一个优秀的 ring buffer 或 cycle buffer 的实现代码

#define CIRCLE_BUFFSIZE 1024 * 1024
#define min(x, y) ((x) < (y) ? (x) : (y))

struct cycle_buffer {
    unsigned char *buf;
    unsigned int size;
    unsigned int in;
    unsigned int out;
    pthread_mutex_t lock;
}; 

static struct cycle_buffer *fifo = NULL;  

static int init_cycle_buffer(void)
{
    int size = CIRCLE_BUFFSIZE, ret;  

    ret = size & (size - );
    if (ret)
        return ret;
    fifo = (struct cycle_buffer *) malloc(sizeof(struct cycle_buffer));
    if (!fifo)
        return -;  

    memset(fifo, , sizeof(struct cycle_buffer));
    fifo->size = size;
    fifo->in = fifo->out = ;
    pthread_mutex_init(&fifo->lock, NULL);
    fifo->buf = (unsigned char *) malloc(size);
    if (!fifo->buf)
        free(fifo);
    else
        memset(fifo->buf, , size);
    return ;
} 
static int uninit_cycle_buffer(void)
{
     if(!fifo)
         return -;
     pthread_mutex_destroy(&fifo->lock);
     if(fifo->buf)
         free(fifo->buf);
     free(fifo);
}
unsigned int fifo_get(unsigned char *buf, unsigned int len)
{
    unsigned int l;
    len = min(len, fifo->in - fifo->out);
    if(len <= )
        return ;

    l = min(len, fifo->size - (fifo->out & (fifo->size - )));
    memcpy(buf, fifo->buf + (fifo->out & (fifo->size - )), l);
    memcpy(buf + l, fifo->buf, len - l);
    fifo->out += len;
    return len;
}  

unsigned int fifo_put(unsigned char *buf, unsigned int len)
{
    unsigned int l;
    len = min(len, fifo->size - fifo->in + fifo->out);
    l = min(len, fifo->size - (fifo->in & (fifo->size - )));
    memcpy(fifo->buf + (fifo->in & (fifo->size - )), buf, l);
    memcpy(fifo->buf, buf + l, len - l);
    fifo->in += len;
    return len;
} 

这个实现比较优秀，可自行改成java的实现。