具有阻塞读取和非阻塞写入的循环/环形缓冲区？

Question

我在用户空间中搜索C中的ringbuffer实现,所以我可以在我的库中使用它.

因为我需要一个铃声缓冲器

• 非阻塞写入(=覆盖最旧的数据)
• 如果为空则阻止读取

我搜索了一段时间,并记得我在内核模式中使用wait_event_interruptible&wake_up_interruptible做了类似的事情.

但是在用户空间中使用了什么,所以我可以搜索与该方法结合的ringbuffer？我不想重新发明轮子 - 周围有许多环形缓冲解决方案.

在此先感谢并亲切的问候!

编辑:

似乎也许pthread_cond_wait可能相当于wait_event_interruptible.

Answer 1

添加一些代码的另一个答案,在我的另一个答案中不是1:1匹配pseudocde.将此标记为维基答案,以防有人想要添加评论或进行其他改进.C phtread互斥+条件变量实现非常简单的ringbuffer:

#include <stdio.h>
#include <pthread.h>

#define RINGBUFFER_SIZE (5)
int ringbuffer[RINGBUFFER_SIZE];
unsigned reader_unread = 0;
unsigned writer_next = 0;
pthread_mutex_t ringbuffer_mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t ringbuffer_written_cond = PTHREAD_COND_INITIALIZER;

void process_code(int ch) {
    int counter;
    printf("Processing code %d", ch);
    for(counter=5; counter>0; --counter) {
        putchar('.');
        fflush(stdout);
        sleep(1);
    }
    printf("done.\n");

}

void *reader() {
    pthread_mutex_lock(&ringbuffer_mutex);
    for(;;) {
        if (reader_unread == 0) {
            pthread_cond_wait(&ringbuffer_written_cond, &ringbuffer_mutex);
        }
        if (reader_unread > 0) {

            int ch;
            int pos = writer_next - reader_unread;
            if (pos < 0) pos += RINGBUFFER_SIZE;
            ch = ringbuffer[pos];
            --reader_unread;

            if (ch == EOF) break;

            pthread_mutex_unlock(&ringbuffer_mutex);
            process_code(ch);
            pthread_mutex_lock(&ringbuffer_mutex);
        }
    }
    pthread_mutex_unlock(&ringbuffer_mutex);

    puts("READER THREAD GOT EOF");
    return NULL;
}

void *writer() {
    int ch;
    do {
        int overflow = 0;
        ch = getchar();

        pthread_mutex_lock(&ringbuffer_mutex);

        ringbuffer[writer_next] = ch;

        ++writer_next;
        if (writer_next == RINGBUFFER_SIZE) writer_next = 0;

        if (reader_unread < RINGBUFFER_SIZE) ++reader_unread;
        else overflow = 1;

        pthread_cond_signal(&ringbuffer_written_cond);
        pthread_mutex_unlock(&ringbuffer_mutex);

        if (overflow) puts("WARNING: OVERFLOW!");

    } while(ch != EOF);

    puts("WRITER THREAD GOT EOF");
    return NULL;
}

int main(void)
{
    pthread_t reader_thread, writer_thread;

    puts("Starting threads. Type text and press enter, or type ctrl-d at empty line to quit.");
    pthread_create(&reader_thread, NULL, reader, NULL);
    pthread_create(&writer_thread, NULL, writer, NULL);

    pthread_join(writer_thread, NULL);
    pthread_join(reader_thread, NULL);

    return 0;
}