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