4.3BSD - /usr/src/new/icon/functions/reverse.c

   1: #include "../h/rt.h"
   2: 
   3: /*
   4:  * reverse(s) - reverse string s.
   5:  */
   6: 
   7: Xreverse(nargs, arg1, arg0)
   8: int nargs;
   9: struct descrip arg1, arg0;
  10:    {
  11:    register char c, *floc, *lloc;
  12:    register int slen;
  13:    char sbuf[MAXSTRING];
  14:    extern char *alcstr();
  15: 
  16:    /*
  17:     * Make sure that s is a string.
  18:     */
  19:    if (cvstr(&arg1, sbuf) == NULL)
  20:       runerr(103, &arg1);
  21: 
  22:    /*
  23:     * Ensure that there is enough room and allocate a copy of s.
  24:     */
  25:    slen = STRLEN(arg1);
  26:    sneed(slen);
  27:    STRLEN(arg0) = slen;
  28:    STRLOC(arg0) = alcstr(STRLOC(arg1), slen);
  29: 
  30:    /*
  31:     * Point floc at the start of s and lloc at the end of s.  Work floc
  32:     *  and sloc along s in opposite directions, swapping the characters
  33:     *  at floc and lloc.
  34:     */
  35:    floc = STRLOC(arg0);
  36:    lloc = floc + --slen;
  37:    while (floc < lloc) {
  38:       c = *floc;
  39:       *floc++ = *lloc;
  40:       *lloc-- = c;
  41:       }
  42:    }
  43: 
  44: Procblock(reverse,1)

Defined functions