Function strstri

src/hacklib.c:739–779

case-insensitive substring search */

#ifndef STRSTRI
/* case-insensitive substring search */
char *
strstri(const char *str, const char *sub)
{
    const char *s1, *s2;
    int i, k;
#define TABSIZ 0x20                  /* 0x40 would be case-sensitive */
    char tstr[TABSIZ], tsub[TABSIZ]; /* nibble count tables */
#if 0
    assert( (TABSIZ & ~(TABSIZ-1)) == TABSIZ ); /* must be exact power of 2 */
    assert( &lowc != 0 );                       /* can't be unsafe macro */
#endif

    /* special case: empty substring */
    if (!*sub)
        return (char *) str;

    /* do some useful work while determining relative lengths */
    for (i = 0; i < TABSIZ; i++)
        tstr[i] = tsub[i] = 0; /* init */
    for (k = 0, s1 = str; *s1; k++)
        tstr[*s1++ & (TABSIZ - 1)]++;
    for (s2 = sub; *s2; --k)
        tsub[*s2++ & (TABSIZ - 1)]++;

    /* evaluate the info we've collected */
    if (k < 0)
        return (char *) 0;       /* sub longer than str, so can't match */
    for (i = 0; i < TABSIZ; i++) /* does sub have more 'x's than str? */
        if (tsub[i] > tstr[i])
            return (char *) 0; /* match not possible */

    /* now actually compare the substring repeatedly to parts of the string */
    for (i = 0; i <= k; i++) {
        s1 = &str[i];
        s2 = sub;
        while (lowc(*s1++) == lowc(*s2++))
            if (!*s2)
                return (char *) &str[i]; /* full match */
    }
    return (char *) 0; /* not found */
}
#endif /* STRSTRI */

/* compare two strings for equality, ignoring the presence of specified