ring-buffer（C 语言实现）

        下面是一个 ring-buffer 的 C 语言实现，采用 Mirroring 方式实现空、满判断。通过 void 指针模拟泛型，可以在初始化时灵活定义 ring-buffer 中的元素类型（例如 char 类型，int 类型，数组类型，结构体类型等）。

        首先给出头文件定义：

/** * File: ring_buf.h * * Description: *   Header file for ring-buffer. *   Implemented according to the 'Mirroring' solution: *   http://en.wikipedia.org/wiki/Circular_buffer#Mirroring * * Change Logs: *   Date           Author       Notes *   2013-12-16     Glen         first implementation */#ifndef _RING_BUF_H_#define _RING_BUF_H_#include <stdint.h>#include <stdbool.h>#include <stddef.h>#define IDX_MASK (SIZE_MAX>>1)#define MSB_MASK (~IDX_MASK)   /* also the maximum value of the buffer depth *//* ring buffer structure */struct ring_buf{    size_t depth ;             /* maximum element number */    size_t width ;             /* sizeof each element */    size_t rd_idx;             /* MSB is used for the 'mirror' flag */    size_t wr_idx;             /* MSB is used for the 'mirror' flag */    void   *buf  ;};typedef struct ring_buf  ring_buf_t;typedef struct ring_buf* ring_buf_p;bool ring_buf_init (ring_buf_p rbuf, size_t depth, size_t width);void ring_buf_free (ring_buf_p rbuf);void ring_buf_clear(ring_buf_p rbuf);bool ring_buf_full (ring_buf_p rbuf);bool ring_buf_empty(ring_buf_p rbuf);bool ring_buf_write(ring_buf_p rbuf, void *wr_data);bool ring_buf_read (ring_buf_p rbuf, void *rd_data);#endif

        下面是对应的 C 文件：

/** * File: ring_buf.c * * Description: *   Ring-buffer implemented according to the 'Mirroring' solution: *   http://en.wikipedia.org/wiki/Circular_buffer#Mirroring * * Change Logs: *   Date           Author       Notes *   2013-12-16     Glen         first implementation */#include "ring_buf.h"#include <stdlib.h>#include <string.h>#include <assert.h>/** * @brief  Initialize the ring-buffer. Allocate necessary memory for the buffer. * * @param  rbuf : Pointer to the ring-buffer object * @param  depth: Maximum element number of the buffer * @param  width: sizeof each element * * @return true : Succeeded *         false: Failed */bool ring_buf_init(ring_buf_p rbuf, size_t depth, size_t width){    assert(depth > 0 && depth < MSB_MASK && width > 0);    rbuf->depth  = depth;    rbuf->width  = width;    rbuf->rd_idx = 0;    rbuf->wr_idx = 0;    rbuf->buf    = calloc(depth, width);    return rbuf->buf != NULL;}/** * @brief  Release the ring-buffer object. Deallocate the buffer memory. * * @param  rbuf: Pointer to the ring-buffer object */void ring_buf_free(ring_buf_p rbuf){    free(rbuf->buf);    rbuf->buf = NULL;}/** * @brief  Clear the ring-buffer object. * * @param  rbuf: Pointer to the ring-buffer object */void ring_buf_clear(ring_buf_p rbuf){    rbuf->rd_idx = 0;    rbuf->wr_idx = 0;}/** * @brief  Whether the ring-buffer is empty or not. * * @param  rbuf: Pointer to the ring-buffer * * @return true : Empty. There's no elements stored in the buffer. *         false: Not empty */bool ring_buf_is_empty(ring_buf_p rbuf){    return rbuf->rd_idx == rbuf->wr_idx;}/** * @brief  Whether the ring-buffer is full or not. * * @param  rbuf: Pointer to the ring-buffer * * @return true : Full *         false: Not full */bool ring_buf_is_full(ring_buf_p rbuf){    return (rbuf->rd_idx & IDX_MASK) == (rbuf->wr_idx & IDX_MASK) &&           (rbuf->rd_idx & MSB_MASK) != (rbuf->wr_idx & MSB_MASK);}/** * @brief  Increase the buffer index while writing or reading the ring-buffer. *         This is implemented according to the 'mirroring' solution: *         http://en.wikipedia.org/wiki/Circular_buffer#Mirroring * * @param  rbuf : Pointer to the ring-buffer * @param  p_idx: Pointer to the buffer index to be increased */inline void ring_buf_incr(ring_buf_p rbuf, size_t *p_idx){    size_t idx = *p_idx & IDX_MASK;    size_t msb = *p_idx & MSB_MASK;    if (++idx == rbuf->depth) {        msb ^= MSB_MASK;        idx = 0;    }    *p_idx = msb | idx;}/** * @brief  Write new element to the ring-buffer. * * @param  rbuf   : Pointer to the ring-buffer object * @param  wr_data: Pointer of the new element to be written to the buffer * * @return true : Succeeded *         false: Failed */bool ring_buf_write(ring_buf_p rbuf, void *wr_data){    if (ring_buf_is_full(rbuf))        return false;    else {        memcpy(rbuf->buf + rbuf->wr_idx * rbuf->width, wr_data, rbuf->width);        ring_buf_incr(rbuf, &rbuf->wr_idx);        return true;    }}/** * @brief  Read from the ring-buffer * * @param  rbuf   : Pointer to the ring-buffer object * @param  rd_data: Pointer to the read result * * @return true : Succeeded *         false: Failed */bool ring_buf_read(ring_buf_p rbuf, void *rd_data){    if (ring_buf_is_empty(rbuf))        return false;    else {memcpy(rd_data, rbuf->buf + rbuf->rd_idx * rbuf->width, rbuf->width);        ring_buf_incr(rbuf, &rbuf->rd_idx);        return true;    }}

        最后给出一个简单的应用示例，将字符数组写入 ring-buffer，然后读出、显示：

int main(){    ring_buf_t rbuf;    char str[10];    ring_buf_init(&rbuf, 8, sizeof(str));    ring_buf_write(&rbuf, "str 0");    ring_buf_write(&rbuf, "str 1");    ring_buf_write(&rbuf, "str 2");    ring_buf_write(&rbuf, "str 3");    int k = 0;    for (k = 0; k < 8; k++)        if (ring_buf_read(&rbuf, str))            printf("%s\n", str);    ring_buf_free(&rbuf);    return 0;}