libuv源码阅读(20)--uvcat

#include <assert.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <uv.h>

void on_read(uv_fs_t *req);

// 几个req请求
uv_fs_t open_req;
uv_fs_t read_req;
uv_fs_t write_req;

// 读写的缓冲区都是这个
static char buffer[1024];

static uv_buf_t iov;

// 依次写req结束之后的回调 再次读取文件的内容
void on_write(uv_fs_t *req) {
    if (req->result < 0) {
        fprintf(stderr, "Write error: %s\n", uv_strerror((int)req->result));
    }
    else {
        uv_fs_read(uv_default_loop(), &read_req, open_req.result, &iov, 1, -1, on_read);
    }
}

// 打开文件之后读取文件内容 读到0意味着结束了
void on_read(uv_fs_t *req) {
    if (req->result < 0) {
        fprintf(stderr, "Read error: %s\n", uv_strerror(req->result));
    }
    else if (req->result == 0) {
        uv_fs_t close_req;
        // synchronous
        // 关闭文件fd 注意这个调用没有cb 直接同步执行了 
        uv_fs_close(uv_default_loop(), &close_req, open_req.result, NULL);
    }
    else if (req->result > 0) {
        // 提交一个写req来消费数据
        iov.len = req->result;
        uv_fs_write(uv_default_loop(), &write_req, 1, &iov, 1, -1, on_write);
    }
}

// 打开文件req
void on_open(uv_fs_t *req) {
    // The request passed to the callback is the same as the one the call setup
    // function was passed.
    assert(req == &open_req);
    if (req->result >= 0) {
        iov = uv_buf_init(buffer, sizeof(buffer));
        uv_fs_read(uv_default_loop(), &read_req, req->result,
                   &iov, 1, -1, on_read);
    }
    else {
        fprintf(stderr, "error opening file: %s\n", uv_strerror((int)req->result));
    }
}

// 以上3个任务都是提交为异步任务 由工作线程完成
int main(int argc, char **argv) {
    uv_fs_open(uv_default_loop(), &open_req, argv[1], O_RDONLY, 0, on_open);
    uv_run(uv_default_loop(), UV_RUN_DEFAULT);

    uv_fs_req_cleanup(&open_req);
    uv_fs_req_cleanup(&read_req);
    uv_fs_req_cleanup(&write_req);
    return 0;
}

int uv_fs_open(uv_loop_t* loop,
               uv_fs_t* req,
               const char* path,
               int flags,
               int mode,
               uv_fs_cb cb) {
  INIT(OPEN);
  PATH;
  req->flags = flags;
  req->mode = mode;
  POST;
}

#define INIT(subtype)                                                         \
  do {                                                                        \
    if (req == NULL)                                                          \
      return UV_EINVAL;                                                       \
    UV_REQ_INIT(req, UV_FS);                                                  \
    req->fs_type = UV_FS_ ## subtype;                                         \
    req->result = 0;                                                          \
    req->ptr = NULL;                                                          \
    req->loop = loop;                                                         \
    req->path = NULL;                                                         \
    req->new_path = NULL;                                                     \
    req->bufs = NULL;                                                         \
    req->cb = cb;                                                             \
  }                                                                           \
  while (0)
  
#define POST                                                                  \
  do {                                                                        \
    if (cb != NULL) {                                                         \
      uv__req_register(loop, req);                                            \
      uv__work_submit(loop,                                                   \
                      &req->work_req,                                         \
                      UV__WORK_FAST_IO,                                       \
                      uv__fs_work,                                            \
                      uv__fs_done);                                           \
      return 0;                                                               \
    }                                                                         \
    else {                                                                    \
      uv__fs_work(&req->work_req);                                            \
      return req->result;                                                     \
    }                                                                         \
  }                                                                           \
  while (0)
  
  

void uv_fs_req_cleanup(uv_fs_t* req) {
  if (req == NULL)
    return;

  /* Only necessary for asychronous requests, i.e., requests with a callback.
   * Synchronous ones don't copy their arguments and have req->path and
   * req->new_path pointing to user-owned memory.  UV_FS_MKDTEMP and
   * UV_FS_MKSTEMP are the exception to the rule, they always allocate memory.
   */
  if (req->path != NULL &&
      (req->cb != NULL ||
        req->fs_type == UV_FS_MKDTEMP || req->fs_type == UV_FS_MKSTEMP))
    uv__free((void*) req->path);  /* Memory is shared with req->new_path. */

  req->path = NULL;
  req->new_path = NULL;

  if (req->fs_type == UV_FS_READDIR && req->ptr != NULL)
    uv__fs_readdir_cleanup(req);

  if (req->fs_type == UV_FS_SCANDIR && req->ptr != NULL)
    uv__fs_scandir_cleanup(req);

  if (req->bufs != req->bufsml)
    uv__free(req->bufs);
  req->bufs = NULL;

  if (req->fs_type != UV_FS_OPENDIR && req->ptr != &req->statbuf)
    uv__free(req->ptr);
  req->ptr = NULL;
}

#ifdef _WIN32
# define uv__fs_scandir_free uv__free
#else
# define uv__fs_scandir_free free
#endif

void uv__fs_scandir_cleanup(uv_fs_t* req) {
  uv__dirent_t** dents;

  unsigned int* nbufs = uv__get_nbufs(req);

  dents = req->ptr;
  if (*nbufs > 0 && *nbufs != (unsigned int) req->result)
    (*nbufs)--;
  for (; *nbufs < (unsigned int) req->result; (*nbufs)++)
    uv__fs_scandir_free(dents[*nbufs]);

  uv__fs_scandir_free(req->ptr);
  req->ptr = NULL;
}