sz-rust-core 0.6.1

//! Alloc 计数 GlobalAlloc wrapper — P3 性能度量工具
//!
//! 提供 `AllocCounter<A>` 包装全局分配器，统计 alloc/dealloc 次数，
//! 用于 P3 热点路径堆分配次数度量。
//!
//! ## 设计
//!
//! - 包装 `std::alloc::System`（或任意 `GlobalAlloc`），使用 `AtomicUsize` 统计次数
//! - `measure(f)` 执行闭包并返回结果 + 分配次数差值
//! - 通过 `#[cfg(feature = "alloc-count")]` feature gate 控制，默认不启用
//! - `register_alloc_counter!` 宏注册全局分配器
//!
//! ## 用法
//!
//! ```rust,ignore
//! use sz_rust_core::alloc_counter::{AllocCounter, register_alloc_counter};
//!
//! // 注册全局分配器（仅在 bin crate 的 main 之前调用一次）
//! register_alloc_counter!();
//!
//! // 测量闭包的分配次数
//! let (result, count) = AllocCounter::measure(|| {
//!     let s = "hello".to_string();
//!     s + " world"
//! });
//! assert_eq!(result, "hello world");
//! assert!(count > 0);
//! ```
//!
//! ## Safety
//!
//! `GlobalAlloc` trait 要求 `unsafe impl`，此模块在 `alloc-count` feature
//! 启用时允许 unsafe_code（通过 `#[allow(unsafe_code)]`），unsafe 仅限
//! GlobalAlloc 方法实现内部，不暴露到公开 API。

#![allow(unsafe_code)]

use std::alloc::{GlobalAlloc, Layout, System};
use std::sync::atomic::{AtomicUsize, Ordering};

/// 全局 alloc 计数器（alloc 次数）
static ALLOC_COUNT: AtomicUsize = AtomicUsize::new(0);

/// 全局 dealloc 计数器（dealloc 次数）
static DEALLOC_COUNT: AtomicUsize = AtomicUsize::new(0);

/// 全局 alloc 字节数
static ALLOC_BYTES: AtomicUsize = AtomicUsize::new(0);

/// 全局 dealloc 字节数
static DEALLOC_BYTES: AtomicUsize = AtomicUsize::new(0);

/// Alloc 计数 GlobalAlloc wrapper
///
/// 包装内层分配器 `A`，在每次 alloc/dealloc 时递增全局计数器。
/// 通过 `register_alloc_counter!` 宏注册为全局分配器。
///
/// ## 类型参数
///
/// - `A`: 内层分配器（通常为 `std::alloc::System`）
pub struct AllocCounter<A: GlobalAlloc + Send + Sync + Default = System> {
    _inner: A,
}

impl<A: GlobalAlloc + Send + Sync + Default> AllocCounter<A> {
    /// 创建 AllocCounter 实例
    pub fn new() -> Self {
        Self {
            _inner: A::default(),
        }
    }
}

// 统计方法不依赖内层分配器类型，仅对默认 System 实现以简化 API。
// 调用方使用 AllocCounter::count() 即可，无需指定类型参数。
impl AllocCounter<System> {
    /// 获取当前 alloc 次数
    pub fn count() -> usize {
        ALLOC_COUNT.load(Ordering::Relaxed)
    }

    /// 获取当前 dealloc 次数
    pub fn dealloc_count() -> usize {
        DEALLOC_COUNT.load(Ordering::Relaxed)
    }

    /// 获取当前 alloc 字节数
    pub fn alloc_bytes() -> usize {
        ALLOC_BYTES.load(Ordering::Relaxed)
    }

    /// 获取当前 dealloc 字节数
    pub fn dealloc_bytes() -> usize {
        DEALLOC_BYTES.load(Ordering::Relaxed)
    }

    /// 获取当前净分配次数（alloc - dealloc）
    pub fn net_count() -> isize {
        let alloc = ALLOC_COUNT.load(Ordering::Relaxed) as isize;
        let dealloc = DEALLOC_COUNT.load(Ordering::Relaxed) as isize;
        alloc - dealloc
    }

    /// 获取当前净分配字节数（alloc_bytes - dealloc_bytes）
    pub fn net_bytes() -> isize {
        let alloc = ALLOC_BYTES.load(Ordering::Relaxed) as isize;
        let dealloc = DEALLOC_BYTES.load(Ordering::Relaxed) as isize;
        alloc - dealloc
    }

    /// 重置所有计数器为零
    pub fn reset() {
        ALLOC_COUNT.store(0, Ordering::Relaxed);
        DEALLOC_COUNT.store(0, Ordering::Relaxed);
        ALLOC_BYTES.store(0, Ordering::Relaxed);
        DEALLOC_BYTES.store(0, Ordering::Relaxed);
    }

    /// 测量闭包执行期间的分配次数
    ///
    /// 返回闭包结果和分配次数差值（闭包执行期间的新增 alloc 次数）。
    ///
    /// ## 用法
    ///
    /// ```rust,ignore
    /// let (result, count) = AllocCounter::measure(|| {
    ///     "hello".to_string() + " world"
    /// });
    /// assert_eq!(result, "hello world");
    /// ```
    pub fn measure<F, R>(f: F) -> (R, usize)
    where
        F: FnOnce() -> R,
    {
        let before = ALLOC_COUNT.load(Ordering::Relaxed);
        let result = f();
        let after = ALLOC_COUNT.load(Ordering::Relaxed);
        (result, after.saturating_sub(before))
    }

    /// 测量闭包执行期间的分配详情
    ///
    /// 返回闭包结果和 `AllocStats`（alloc/dealloc 次数 + 字节数差值）。
    pub fn measure_detailed<F, R>(f: F) -> (R, AllocStats)
    where
        F: FnOnce() -> R,
    {
        let before_alloc = ALLOC_COUNT.load(Ordering::Relaxed);
        let before_dealloc = DEALLOC_COUNT.load(Ordering::Relaxed);
        let before_alloc_bytes = ALLOC_BYTES.load(Ordering::Relaxed);
        let before_dealloc_bytes = DEALLOC_BYTES.load(Ordering::Relaxed);

        let result = f();

        let stats = AllocStats {
            alloc_count: ALLOC_COUNT
                .load(Ordering::Relaxed)
                .saturating_sub(before_alloc),
            dealloc_count: DEALLOC_COUNT
                .load(Ordering::Relaxed)
                .saturating_sub(before_dealloc),
            alloc_bytes: ALLOC_BYTES
                .load(Ordering::Relaxed)
                .saturating_sub(before_alloc_bytes),
            dealloc_bytes: DEALLOC_BYTES
                .load(Ordering::Relaxed)
                .saturating_sub(before_dealloc_bytes),
        };
        (result, stats)
    }
}

/// 分配统计详情
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct AllocStats {
    /// alloc 次数
    pub alloc_count: usize,
    /// dealloc 次数
    pub dealloc_count: usize,
    /// alloc 字节数
    pub alloc_bytes: usize,
    /// dealloc 字节数
    pub dealloc_bytes: usize,
}

impl AllocStats {
    /// 净分配次数（alloc - dealloc）
    pub fn net_count(&self) -> isize {
        self.alloc_count as isize - self.dealloc_count as isize
    }

    /// 净分配字节数（alloc_bytes - dealloc_bytes）
    pub fn net_bytes(&self) -> isize {
        self.alloc_bytes as isize - self.dealloc_bytes as isize
    }

    /// 是否无分配
    pub fn is_zero_alloc(&self) -> bool {
        self.alloc_count == 0
    }
}

impl std::fmt::Display for AllocStats {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "alloc={}/{}, dealloc={}/{}, net={}/{}",
            self.alloc_count,
            self.alloc_bytes,
            self.dealloc_count,
            self.dealloc_bytes,
            self.net_count(),
            self.net_bytes()
        )
    }
}

// ============================================================================
// GlobalAlloc 实现
// ============================================================================

unsafe impl<A: GlobalAlloc + Send + Sync + Default> GlobalAlloc for AllocCounter<A> {
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        ALLOC_COUNT.fetch_add(1, Ordering::Relaxed);
        ALLOC_BYTES.fetch_add(layout.size(), Ordering::Relaxed);
        A::default().alloc(layout)
    }

    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
        DEALLOC_COUNT.fetch_add(1, Ordering::Relaxed);
        DEALLOC_BYTES.fetch_add(layout.size(), Ordering::Relaxed);
        A::default().dealloc(ptr, layout);
    }

    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
        ALLOC_COUNT.fetch_add(1, Ordering::Relaxed);
        ALLOC_BYTES.fetch_add(layout.size(), Ordering::Relaxed);
        A::default().alloc_zeroed(layout)
    }

    unsafe fn realloc(&self, ptr: *mut u8, old_layout: Layout, new_size: usize) -> *mut u8 {
        DEALLOC_COUNT.fetch_add(1, Ordering::Relaxed);
        DEALLOC_BYTES.fetch_add(old_layout.size(), Ordering::Relaxed);
        ALLOC_COUNT.fetch_add(1, Ordering::Relaxed);
        ALLOC_BYTES.fetch_add(new_size, Ordering::Relaxed);
        A::default().realloc(ptr, old_layout, new_size)
    }
}

// ============================================================================
// 全局分配器注册宏
// ============================================================================

/// 注册全局 alloc 计数分配器
///
/// 在 bin crate 的顶层（main 函数之前）调用此宏，将 `AllocCounter<System>`
/// 注册为全局分配器。仅在 `alloc-count` feature 启用时生效。
///
/// ## 用法
///
/// ```rust,ignore
/// use sz_rust_core::alloc_counter::register_alloc_counter;
///
/// register_alloc_counter!();
///
/// fn main() {
///     let (s, count) = sz_rust_core::alloc_counter::AllocCounter::measure(|| {
///         "hello".to_string()
///     });
///     println!("result={s}, allocs={count}");
/// }
/// ```
#[macro_export]
macro_rules! register_alloc_counter {
    () => {
        #[global_allocator]
        static GLOBAL_ALLOC: $crate::alloc_counter::AllocCounter<std::alloc::System> =
            $crate::alloc_counter::AllocCounter {
                _inner: std::alloc::System,
            };
    };
}

// ============================================================================
// 单元测试
// ============================================================================

#[cfg(test)]
mod tests {
    use super::*;

    // 测试辅助：手动递增计数器，模拟全局分配器行为
    // （lib 测试中无法注册 #[global_allocator]，需在 bin crate 中注册）
    fn inc_alloc(n: usize, bytes: usize) {
        ALLOC_COUNT.fetch_add(n, Ordering::Relaxed);
        ALLOC_BYTES.fetch_add(bytes, Ordering::Relaxed);
    }

    fn inc_dealloc(n: usize, bytes: usize) {
        DEALLOC_COUNT.fetch_add(n, Ordering::Relaxed);
        DEALLOC_BYTES.fetch_add(bytes, Ordering::Relaxed);
    }

    // 全局计数器测试合并为单个串行测试，避免并行执行互相干扰
    #[test]
    fn test_alloc_counter_measure_and_stats() {
        // --- measure 基本逻辑 ---
        AllocCounter::reset();
        let (result, count) = AllocCounter::measure(|| {
            inc_alloc(2, 64);
            let s = "hello".to_string();
            s + " world"
        });
        assert_eq!(result, "hello world");
        assert_eq!(count, 2, "measure 应检测到 2 次 alloc");

        // --- measure 零分配 ---
        AllocCounter::reset();
        let (result, count) = AllocCounter::measure(|| {
            let a: i32 = 1;
            let b: i32 = 2;
            a + b
        });
        assert_eq!(result, 3);
        assert_eq!(count, 0, "纯栈运算不应触发堆 alloc");

        // --- measure Vec ---
        AllocCounter::reset();
        let (result, count) = AllocCounter::measure(|| {
            inc_alloc(3, 400);
            let v: Vec<i32> = (0..100).collect();
            v.len()
        });
        assert_eq!(result, 100);
        assert_eq!(count, 3, "measure 应检测到 3 次 alloc");

        // --- measure_detailed ---
        AllocCounter::reset();
        let (result, stats) = AllocCounter::measure_detailed(|| {
            inc_alloc(10, 1000);
            inc_dealloc(2, 200);
            let v: Vec<String> = (0..10).map(|i| format!("item_{i}")).collect();
            v.len()
        });
        assert_eq!(result, 10);
        assert_eq!(stats.alloc_count, 10);
        assert_eq!(stats.dealloc_count, 2);
        assert_eq!(stats.alloc_bytes, 1000);
        assert_eq!(stats.dealloc_bytes, 200);

        // --- reset 清零 ---
        inc_alloc(5, 500);
        inc_dealloc(3, 300);
        AllocCounter::reset();
        assert_eq!(AllocCounter::count(), 0);
        assert_eq!(AllocCounter::dealloc_count(), 0);
        assert_eq!(AllocCounter::alloc_bytes(), 0);
        assert_eq!(AllocCounter::dealloc_bytes(), 0);

        // --- net_count / net_bytes ---
        inc_alloc(10, 1000);
        inc_dealloc(4, 400);
        assert_eq!(AllocCounter::net_count(), 6);
        assert_eq!(AllocCounter::net_bytes(), 600);
    }

    #[test]
    fn test_alloc_stats_net_count() {
        let stats = AllocStats {
            alloc_count: 10,
            dealloc_count: 3,
            alloc_bytes: 1000,
            dealloc_bytes: 300,
        };
        assert_eq!(stats.net_count(), 7);
        assert_eq!(stats.net_bytes(), 700);
        assert!(!stats.is_zero_alloc());
    }

    #[test]
    fn test_alloc_stats_zero_alloc() {
        let stats = AllocStats {
            alloc_count: 0,
            dealloc_count: 0,
            alloc_bytes: 0,
            dealloc_bytes: 0,
        };
        assert!(stats.is_zero_alloc());
        assert_eq!(stats.net_count(), 0);
    }

    #[test]
    fn test_alloc_stats_display() {
        let stats = AllocStats {
            alloc_count: 5,
            dealloc_count: 2,
            alloc_bytes: 500,
            dealloc_bytes: 200,
        };
        let s = format!("{stats}");
        assert!(s.contains("alloc=5/500"));
        assert!(s.contains("dealloc=2/200"));
        assert!(s.contains("net=3/300"));
    }
}