linux 内核RingBuffer实现
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- #linux
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- 实现方式非常巧妙，刚开始看的有点奇怪，当发现实现原理后惊讶了一番..
-/**@brief 仿照linux kfifo写的ring buffer
-* ring_buffer.h
- * */
-
-#ifndef KFIFO_HEADER_H
-#define KFIFO_HEADER_H
-
-#include <inttypes.h>
-#include <string.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <errno.h>
-#include <assert.h>
-
-//判断x是否是2的次方
-#define is_power_of_2(x) ((x) != 0 && (((x) & ((x) - 1)) == 0))
-//取a和b中最小值
-#define min(a, b) (((a) < (b)) ? (a) : (b))
-
-struct ring_buffer
-{
- void *buffer; //缓冲区
- uint32_t size; //大小
- uint32_t in; //入口位置
- uint32_t out; //出口位置
- pthread_mutex_t *f_lock; //互斥锁
-};
-//初始化缓冲区
-struct ring_buffer* ring_buffer_init(void *buffer, uint32_t size, pthread_mutex_t *f_lock)
-{
- assert(buffer);
- struct ring_buffer *ring_buf = NULL;
- if (!is_power_of_2(size))
- {
- fprintf(stderr,"size must be power of 2.\n");
- return ring_buf;
- }
- ring_buf = (struct ring_buffer *)malloc(sizeof(struct ring_buffer));
- if (!ring_buf)
- {
- fprintf(stderr,"Failed to malloc memory,errno:%u,reason:%s",
- errno, strerror(errno));
- return ring_buf;
- }
- memset(ring_buf, 0, sizeof(struct ring_buffer));
- ring_buf->buffer = buffer;
- ring_buf->size = size;
- ring_buf->in = 0;
- ring_buf->out = 0;
- ring_buf->f_lock = f_lock;
- return ring_buf;
-}
-//释放缓冲区
-void ring_buffer_free(struct ring_buffer *ring_buf)
-{
- if (ring_buf)
- {
- if (ring_buf->buffer)
- {
- free(ring_buf->buffer);
- ring_buf->buffer = NULL;
- }
- free(ring_buf);
- ring_buf = NULL;
- }
-}
-
-//缓冲区的长度
-uint32_t __ring_buffer_len(const struct ring_buffer *ring_buf)
-{
- return (ring_buf->in - ring_buf->out);
-}
-
-//从缓冲区中取数据
-uint32_t __ring_buffer_get(struct ring_buffer *ring_buf, void * buffer, uint32_t size)
-{
- assert(ring_buf || buffer);
- uint32_t len = 0;
- size = min(size, ring_buf->in - ring_buf->out);
- /* first get the data from fifo->out until the end of the buffer */
- len = min(size, ring_buf->size - (ring_buf->out & (ring_buf->size - 1)));
- memcpy(buffer, ring_buf->buffer + (ring_buf->out & (ring_buf->size - 1)), len);
- /* then get the rest (if any) from the beginning of the buffer */
- memcpy(buffer + len, ring_buf->buffer, size - len);
- ring_buf->out += size;
- return size;
-}
-//向缓冲区中存放数据
-uint32_t __ring_buffer_put(struct ring_buffer *ring_buf, void *buffer, uint32_t size)
-{
- assert(ring_buf || buffer);
- uint32_t len = 0;
- size = min(size, ring_buf->size - ring_buf->in + ring_buf->out);
- /* first put the data starting from fifo->in to buffer end */
- len = min(size, ring_buf->size - (ring_buf->in & (ring_buf->size - 1)));
- memcpy(ring_buf->buffer + (ring_buf->in & (ring_buf->size - 1)), buffer, len);
- /* then put the rest (if any) at the beginning of the buffer */
- memcpy(ring_buf->buffer, buffer + len, size - len);
- ring_buf->in += size;
- return size;
-}
-
-uint32_t ring_buffer_len(const struct ring_buffer *ring_buf)
-{
- uint32_t len = 0;
- pthread_mutex_lock(ring_buf->f_lock);
- len = __ring_buffer_len(ring_buf);
- pthread_mutex_unlock(ring_buf->f_lock);
- return len;
-}
-
-uint32_t ring_buffer_get(struct ring_buffer *ring_buf, void *buffer, uint32_t size)
-{
- uint32_t ret;
- pthread_mutex_lock(ring_buf->f_lock);
- ret = __ring_buffer_get(ring_buf, buffer, size);
- //buffer中没有数据
- if (ring_buf->in == ring_buf->out)
- ring_buf->in = ring_buf->out = 0;
- pthread_mutex_unlock(ring_buf->f_lock);
- return ret;
-}
-
-uint32_t ring_buffer_put(struct ring_buffer *ring_buf, void *buffer, uint32_t size)
-{
- uint32_t ret;
- pthread_mutex_lock(ring_buf->f_lock);
- ret = __ring_buffer_put(ring_buf, buffer, size);
- pthread_mutex_unlock(ring_buf->f_lock);
- return ret;
-}
-#endif
-使用栗子，采用多线程模拟生产者和消费者编写测试程序，如下所示：
-/**@brief ring buffer测试程序，创建两个线程，一个生产者，一个消费者。
- * 生产者每隔1秒向buffer中投入数据，消费者每隔2秒去取数据。
- * */
-#include "ring_buffer.h"
-#include <pthread.h>
-#include <time.h>
-
-#define BUFFER_SIZE 1024 * 1024
-
-typedef struct student_info
-{
- uint64_t stu_id;
- uint32_t age;
- uint32_t score;
-}student_info;
-
-
-void print_student_info(const student_info *stu_info)
-{
- assert(stu_info);
- printf("id:%lu\t",stu_info->stu_id);
- printf("age:%u\t",stu_info->age);
- printf("score:%u\n",stu_info->score);
-}
-
-student_info * get_student_info(time_t timer)
-{
- student_info *stu_info = (student_info *)malloc(sizeof(student_info));
- if (!stu_info)
- {
- fprintf(stderr, "Failed to malloc memory.\n");
- return NULL;
- }
- srand(timer);
- stu_info->stu_id = 10000 + rand() % 9999;
- stu_info->age = rand() % 30;
- stu_info->score = rand() % 101;
- print_student_info(stu_info);
- return stu_info;
-}
-
-void * consumer_proc(void *arg)
-{
- struct ring_buffer *ring_buf = (struct ring_buffer *)arg;
- student_info stu_info;
- while(1)
- {
- sleep(2);
- printf("------------------------------------------\n");
- printf("get a student info from ring buffer.\n");
- ring_buffer_get(ring_buf, (void *)&stu_info, sizeof(student_info));
- printf("ring buffer length: %u\n", ring_buffer_len(ring_buf));
- print_student_info(&stu_info);
- printf("------------------------------------------\n");
- }
- return (void *)ring_buf;
-}
-
-void * producer_proc(void *arg)
-{
- time_t cur_time;
- struct ring_buffer *ring_buf = (struct ring_buffer *)arg;
- while(1)
- {
- time(&cur_time);
- srand(cur_time);
- int seed = rand() % 11111;
- printf("******************************************\n");
- student_info *stu_info = get_student_info(cur_time + seed);
- printf("put a student info to ring buffer.\n");
- ring_buffer_put(ring_buf, (void *)stu_info, sizeof(student_info));
- printf("ring buffer length: %u\n", ring_buffer_len(ring_buf));
- printf("******************************************\n");
- sleep(1);
- }
- return (void *)ring_buf;
-}
-
-int consumer_thread(void *arg)
-{
- int err;
- pthread_t tid;
- err = pthread_create(&tid, NULL, consumer_proc, arg);
- if (err != 0)
- {
- fprintf(stderr, "Failed to create consumer thread.errno:%u, reason:%s\n",
- errno, strerror(errno));
- return -1;
- }
- return tid;
-}
-int producer_thread(void *arg)
-{
- int err;
- pthread_t tid;
- err = pthread_create(&tid, NULL, producer_proc, arg);
- if (err != 0)
- {
- fprintf(stderr, "Failed to create consumer thread.errno:%u, reason:%s\n",
- errno, strerror(errno));
- return -1;
- }
- return tid;
-}
-
-
-int main()
-{
- void * buffer = NULL;
- uint32_t size = 0;
- struct ring_buffer *ring_buf = NULL;
- pthread_t consume_pid, produce_pid;
-
- pthread_mutex_t *f_lock = (pthread_mutex_t *)malloc(sizeof(pthread_mutex_t));
- if (pthread_mutex_init(f_lock, NULL) != 0)
- {
- fprintf(stderr, "Failed init mutex,errno:%u,reason:%s\n",
- errno, strerror(errno));
- return -1;
- }
- buffer = (void *)malloc(BUFFER_SIZE);
- if (!buffer)
- {
- fprintf(stderr, "Failed to malloc memory.\n");
- return -1;
- }
- size = BUFFER_SIZE;
- ring_buf = ring_buffer_init(buffer, size, f_lock);
- if (!ring_buf)
- {
- fprintf(stderr, "Failed to init ring buffer.\n");
- return -1;
- }
-#if 0
- student_info *stu_info = get_student_info(638946124);
- ring_buffer_put(ring_buf, (void *)stu_info, sizeof(student_info));
- stu_info = get_student_info(976686464);
- ring_buffer_put(ring_buf, (void *)stu_info, sizeof(student_info));
- ring_buffer_get(ring_buf, (void *)stu_info, sizeof(student_info));
- print_student_info(stu_info);
-#endif
- printf("multi thread test.......\n");
- produce_pid = producer_thread((void*)ring_buf);
- consume_pid = consumer_thread((void*)ring_buf);
- pthread_join(produce_pid, NULL);
- pthread_join(consume_pid, NULL);
- ring_buffer_free(ring_buf);
- free(f_lock);
- return 0;
-}
-
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