I’ll add a patch for this.

Original C

memcpy((BYTE*)output->dst + output->pos,
               tmp + (fl->seekTablePos - offset), lenWrite);

Current Rust

output[*pos..*pos + len_write].copy_from_slice(&bytes[..len_write]);

Possibly right version

let start_write = (self.seek_table_pos - offset) as usize;
output[*pos..*pos + len_write].copy_from_slice(&bytes[start_write .. start_write + len_write]);