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Annotation of 43BSD/contrib/icon/functions/center.c, revision 1.1.1.1

1.1       root        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)

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