前言

有个需求，要求一个客户端不断地接收数据与发送数据，特别是发送数据，既要求接收数据后立即发送，还要求该数据在经过一段时间后再发送一遍。因此决定使用一个循环队列来实现

实现

结构实现

#include <stdio.h>
#include <string.h>
#define BUF_SIZE 1000
#define DATA_LEN 256

typedef struct
{
	char buf[BUF_SIZE][DATA_LEN];         // 数据域
	unsigned int readpos;       // 延时读指针
	unsigned int writepos;      // 延时写指针
	unsigned int rtreadpos;     // 实时读指针
	unsigned int rtwritepos;    // 实时写指针

} queue;

// 向循环队列中写入数据
void write_data(queue *m_queue, char *data, int data_len)
{
	if (data_len <= 0)
	{
		printf("No data to write\n");
		return;
	}

	// 加锁
	unsigned int wpos = m_queue->writepos;
	memcpy(m_queue->buf[wpos], data, data_len);
	// 写完数据后，要移动写指针
	m_queue->writepos = (m_queue->writepos + 1 + BUF_SIZE) % 	BUF_SIZE;
	m_queue->rtwritepos = (m_queue->rtwritepos + 1 + BUF_SIZE) % BUF_SIZE;

	// 解锁
	return;

}

void read_pos(queue *m_queue, int delay)
{
	// 上锁
	unsigned int j = 0;
	unsigned int rtpos = m_queue->rtreadpos;
	unsigned int dpos = m_queue->readpos;
	unsigned int datalen;
	if (delay == 0)
	{
		j = 0;
		if (m_queue->rtreadpos == m_queue->rtwritepos)
		{
			return;
		}
		rtpos = m_queue->rtreadpos;
		datalen = (m_queue->rtwritepos - m_queue->rtreadpos + BUF_SIZE) % BUF_SIZE;
		while (j < datalen)
		{
			rtpos = (j + m_queue->rtreadpos) % BUF_SIZE;
			// 这里发送数据
			j++;
		}
		// 说明是实时发送
	}
	else
	{
		// 延时发送
		dpos = m_queue->readpos;
		datalen = (m_queue->writepos - m_queue->readpos + BUF_SIZE) % BUF_SIZE;
		while (j < datalen)
		{
			// 延时发送还需要判断延时时间
			// 这里不再加这一层判断
			dpos = (j + m_queue->readpos) % BUF_SIZE;
			// 发送数据
			j++;
		}

	}
	// 这里要更新两个读指针的位置
	if (m_queue->rtreadpos != rtpos)
	{
		m_queue->rtreadpos = (rtpos + 1 + BUF_SIZE) % BUF_SIZE;
	}
	if (m_queue->readpos != dpos)
	{
		m_queue->readpos = (dpos + 1 + BUF_SIZE) % BUF_SIZE;
	}
	// 解锁
	return;

}