libuv 写文件

#include <stdio.h>
#include <spdlog/spdlog.h>
#include <string>
#include <uv.h>


typedef struct {
    std::string data;
    char buffer[10];

    uv_file open_file_no;
    size_t  wirte_index;

} write_context;


void on_write_cb(uv_fs_t *req)
{
    auto data = (write_context*)req->data;
    uv_fs_req_cleanup(req);
    if (req->result < 0)
    {
        spdlog::error("Write Error");
    }
    else if (req->result == 0)
    {
        spdlog::info("Close");
        uv_fs_close(uv_default_loop(), req, data->open_file_no, nullptr);
    }
    else
    {
        data->wirte_index = data->wirte_index + req->result;
        int size = sizeof(data->buffer);
        int index = data->wirte_index + size;
        if (index > data->data.length()){
            size = data->data.length() - data->wirte_index;
        }
        uv_buf_t uv_buf = uv_buf_init(data->buffer, size);
        strncpy(data->buffer, data->data.data() + data->wirte_index,  size);
        uv_fs_t write_fs;
        write_fs.data = data;
        uv_fs_write(uv_default_loop(), &write_fs, data->open_file_no, &uv_buf, 1, data->wirte_index, on_write_cb);
    }
}

void on_open_cb(uv_fs_t *req)
{
    uv_fs_req_cleanup(req);
    if (req->result <= 0)
    {
        spdlog::error("Open File fail:{}", uv_strerror(req->result));
    }
    else
    {
        auto data = (write_context*)req->data;
        data->open_file_no = req->result;
        int size = sizeof(data->buffer);
        int index = data->wirte_index + size;
        if (index > data->data.length()){
            size = data->data.length() - data->wirte_index;
        }
        uv_buf_t uv_buf = uv_buf_init(data->buffer, size);
        strncpy(data->buffer, data->data.data() + data->wirte_index,  size);
        uv_fs_t write_fs;
        write_fs.data = req->data;
        uv_fs_write(uv_default_loop(), &write_fs, data->open_file_no, &uv_buf, 1, 0, on_write_cb);
    }
}

int main()
{
    write_context context;
    context.data = "Winky’s lip quivered. Then she burst into tears, which spilled out of her great brown eyes and splashed down her front, just as they had done at the Quidditch World Cup.  ‘Oh, dear,’ said Hermione. She and Ron had followed Harry and Dobby to the end of the kitchen. ‘Winky, don’t cry, please don’t …’ But Winky cried harder than ever. Dobby, on the other hand, beamed up at Harry.  ‘Would Harry Potter like a cup of tea?’ he squeaked loudly, over Winky’s sobs.  ‘Er – yeah, OK,’ said Harry.  Instantly, about six house-elves came trotting up behind him, bearing a large silver tray laden with a teapot, cups for Harry, Ron and Hermione, a milk jug and a large plate of biscuits.  ‘Good service!’ Ron said, in an impressed voice. Hermione frowned at him, but the elves all looked delighted; they bowed very low and retreated.  ‘How long have you been here, Dobby?’ Harry asked, as Dobby handed round the tea.  ‘Only a week, Harry Potter, sir!’ said Dobby happily. ‘Dobby came to see Professor Dumbledore, sir. You see, sir, it is very difficult for a house-elf who has been dismissed to get a new position, sir, very difficult indeed";

    uv_fs_t open_fs;
    open_fs.data = (void*)&context;

    uv_fs_open(uv_default_loop(), &open_fs, "./text_write.txt", O_CREAT | O_WRONLY, 0, on_open_cb);
    return uv_run(uv_default_loop(), UV_RUN_DEFAULT);
}