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Annotation of 43BSD/contrib/icon/functions/reverse.c, revision 1.1

1.1     ! root        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)

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