Go style channels

Cookbook
1

This is a super simple example of Go-style blocking channels. Note that this channel implementation is so simplistic it doesn’t do any locking. It should work fine in certain situations but you may want to add locking.

These channels are bounded, synchronous, blocking, and optionally buffered. To turn off buffering, set n=1. It is obviously meaningless to set n=0.

Channel :: struct(T: Type, n: u64) {
    buffer      : [n]T;
    writeidx    : u64 = 0;
    readidx     : u64 = 0;
    unread      : u64 = 0;
}

channel_reset :: (c: Channel) {
    c.input = 0;
    c.output = 0;
}

channel_write :: (using c: *Channel($T, $n), data: T) {
    while unread == buffer.count sleep_milliseconds(50);

    buffer[writeidx] = data;
    writeidx = (writeidx + 1) % buffer.count;
    unread += 1;
}

channel_read :: (using c: *Channel($T, $n)) -> T {
    while unread == 0 sleep_milliseconds(50);

    val := buffer[readidx];
    readidx = (readidx + 1) % buffer.count;
    unread -= 1;
    return val;
}

channel_write_array :: (c: *Channel($T, $n), data: []T) {
    // Note: This will block if the channel buffer is full.
    for data channel_write(c, it);
}

channel_read_all :: (c: *Channel($T, $n)) -> [..]T {
    // Note: This will read everything there is currently in the channel.
    out : [..]T;

    while c.unread > 0 array_add(*out, channel_read(c));
    return out;
}

channel_reset :: (c: *Channel($T, $n)) {
    c.unread = 0;
}

Obviously, you probably want to use these in a multithreaded situation, and if you use it uncareful you might end up hanging. But here’s a single-thread linear example:

d : Channel(int, 20);

print("channel d has buffer of %\n", d.buffer.count);

channel_write(*d, 1);
print("Read from d: %\n", channel_read(*d));
channel_write(*d, 2);
print("Read from d: %\n", channel_read(*d));
channel_write(*d, 3);
channel_write(*d, 4);
print("Read from d: %\n", channel_read(*d));
channel_write(*d, 5);
print("Read from d: %\n", channel_read_all(*d));

channel_write_array(*d, int.[10, 20, 30]);
print("Read from d: %\n", channel_read(*d));
channel_reset(*d);
print("Read from d: %\n", channel_read_all(*d));