tmptov.c - plan9port - [fork] Plan 9 from user space
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       ---
       tmptov.c (1254B)
       ---
            1 #include "os.h"
            2 #include <mp.h>
            3 #include "dat.h"
            4 
            5 #define VLDIGITS (sizeof(vlong)/sizeof(mpdigit))
            6 
            7 /*
            8  *  this code assumes that a vlong is an integral number of
            9  *  mpdigits long.
           10  */
           11 mpint*
           12 vtomp(vlong v, mpint *b)
           13 {
           14         int s;
           15         uvlong uv;
           16 
           17         if(b == nil)
           18                 b = mpnew(VLDIGITS*sizeof(mpdigit));
           19         else
           20                 mpbits(b, VLDIGITS*sizeof(mpdigit));
           21         mpassign(mpzero, b);
           22         if(v == 0)
           23                 return b;
           24         if(v < 0){
           25                 b->sign = -1;
           26                 uv = -v;
           27         } else
           28                 uv = v;
           29         for(s = 0; s < VLDIGITS && uv != 0; s++){
           30                 b->p[s] = uv;
           31         /* !@*$&!@$ gcc gives warnings about the >> here
           32          * when running on 64-bit machines, even though
           33          * it's in dead code.  fake it out with two shifts.
           34                 if(sizeof(mpdigit) == sizeof(uvlong))
           35                         uv = 0;
           36                 else
           37                         uv >>= sizeof(mpdigit)*8;
           38         */
           39                 uv >>= sizeof(mpdigit)*4;
           40                 uv >>= sizeof(mpdigit)*4;
           41         }
           42         b->top = s;
           43         return b;
           44 }
           45 
           46 vlong
           47 mptov(mpint *b)
           48 {
           49         uvlong v;
           50         int s;
           51 
           52         if(b->top == 0)
           53                 return 0LL;
           54 
           55         mpnorm(b);
           56         if(b->top > VLDIGITS){
           57                 if(b->sign > 0)
           58                         return (vlong)MAXVLONG;
           59                 else
           60                         return (vlong)MINVLONG;
           61         }
           62 
           63         v = 0ULL;
           64         for(s = 0; s < b->top; s++)
           65                 v |= b->p[s]<<(s*sizeof(mpdigit)*8);
           66 
           67         if(b->sign > 0){
           68                 if(v > MAXVLONG)
           69                         v = MAXVLONG;
           70         } else {
           71                 if(v > MINVLONG)
           72                         v = MINVLONG;
           73                 else
           74                         v = -(vlong)v;
           75         }
           76 
           77         return (vlong)v;
           78 }