haste-compiler-0.2: lib/pointers.js

// An attempt at emulating pointers enough for ByteString and Text to be
// usable without patching the hell out of them.
// The general idea is that Addr# is a byte array with an associated offset.

function plusAddr(addr, off) {
    var newaddr = {};
    newaddr['off'] = addr['off'] + off;
    newaddr['b']   = addr['b'];
    newaddr['v']   = addr['v'];
    return newaddr;
}

function writeOffAddr(type, elemsize, addr, off, x) {
    addr['v'][type][addr.off/elemsize + off] = x;
}

function readOffAddr(type, elemsize, addr, off) {
    return addr['v'][type][addr.off/elemsize + off];
}

// Two addresses are equal if they point to the same buffer and have the same
// offset. For other comparisons, just use the offsets - nobody in their right
// mind would check if one pointer is less than another, completely unrelated,
// pointer and then act on that information anyway.
function addrEq(a, b) {
    if(a == b) {
        return true;
    }
    return a && b && a['b'] == b['b'] && a['off'] == b['off'];
}

function addrLT(a, b) {
    if(a) {
        return b && a['off'] < b['off'];
    } else {
        return (b != 0); 
    }
}

function addrGT(a, b) {
    if(b) {
        return a && a['off'] > b['off'];
    } else {
        return (a != 0);
    }
}