fn opened_split(raw: &[u8]) -> Option<usize>Expand description
The head of a message as open rebuilds an encrypted one: its outer
header lines (none of them Content- nor MIME-Version), the line
MIME-Version: 1.0 it adds after them, then the opened entity’s own
header lines, a Content- one among them. Where that line is, when the
head has that shape: what a copy decrypted by Sioul before 19 October
2026 looks like (a message that came in clear may too).