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

   1: #include "../h/rt.h"
   2: 
   3: /*
   4:  * center(s1,n,s2) - pad s1 on left and right with s2 to length n.
   5:  */
   6: 
   7: Xcenter(nargs, arg3, arg2, arg1, arg0)
   8: int nargs;
   9: struct descrip arg3, arg2, arg1, arg0;
  10:    {
  11:    register char *s, *st;
  12:    int cnt, slen, hcnt;
  13:    char *sbuf, *s3;
  14:    char sbuf1[MAXSTRING], sbuf2[MAXSTRING];
  15:    extern char *alcstr();
  16: 
  17:    /*
  18:     * s1 must be a string.  n must be a non-negative integer and defaults
  19:     *  to 1.  s2 must be a string and defaults to a blank.
  20:     */
  21:    if (cvstr(&arg1, sbuf1) == NULL)
  22:       runerr(103, &arg1);
  23:    defshort(&arg2, 1);
  24:    if ((cnt = INTVAL(arg2)) < 0)
  25:       runerr(205, &arg2);
  26:    defstr(&arg3, sbuf2, &blank);
  27: 
  28:    sneed(cnt);
  29: 
  30:    if (STRLEN(arg3) == 0) {
  31:       /*
  32:        * The padding string is null, make it a blank.
  33:        */
  34:       slen = 1;
  35:       s3 = " ";
  36:       }
  37:    else {
  38:       slen = STRLEN(arg3);
  39:       s3 = STRLOC(arg3);
  40:       }
  41: 
  42:    /*
  43:     * Get n bytes of string space for the new string.  Start at the right
  44:     *  of the new string and copy s2 into it from right to left as
  45:     *  many times as will fit in the right half of the new string.
  46:     */
  47:    sbuf = alcstr(NULL, cnt);
  48:    hcnt = cnt / 2;
  49:    s = sbuf + cnt;
  50:    while (s > sbuf + hcnt) {
  51:       st = s3 + slen;
  52:       while (st > s3 && s > sbuf + hcnt)
  53:          *--s = *--st;
  54:       }
  55: 
  56:    /*
  57:     * Start at the left end of the new string and copy s1 into it from
  58:     *  left to right as many time as will fit in the left half of the
  59:     *  new string.
  60:     */
  61:    s = sbuf;
  62:    while (s < sbuf + hcnt) {
  63:       st = s3;
  64:       while (st < s3 + slen && s < sbuf + hcnt)
  65:          *s++ = *st++;
  66:       }
  67: 
  68:    slen = STRLEN(arg1);
  69:    if (cnt < slen) {
  70:       /*
  71:        * s1 is larger than the field to center it in.  The source for the
  72:        *  copy starts at the appropriate point in s1 and the destination
  73:        *  starts at the left end of of the new string.
  74:        */
  75:       s = sbuf;
  76:       st = STRLOC(arg1) + slen/2 - hcnt + (~cnt&slen&1);
  77:       }
  78:    else {
  79:       /*
  80:        * s1 is smaller than the field to center it in.  The source for the
  81:        *  copy starts at the left end of s1 and the destination starts at
  82:        *  the appropriate point in the new string.
  83:        */
  84:       s = sbuf + hcnt - slen/2 - (~cnt&slen&1);
  85:       st = STRLOC(arg1);
  86:       }
  87:    /*
  88:     * Perform the copy, moving min(*s1,n) bytes from st to s.
  89:     */
  90:    if (slen > cnt)
  91:       slen = cnt;
  92:    while (slen-- > 0)
  93:       *s++ = *st++;
  94: 
  95:    /*
  96:     * Return the new string.
  97:     */
  98:    STRLEN(arg0) = cnt;
  99:    STRLOC(arg0) = sbuf;
 100:    }
 101: 
 102: Procblock(center,3)

Defined functions