The realization method of the circular queue FIFO

Some SCM serial port does not have FIFO, or can be assigned to the FIFO size is very limited, if the program needs to send a large packet to the peripheral, it takes a long time, in order to solve the application and peripherals hardware read and write synchronization problem, it is necessary to realize the circular FIFO.

#include "stdafx.h"
#include <string>
#include <iostream>
using namespace Std;

#define Error_full_w-1
#define Error_empty_r-2

#define TRUE 0
#define FULL 1
#define EMPTY 1
#define UCHAR unsigned char
#define UINT unsigned int

First, the definition of circular FIFO

struct fifo{
Uchar *m_buf;
UINT m_bufsize;
UINT m_wp;
UINT M_RP;
UINT Fullflag;
UINT Emptyflag;
};
typedef struct FIFO Cfifo;

Second, write queue

int Ffifopush (Cfifo *myfifo, Uchar c) {
UINT Tmp_len;
if (Myfifo->fullflag!= full) {
Tmp_len = myfifo->m_wp;
Myfifo->m_buf[tmp_len] = c;
tmp_len++;
if (Tmp_len >= myfifo->m_bufsize) tmp_len = 0;
if (Tmp_len = = MYFIFO-&GT;M_RP) {
myfifo-> Fullflag = full;
}
MYFIFO-&GT;M_WP = Tmp_len;
Myfifo-> Emptyflag =! EMPTY;
return TRUE;
}

else return error_full_w;
}

3. Read the data from the queue

int Ffifopop (Cfifo *myfifo, int *data) {
UINT Tmp_len;
Uchar Tmp_char;
if (Myfifo->emptyflag!= EMPTY) {
Tmp_len = myfifo->m_rp;
Tmp_char = myfifo->m_buf[tmp_len];
*data = Tmp_char;
tmp_len++;
if (Tmp_len >= myfifo->m_bufsize) tmp_len = 0;
MYFIFO-&GT;M_RP = Tmp_len;
if (Tmp_len = = myfifo->m_wp) {
Myfifo->emptyflag = EMPTY;
}
Myfifo-> Fullflag =! Full;
return TRUE;
}
else return error_empty_r;
}

4. Calculate the length of data in the queue

UINT Ffifochecklen (Cfifo *myfifo) {

if (Myfifo->emptyflag = = EMPTY) return 0;
else if (Myfifo->fullflag = Full) return myfifo->m_bufsize;
if (myfifo->m_wp >= myfifo->m_rp) {
return MYFIFO->M_WP-MYFIFO->M_RP;
}
else{
return MYFIFO->M_BUFSIZE-MYFIFO->M_RP + myfifo->m_wp;
}
}

5. Empty queues

void Ffifoempty (Cfifo *myfifo) {
myfifo->m_wp = 0;
MYFIFO->M_RP = 0;
Myfifo->emptyflag = EMPTY;
Myfifo->fullflag =! Full;
}

6. Initializing queues

void Ffifoinit (Cfifo *myfifo, Uchar *tmp_buf, UINT tmp_size) {
Myfifo->m_buf = Tmp_buf;
Myfifo->m_bufsize = tmp_size;
Ffifoempty (MYFIFO);
}

7. Test queue

int main (void) {
Cfifo *myfifo;
Uchar cnt = 0;
int i = 0;
int data = 0;
if ((Myfifo = (Cfifo *) calloc (1,sizeof (CFIFO))) = = NULL) {
cout<< "malloc failed" <<endl;
}
Uchar DATA_BUF[20];
Ffifoinit (myfifo,data_buf,20);

for (i = 0; i<21;i++) {
if (Ffifopush (myfifo,i*2) = = TRUE)
cout<< "The Push data is" <<i*2<< "the Lengh is" <<ffifochecklen (MYFIFO) <<endl;
else break;
}
for (i = 0; i<22;i++) {
if (Ffifopop (Myfifo, &data) = = TRUE)
cout<< "The pop data is" <<data<< "the Lengh is" <<ffifochecklen (MYFIFO) <<endl;
else break;
}
}

8. Running results in VC6.0