fd.c

   1 /*
   2  * Copyright (C) 2006-2007 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file fd.c helper functions for file descriptor handling */
   8
   9 #include "para.h"
  10 #include <sys/mman.h>
  11 #include <fcntl.h>
  12 #include <sys/select.h>
  13
  14 #include "error.h"
  15 /**
  16  * check whether a file exists
  17  *
  18  * \param fn the file name
  19  *
  20  * \return Non-zero iff file exists.
  21  */
  22 int file_exists(const char *fn)
  23 {
  24         struct stat statbuf;
  25
  26         return !stat(fn, &statbuf);
  27 }
  28
  29 /**
  30  * paraslash's wrapper for select(2)
  31  *
  32  * It calls select(2) (with no exceptfds) and starts over if select() was
  33  * interrupted by a signal.
  34  *
  35  * \param n the highest-numbered descriptor in any of the two sets, plus 1
  36  * \param readfds fds that should be checked for readability
  37  * \param writefds fds that should be checked for writablility
  38  * \param timeout_tv upper bound on the amount of time elapsed before select()
  39  * returns
  40  *
  41  * \return The return value of the underlying select() call.
  42  *
  43  * All arguments are passed verbatim to select(2).
  44  * \sa select(2) select_tut(2)
  45  */
  46 int para_select(int n, fd_set *readfds, fd_set *writefds,
  47                 struct timeval *timeout_tv)
  48 {
  49         int ret, err;
  50         do {
  51                 ret = select(n, readfds, writefds, NULL, timeout_tv);
  52                 err = errno;
  53         } while (ret < 0 && err == EINTR);
  54         if (ret < 0)
  55                 PARA_CRIT_LOG("select error: %s, max_fileno: %d\n",
  56                         strerror(err), n);
  57         return ret;
  58 }
  59
  60 /**
  61  * set a file descriptor to non-blocking mode
  62  *
  63  * \param fd The file descriptor
  64  *
  65  * \returns 1 on success, -E_F_GETFL, -E_F_SETFL, on errors.
  66  */
  67 int mark_fd_nonblock(int fd)
  68 {
  69         int flags = fcntl(fd, F_GETFL);
  70         if (flags < 0)
  71                 return -E_F_GETFL;
  72         if (fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK) < 0)
  73                 return -E_F_SETFL;
  74         return 1;
  75 }
  76
  77 /**
  78  * set a file descriptor in a fd_set
  79  *
  80  * \param fd the file descriptor to be set
  81  * \param fds the file descriptor set
  82  * \param max_fileno highest-numbered file descriptor
  83  *
  84  * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
  85  * return, \a max_fileno contains the maximum of the old_value and \a fd.
  86  *
  87  * \sa para_select
  88 */
  89 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
  90 {
  91
  92         if (fd < 0 || fd >= FD_SETSIZE) {
  93                 PARA_EMERG_LOG("fatal: tried to add invalid fd %d\n", fd);
  94                 exit(EXIT_FAILURE);
  95         }
  96 #if 0
  97         {
  98                 int flags = fcntl(fd, F_GETFL);
  99                 if (!(flags & O_NONBLOCK)) {
 100                         PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
 101                         exit(EXIT_FAILURE);
 102                 }
 103         }
 104 #endif
 105         FD_SET(fd, fds);
 106         *max_fileno = PARA_MAX(*max_fileno, fd);
 107 }
 108
 109 /**
 110 * paraslash's wrapper for fgets(3)
 111 * \param line pointer to the buffer to store the line
 112 * \param size the size of the buffer given by \a line
 113 * \param f the stream to read from
 114 *
 115 * \return Unlike the standard fgets() function, an integer value
 116 * is returned. On success, this function returns 1. On errors, -E_FGETS
 117 * is returned. A zero return value indicates an end of file condition.
 118 */
 119 __must_check int para_fgets(char *line, int size, FILE *f)
 120 {
 121 again:
 122         if (fgets(line, size, f))
 123                 return 1;
 124         if (feof(f))
 125                 return 0;
 126         if (!ferror(f))
 127                 return -E_FGETS;
 128         if (errno != EINTR) {
 129                 PARA_ERROR_LOG("%s\n", strerror(errno));
 130                 return -E_FGETS;
 131         }
 132         clearerr(f);
 133         goto again;
 134 }
 135
 136 /**
 137  * *paraslash's wrapper for mmap
 138  *
 139  * \param length number of bytes to mmap
 140  * \param prot either PROT_NONE or the bitwise OR of one or more of
 141  * PROT_EXEC PROT_READ PROT_WRITE
 142  * \param flags exactly one of MAP_SHARED and MAP_PRIVATE
 143  * \param fd the file to mmap from
 144  * \param offset mmap start
 145  *
 146  * \return This function either returns a valid pointer to the mapped area
 147  * or calls exit() on errors.
 148  */
 149 void *para_mmap(size_t length, int prot, int flags, int fd, off_t offset)
 150 {
 151         void *ret = mmap(NULL, length, prot, flags, fd, offset);
 152         if (ret != MAP_FAILED)
 153                 return ret;
 154         PARA_EMERG_LOG("mmap failed: %s\n", strerror(errno));
 155         PARA_EMERG_LOG("length: %zu, flags: %d, fd: %d, offset: %zu\n",
 156                 length, flags, fd, (size_t)offset);
 157         exit(EXIT_FAILURE);
 158 }
 159