tiny.choir.composition.loaded.gate

1const std = @import("std");23const closing_mask: u64 = 1 << 63;4const invocation_count_mask: u64 = closing_mask - 1;56pub const Gate = struct {7    next_id: std.atomic.Value(u64) = std.atomic.Value(u64).init(1),8    state: std.atomic.Value(u64) = std.atomic.Value(u64).init(0),910    pub fn reserve(self: *Gate) ?u64 {11        var state = self.state.load(.acquire);12        while (true) {13            if (state & closing_mask != 0 or state & invocation_count_mask == invocation_count_mask) return null;14            if (self.state.cmpxchgWeak(state, state + 1, .acq_rel, .acquire)) |observed| {15                state = observed;16                continue;17            }18            break;19        }20        return self.next_id.fetchAdd(1, .monotonic);21    }2223    pub fn release(self: *Gate) void {24        const previous_state = self.state.fetchSub(1, .acq_rel);25        if (previous_state & invocation_count_mask == 0) @panic("released inactive composition invocation");26    }2728    pub fn close(self: *Gate) void {29        const previous_state = self.state.fetchOr(closing_mask, .acq_rel);30        if (previous_state & invocation_count_mask != 0) @panic("composition destroyed with active invocations");31    }3233    pub fn activeCount(self: *const Gate) u64 {34        return self.state.load(.acquire) & invocation_count_mask;35    }3637    pub fn isClosing(self: *const Gate) bool {38        return self.state.load(.acquire) & closing_mask != 0;39    }40};

1pub const gate = @import("gate.zig");