UNIX 7th Ed. - /usr/src/libmp/mdiv.c

   1: #include <mp.h>
   2: mdiv(a,b,q,r) MINT *a,*b,*q,*r;
   3: {   MINT x,y;
   4:     int sign;
   5:     sign=1;
   6:     x.val=a->val;
   7:     y.val=b->val;
   8:     x.len=a->len;
   9:     if(x.len<0) {sign= -1; x.len= -x.len;}
  10:     y.len=b->len;
  11:     if(y.len<0) {sign= -sign; y.len= -y.len;}
  12:     xfree(q);
  13:     xfree(r);
  14:     m_div(&x,&y,q,r);
  15:     if(sign==-1)
  16:     {   q->len= -q->len;
  17:         r->len = - r->len;
  18:     }
  19:     return;
  20: }
  21: m_dsb(q,n,a,b) short *a,*b;
  22: {   long int x,qx;
  23:     int borrow,j,u;
  24:     qx=q;
  25:     borrow=0;
  26:     for(j=0;j<n;j++)
  27:     {   x=borrow-a[j]*qx+b[j];
  28:         b[j]=x&077777;
  29:         borrow=x>>15;
  30:     }
  31:     x=borrow+b[j];
  32:     b[j]=x&077777;
  33:     if(x>>15 ==0) { return(0);}
  34:     borrow=0;
  35:     for(j=0;j<n;j++)
  36:     {   u=a[j]+b[j]+borrow;
  37:         if(u<0) borrow=1;
  38:         else borrow=0;
  39:         b[j]=u&077777;
  40:     }
  41:     { return(1);}
  42: }
  43: m_trq(v1,v2,u1,u2,u3)
  44: {   long int d;
  45:     long int x1;
  46:     if(u1==v1) d=077777;
  47:     else d=(u1*0100000L+u2)/v1;
  48:     while(1)
  49:     {   x1=u1*0100000L+u2-v1*d;
  50:         x1=x1*0100000L+u3-v2*d;
  51:         if(x1<0) d=d-1;
  52:         else {return(d);}
  53:     }
  54: }
  55: m_div(a,b,q,r) MINT *a,*b,*q,*r;
  56: {   MINT u,v,x,w;
  57:     short d,*qval;
  58:     int qq,n,v1,v2,j;
  59:     u.len=v.len=x.len=w.len=0;
  60:     if(b->len==0) { fatal("mdiv divide by zero"); return;}
  61:     if(b->len==1)
  62:     {   r->val=xalloc(1,"m_div1");
  63:         sdiv(a,b->val[0],q,r->val);
  64:         if(r->val[0]==0)
  65:         {   shfree(r->val);
  66:             r->len=0;
  67:         }
  68:         else r->len=1;
  69:         return;
  70:     }
  71:     if(a->len < b->len)
  72:     {   q->len=0;
  73:         r->len=a->len;
  74:         r->val=xalloc(r->len,"m_div2");
  75:         for(qq=0;qq<r->len;qq++) r->val[qq]=a->val[qq];
  76:         return;
  77:     }
  78:     x.len=1;
  79:     x.val = &d;
  80:     n=b->len;
  81:     d=0100000L/(b->val[n-1]+1L);
  82:     mult(a,&x,&u); /*subtle: relies on fact that mult allocates extra space */
  83:     mult(b,&x,&v);
  84:     v1=v.val[n-1];
  85:     v2=v.val[n-2];
  86:     qval=xalloc(a->len-n+1,"m_div3");
  87:     for(j=a->len-n;j>=0;j--)
  88:     {   qq=m_trq(v1,v2,u.val[j+n],u.val[j+n-1],u.val[j+n-2]);
  89:         if(m_dsb(qq,n,v.val,&(u.val[j]))) qq -= 1;
  90:         qval[j]=qq;
  91:     }
  92:     x.len=n;
  93:     x.val=u.val;
  94:     mcan(&x);
  95:     sdiv(&x,d,&w,(short *)&qq);
  96:     r->len=w.len;
  97:     r->val=w.val;
  98:     q->val=qval;
  99:     qq=a->len-n+1;
 100:     if(qq>0 && qval[qq-1]==0) qq -= 1;
 101:     q->len=qq;
 102:     if(qq==0) shfree(qval);
 103:     if(x.len!=0) xfree(&u);
 104:     xfree(&v);
 105:     return;
 106: }

Defined functions