text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
   *
   * This software is licensed as described in the file COPYING, which
   * you should have received as part of this distribution. The terms
   * are also available at https://curl.se/docs/copyright.html.
   *
   * You may opt to use, copy, modify, merge, publish, distribute and/or sell
   * copies of the Software, and permit persons to whom the Software is
   * furnished to do so, under the terms of the COPYING file.
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
   * KIND, either express or implied.
   *
   ***************************************************************************/
  
  #include "curl_setup.h"
  
  #include <limits.h>
  
  #ifdef HAVE_SYS_SELECT_H
  #include <sys/select.h>
  #elif defined(HAVE_UNISTD_H)
  #include <unistd.h>
  #endif
  
  #if !defined(HAVE_SELECT) && !defined(HAVE_POLL_FINE)
  #error "We can't compile without select() or poll() support."
  #endif
  
  #ifdef MSDOS
  #include <dos.h>  /* delay() */
  #endif
  
  #include <curl/curl.h>
  
  #include "urldata.h"
  #include "connect.h"
  #include "select.h"
  #include "timediff.h"
  #include "warnless.h"
  
  /*
   * Internal function used for waiting a specific amount of ms
   * in Curl_socket_check() and Curl_poll() when no file descriptor
   * is provided to wait on, just being used to delay execution.
   * WinSock select() and poll() timeout mechanisms need a valid
   * socket descriptor in a not null file descriptor set to work.
   * Waiting indefinitely with this function is not allowed, a
   * zero or negative timeout value will return immediately.
   * Timeout resolution, accuracy, as well as maximum supported
   * value is system dependent, neither factor is a critical issue
   * for the intended use of this function in the library.
   *
   * Return values:
   *   -1 = system call error, invalid timeout value, or interrupted
   *    0 = specified timeout has elapsed
   */
  int Curl_wait_ms(timediff_t timeout_ms)
  {
    int r = 0;
  
    if(!timeout_ms)
      return 0;
    if(timeout_ms < 0) {
      SET_SOCKERRNO(EINVAL);
      return -1;
    }
  #if defined(MSDOS)
    delay(timeout_ms);
  #elif defined(WIN32)
    /* prevent overflow, timeout_ms is typecast to ULONG/DWORD. */
  #if TIMEDIFF_T_MAX >= ULONG_MAX
    if(timeout_ms >= ULONG_MAX)
      timeout_ms = ULONG_MAX-1;
      /* don't use ULONG_MAX, because that is equal to INFINITE */
  #endif
    Sleep((ULONG)timeout_ms);
  #else
  #if defined(HAVE_POLL_FINE)
    /* prevent overflow, timeout_ms is typecast to int. */
  #if TIMEDIFF_T_MAX > INT_MAX
    if(timeout_ms > INT_MAX)
      timeout_ms = INT_MAX;
  #endif
    r = poll(NULL, 0, (int)timeout_ms);
  #else
    {
      struct timeval pending_tv;
      r = select(0, NULL, NULL, NULL, curlx_mstotv(&pending_tv, timeout_ms));
    }
  #endif /* HAVE_POLL_FINE */
  #endif /* USE_WINSOCK */
    if(r)
      r = -1;
    return r;
  }
  
  #ifndef HAVE_POLL_FINE
  /*
   * This is a wrapper around select() to aid in Windows compatibility.
   * A negative timeout value makes this function wait indefinitely,
   * unless no valid file descriptor is given, when this happens the
   * negative timeout is ignored and the function times out immediately.
   *
   * Return values:
   *   -1 = system call error or fd >= FD_SETSIZE
   *    0 = timeout
   *    N = number of signalled file descriptors
   */
  static int our_select(curl_socket_t maxfd,   /* highest socket number */
                        fd_set *fds_read,      /* sockets ready for reading */
                        fd_set *fds_write,     /* sockets ready for writing */
                        fd_set *fds_err,       /* sockets with errors */
                        timediff_t timeout_ms) /* milliseconds to wait */
  {
    struct timeval pending_tv;
    struct timeval *ptimeout;
  
  #ifdef USE_WINSOCK
    /* WinSock select() can't handle zero events.  See the comment below. */
    if((!fds_read || fds_read->fd_count == 0) &&
       (!fds_write || fds_write->fd_count == 0) &&
       (!fds_err || fds_err->fd_count == 0)) {
      /* no sockets, just wait */
      return Curl_wait_ms(timeout_ms);
    }
  #endif
  
    ptimeout = curlx_mstotv(&pending_tv, timeout_ms);
  
  #ifdef USE_WINSOCK
    /* WinSock select() must not be called with an fd_set that contains zero
      fd flags, or it will return WSAEINVAL.  But, it also can't be called
      with no fd_sets at all!  From the documentation:
  
      Any two of the parameters, readfds, writefds, or exceptfds, can be
      given as null. At least one must be non-null, and any non-null
      descriptor set must contain at least one handle to a socket.
  
      It is unclear why WinSock doesn't just handle this for us instead of
      calling this an error. Luckily, with WinSock, we can _also_ ask how
      many bits are set on an fd_set. So, let's just check it beforehand.
    */
    return select((int)maxfd + 1,
                  fds_read && fds_read->fd_count ? fds_read : NULL,
                  fds_write && fds_write->fd_count ? fds_write : NULL,
                  fds_err && fds_err->fd_count ? fds_err : NULL, ptimeout);
  #else
    return select((int)maxfd + 1, fds_read, fds_write, fds_err, ptimeout);
  #endif
  }
  
  #endif
  
  /*
   * Wait for read or write events on a set of file descriptors. It uses poll()
   * when a fine poll() is available, in order to avoid limits with FD_SETSIZE,
   * otherwise select() is used.  An error is returned if select() is being used
   * and a file descriptor is too large for FD_SETSIZE.
   *
   * A negative timeout value makes this function wait indefinitely,
   * unless no valid file descriptor is given, when this happens the
   * negative timeout is ignored and the function times out immediately.
   *
   * Return values:
   *   -1 = system call error or fd >= FD_SETSIZE
   *    0 = timeout
   *    [bitmask] = action as described below
   *
   * CURL_CSELECT_IN - first socket is readable
   * CURL_CSELECT_IN2 - second socket is readable
   * CURL_CSELECT_OUT - write socket is writable
   * CURL_CSELECT_ERR - an error condition occurred
   */
  int Curl_socket_check(curl_socket_t readfd0, /* two sockets to read from */
                        curl_socket_t readfd1,
                        curl_socket_t writefd, /* socket to write to */
                        timediff_t timeout_ms) /* milliseconds to wait */
  {
    struct pollfd pfd[3];
    int num;
    int r;
  
    if((readfd0 == CURL_SOCKET_BAD) && (readfd1 == CURL_SOCKET_BAD) &&
       (writefd == CURL_SOCKET_BAD)) {
      /* no sockets, just wait */
      return Curl_wait_ms(timeout_ms);
    }
  
    /* Avoid initial timestamp, avoid Curl_now() call, when elapsed
       time in this function does not need to be measured. This happens
       when function is called with a zero timeout or a negative timeout
       value indicating a blocking call should be performed. */
  
    num = 0;
    if(readfd0 != CURL_SOCKET_BAD) {
      pfd[num].fd = readfd0;
      pfd[num].events = POLLRDNORM|POLLIN|POLLRDBAND|POLLPRI;
      pfd[num].revents = 0;
      num++;
    }
    if(readfd1 != CURL_SOCKET_BAD) {
      pfd[num].fd = readfd1;
      pfd[num].events = POLLRDNORM|POLLIN|POLLRDBAND|POLLPRI;
      pfd[num].revents = 0;
      num++;
    }
    if(writefd != CURL_SOCKET_BAD) {
      pfd[num].fd = writefd;
      pfd[num].events = POLLWRNORM|POLLOUT|POLLPRI;
      pfd[num].revents = 0;
      num++;
    }
  
    r = Curl_poll(pfd, num, timeout_ms);
    if(r <= 0)
      return r;
  
    r = 0;
    num = 0;
    if(readfd0 != CURL_SOCKET_BAD) {
      if(pfd[num].revents & (POLLRDNORM|POLLIN|POLLERR|POLLHUP))
        r |= CURL_CSELECT_IN;
      if(pfd[num].revents & (POLLRDBAND|POLLPRI|POLLNVAL))
        r |= CURL_CSELECT_ERR;
      num++;
    }
    if(readfd1 != CURL_SOCKET_BAD) {
      if(pfd[num].revents & (POLLRDNORM|POLLIN|POLLERR|POLLHUP))
        r |= CURL_CSELECT_IN2;
      if(pfd[num].revents & (POLLRDBAND|POLLPRI|POLLNVAL))
        r |= CURL_CSELECT_ERR;
      num++;
    }
    if(writefd != CURL_SOCKET_BAD) {
      if(pfd[num].revents & (POLLWRNORM|POLLOUT))
        r |= CURL_CSELECT_OUT;
      if(pfd[num].revents & (POLLERR|POLLHUP|POLLPRI|POLLNVAL))
        r |= CURL_CSELECT_ERR;
    }
  
    return r;
  }
  
  /*
   * This is a wrapper around poll().  If poll() does not exist, then
   * select() is used instead.  An error is returned if select() is
   * being used and a file descriptor is too large for FD_SETSIZE.
   * A negative timeout value makes this function wait indefinitely,
   * unless no valid file descriptor is given, when this happens the
   * negative timeout is ignored and the function times out immediately.
   *
   * Return values:
   *   -1 = system call error or fd >= FD_SETSIZE
   *    0 = timeout
   *    N = number of structures with non zero revent fields
   */
  int Curl_poll(struct pollfd ufds[], unsigned int nfds, timediff_t timeout_ms)
  {
  #ifdef HAVE_POLL_FINE
    int pending_ms;
  #else
    fd_set fds_read;
    fd_set fds_write;
    fd_set fds_err;
    curl_socket_t maxfd;
  #endif
    bool fds_none = TRUE;
    unsigned int i;
    int r;
  
    if(ufds) {
      for(i = 0; i < nfds; i++) {
        if(ufds[i].fd != CURL_SOCKET_BAD) {
          fds_none = FALSE;
          break;
        }
      }
    }
    if(fds_none) {
      /* no sockets, just wait */
      return Curl_wait_ms(timeout_ms);
    }
  
    /* Avoid initial timestamp, avoid Curl_now() call, when elapsed
       time in this function does not need to be measured. This happens
       when function is called with a zero timeout or a negative timeout
       value indicating a blocking call should be performed. */
  
  #ifdef HAVE_POLL_FINE
  
    /* prevent overflow, timeout_ms is typecast to int. */
  #if TIMEDIFF_T_MAX > INT_MAX
    if(timeout_ms > INT_MAX)
      timeout_ms = INT_MAX;
  #endif
    if(timeout_ms > 0)
      pending_ms = (int)timeout_ms;
    else if(timeout_ms < 0)
      pending_ms = -1;
    else
      pending_ms = 0;
    r = poll(ufds, nfds, pending_ms);
    if(r <= 0)
      return r;
  
    for(i = 0; i < nfds; i++) {
      if(ufds[i].fd == CURL_SOCKET_BAD)
        continue;
      if(ufds[i].revents & POLLHUP)
        ufds[i].revents |= POLLIN;
      if(ufds[i].revents & POLLERR)
        ufds[i].revents |= POLLIN|POLLOUT;
    }
  
  #else  /* HAVE_POLL_FINE */
  
    FD_ZERO(&fds_read);
    FD_ZERO(&fds_write);
    FD_ZERO(&fds_err);
    maxfd = (curl_socket_t)-1;
  
    for(i = 0; i < nfds; i++) {
      ufds[i].revents = 0;
      if(ufds[i].fd == CURL_SOCKET_BAD)
        continue;
      VERIFY_SOCK(ufds[i].fd);
      if(ufds[i].events & (POLLIN|POLLOUT|POLLPRI|
                           POLLRDNORM|POLLWRNORM|POLLRDBAND)) {
        if(ufds[i].fd > maxfd)
          maxfd = ufds[i].fd;
        if(ufds[i].events & (POLLRDNORM|POLLIN))
          FD_SET(ufds[i].fd, &fds_read);
        if(ufds[i].events & (POLLWRNORM|POLLOUT))
          FD_SET(ufds[i].fd, &fds_write);
        if(ufds[i].events & (POLLRDBAND|POLLPRI))
          FD_SET(ufds[i].fd, &fds_err);
      }
    }
  
    /*
       Note also that WinSock ignores the first argument, so we don't worry
       about the fact that maxfd is computed incorrectly with WinSock (since
       curl_socket_t is unsigned in such cases and thus -1 is the largest
       value).
    */
    r = our_select(maxfd, &fds_read, &fds_write, &fds_err, timeout_ms);
    if(r <= 0) {
      if((r == -1) && (SOCKERRNO == EINTR))
        /* make EINTR from select or poll not a "lethal" error */
        r = 0;
      return r;
    }
  
    r = 0;
    for(i = 0; i < nfds; i++) {
      ufds[i].revents = 0;
      if(ufds[i].fd == CURL_SOCKET_BAD)
        continue;
      if(FD_ISSET(ufds[i].fd, &fds_read)) {
        if(ufds[i].events & POLLRDNORM)
          ufds[i].revents |= POLLRDNORM;
        if(ufds[i].events & POLLIN)
          ufds[i].revents |= POLLIN;
      }
      if(FD_ISSET(ufds[i].fd, &fds_write)) {
        if(ufds[i].events & POLLWRNORM)
          ufds[i].revents |= POLLWRNORM;
        if(ufds[i].events & POLLOUT)
          ufds[i].revents |= POLLOUT;
      }
      if(FD_ISSET(ufds[i].fd, &fds_err)) {
        if(ufds[i].events & POLLRDBAND)
          ufds[i].revents |= POLLRDBAND;
        if(ufds[i].events & POLLPRI)
          ufds[i].revents |= POLLPRI;
      }
      if(ufds[i].revents)
        r++;
    }
  
  #endif  /* HAVE_POLL_FINE */
  
    return r;
  }
  