newlib/libc/stdlib/utoa.c

   1 /*
   2 FUNCTION
   3 <<utoa>>---unsigned integer to string
   4
   5 INDEX
   6         utoa
   7
   8 SYNOPSIS
   9         #include <stdlib.h>
  10         char *utoa(unsigned <[value]>, char *<[str]>, int <[base]>);
  11         char *__utoa(unsigned <[value]>, char *<[str]>, int <[base]>);
  12
  13 DESCRIPTION
  14 <<utoa>> converts the unsigned integer [<value>] to a null-terminated string
  15 using the specified base, which must be between 2 and 36, inclusive.
  16 <[str]> should be an array long enough to contain the converted
  17 value, which in the worst case is sizeof(int)*8+1 bytes.
  18
  19 RETURNS
  20 A pointer to the string, <[str]>, or NULL if <[base]> is invalid.
  21
  22 PORTABILITY
  23 <<utoa>> is non-ANSI.
  24
  25 No supporting OS subroutine calls are required.
  26 */
  27
  28 #include <stdlib.h>
  29
  30 char *
  31 __utoa (unsigned value,
  32         char *str,
  33         int base)
  34 {
  35   const char digits[] = "0123456789abcdefghijklmnopqrstuvwxyz";
  36   int i, j;
  37   unsigned remainder;
  38   char c;
  39
  40   /* Check base is supported. */
  41   if ((base < 2) || (base > 36))
  42     {
  43       str[0] = '\0';
  44       return NULL;
  45     }
  46
  47   /* Convert to string. Digits are in reverse order.  */
  48   i = 0;
  49   do
  50     {
  51       remainder = value % base;
  52       str[i++] = digits[remainder];
  53       value = value / base;
  54     } while (value != 0);
  55   str[i] = '\0';
  56
  57   /* Reverse string.  */
  58   for (j = 0, i--; j < i; j++, i--)
  59     {
  60       c = str[j];
  61       str[j] = str[i];
  62       str[i] = c;
  63     }
  64
  65   return str;
  66 }
  67
  68 char *
  69 utoa (unsigned value,
  70         char *str,
  71         int base)
  72 {
  73   return __utoa (value, str, base);
  74 }