1. Cấu trúc

 #ifndef RINGBUFFER_H  
 #define RINGBUFFER_H  
   
 #ifdef __cplusplus  
 extern "C" {  
 #endif  
   
 #include <stddef.h>  
 #include <stdbool.h>  
   
 /*  
  * ringbuffer.h - C ring buffer (FIFO) interface.  
  */  
 typedef struct ringbuffer_t  
 {  
   void *buffer;   // data buffer  
   void *buffer_end; // end of data buffer  
   size_t capacity; // maximum number of items in the buffer  
   size_t count;   // number of items in the buffer  
   size_t sz;    // size of each item in the buffer  
   void *head;    // pointer to head  
   void *tail;    // pointer to tail  
 } ringbuffer_t;  
   
 bool ring_init(ringbuffer_t *cb, size_t capacity, size_t sz);  
   
 bool ring_free(ringbuffer_t *cb);  
   
 bool ring_push_head(ringbuffer_t *cb, const void *item);  
   
 bool ring_pop_tail(ringbuffer_t *cb, void *item);  
   
 #ifdef __cplusplus  
 }  
 #endif  
   
 #endif /* RINGBUFFER_H */  
   

 #include "ringbuffer.h"  
 #include <assert.h>  
 #include <stdlib.h>  
 #include <string.h>  
 #include <stdio.h>  
   
 bool ring_init(ringbuffer_t *cb, size_t capacity, size_t sz)  
 {  
   cb->buffer = malloc(capacity * sz);  
   if(cb->buffer == NULL){  
     printf("ring_init FAIL ! \n");  
     return false;  
   }  
   
   cb->buffer_end = (char *)cb->buffer + capacity * sz;  
   cb->capacity = capacity;  
   cb->count = 0;  
   cb->sz = sz;  
   cb->head = cb->buffer;  
   cb->tail = cb->buffer;  
   return true;  
 }  
   
 bool ring_free(ringbuffer_t *cb)  
 {  
   if(cb->buffer){  
     free(cb->buffer);  
     cb->buffer = NULL;  
   }else{  
     return false;  
   }  
   return true;  
 }  
   
 bool ring_push_head(ringbuffer_t *cb, const void *item)  
 {  
   if(cb->count == cb->capacity){  
     printf("Ringbuffer is Full ! \n");  
     return false;  
   }  
   
   memcpy(cb->head, item, cb->sz);  
   cb->head = (char*)cb->head + cb->sz;  
   if(cb->head == cb->buffer_end)  
     cb->head = cb->buffer;  
   cb->count++;  
   
   return true;  
 }  
   
 bool ring_pop_tail(ringbuffer_t *cb, void *item)  
 {  
   if(cb->count == 0){  
     printf("Ringbuffer is Empty ! \n");  
     return false;  
   }  
   
   memcpy(item, cb->tail, cb->sz);  
   cb->tail = (char*)cb->tail + cb->sz;  
   if(cb->tail == cb->buffer_end)  
     cb->tail = cb->buffer;  
   cb->count--;  
   return true;  
 }  
   

 #include <string.h>  
 #include <unistd.h>  
 #include <stdio.h>  
 #include <stdlib.h>  
 #include <assert.h>  
 #include "ringbuffer.h"  
   
 #define CAPACITY 10  
 typedef struct data_t{  
   int idata;  
   float fdata;  
 }data_t;  
   
 ringbuffer_t ringbf;  
   
   
 int main(int argc, char **argv)  
 {  
     
   ring_init(&ringbf, CAPACITY, sizeof(data_t));  
   
   int i;  
   data_t tmpdata;  
   
   for(i = 0; i < CAPACITY; i++){  
     tmpdata.idata = i;  
     tmpdata.fdata = i+1;  
     ring_push_head(&ringbf, (void*)&tmpdata);  
     printf("number of items: %d \n", ringbf.count);  
   }  
   
   for(i = 0; i < CAPACITY; i++){  
     ring_pop_tail(&ringbf, (void*)&tmpdata);  
   
     printf("number of items: %d, idata: %d, fdata: %f \n", ringbf.count, tmpdata.idata, tmpdata.fdata);  
   
   }  
     
   ring_free(&ringbf);  
   return 0;  
 }