text: /*
   * Coroutine-aware I/O functions
   *
   * Copyright (C) 2009-2010 Nippon Telegraph and Telephone Corporation.
   * Copyright (c) 2011, Red Hat, Inc.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  #include "qemu/osdep.h"
  #include "qemu-common.h"
  #include "qemu/sockets.h"
  #include "qemu/coroutine.h"
  #include "qemu/iov.h"
  #include "qemu/main-loop.h"
  
  ssize_t coroutine_fn
  qemu_co_sendv_recvv(int sockfd, struct iovec *iov, unsigned iov_cnt,
                      size_t offset, size_t bytes, bool do_send)
  {
      size_t done = 0;
      ssize_t ret;
      while (done < bytes) {
          ret = iov_send_recv(sockfd, iov, iov_cnt,
                              offset + done, bytes - done, do_send);
          if (ret > 0) {
              done += ret;
          } else if (ret < 0) {
              if (errno == EAGAIN || errno == EWOULDBLOCK) {
                  qemu_coroutine_yield();
              } else if (done == 0) {
                  return -errno;
              } else {
                  break;
              }
          } else if (ret == 0 && !do_send) {
              /* write (send) should never return 0.
               * read (recv) returns 0 for end-of-file (-data).
               * In both cases there's little point retrying,
               * but we do for write anyway, just in case */
              break;
          }
      }
      return done;
  }
  
  ssize_t coroutine_fn
  qemu_co_send_recv(int sockfd, void *buf, size_t bytes, bool do_send)
  {
      struct iovec iov = { .iov_base = buf, .iov_len = bytes };
      return qemu_co_sendv_recvv(sockfd, &iov, 1, 0, bytes, do_send);
  }
  
  typedef struct {
      Coroutine *co;
      int fd;
  } FDYieldUntilData;
  
  static void fd_coroutine_enter(void *opaque)
  {
      FDYieldUntilData *data = opaque;
      qemu_set_fd_handler(data->fd, NULL, NULL, NULL);
      qemu_coroutine_enter(data->co);
  }
  
  void coroutine_fn yield_until_fd_readable(int fd)
  {
      FDYieldUntilData data;
  
      assert(qemu_in_coroutine());
      data.co = qemu_coroutine_self();
      data.fd = fd;
      qemu_set_fd_handler(fd, fd_coroutine_enter, NULL, &data);
      qemu_coroutine_yield();
  }
  