/* < 0 means right shift, > 0 means left shift */
void
mpi_shift(const mpi *p, int bits, mpi *q)
{
if (bits < 0)
mpi_rshift(p, -bits, q);
else if (bits > 0)
mpi_lshift(p, +bits, q);
}
void
mpi_mul_u64(const mpi *a, uint64_t b, mpi *p)
{
if (mpi_is_zero(a) || b == 0) {
mpi_zero(p);
return;
} else if (b == 1) {
if (a != p)
mpi_set_mpi(p, a);
return;
} else if ((b & (b-1)) == 0) { /* B is a power of 2 */
mpi_lshift(a, __builtin_ctzll(b), p);
return;
} else if (b == (mp_digit)b) { /* B fits in an mp_digit */
if (a == p) {
mp_digit cy = mp_dmuli(p->digits, p->size, (mp_digit)b);
if (cy) {
MPI_MIN_ALLOC(p, p->size + 1);
p->digits[p->size++] = cy;
}
} else {
MPI_MIN_ALLOC(p, a->size);
mp_digit cy = mp_dmul(a->digits, a->size, (mp_digit)b, p->digits);
if (cy) {
MPI_MIN_ALLOC(p, a->size + 1);
p->digits[a->size] = cy;
p->size = a->size + 1;
} else {
p->size = a->size;
}
}
} else {
unsigned bits = CHAR_BIT * sizeof(uint64_t) - __builtin_clzll(b);
mp_size size = (bits + MP_DIGIT_BITS - 1) / MP_DIGIT_BITS;
mp_digit *bp = MP_TMP_ALLOC(size);
#if MP_DIGIT_BITS >= 64
bp[0] = b;
#else
for (mp_size j=0; j<size; j++) {
bp[j] = (mp_digit)b;
b >>= MP_DIGIT_BITS;
}
#endif
if (a == p) {
mp_digit *tmp = MP_TMP_ALLOC(p->size + size);
mp_mul(p->digits, p->size, bp, size, tmp);
MPI_MIN_ALLOC(p, p->size + size);
mp_copy(tmp, p->size + size, p->digits);
p->size = mp_rsize(p->digits, p->size + size);
MP_TMP_FREE(tmp);
} else {
MPI_MIN_ALLOC(p, a->size + size);
mp_mul(a->digits, a->size, bp, size, p->digits);
p->size = mp_rsize(p->digits, a->size + size);
}
MP_TMP_FREE(bp);
}
}
static void
do_lshift (void)
{
if (stackidx < 1)
{
fputs ("stack underflow\n", stderr);
return;
}
mpi_lshift (stack[stackidx - 1], stack[stackidx - 1], 1);
}
