for (; n && *s-'0'<10U && v->small<=SLIM; n--, s++)
v->small = v->small * 10 + (*s-'0');
} else if ((b&-b) == b) {
+ /* Compute bitshift for power-of-two bases
+ * using a De Bruijn B(2,3) sequence. */
int bs = "\0\1\2\4\7\3\6\5"[(0x17*b)>>5&7];
for (; n && (d=digits[*s])<b && v->small<=SLIM; n--, s++)
v->small = (v->small<<bs) + d;