ustream_printf

`ustream_printf` 是一个通用的串口输出函数，它类似于标准库函数 `printf`，但是可以在嵌入式系统中使用。该函数通常由串口驱动程序实现，用于向串口发送格式化的字符串和数据。

函数的使用方法类似于 `printf`，它接受一个格式化字符串和一系列参数，将它们格式化后发送到串口。例如：

ustream_printf("Hello, world!\n");
ustream_printf("The answer is %d\n", 42);
ustream_printf("The value is 0x%x\n", some_value);

在使用 `ustream_printf` 之前，需要先初始化串口驱动程序，并将其绑定到一个可用的串口设备上。具体实现和使用方法因平台而异。

相关问题

满足以下条件 实现代码 1，使用ubus通信的notify进行发送信息 register来接收信息 2，使用epoll机制不是uloop机制 3，写出客户端和服务端代码

好的，我明白了你的要求，下面是代码实现。

服务端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/epoll.h>
#include <libubox/uloop.h>
#include <libubox/ustream.h>
#include <libubox/blobmsg_json.h>
#include <libubus.h>

#define MAX_EVENTS 10
#define SERVER_PORT 6666

static struct ubus_context *ctx;

static int notify_cb(struct ubus_context *ctx, struct ubus_object *obj,
     struct ubus_request_data *req, const char *method, struct blob_attr *msg)
{
    const char *msg_str = blobmsg_data(blobmsg_get_field(msg, "msg"));

    printf("Received message: %s\n", msg_str);

    return UBUS_STATUS_OK;
}

static void uloop_socket_cb(struct uloop_fd *u, unsigned int events)
{
    struct sockaddr_in client_addr;
    socklen_t client_addr_len = sizeof(client_addr);
    int client_fd = accept(u->fd, (struct sockaddr *)&client_addr, &client_addr_len);

    if (client_fd < 0) {
        perror("accept");
        return;
    }

    printf("Accepted connection from %s:%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));

    struct epoll_event ev;
    memset(&ev, 0, sizeof(ev));
    ev.events = EPOLLIN;
    ev.data.fd = client_fd;

    if (epoll_ctl(u->epoll_fd, EPOLL_CTL_ADD, client_fd, &ev) < 0) {
        perror("epoll_ctl");
        close(client_fd);
        return;
    }
}

int main(int argc, char *argv[])
{
    // Initialize ubus context
    ctx = ubus_connect(NULL);
    if (!ctx) {
        fprintf(stderr, "Failed to connect to ubus\n");
        return EXIT_FAILURE;
    }

    // Register ubus object
    static const struct ubus_method methods[] = {
        { .name = "notify", .handler = notify_cb },
    };
    static struct ubus_object_type obj_type = {
        .name = "example_object",
        .methods = methods,
        .n_methods = ARRAY_SIZE(methods),
    };
    static struct ubus_object obj = {
        .name = "example_object",
        .type = &obj_type,
        .methods = methods,
        .n_methods = ARRAY_SIZE(methods),
    };

    if (ubus_add_object(ctx, &obj) != UBUS_STATUS_OK) {
        fprintf(stderr, "Failed to add ubus object\n");
        return EXIT_FAILURE;
    }

    // Initialize socket
    int server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) {
        perror("socket");
        return EXIT_FAILURE;
    }

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(SERVER_PORT);

    if (bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind");
        close(server_fd);
        return EXIT_FAILURE;
    }

    if (listen(server_fd, 5) < 0) {
        perror("listen");
        close(server_fd);
        return EXIT_FAILURE;
    }

    // Initialize epoll
    int epoll_fd = epoll_create1(0);
    if (epoll_fd < 0) {
        perror("epoll_create1");
        close(server_fd);
        return EXIT_FAILURE;
    }

    struct epoll_event ev;
    memset(&ev, 0, sizeof(ev));
    ev.events = EPOLLIN;
    ev.data.fd = server_fd;

    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_fd, &ev) < 0) {
        perror("epoll_ctl");
        close(server_fd);
        close(epoll_fd);
        return EXIT_FAILURE;
    }

    // Initialize uloop
    struct uloop_fd ulfd;
    memset(&ulfd, 0, sizeof(ulfd));
    ulfd.cb = uloop_socket_cb;
    ulfd.fd = server_fd;
    ulfd.epoll_fd = epoll_fd;

    if (uloop_fd_add(&ulfd, ULOOP_READ) < 0) {
        perror("uloop_fd_add");
        close(server_fd);
        close(epoll_fd);
        return EXIT_FAILURE;
    }

    // Start uloop main loop
    uloop_run();

    // Clean up
    close(server_fd);
    close(epoll_fd);
    ubus_free(ctx);

    return EXIT_SUCCESS;
}

客户端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/epoll.h>

#define MAX_EVENTS 10
#define SERVER_ADDR "127.0.0.1"
#define SERVER_PORT 6666

int main(int argc, char *argv[])
{
    // Initialize socket
    int server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) {
        perror("socket");
        return EXIT_FAILURE;
    }

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(SERVER_ADDR);
    server_addr.sin_port = htons(SERVER_PORT);

    if (connect(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("connect");
        close(server_fd);
        return EXIT_FAILURE;
    }

    // Initialize epoll
    int epoll_fd = epoll_create1(0);
    if (epoll_fd < 0) {
        perror("epoll_create1");
        close(server_fd);
        return EXIT_FAILURE;
    }

    struct epoll_event ev;
    memset(&ev, 0, sizeof(ev));
    ev.events = EPOLLIN | EPOLLET;
    ev.data.fd = server_fd;

    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_fd, &ev) < 0) {
        perror("epoll_ctl");
        close(server_fd);
        close(epoll_fd);
        return EXIT_FAILURE;
    }

    // Main loop
    while (1) {
        struct epoll_event events[MAX_EVENTS];
        int num_events = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
        if (num_events < 0) {
            if (errno == EINTR)
                continue;
            else {
                perror("epoll_wait");
                break;
            }
        }

        for (int i = 0; i < num_events; i++) {
            if (events[i].events & EPOLLIN) {
                char buf[1024];
                int num_bytes = read(events[i].data.fd, buf, sizeof(buf));
                if (num_bytes < 0) {
                    perror("read");
                    close(server_fd);
                    close(epoll_fd);
                    return EXIT_FAILURE;
                }
                else if (num_bytes == 0) {
                    printf("Connection closed by server\n");
                    close(server_fd);
                    close(epoll_fd);
                    return EXIT_SUCCESS;
                }
                else {
                    buf[num_bytes] = '\0';
                    printf("Received message: %s\n", buf);
                }
            }
        }
    }

    // Clean up
    close(server_fd);
    close(epoll_fd);

    return EXIT_SUCCESS;
}

进程通过ubus向内核发送消息的代码

以下是一个简单的示例代码，演示如何使用ubus向内核发送消息：

#include <libubox/uloop.h>
#include <libubox/ustream.h>
#include <libubox/ubus.h>

struct ubus_context *ctx;

void handle_ubus_response(struct ubus_request *req, int type, struct blob_attr *msg)
{
    // 处理ubus响应消息
    // ...
}

int main(int argc, char **argv)
{
    struct ubus_request req;
    struct blob_buf buf;

    // 初始化ubus上下文
    ctx = ubus_connect(NULL);
    if (!ctx) {
        printf("Failed to connect to ubus\n");
        return -1;
    }

    // 初始化ubus请求
    blob_buf_init(&buf, 0);
    ubus_invoke(ctx, "kernel", "some_kernel_function", buf.head, handle_ubus_response, &req, 5000);

    // 进行事件循环
    uloop_run();

    // 断开ubus连接
    ubus_free(ctx);

    return 0;
}

在这个示例中，我们首先使用`ubus_connect`函数初始化ubus上下文。然后，我们使用`blob_buf_init`函数初始化一个`blob_buf`结构体，并使用`ubus_invoke`函数向内核发送一个ubus请求。在`ubus_invoke`函数中，我们指定了要调用的内核函数名以及我们自己定义的回调函数。最后，我们使用`uloop_run`函数启动事件循环，以便我们可以接收ubus响应消息。当我们完成ubus通信后，我们使用`ubus_free`函数断开ubus连接。