newlib/libc/stdlib/l64a.c

   1 /* l64a - convert long to radix-64 ascii string
   2  *
   3  * Conversion is performed on at most 32-bits of input value starting
   4  * from least significant bits to the most significant bits.
   5  *
   6  * The routine splits the input value into groups of 6 bits for up to
   7  * 32 bits of input.  This means that the last group may be 2 bits
   8  * (bits 30 and 31).
   9  *
  10  * Each group of 6 bits forms a value from 0-63 which is converted into
  11  * a character as follows:
  12  *         0 = '.'
  13  *         1 = '/'
  14  *         2-11 = '0' to '9'
  15  *        12-37 = 'A' to 'Z'
  16  *        38-63 = 'a' to 'z'
  17  *
  18  * When the remaining bits are zero or all 32 bits have been translated,
  19  * a nul terminator is appended to the resulting string.  An input value of
  20  * 0 results in an empty string.
  21  */
  22
  23 #include <_ansi.h>
  24 #include <stdlib.h>
  25 #include <reent.h>
  26
  27 #ifdef _REENT_THREAD_LOCAL
  28 _Thread_local char _tls_l64a_buf[8];
  29 #endif
  30
  31 static const char R64_ARRAY[] = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  32
  33 char *
  34 l64a (long value)
  35 {
  36   return _l64a_r (_REENT, value);
  37 }
  38
  39 char *
  40 _l64a_r (struct _reent *rptr,
  41      long value)
  42 {
  43   char *ptr;
  44   char *result;
  45   int i, index;
  46   unsigned long tmp = (unsigned long)value & 0xffffffff;
  47
  48   _REENT_CHECK_MISC(rptr);
  49   result = _REENT_L64A_BUF(rptr);
  50   ptr = result;
  51
  52   for (i = 0; i < 6; ++i)
  53     {
  54       if (tmp == 0)
  55         {
  56           *ptr = '\0';
  57           break;
  58         }
  59
  60       index = tmp & (64 - 1);
  61       *ptr++ = R64_ARRAY[index];
  62       tmp >>= 6;
  63     }
  64
  65   return result;
  66 }