目录
- 环形缓冲区核心概念
- 完整实现代码
- 关键注意事项
- 1. 线程安全设计
- 2. 空满判断策略
- 3. 指针管理
- 4. 异常安全
- 编译和运行
- 性能优化建议
- 适用场景
环形缓冲区（Circular Buffer）是一种高效的数据结构，特别适用于生产者-消费者场景、数据流处理和缓存管理。下面我将详细介绍环形缓冲区的实现原理、代码实践和注意事项。
环形缓冲区核心概念
环形缓冲区通过固定大小的数组和两个指针（读指针和写指针）实现循环使用存储空间。当指针到达数组末尾时，会回到数组开头继续操作。
完整实现代码
#include <IOStream>
#include <vector>
#include <mutex>
#include <condition_variable>
#include <thread>
#include <chrono>
#include <atomic>
#include <stdexcept>
template<typename T>
class CircularBuffer {
public:
// 构造函数
explicit CircularBuffer(size_t size)
: buffer_(size), capacity_(size), read_pos_(0), write_pos_(0),
count_(0), is_full_(false) {
if (size == 0) {
throw std::invalid_argument("Buffer size must be greater than 0");
}
}
// 默认析构函数
~CircularBuffer() = default;
// 禁止拷贝和赋值
CircularBuffer(const CircularBuffer&) = delete;
CircularBuffer& operator=(const CircularBuffer&) = delete;
// 写入数据（非阻塞）
www.devze.com bool push(const T& item) {
std::lock_guard<std::mutex> lock(mutex_);
if (is_full_) {
return false; // 缓冲区已满
}
buffer_[write_pos_] = item;
write_pos_ = (write_pos_ + 1) % capacity_;
++count_;
is_full_ = (write_pos_ == read_pos_);
not_empty_.notify_one();
return true;
}
// 写入数据（阻塞）
bool push_blocking(const T& item, std::chrono::milliseconds timeout = std::chrono::milliseconds(0)) {
std::unique_lock<std::mutex> lock(mutex_);
if (timeout.count() > 0) {
// 带超时的等待
if (!not_full_.wait_for(lock, timeout, [this]() { return !is_full_; })) {
return false; // 超时
}
} else {
// 无限等待
not_full_.wait(lock, [this]() { return !is_full_; });
}
buffer_[write_pos_] = item;
write_pos_ = (write_pos_ + 1) % capacity_;
++count_;
is_full_ = (write_pos_ == read_pos_);
not_empty_.notify_one();
return true;
}
// 读取数据（非阻塞）
bool pop(T& item) {
std::lock_guard<std::mutex> lock(mutex_);
if (eandroidmpty()) {
return false; // 缓冲区为空
}
item = buffer_[read_pos_];
read_pos_ = (read_pos_ + 1) % capacity_;
--count_;
is_full_ = false;
not_full_.notify_one();
return true;
}
// 读取数据（阻塞）
bool pop_blocking(T& item, std::chrono::milliseconds timeout = std::chrono::milliseconds(0)) {
std::unique_lock<std::mutex> lock(mutex_);
if (timeout.count() > 0) {
// 带超时的等待
if (!not_empty_.wait_for(lock, timeout, [this]() { return !empty(); })) {
return false; // 超时
}
} else {
// 无限等待
not_empty_.wait(lock, [this]() { return !empty(); });
}
item = buffer_[read_pos_];
read_pos_ = (read_pos_ + 1) % capacity_;
--count_;
is_full_ = false;
not_full_.notify_one();
return true;
}
// 查看但不移除数据
bool peek(T& item) const {
std::lock_guard<std::mutex> lock(mutex_);
if (empty()) {
return false;
}
item = buffer_[read_pos_];
return true;
}
// 清空缓冲区
void clear() {
std::lock_guard<std::mutex> lock(mutex_);
read_pos_ = write_pos_;
count_ = 0;
is_full_ = false;
// 注意：这里不需要通知条件变量，因为清空操作不会让缓冲区变满
}
// 判断是否为空
bool empty() const {
// 注意：当 read_pos_ == write_pos_ 且 !is_full_ 时为空
return (!is_full_ && (read_pos_ == write_pos_));
}
// 判断是否已满
bool full() const {
return is_full_;
}
// 获取当前元素数量
size_t size() const {
return count_;
}
// 获取容量
size_t capacity() const {
return capacity_;
}
// 获取剩余空间
size_t available() const {
return capacity_ - count_;
}
private:
std::vector<T> buffer_;
size_t capacity_;
mutable std::mutex mutex_;
std::condition_variable not_empty_;
std::condition_variable not_full_;
size_t read_pos_; // 读位置
size_t write_pos_; // 写位置
size_t count_; // 当前元素数量
bool is_full_; // 是否已满标志
};
// 无锁环形缓冲区（适用于单生产者单消费者场景）
template<typename T, size_t Size>
class LockFreeCircularBuffer {
public:
LockFreeCircularBuffer() : read_index_(0), write_index_(0) android{}
bool push(const T& item) {
size_t current_write = write_index_.load(std::memory_order_relaxed);
size_t next_write = next_index(current_write);
// 检查是否已满
if (next_write == read_index_.load(std::memory_order_acquire)) {
return false;
}
buffer_[current_write] = item;
write_index_.store(next_write, std::memory_order_release);
return true;
}
bool pop(T& item) {
size_t current_read = read_index_.load(std::memory_order_relaxed);
// 检查是否为空
if (current_read == write_index_.load(std::memory_order_acquire)) {
return false;
}
item = buffer_[current_read];
read_index_.store(next_index(current_read), std::memory_order_release);
return true;
}
bool empty() const {
return read_index_.load(std::memory_order_acquire) ==
write_index_.load(std::memory_order_acquire);
}
bool full() const {
size_t next_write = next_index(write_index_.load(std::memory_order_relaxed));
return next_write == read_index_.load(std::memory_order_acquire);
}
size_t size() const {
size_t write = write_index_.load(std::memory_order_acquire);
size_t read = read_index_.load(std::memory_order_acquire);
if (write >= read) {
return write - read;
} else {
return Size - read + write;
}
}
private:
size_t next_index(size_t current) const {
return (current + 1) % Size;
}
T buffer_[Size];
std::atomic<size_t> read_index_;
std::atomic<size_t> write_index_;
};
// 演示使用示例
void demo_usage() {
std::cout << "=== 环形缓冲区演示 ===" << std::endl;
// 创建容量为5的环形缓冲区
CircularBuffer<int> buffer(5);
// 基本操作演示
std::cout << "缓冲区容量: " << buffer.capacity() << std::endl;
std::cout << "初始大小: " << buffer.size() << std::endl;
std::cout << "是否为空: " << buffer.empty() << std::endl;
// 写入数据
for (int i = 1; i <= 5; ++i) {
if (buffer.push(i)) {
std::cout << "写入: " << i << std::endl;
}
}
std::cout << "写入5个数据后大小: " << buffer.size() << std::endl;
std::cout << "是否已满: " << buffer.full() << std::endl;编程客栈
// 尝试写入第6个数据（应该失败）
if (!buffer.push(6)) {
std::cout << "写入失败 - 缓冲区已满" << std::endl;
}
// 读取数据
int value;
while (buffer.pop(value)) {
std::cout << "读取: " << value << std::endl;
}
std::cout << "读取所有数据后大小: " << buffer.size() << std::endl;
std::cout << "是否为空: " << buffer.empty() << std::endl;
}
// 生产者-消费者演示
void producer_consumer_demo() {
std::cout << "\n=== 生产者-消费者演示 ===" << std::endl;
CircularBuffer<int> buffer(10);
std::atomic<bool> stop_producer(false);
std::atomic<bool> stop_consumer(false);
// 生产者线程
std::thread producer([&]() {
for (int i = 1; i <= 15; ++i) {
if (buffer.push_blocking(i, std::chrono::milliseconds(100))) {
std::cout << "生产: " << i << std::endl;
} else {
std::cout << "生产超时: " << i << std::endl;
}
std::this_thread::sleep_for(std::chrono::milliseconds(50));
}
stop_producer.store(true);
});
// 消费者线程
std::thread consumer([&]() {
int value;
while (!stop_producer.load() || !buffer.empty()) {
if (buffer.pop_blocking(value, std::chrono::milliseconds(200))) {
std::cout << "消费: " << value << std::endl;
}
std::this_thread::sleep_for(std::chrono::milliseconds(100));
}
stop_consumer.store(true);
});
producer.join();
consumer.join();
std::cout << "生产者-消费者演示结束" << std::endl;
}
// 性能测试
void performance_test() {
std::cout << "\n=== 性能测试 ===" << std::endl;
const int ITERATIONS = 1000000;
CircularBuffer<int> buffer(1000);
auto start = std::chrono::high_resolution_clock::now();
std::thread producer([&]() {
for (int i = 0; i < ITERATIONS; ++i) {
while (!buffer.push(i)) {
std::this_thread::yield();
}
}
});
std::thread consumer([&]() {
int value;
for (int i = 0; i < ITERATIONS; ++i) {
while (!buffer.pop(value)) {
std::this_thread::yield();
}
// 验证数据完整性
if (value != i) {
std::cerr << "数据损坏: 期望 " << i << ", 得到 " << value << std::endl;
}
}
});
producer.join();
consumer.join();
auto end = std::chrono::high_resolution_clock::now();
auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
std::cout << "处理 " << ITERATIONS << " 个元素耗时: "
<< duration.count() << " ms" << std::endl;
std::cout << "吞吐量: "
<< (ITERATIONS * 1000.0 / duration.count()) << " 操作/秒" << std::endl;
}
int main() {
try {
demo_usage();
producer_consumer_demo();
performance_test();
// 无锁缓冲区演示
std::cout << "\n=== 无锁环形缓冲区演示 ===" << std::endl;
LockFreeCircularBuffer<int, 5> lock_free_buffer;
for (int i = 1; i <= 3; ++i) {
if (lock_free_buffer.push(i)) {
std::cout << "无锁缓冲区写入: " << i << std::endl;
}
}
int value;
while (lock_free_buffer.pop(value)) {
std::cout << "无锁缓冲区读取: " << value << std::endl;
}
} catch (const std::exception&python e) {
std::cerr << "错误: " << e.what() << std::endl;
return 1;
}
return 0;
}
关键注意事项
1. 线程安全设计
- 互斥锁保护：使用
std::mutex保护共享数据 - 条件变量：使用
std::condition_variable实现高效的等待通知机制 - 内存序：无锁版本中正确使用内存序保证数据一致性
2. 空满判断策略
// 方法1：使用计数变量（推荐）
bool empty() const { return count_ == 0; }
bool full() const { return count_ == capacity_; }
// 方法2：使用标志位
bool empty() const { return !is_full_ && (read_pos_ == write_pos_); }
bool full() const { return is_full_; }
3. 指针管理
// 指针前进 read_pos_ = (read_pos_ + 1) % capacity_; write_pos_ = (write_pos_ + 1) % capacity_;
4. 异常安全
- 构造函数验证参数有效性
- 使用 RAII 管理资源
- 提供强异常安全保证
编译和运行
使用以下命令编译：
g++ -std=c++11 -pthread -O2 circular_buffer.cpp -o circular_buffer
运行：
./circular_buffer
性能优化建议
- 缓存友好：确保数据连续存储，提高缓存命中率
- 减少锁竞争：使用细粒度锁或无锁设计
- 批量操作：支持批量读写减少锁开销
- 内存预分配：避免动态内存分配
适用场景
- 数据流处理（音频、视频流）
- 生产者-消费者模式
- 网络数据包缓冲
- 实时系统数据交换
- 日志记录系统
这个实现提供了完整的环形缓冲区功能，包括线程安全、阻塞/非阻塞操作、异常安全等特性，可以直接在生产环境中使用。
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