qubit-function 0.16.0

Functional programming traits and Box/Rc/Arc adapters for Rust, inspired by Java functional interfaces
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111

// =============================================================================
//    Copyright (c) 2025 - 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================
//! Defines the `BoxConsumerOnce` public type.

use {
    crate::BoxConditionalConsumerOnce,
    crate::Predicate,
};
use {
    crate::ConsumerOnce,
    crate::consumers::macros::impl_box_consumer_methods,
    crate::consumers::macros::impl_consumer_common_methods,
    crate::consumers::macros::impl_consumer_debug_display,
    crate::macros::impl_closure_once_trait,
};

// ============================================================================
// 2. BoxConsumerOnce - Single Ownership Implementation
// ============================================================================

/// BoxConsumerOnce struct
///
/// One-time consumer implementation based on `Box<dyn FnOnce(&T)>` for single
/// ownership scenarios. This is the simplest consumer type for truly one-time
/// use.
///
/// # Features
///
/// - **Single Ownership**: Not cloneable, transfers ownership on use
/// - **Runtime cost**: One heap allocation and dynamic dispatch; no reference
///   counting or locking
/// - **One-time Use**: Consumes self on first call
/// - **Builder Pattern**: Method chaining naturally consumes `self`
///
/// # Use Cases
///
/// Choose `BoxConsumerOnce` when:
/// - Consumer is truly used only once
/// - Building pipelines where ownership flows naturally
/// - Consumer captures values that should be consumed
/// - Performance critical and cannot accept shared overhead
///
/// # Performance
///
/// `BoxConsumerOnce` has the best performance:
/// - No reference counting overhead
/// - No lock acquisition or runtime borrow checking
/// - Direct function call through vtable
/// - Minimal memory footprint (single pointer)
///
/// # Examples
///
/// ```rust
/// use qubit_function::{ConsumerOnce, BoxConsumerOnce};
///
/// let consumer = BoxConsumerOnce::new(|x: &i32| {
///     println!("Value: {}", x);
/// });
/// consumer.accept(&5);
/// ```
#[must_use = "callback wrappers do nothing unless stored or invoked"]
pub struct BoxConsumerOnce<T> {
    /// The wrapped callback implementation.
    pub(super) function: Box<dyn FnOnce(&T)>,
    /// Diagnostic metadata associated with this callback.
    pub(super) metadata: crate::internal::CallbackMetadata,
}

// All methods require T: 'static because Box<dyn FnOnce(&T)> requires it
impl<T> BoxConsumerOnce<T> {
    // Generates: new(), new_with_name(), name(), set_name(), noop()
    impl_consumer_common_methods!(
        BoxConsumerOnce<T>,
        (FnOnce(&T) + 'static),
        |f| Box::new(f)
    );

    // Generates: when() and and_then() methods that consume self
    impl_box_consumer_methods!(
        BoxConsumerOnce<T>,
        BoxConditionalConsumerOnce,
        ConsumerOnce
    );
}

impl<T> ConsumerOnce<T> for BoxConsumerOnce<T> {
    #[inline(always)]
    fn accept(self, value: &T) {
        (self.function)(value)
    }
}

// Use macro to generate Debug and Display implementations
impl_consumer_debug_display!(BoxConsumerOnce<T>);

// ============================================================================
// 3. Implement ConsumerOnce trait for closures
// ============================================================================

// Implement ConsumerOnce for all FnOnce(&T) using macro
impl_closure_once_trait!(
    ConsumerOnce<T>,
    accept,
    BoxConsumerOnce,
    FnOnce(value: &T)
);