list.c

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#include "c.h"


static List freenodes;      /* free list nodes */

/* append - append x to list, return new list */
List append(void *x, List list) {
    List new;

    if ((new = freenodes) != NULL)
        freenodes = freenodes->link;
    else
        NEW(new, PERM);
    if (list) {
        new->link = list->link;
        list->link = new;
    } else
        new->link = new;
    new->x = x;
    return new;
}

/* length - # elements in list */
int length(List list) {
    int n = 0;

    if (list) {
        List lp = list;
        do
            n++;
        while ((lp = lp->link) != list);
    }
    return n;
}

/* ltov - convert list to an NULL-terminated vector allocated in arena */
void *ltov(List *list, unsigned arena) {
    int i = 0;
    void **array = newarray(length(*list) + 1, sizeof array[0], arena);

    if (*list) {
        List lp = *list;
        do {
            lp = lp->link;
            array[i++] = lp->x;
        } while (lp != *list);
#ifndef PURIFY
        lp = (*list)->link;
        (*list)->link = freenodes;
        freenodes = lp;
#endif
    }
    *list = NULL;
    array[i] = NULL;
    return array;
}

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