ref: a69ae5ed2a33e8d1a62391e57347285228ba4054
dir: /3rd/mp/mpdigdiv.c/
#include "platform.h" // // divide two digits by one and return quotient // void mpdigdiv(mpdigit *dividend, mpdigit divisor, mpdigit *quotient) { mpdigit hi, lo, q, x, y; int i; hi = dividend[1]; lo = dividend[0]; // return highest digit value if the result >= 2**32 if(hi >= divisor || divisor == 0){ divisor = 0; *quotient = ~divisor; return; } // very common case if(~divisor == 0){ lo += hi; if(lo < hi){ hi++; lo++; } if(lo+1 == 0) hi++; *quotient = hi; return; } // at this point we know that hi < divisor // just shift and subtract till we're done q = 0; x = divisor; for(i = Dbits-1; hi > 0 && i >= 0; i--){ x >>= 1; if(x > hi) continue; y = divisor<<i; if(x == hi && y > lo) continue; if(y > lo) hi--; lo -= y; hi -= x; q |= (mpdigit)1<<i; } q += lo/divisor; *quotient = q; }