Function Bitmaps

docs/app/js/sanddance-app.js:141167–141221

* Maintains CrossFilter state.

()

/**
 * Maintains CrossFilter state.
 */ function Bitmaps() {
    let width = 8, data = [], seen = array32(0), curr = array(0, width), prev = array(0, width);
    return {
        data: ()=>data,
        seen: ()=>seen = lengthen(seen, data.length),
        add (array1) {
            for(let i = 0, j = data.length, n = array1.length, t; i < n; ++i){
                t = array1[i];
                t._index = j++;
                data.push(t);
            }
        },
        remove (num, map) {
            // map: index -> boolean (true => remove)
            const n = data.length, copy = Array(n - num), reindex = data; // reuse old data array for index map
            let t, i, j; // seek forward to first removal
            for(i = 0; !map[i] && i < n; ++i){
                copy[i] = data[i];
                reindex[i] = i;
            } // condense arrays
            for(j = i; i < n; ++i){
                t = data[i];
                if (!map[i]) {
                    reindex[i] = j;
                    curr[j] = curr[i];
                    prev[j] = prev[i];
                    copy[j] = t;
                    t._index = j++;
                } else reindex[i] = -1;
                curr[i] = 0; // clear unused bits
            }
            data = copy;
            return reindex;
        },
        size: ()=>data.length,
        curr: ()=>curr,
        prev: ()=>prev,
        reset: (k)=>prev[k] = curr[k],
        all: ()=>width < 0x101 ? 0xff : width < 0x10001 ? 0xffff : 0xffffffff,
        set (k, one) {
            curr[k] |= one;
        },
        clear (k, one) {
            curr[k] &= ~one;
        },
        resize (n, m) {
            const k = curr.length;
            if (n > k || m > width) {
                width = Math.max(m, width);
                curr = array(n, width, curr);
                prev = array(n, width);
            }
        }
    };
}
function lengthen(array2, length, copy) {
    if (array2.length >= length) return array2;
    copy = copy || new array2.constructor(length);