struct kfifo {unsigned char *buffer;  /* the buffer holding the data */unsigned int size;  /* the size of the allocated buffer */unsigned int in;    /* data is added at offset (in % size) */unsigned int out;   /* data is extracted from off. (out % size) */spinlock_t *lock;   /* protects concurrent modifications */
};extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask,spinlock_t *lock);
extern void kfifo_free(struct kfifo *fifo);
static inline void kfifo_reset(struct kfifo *fifo);
static inline unsigned int kfifo_put(struct kfifo *fifo,const unsigned char *buffer, unsigned int len);
static inline unsigned int kfifo_get(struct kfifo *fifo,unsigned char *buffer, unsigned int len);
static inline unsigned int kfifo_len(struct kfifo *fifo);                     

unsigned int __kfifo_put(struct kfifo *fifo,const unsigned char *buffer, unsigned int len)
{unsigned int l;len = min(len, fifo->size - fifo->in + fifo->out);/* first put the data starting from fifo->in to buffer end */l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);/* then put the rest (if any) at the beginning of the buffer */memcpy(fifo->buffer, buffer + l, len - l);fifo->in += len;return len;
}

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "fifo.h"static inline int is_power_of_2(unsigned int n)
{return !((n - 1) & n);
}unsigned int roundup_pow_of_two(unsigned int n)
{if(is_power_of_2(n))return n;int i = 32;while(i--){if((n >> i) & 1)break;}n = 1 << (i + 1);return n;
} struct fifo *fifo_init(unsigned char *buffer, unsigned int size)
{struct fifo *fifo;fifo = malloc(sizeof(struct fifo));if (!fifo){fprintf(stderr, "malloc %ubyte failed\n", sizeof(struct fifo));return NULL;}fifo->buffer = buffer;fifo->size = size;fifo->in = fifo->out = 0;return fifo;
}struct fifo *fifo_alloc(unsigned int size)
{unsigned char *buffer;struct fifo *ret;/* round up to the next power of 2 */if(size > 0x80000000){fprintf(stderr, "The size is too lager\n");return NULL;}size = roundup_pow_of_two(size);buffer = malloc(size);if (!buffer){fprintf(stderr, "malloc %ubyte failed\n", size);return NULL;}ret = fifo_init(buffer, size);if (!ret)free(buffer);return ret;
}void fifo_free(struct fifo *fifo)
{free(fifo->buffer);free(fifo);
}unsigned int _fifo_put(struct fifo *fifo, const unsigned char *buffer, unsigned int len)
{unsigned int l;len = min(len, fifo->size - fifo->in + fifo->out);/* first put the data starting from fifo->in to buffer end */l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);/* then put the rest (if any) at the beginning of the buffer */memcpy(fifo->buffer, buffer + l, len - l);fifo->in += len;return len;
}unsigned int _fifo_get(struct fifo *fifo, unsigned char *buffer, unsigned int len)
{unsigned int l;len = min(len, fifo->in - fifo->out);/* first get the data from fifo->out until the end of the buffer */l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);/* then get the rest (if any) from the beginning of the buffer */memcpy(buffer + l, fifo->buffer, len - l);fifo->out += len;return len;
}

#ifndef _FIFO_H_
#define _FIFO_H_struct fifo {unsigned char *buffer;  /* the buffer holding the data */unsigned int size;  /* the size of the allocated buffer */unsigned int in;    /* data is added at offset (in % size) */unsigned int out;   /* data is extracted from off. (out % size) */
};#define min(a, b) ((a) > (b) ? (b) : (a))extern struct fifo *fifo_alloc(unsigned int size);
extern void fifo_free(struct fifo *fifo);
extern unsigned int _fifo_put(struct fifo *fifo, const unsigned char *buffer, unsigned int len);
extern unsigned int _fifo_get(struct fifo *fifo,unsigned char *buffer, unsigned int len);static inline void _fifo_reset(struct fifo *fifo)
{fifo->in = fifo->out = 0;
}static inline unsigned int _fifo_len(struct fifo *fifo)
{return fifo->in - fifo->out;
}/****************************************************/
/* 根据需要进行封装，这儿我封装为保存int数
/****************************************************/static inline void fifo_reset(struct fifo *fifo)
{_fifo_reset(fifo);
}static inline unsigned int fifo_len(struct fifo *fifo)
{return _fifo_len(fifo)/4;
}static inline unsigned int fifo_put(struct fifo *fifo, int n)
{return _fifo_put(fifo, (unsigned char *)&n, sizeof(int));
}static inline unsigned int fifo_get(struct fifo *fifo, int *n)
{return _fifo_get(fifo, (unsigned char *)n, sizeof(int));
}#endif