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Source code

const std = @import("std");

export fn huh(addr: *u64, val: *[32]u32) void {
    @fence(.Release);
    const t = @atomicRmw(u64, addr, .Sub, 1, .Monotonic);
    if (t == 1) {
        @fence(.Acquire);
        @memset(val, 2);
    }
}

export fn try_find_unoccupied_index(map: *u64) u64 {
        var bits : u64 = 0;
        while (true) {
            const free_index = @ctz(~bits);
            const all_workers_are_busy = free_index == 64;
            if (all_workers_are_busy) {
                // try with outliers
                return ~@as(u64,0); // null
            }
            const free_index_bit: u64 = @as(u64,1) << @intCast(free_index);
            const prior = @atomicRmw(
                u64,
                map,
                .Or,
                free_index_bit,
                .Monotonic);
            const we_have_it = prior & free_index_bit == 0;
            if (we_have_it) return free_index;
            bits = prior;
        }
    }

export fn huh2(addr:*u64) void {
    _ = @atomicRmw(u64, addr, .Or, 1, .Monotonic);
}

export fn main() void {
    
    //@fence(std.builtin.AtomicOrder.SeqCst);
}