Function shachain_index

common/derive_basepoints.h:137–142

BOLT #3: * * The first secret used: * - MUST be index 281474976710655, * - and from there, the index is decremented. */

 *     - and from there, the index is decremented.
 */
static inline u64 shachain_index(u64 per_commit_index)
{
	BUILD_ASSERT((1ULL << SHACHAIN_BITS)-1 == 281474976710655);
	assert(per_commit_index < (1ULL << SHACHAIN_BITS));
	return (1ULL << SHACHAIN_BITS)-1 - per_commit_index;
}

static inline u64 revocations_received(const struct shachain *shachain)
{