uv_check() を利用した thread worker からのメッセージの出力 (worker 内の sleep 処理に依存しない方法）

main.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <queue>
#include "uv.h"

using namespace std;

uv_loop_t *loop;
static int check_called = 0;
static int worker_finished = 0;
static queue<char*> g_msgQueue;
static uv_mutex_t g_mutex;
static int g_line_count = 0;
const int WORKER_MAX = 10;


void print_progress(uv_check_t *handle, int status /*UNUSED*/) {
  check_called++;
  uv_mutex_lock(&g_mutex);
  while ( !g_msgQueue.empty()) {
    char* msg = g_msgQueue.front();
    g_msgQueue.pop();

    fprintf(stderr, "%2d: check_called=%3d, thread=%lud: %s\n",
            ++g_line_count, check_called, uv_thread_self(), msg);
    // fflush( stderr);
    free(msg);
  }
  uv_mutex_unlock(&g_mutex);
}


void fake_download0(uv_work_t *req) {
  int size = *((int*) req->data);
  const int MSG_SIZE = 256;
  double percentage;
  int downloaded = 0;
  int send_count = 0;
  while (downloaded < size) {
    send_count++;
    percentage = downloaded*100.0/size;
    char* msg = (char*)malloc( MSG_SIZE);
    sprintf(msg, "from=%lud(send_count=%d) Downloaded %.2f%%", uv_thread_self(), send_count, percentage);

    uv_mutex_lock(&g_mutex);
    g_msgQueue.push(msg);
    uv_mutex_unlock(&g_mutex);

    downloaded++;
  }
  req->data = (void*) &downloaded;
}


void after0(uv_work_t *req, int status) {
  int downloaded = *((int*) req->data);
  fprintf(stderr, "%2d: worker_finished=%3d, thread=%lud: after()\n",
          ++g_line_count, ++worker_finished, uv_thread_self());
}


int main() {
  loop = uv_default_loop();
  int size = 5;
  uv_work_t req[ WORKER_MAX];
  uv_check_t check;

  uv_check_init(loop, &check);
  uv_check_start(&check, print_progress);
  uv_unref((uv_handle_t *)&check);
  uv_mutex_init(&g_mutex);

  fprintf(stderr, "%2d: worker_finished=%3d, thread=%lud: %s\n",
          ++g_line_count, worker_finished, uv_thread_self(), "main() start");
  for ( int i = 0; i < WORKER_MAX; i++) {
    req[ i].data = (void*) &size;
    uv_queue_work(loop, req+i, fake_download0, after0);
  }
  uv_run(loop, UV_RUN_DEFAULT);
  fprintf(stderr, "%2d: worker_finished=%3d, thread=%lud: %s\n",
          ++g_line_count, worker_finished, uv_thread_self(), "main() end");
}