Support span based collations comparison functions in Sqlite #35236
Description
Sqlite supports creating custom collations via SqliteConnection.CreateCollation
this calls
sqlite3_create_collation, however this function allocates strings for every comparison.
I'd like to have a function which works with spans, there's already the function sqlite3__create_collation_utf8 which exposes the span based API we just need to wire it up. I'm happy to contribute a PR if it would be accepted.
private void CreateSpanCollation<T>(SqliteConnection connection,
string name, T state,
Func<T, ReadOnlySpan<char>, ReadOnlySpan<char>, int> compare)
{
if (connection.State != ConnectionState.Open)
throw new InvalidOperationException("Unable to create custom collation Connection must be open.");
var rc = SQLitePCL.raw.sqlite3__create_collation_utf8(connection.Handle,
name,
Tuple.Create(state, compare),
static (s, x, y) =>
{
var (state, compare) = (Tuple<T, Func<T, ReadOnlySpan<char>, ReadOnlySpan<char>, int>>) s;
Span<char> xSpan = stackalloc char[Encoding.UTF8.GetCharCount(x)];
Span<char> ySpan = stackalloc char[Encoding.UTF8.GetCharCount(y)];
Encoding.UTF8.GetChars(x, xSpan);
Encoding.UTF8.GetChars(y, ySpan);
return compare(state, xSpan, ySpan);
});
SqliteException.ThrowExceptionForRC(rc, connection.Handle);
}