Function strNsubst

src/hacklib.c:556–597

substitute the Nth occurrence of a substring within a string (in place); if N is 0, substitute all occurrences; returns the number of substitutions; maximum output length is BUFSZ (BUFSZ-1 chars + terminating '\0') */

   if N is 0, substitute all occurrences; returns the number of substitutions;
   maximum output length is BUFSZ (BUFSZ-1 chars + terminating '\0') */
int
strNsubst(
    char *inoutbuf,   /* current string, and result buffer */
    const char *orig, /* old substring; if "", insert in front of Nth char */
    const char *replacement, /* new substring; if "", delete old substring */
    int n) /* which occurrence to replace; 0 => all */
{
    char *bp, *op, workbuf[BUFSZ];
    const char *rp;
    unsigned len = (unsigned) strlen(orig);
    int ocount = 0, /* number of times 'orig' has been matched */
        rcount = 0; /* number of substitutions made */

    for (bp = inoutbuf, op = workbuf; *bp && op < &workbuf[BUFSZ - 1]; ) {
        if ((!len || !strncmp(bp, orig, len)) && (++ocount == n || n == 0)) {
            /* Nth match found */
            for (rp = replacement; *rp && op < &workbuf[BUFSZ - 1]; )
                *op++ = *rp++;
            ++rcount;
            if (len) {
                bp += len; /* skip 'orig' */
                continue;
            }
        }
        /* no match (or len==0) so retain current character */
        *op++ = *bp++;
    }
    if (!len && n == ocount + 1) {
        /* special case: orig=="" (!len) and n==strlen(inoutbuf)+1,
           insert in front of terminator (in other words, append);
           [when orig=="", ocount will have been incremented once for
           each input char] */
        for (rp = replacement; *rp && op < &workbuf[BUFSZ - 1]; )
            *op++ = *rp++;
        ++rcount;
    }
    if (rcount) {
        *op = '\0';
        Strcpy(inoutbuf, workbuf);
    }
    return rcount;
}

/* search for a word in a space-separated list; returns non-Null if found */
const char *