"math/bits" ) type CTR struct { b Block ivlo, ivhi uint64 // start counter as 64-bit limbs offset uint64 // for XORKeyStream only } func NewCTR(b *Block, iv []byte) *CTR { // Allocate the CTR here, in an easily inlineable function, so // the allocation can be done in the caller's stack frame // instead of the heap. See issue 70499. c := newCTR(b, iv) return &c } func newCTR(b *Block, iv []byte) CTR { if len(iv) != BlockSize { panic("bad IV length") } return CTR{ b: *b, ivlo: byteorder.BEUint64(iv[8:16]),...