mango/libc/string/strtok.c

#include <limits.h>
#include <mango/libc/string.h>

#define ALIGN (sizeof(size_t))
#define ONES ((size_t)-1 / UCHAR_MAX)
#define HIGHS (ONES * (UCHAR_MAX / 2 + 1))
#define HASZERO(X) (((X)-ONES) & ~(X)&HIGHS)
#define BITOP(A, B, OP)                                                        \
    ((A)[(size_t)(B) / (8 * sizeof *(A))] OP(size_t) 1                         \
     << ((size_t)(B) % (8 * sizeof *(A))))

char *strchrnul(const char *s, int c) {
    size_t *w;
    size_t k;

    c = (unsigned char)c;
    if (!c) {
        return (char *)s + strlen(s);
    }

    for (; (uintptr_t)s % ALIGN; s++) {
        if (!*s || *(unsigned char *)s == c) {
            return (char *)s;
        }
    }

    k = ONES * c;
    for (w = (void *)s; !HASZERO(*w) && !HASZERO(*w ^ k); w++)
        ;
    for (s = (void *)w; *s && *(unsigned char *)s != c; s++)
        ;
    return (char *)s;
}

char *strchr(const char *s, int c) {
    char *r = strchrnul(s, c);
    return *(unsigned char *)r == (unsigned char)c ? r : 0;
}

size_t lfind(const char *str, const char accept) {
    return (size_t)strchr(str, accept);
}

size_t strspn(const char *s, const char *c) {
    const char *a                       = s;
    size_t byteset[32 / sizeof(size_t)] = {0};

    if (!c[0]) {
        return 0;
    }

    if (!c[1]) {
        for (; *s == *c; s++) {
            return s - a;
        }
    }

    for (; *c && BITOP(byteset, *(unsigned char *)c, |=); c++)
        ;
    for (; *s && BITOP(byteset, *(unsigned char *)s, &); s++)
        ;
    return s - a;
}

size_t strcspn(const char *s, const char *c) {
    const char *a = s;

    if (c[0] && c[1]) {
        size_t byteset[32 / sizeof(size_t)] = {0};
        for (; *c && BITOP(byteset, *(unsigned char *)c, |=); c++)
            ;
        for (; *s && !BITOP(byteset, *(unsigned char *)s, &); s++)
            ;
        return s - a;
    }

    return strchrnul(s, *c) - a;
}

char *strpbrk(const char *s, const char *b) {
    s += strcspn(s, b);
    return *s ? (char *)s : 0;
}

char *strtok_r(char *str, const char *delim, char **sp) {
    int i   = 0;
    int len = strlen(delim);

    /* Were we given any delimiters? */
    if (len == 0) {
        return NULL;
    }

    /* If we weren't given a string, and save pointer is NULL, return. */
    if (!str && !sp) {
        return NULL;
    }

    /* If we were given a string, initialise sp for subsequent calls. */
    if (str) {
        *sp = str;
    }

    /* Go to the start of the substring, skipping any delimiters. */
    char *p_start = *sp;
    while (1) {
        for (i = 0; i < len; i++) {
            if (*p_start == delim[i]) {
                p_start++;
                break;
            }
        }

        if (i == len) {
            *sp = p_start;
            break;
        }
    }

    /* Are we at the end of the string? */
    if (**sp == '\0') {
        *sp = NULL;
        return *sp;
    }

    /* Find the end of the substring, and
       replace the delimiter with null */
    while (**sp != '\0') {
        for (i = 0; i < len; i++) {
            if (**sp == delim[i]) {
                **sp = '\0';
                break;
            }
        }

        (*sp)++;
        if (i < len) {
            break;
        }
    }

    return p_start;
}