单片机模块化编程之循环队列

​ 队列是常用的数据结构之一，根据百度百科的说明，队列是一种特殊的线性表，特殊之处在于它只允许在表的前端（front）进行删除操作，而在表的后端（rear）进行插入操作，和栈一样，队列是一种操作受限制的线性表。进行插入操作的端称为队尾，进行删除操作的端称为队头。在我们的实际生产应用中，串口解析数据是最常用这种数据结构的。

​ 今天在面包板社区看到一篇文件，是使用宏定义来实现循环队列 ，觉得比较好用，特地实操分享下。

1：开发环境

• 电脑系统Windows7
• Keil编译器
• STM32F103开发板

2：模块下载地址

https://github.com/barraq/BRBrain/blob/master/firmware/CBUF.h

具体内容如下：

/****************************************************************************
*
*   Since this code originated from code which is public domain, I
*   hereby declare this code to be public domain as well.
*
****************************************************************************/
/**
*
*   @file   CBUF.h
*
*   @brief  This file contains global definitions for circular buffer
*           manipulation.
*
*   These macros implement a circular buffer which employs get and put
*   pointers, in such a way that mutual exclusion is not required
*   (assumes one reader & one writer).
*
*   It requires that the circular buffer size be a power of two, and the
*   size of the buffer needs to smaller than the index. So an 8 bit index
*   supports a circular buffer upto ( 1 << 7 ) = 128 entries, and a 16 bit index
*   supports a circular buffer upto ( 1 << 15 ) = 32768 entries.
*
*   The basis for these routines came from an article in Jack Ganssle's
*   Embedded Muse: http://www.ganssle.com/tem/tem110.pdf
*
*   In order to offer the most amount of flexibility for embedded environments
*   you need to define a macro for the size.
*
*   First, you need to name your circular buffer. For this example, we'll
*   call it myQ.
*
*   The size macro that needs to be defined will be the name of the
*   circular buffer followed by _SIZE. The size must be a power of two
*   and it needs to fit in the get/put indicies. i.e. if you use an
*   8 bit index, then the maximum supported size would be 128.
*
*   The structure which defines the circular buffer needs to have 3 members
*   m_getIdx, m_putIdx, and m_entry.
*
*   m_getIdx and m_putIdx need to be unsigned integers of the same size.
*
*   m_entry needs to be an array of xxx_SIZE entries, or a pointer to an
*   array of xxx_SIZE entries. The type of each entry is entirely up to the
*   caller.
*
*   #define myQ_SIZE    64
*   
*   volatile struct
*   {
*       uint8_t     m_getIdx;
*       uint8_t     m_putIdx;
*       uint8_t     m_entry[ myQ_SIZE ];
*
*   } myQ;
*
*   You could then use
*
*       CBUF_Push( myQ, 'x' );
*
*   to add a character to the circular buffer, or
*
*       ch = CBUF_Pop( myQ );
*
*   to retrieve an element from the buffer.
*
*   If you happen to prefer to use C++ instead, there is a templatized
*   version which requires no macros. You just declare 3 template parameters:
*
*       - The type that should be used for the index
*       - The size of the circular buffer
*       - The type that should be used for the entry
*
*   For example:
*
*       CBUF< uint8_t, 64, char >   myQ;
*
****************************************************************************/

#if !defined( CBUF_H )
#define CBUF_H       /**< Include Guard                          */

/* ---- Include Files ---------------------------------------------------- */

/* ---- Constants and Types ---------------------------------------------- */

/**
*   Initializes the circular buffer for use.
*/ 

#define CBUF_Init( cbuf )       cbuf.m_getIdx = cbuf.m_putIdx = 0

/**
*   Returns the number of elements which are currently contained in the 
 *  circular buffer.
*/

#define CBUF_Len( cbuf )        ((typeof( cbuf.m_putIdx ))(( cbuf.m_putIdx ) - ( cbuf.m_getIdx )))

/**
*   Appends an element to the end of the circular buffer
*/

#define CBUF_Push( cbuf, elem ) (cbuf.m_entry)[ cbuf.m_putIdx++ & (( cbuf##_SIZE ) - 1 )] = (elem)

/**
*   Retrieves an element from the beginning of the circular buffer
*/

#define CBUF_Pop( cbuf )        (cbuf.m_entry)[ cbuf.m_getIdx++ & (( cbuf##_SIZE ) - 1 )]

/**
*   Retrieves the i'th element from the beginning of the circular buffer
*/

#define CBUF_Get( cbuf, idx )        (cbuf.m_entry)[( cbuf.m_getIdx + idx ) & (( cbuf##_SIZE ) - 1 )]

/**
*   Retrieves the i'th element from the end of the circular buffer
*/

#define CBUF_GetEnd( cbuf, idx )        (cbuf.m_entry)[( cbuf.m_putIdx - idx - 1 ) & (( cbuf##_SIZE ) - 1 )]

/**
*   Determines if the circular buffer is empty
*/

#define CBUF_IsEmpty( cbuf )    ( CBUF_Len( cbuf ) == 0 )

/**
*   Determines if the circular buffer is full.
*/

#define CBUF_IsFull( cbuf )     ( CBUF_Len( cbuf ) == ( cbuf##_SIZE ))

/**
*   Determines if the circular buffer is currenly overflowed or underflowed.
*/

#define CBUF_Error( cbuf )      ( CBUF_Len( cbuf ) > cbuf##_SIZE )

#if defined( __cplusplus )

template < class IndexType, unsigned Size, class EntryType >
class CBUF
{
public:

    CBUF()
    {
        m_getIdx = m_putIdx = 0;
    }

    IndexType Len() const   { return m_putIdx - m_getIdx; }

    bool IsEmpty() const    { return Len() == 0; }
    bool IsFull() const     { return Len() == Size; }
    bool Error() const      { return Len() > Size; }

    void Push( EntryType val )   
    {
        m_entry[ m_putIdx++ & ( Size - 1 )] = val;
    }

    EntryType Pop()
    {
        return m_entry[ m_getIdx++ & ( Size - 1 )];
    }

private:

    volatile IndexType  m_getIdx;
    volatile IndexType  m_putIdx;
    EntryType           m_entry[ Size ];

};

#endif  // __cplusplus

/* ---- Variable Externs ------------------------------------------------- */
/* ---- Function Prototypes ---------------------------------------------- */

/** @} */

#endif // CBUF_H

3：程序移植

3.1、新建STM32工程

首先，打开keil工程，新建工程，平时大家就用自己手上的工程来移植就好了。工程目录如下：

3.2、 添加文件，串口打印输出

​ 新建串口驱动文件，这里使用STM32的串口1来实现串口通讯，串口打印输出的资料有很多，这里也不做多讲，如果能在串口打印输出结果，说明串口工作正常。下面是每隔10秒打印一次数据。

3.3、移植CBUF.h宏定义文件

直接在文件中引用头文件就好

3.4、实现与应用

配置好工作之后，按照cbuf.h文件里面的说明，需要定义一个结构体对象，进行初始化。

具体代码如下：

#define myQ_SIZE    64

typedef volatile struct
{
    uint8_t     m_getIdx;
    uint8_t     m_putIdx;
    uint8_t     m_entry[ myQ_SIZE ];

}myQ;

static myQ   volatile RxBuffer;
static myQ   volatile TxBuffer;

#define RxBuffer_SIZE   myQ_SIZE

定义对象之后，调用初始化函数 ，主要是定义初始化缓冲区，下面定义一个接收和发送的缓冲区。

void  UART1_Buffer_Init(void)
{
    CBUF_Init(RxBuffer);
    CBUF_Init(TxBuffer);   
}

在实际应用中，当串口接收数据之后，有很多种方式处理数据，包括DMA接收数据，串口中断接收等等，本来就直接串口中断处理数据，串口中断函数如下

void USART1_IRQHandler(void)
{
	unsigned char dat;
	if(USART_GetITStatus(USART1,USART_IT_RXNE) != RESET)
	{							
		dat = USART_ReceiveData(USART1);
         /*直接调用宏定义，将接收到的数据插入队列中*/
        CBUF_Push(RxBuffer,dat);  
		USART_ClearITPendingBit(USART1,USART_IT_RXNE);
		
	}
}

到这里，就已经完成数据接收过程。接收数据完成之后，我每一秒读出一个数据并通过串口发送出来，如果没有数据，就不发送。编写一个串口处理数据的任务。

void  UART1_Recv_Task(void)
{  
    unsigned char TxChar=0;
    if(CBUF_Len(RxBuffer)!=0)
    {
        TxChar=CBUF_Pop(RxBuffer);
        printf("%c\r\n",TxChar);        
    }  
}

代码的意思主要是每次读取一个数据并打印，我把这个任务每秒执行一次，

最后，通过串口调试工具，发送12345678这8个数据，串口每一秒读取一个，8秒后读完。

在实际应用中，我们基本上一次读取全部数据，然后去解析，一般都是自定义协议的时候用，来读取有效数据。