minix/lib/libminlib/paramvalue.c

   1 /*      paramvalue() - decode kernel parameter values   Author: Kees J. Bot
   2  *                                                              7 May 1994
   3  * The kernel returns the results of parameter queries
   4  * by the XXQUERYPARAM svrctl calls as an array of hex digits, like this:
   5  * "75020000,080C0000".  These are the values of two four-byte variables.
   6  * Paramvalue() decodes such a string.
   7  */
   8 #define nil 0
   9 #include <stddef.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <sys/types.h>
  13 #include <minix/queryparam.h>
  14
  15 size_t paramvalue(char **value, void *address, size_t size)
  16 /* Decode the string *value storing the result in the object at address with
  17  * the given size.  *value is left at the next parameter, *address is padded
  18  * with zeros if needed, and the actual size of the value is returned.
  19  */
  20 {
  21         unsigned char *addr= address;
  22         char *v= *value;
  23         int nibble;
  24         size_t n;
  25
  26         n= 0;
  27
  28         while (*v != 0 && *v != ',') {
  29                 nibble= *v++ - '0';
  30                 if (nibble > 0x9) nibble= nibble + '0' - 'A' + 0xA;
  31                 if (nibble > 0xF) nibble= nibble + 'A' - 'a';
  32                 if (size > 0) {
  33                         if (n % 2 == 0) {
  34                                 *addr= nibble << 4;
  35                         } else {
  36                                 *addr++|= nibble;
  37                                 size--;
  38                         }
  39                         n++;
  40                 }
  41         }
  42         while (size > 0) { *addr++= 0; size--; }
  43         while (*v != 0 && *v++ != ',') {}
  44         *value= v;
  45         return n / 2;
  46 }
  47
  48
  49 /*
  50  * $PchId: paramvalue.c,v 1.3 1996/02/22 09:15:56 philip Exp $
  51  */