环形队列数据的循环读写

#define R_SIGNATURE 0x860510 typedef struct{ long signature; int *head; int *tail; int *end; int *begin; int buffer[];

}ring_buf; //定义一个环形队列数据结构

#include #include #include \"ring.h\" int tag=0;

int * psudo_head=NULL;

void ring_buf_init(ring_buf *round) {

round->signature=R_SIGNATURE; round->head=round->buffer; round->tail=round->buffer; round->begin=round->buffer;

round->end=&round->buffer[sizeof(round->buffer)-1]; }

/** read the user_defined value from the ring_buffer, ** if no value available 0 is returned, on error -1 is ** returned, on success 1 is returned **/

int ring_buf_read(ring_buf *round,int *val) {

int* tmp=round->tail;//每次调用该函数时都会将round->tail指针的值赋给tmp，因为round->tail始终指向环形队列中未读数据的地址，这是下面round->tail=tmp语句来实现的 if(round->signature !=R_SIGNATURE){ printk(\"ring_buf_read:signature fake/n\"); return(-1); }

if((tmpbegin)||(tmp>round->end)){ printk(\"ring_buf_read:tail bad/n\"); return(-1); }

if(tmp==round->head){ return(0); }

*val=*tmp++;//将*tmp指向的值赋给val,实现数据的读出操作 if(tmp>round->end) tmp=round->begin;

round->tail=tmp;//保证round->tail始终指向环形队列中未读数据的地址，从而实现循环读取 if(tag){

round->head=psudo_head; tag=0; } return(1); }

int ring_buf_write(ring_buf *round,int val) {

int* tmp=round->head;

if(round->signature !=R_SIGNATURE){

printk(\"ring_buf_write:signature fake/n\"); return(-1); }

if((tmpbegin)||(tmp>round->end)){ printk(\"ring_buf_write:head bad/n\"); return(-1); } if(tag) return 0; (*tmp)=val; tmp++;

if(tmp>round->end) tmp = round->begin; if(tmp==round->tail){ tag=1;

psudo_head=tmp; return(1); }

round->head=tmp; return(1); }