#define FN_MAXNUM 32

class FunctionIndex {
    U64 addr;
    U64 prologue;
} fn_index[FN_MAXNUM];
MemSet(fn_index, 0, sizeof(FunctionIndex));

I64 fn_restore(U32 from)
{
    if (!from) {
        return -1;
    }

    I64 i;
    for (i = 0; i < FN_MAXNUM; i++) {
        if (fn_index[i].addr == from) {
            MemCpy(fn_index[i].addr, &fn_index[i].prologue, 8);
            fn_index[i].addr = fn_index[i].prologue = 0;
            return 0;
        }
    }
    return -1;
}

I64 fn_patch(U32 from, U32 to, Bool patch = TRUE)
{
    if (!from || !to) {
        return -1;
    }
    if (!patch) {
        return fn_restore(from);
    }

    I64 i = 0;
    while (i < FN_MAXNUM && fn_index[i].addr) {
        if (fn_index[i].addr == from) {
            // Function already patched
            return -1;
        }
        ++i;
    }
    if (i >= FN_MAXNUM) {
        // Maximum entires reached
        return -1;
    }

    fn_index[i].addr = from;
    MemCpy(&fn_index[i].prologue, from, 8);
    *(from(U8*)) = 0xE9;
    *((from + 1)(I32*)) = to - from - 5;
    return 0;
}