Through experimentation it appears that the signature should be documented
as
void (*xFunc)(sqlite3_context* pCtx, int nArgs, sqlite3_value** apArgs)
Where
sqlite3_context* could be expressed as pCtx (the database connection)
int could be expressed as nArgs (analogous to argc)
sqlite3_value** could be expressed as apArgs (analogous to argv)
I based my experiment on the rankfunc example on the fts docs:
static void rankfunc(sqlite3_context *pCtx, int nVal, sqlite3_value
**apVal){
sqlite3_result_double(pCtx, nVal);
}
// the 3 means that 3 arguments are required.
sqlite3_create_function(db, "testfn", 3, SQLITE_ANY, 0, testfn, 0, 0);
testfn("1", "2", "3"); -- nVal is 3
testfn("1", "2"); -- returns an error
Whereas
// the -1 means that any number of arguments are accepted.
sqlite3_create_function(db, "testfn", -1, SQLITE_ANY, 0, testfn, 0, 0);
testfn("1", "2", "3"); -- nVal is 3
testfn("1", "2"); -- nVal is 2
testfn(matchinfo(documents)); -- nVal is 1
testfn(matchinfo(documents), 2, 3, 4, 5, 6, 7); -- nVal is 7
sqlite3_create_function(db, "rank", -1, SQLITE_ANY, 0, rankfunc, 0, 0);
AJ ONeal
On Sat, Jul 21, 2012 at 2:36 PM, AJ ONeal <coola...@gmail.com> wrote:
> According to
> http://www.sqlite.org/c3ref/create_function.html
>
> `sqlite3_create_function` accepts a callback parameter `void
> (*xFunc)(sqlite_func*,int,const char**)`
>
> However, I can't find the documentation which explains what the parameters
> to `xFunc` mean.
> http://www.sqlite.org/search?q=xfunc
> http://www.sqlite.org/capi3.html
> http://www.sqlite.org/c_interface.html#cfunc
> http://www.sqlite.org/c3ref/value_blob.html
> (I've also googled about outside of sqlite.org)
>
> If the documentation is available, please link me to it.
>
> If not, please explain what these 3 parameters are and how they should be
> used.
>
> AJ ONeal
>
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