Line below was: if( iVal<0 ) iVal = iVal * -1; */
iVal = ( iVal > 0) ? 1: ( iVal < 0 ) ? -1: 0;
sqlite3_result_int64(context, iVal);
break;
}
case SQLITE_NULL: {
sqlite3_result_null(context);
break;
}
default: {
/* 2nd change below. Line for abs was: if( rVal<0 ) rVal = rVal * -1.0; */
double rVal = sqlite3_value_double(argv[0]);
rVal = ( rVal > 0) ? 1: ( rVal < 0 ) ? -1: 0;
sqlite3_result_double(context, rVal);
break;
}
}
}
They then register this function by adding it to the array of existing
functions:
} aFuncs[] = {
{ "min", -1, 0, SQLITE_UTF8, 1, minmaxFunc },
{ "min", 0, 0, SQLITE_UTF8, 1, 0 },
{ "max", -1, 2, SQLITE_UTF8, 1, minmaxFunc },
{ "max", 0, 2, SQLITE_UTF8, 1, 0 },
{ "typeof", 1, 0, SQLITE_UTF8, 0, typeofFunc },
{ "length", 1, 0, SQLITE_UTF8, 0, lengthFunc },
{ "substr", 3, 0, SQLITE_UTF8, 0, substrFunc },
{ "substr", 3, 0, SQLITE_UTF16LE, 0, sqlite3utf16Substr },
{ "abs", 1, 0, SQLITE_UTF8, 0, absFunc },
/* Added here */
{ "sign", 1, 0, SQLITE_UTF8, 0, signFunc },
{ "round", 1, 0, SQLITE_UTF8, 0, roundFunc },
{ "round", 2, 0, SQLITE_UTF8, 0, roundFunc },
This seems to work (I've tried it).
HOWEVER, it means altering func.c and I was looking for how to add these
functions in a separate C file without having to alter any existing code?
Anyone any ideas how best to extend the codebase of SQLite with minimal
alteration to existing code?
Cheers,
Mike
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