C语言实现环形队列（Circular Queue)

ring.c文件的内容：

void dma_ring_init(struct dma_ring_buf *ring)
{
  ring->buf_size = RING_BUF_SIZE;
  ring->w_ptr = 0;
  ring->r_ptr = 0;
  ring->overwrite_cnt = 0;
}

int dma_ring_getc(struct dma_ring_buf *ring, uint8_t *c)
{
  if (ring->r_ptr == ring->w_ptr)
    return RING_FAIL;
  uint16_t next_ptr = ring->r_ptr + 1;
  if (next_ptr >= ring->buf_size)
    next_ptr = 0;

  *c = ring->buf[ring->r_ptr];
  ring->r_ptr = next_ptr;
  return RING_SUCCESS;
}

int dma_ring_putc(struct dma_ring_buf *ring, uint8_t c)
{
  uint16_t next_ptr = ring->w_ptr + 1;
  if (next_ptr >= ring->buf_size)
    next_ptr = 0;

  if (next_ptr == ring->r_ptr)
  {
    ring->overwrite_cnt++;
    return RING_FAIL;
  }
  ring->buf[ring->w_ptr] = c;
  ring->w_ptr = next_ptr;
  return RING_SUCCESS;
}

int dma_ring_available(struct dma_ring_buf *ring)
{
  if (ring->w_ptr >= ring->r_ptr)
  {
    return ring->w_ptr - ring->r_ptr;
  }
  else
  {
    return ring->w_ptr + ring->buf_size - ring->r_ptr;
  }
}

int dma_ring_available_linear(struct dma_ring_buf *ring)
{
  if (ring->w_ptr >= ring->r_ptr)
  {
    return ring->w_ptr - ring->r_ptr;
  }
  else
  {
    return ring->buf_size - ring->r_ptr;
  }
}

uint16_t dma_ring_get_w_ptr(struct dma_ring_buf *ring)
{
  return ring->w_ptr;
}

uint16_t dma_ring_get_r_ptr(struct dma_ring_buf *ring)
{
  return ring->r_ptr;
}

void dma_ring_forward_r_ptr(struct dma_ring_buf *ring, int len)
{
  ring->r_ptr = (ring->r_ptr + len + ring->buf_size) % ring->buf_size;
}

void dma_ring_set_w_ptr(struct dma_ring_buf *ring, uint16_t w_ptr)
{
  ring->w_ptr = w_ptr;
}

ring.h

#define RING_SUCCESS    0
#define RING_FAIL       1
#define RING_BUF_SIZE   2000

struct dma_ring_buf
{
  uint8_t buf[RING_BUF_SIZE];
  uint16_t buf_size;
  uint16_t w_ptr, r_ptr;
  uint16_t overwrite_cnt;
};

void dma_ring_init(struct dma_ring_buf *ring);
int dma_ring_getc(struct dma_ring_buf *ring, uint8_t *c);
int dma_ring_putc(struct dma_ring_buf *ring, uint8_t c);
int dma_ring_available(struct dma_ring_buf *ring);

int dma_ring_available_linear(struct dma_ring_buf *ring);
uint16_t dma_ring_get_w_ptr(struct dma_ring_buf *ring);
uint16_t dma_ring_get_r_ptr(struct dma_ring_buf *ring);

void dma_ring_forward_r_ptr(struct dma_ring_buf *ring, int len);

void dma_ring_set_w_ptr(struct dma_ring_buf *ring, uint16_t w_ptr);