stm32实用循环buffer

本人在实际开发中多次用到串口的循环buffer,最开始在网上搜索了相关文章和资料，感觉通用性不是很高。自己也写过fifo,感觉还是过于臃肿。一直想找个完美的循环buffer。在看linux内核代码时，发现内核里面也经常使用fifo。linux内核代码是最优美、精简的，高效的代码。真是“山穷水尽疑无路，柳暗花明又一村”。特意移植除出来，希望对大家有用。代码设计的相当的巧妙~~~

头文件：

/******************************************************************************** @File   : fifo.h* @Author   : cqx* @Version  : V0.0.1* @Date   : 29-november-2016* @Brief  : This file provides all the fifo functions.********************************************************************************* @Attention:* Non********************************************************************************//* Define to prevent recursive inclusion -------------------------------------*/#ifndef _FIFO_H#define _FIFO_H#include <stm32f10x.h>#ifdef __cplusplus extern "C" {#endif /* Includes ------------------------------------------------------------------*//* Define --------------------------------------------------------------------*/#ifndef min#define min(a, b) (((a) < (b)) ? (a) : (b))#endif#define is_power_of_2(x)((x) != 0 && (((x) & ((x) - 1)) == 0))/* Private typedef -----------------------------------------------------------*/struct fifo {unsigned intin;unsigned intout;unsigned intmask;unsigned char *data;}; /* Function prototypes -------------------------------------------------------*/extern unsigned int fifo_used(struct fifo *fifo);extern signed int fifo_alloc(struct fifo *fifo, unsigned int size);extern void         fifo_free(struct fifo *fifo);extern int          fifo_init(struct fifo *fifo, unsigned char *buffer,unsigned int size);extern unsigned int fifo_in(struct fifo *fifo, unsigned char *buf, unsigned int len);extern unsigned int fifo_out(struct fifo *fifo,unsigned char *buf, unsigned int len); #ifdef __cplusplus}#endif#endif

源文件：

/******************************************************************************* @File   : ringbuffer.c* @Author   : cqx* @Version  : V0.0.1* @Date   : 29-november-2016* @Brief  : This file provides all the fifo functions.******************************************************************************* @Attention:* *******************************************************************************//* Includes -----------------------------------------------------------------*/#include "fifo.h"#include "stdlib.h"#include "string.h"#include "includes.h"/* Variables -----------------------------------------------------------------*//* Private functions ---------------------------------------------------------*//******************************************************************************//* * internal helper to calculate the unused elements in a fifo */static __inline unsigned int fifo_unused(struct fifo *fifo){  return (fifo->mask + 1) - (fifo->in - fifo->out);}unsigned int fifo_used(struct fifo *fifo){  return (fifo->in - fifo->out);}signed int fifo_alloc(struct fifo *fifo, unsigned int size){/* * round down to the next power of 2, since our 'let the indices * wrap' technique works only in this case. */if (!is_power_of_2(size))return -1;fifo->in = 1;fifo->out = 1;if (size < 2){fifo->data = NULL;fifo->mask = 0;return -1;}fifo->data = malloc(size);if (!fifo->data){fifo->mask = 0;return -1;}fifo->mask = size - 1;    return 0;}void fifo_free(struct fifo *fifo){free(fifo->data);fifo->in = 0;fifo->out = 0;fifo->data = NULL;fifo->mask = 0;}int fifo_init(struct fifo *fifo, unsigned char *buffer, unsigned int size){if (!is_power_of_2(size))return -1;fifo->in = 0;fifo->out = 0;fifo->data = buffer;if (size < 2) {fifo->mask = 0;return -1;}fifo->mask = size - 1;return 0;}static void fifo_copy_in(struct fifo *fifo, unsigned char *src, unsigned int len, unsigned int off){unsigned int size = fifo->mask + 1;unsigned int l;off &= fifo->mask;l = min(len, size - off);memcpy(fifo->data + off, src, l);memcpy(fifo->data, src + l, len - l);}unsigned int fifo_in(struct fifo *fifo, unsigned char *buf, unsigned int len){unsigned int l;l = fifo_unused(fifo);if (len > l)len = l;fifo_copy_in(fifo, buf, len, fifo->in);fifo->in += len;return len;}static void fifo_copy_out(struct fifo *fifo, unsigned char *dst, unsigned int len, unsigned int off){unsigned int size = fifo->mask + 1;unsigned int l;off &= fifo->mask;l = min(len, size - off);memcpy(dst, fifo->data + off, l);memcpy(dst + l, fifo->data, len - l);}unsigned int fifo_out_peek(struct fifo *fifo, unsigned char *buf, unsigned int len){unsigned int l;l = fifo->in - fifo->out;if (len > l)len = l;fifo_copy_out(fifo, buf, len, fifo->out);return len;}unsigned int fifo_out(struct fifo *fifo, unsigned char *buf, unsigned int len){len = fifo_out_peek(fifo, buf, len);fifo->out += len;return len;}