Converting between bases

[Paul Falstad]

cloos at acsu.buffalo.edu (James H. Cloos) wrote:
>I need to be able to convert arbitrarily long strings which a guaenteed to
>match one of the regexps below (each one gets a different function) and
>output the hex equivilent (again in a string) optionally cut down to a
>specified number of hex digits.  (The least significant ones.)  The latter
>part I can take care of, but the former is giving me trouble.
>
>[01]+
>[0-7]+
>[0-9]+

strtol(3).

long binarytoi(char *s)
{
   return strtol(s,NULL,2);
}

long octaltoi(char *s)
{
   return strtol(s,NULL,8);
}

..

If you don't have strtol(3), here's a crippled version that will work
here: (hex conversions, as well as the base == 0 case, are left as an
exercise for the reader)

long strtol(char *s,char **x,int base)
{
long z;

   while (*s >= '0' && *s < '0'+base)
      z = z*base+(*s++-'0');
   if (x)
      *x = s;
   return z;
}

You can print hex with printf("%x\n",foo).

--
Paul Falstad, pfalstad at phoenix.princeton.edu PLink:HYPNOS GEnie:P.FALSTAD
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