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 <sys/types.h>
  10 #include <dirent.h>
  11 #include <sys/mman.h>
  12 #include <fcntl.h>
  13 #include <sys/select.h>
  14
  15 #include "para.h"
  16 #include "error.h"
  17 /**
  18  * check whether a file exists
  19  *
  20  * \param fn the file name
  21  *
  22  * \return Non-zero iff file exists.
  23  */
  24 int file_exists(const char *fn)
  25 {
  26         struct stat statbuf;
  27
  28         return !stat(fn, &statbuf);
  29 }
  30
  31 /**
  32  * paraslash's wrapper for select(2)
  33  *
  34  * It calls select(2) (with no exceptfds) and starts over if select() was
  35  * interrupted by a signal.
  36  *
  37  * \param n the highest-numbered descriptor in any of the two sets, plus 1
  38  * \param readfds fds that should be checked for readability
  39  * \param writefds fds that should be checked for writablility
  40  * \param timeout_tv upper bound on the amount of time elapsed before select()
  41  * returns
  42  *
  43  * \return The return value of the underlying select() call.
  44  *
  45  * All arguments are passed verbatim to select(2).
  46  * \sa select(2) select_tut(2)
  47  */
  48 int para_select(int n, fd_set *readfds, fd_set *writefds,
  49                 struct timeval *timeout_tv)
  50 {
  51         int ret, err;
  52         do {
  53                 ret = select(n, readfds, writefds, NULL, timeout_tv);
  54                 err = errno;
  55         } while (ret < 0 && err == EINTR);
  56         if (ret < 0)
  57                 PARA_CRIT_LOG("select error: %s, max_fileno: %d\n",
  58                         strerror(err), n);
  59         return ret;
  60 }
  61
  62 /**
  63  * set a file descriptor to non-blocking mode
  64  *
  65  * \param fd The file descriptor
  66  *
  67  * \returns 1 on success, -E_F_GETFL, -E_F_SETFL, on errors.
  68  */
  69 int mark_fd_nonblock(int fd)
  70 {
  71         int flags = fcntl(fd, F_GETFL);
  72         if (flags < 0)
  73                 return -E_F_GETFL;
  74         if (fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK) < 0)
  75                 return -E_F_SETFL;
  76         return 1;
  77 }
  78
  79 /**
  80  * set a file descriptor in a fd_set
  81  *
  82  * \param fd the file descriptor to be set
  83  * \param fds the file descriptor set
  84  * \param max_fileno highest-numbered file descriptor
  85  *
  86  * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
  87  * return, \a max_fileno contains the maximum of the old_value and \a fd.
  88  *
  89  * \sa para_select
  90 */
  91 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
  92 {
  93
  94         if (fd < 0 || fd >= FD_SETSIZE) {
  95                 PARA_EMERG_LOG("fatal: tried to add invalid fd %d\n", fd);
  96                 exit(EXIT_FAILURE);
  97         }
  98 #if 0
  99         {
 100                 int flags = fcntl(fd, F_GETFL);
 101                 if (!(flags & O_NONBLOCK)) {
 102                         PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
 103                         exit(EXIT_FAILURE);
 104                 }
 105         }
 106 #endif
 107         FD_SET(fd, fds);
 108         *max_fileno = PARA_MAX(*max_fileno, fd);
 109 }
 110
 111 /**
 112 * paraslash's wrapper for fgets(3)
 113 * \param line pointer to the buffer to store the line
 114 * \param size the size of the buffer given by \a line
 115 * \param f the stream to read from
 116 *
 117 * \return Unlike the standard fgets() function, an integer value
 118 * is returned. On success, this function returns 1. On errors, -E_FGETS
 119 * is returned. A zero return value indicates an end of file condition.
 120 */
 121 __must_check int para_fgets(char *line, int size, FILE *f)
 122 {
 123 again:
 124         if (fgets(line, size, f))
 125                 return 1;
 126         if (feof(f))
 127                 return 0;
 128         if (!ferror(f))
 129                 return -E_FGETS;
 130         if (errno != EINTR) {
 131                 PARA_ERROR_LOG("%s\n", strerror(errno));
 132                 return -E_FGETS;
 133         }
 134         clearerr(f);
 135         goto again;
 136 }
 137
 138 /**
 139  * Paraslash's wrapper for mmap.
 140  *
 141  * \param length number of bytes to mmap
 142  * \param prot either PROT_NONE or the bitwise OR of one or more of
 143  * PROT_EXEC PROT_READ PROT_WRITE
 144  * \param flags exactly one of MAP_SHARED and MAP_PRIVATE
 145  * \param fd the file to mmap from
 146  * \param offset mmap start
 147  *
 148  * \return This function either returns a valid pointer to the mapped area
 149  * or calls exit() on errors.
 150  */
 151 void *para_mmap(size_t length, int prot, int flags, int fd, off_t offset)
 152 {
 153         void *ret = mmap(NULL, length, prot, flags, fd, offset);
 154         if (ret != MAP_FAILED)
 155                 return ret;
 156         PARA_EMERG_LOG("mmap failed: %s\n", strerror(errno));
 157         PARA_EMERG_LOG("length: %zu, flags: %d, fd: %d, offset: %zu\n",
 158                 length, flags, fd, (size_t)offset);
 159         exit(EXIT_FAILURE);
 160 }
 161
 162 /**
 163  * Wrapper for the open(2) system call.
 164  *
 165  * \param path The filename.
 166  * \param flags The usual open(2) flags.
 167  * \param mode Specifies the permissions to use.
 168  *
 169  * The mode parameter must be specified when O_CREAT is in the flags, and is ignored
 170  * otherwise.
 171  *
 172  * \return Positive on success, negative on errors.
 173  *
 174  * \sa open(2).
 175  */
 176 int para_open(const char *path, int flags, mode_t mode)
 177 {
 178         int ret = open(path, flags, mode);
 179
 180         if (ret >= 0)
 181                 return ret;
 182         switch (errno) {
 183         case EEXIST:
 184                 ret = -E_EXIST;
 185                 break;
 186         case EISDIR:
 187                 ret = -E_ISDIR;
 188                 break;
 189         case ENOENT:
 190                 ret = -E_NOENT;
 191                 break;
 192         case EPERM:
 193                 ret = -E_OPEN_PERM;
 194                 break;
 195         };
 196         PARA_ERROR_LOG("failed to open %s: %s\n", path, strerror(errno));
 197         return ret;
 198 }
 199
 200 /**
 201  * Save the cwd and open a given directory.
 202  *
 203  * \param dirname Path to the directory to open.
 204  * \param dir Result pointer.
 205  * \param cwd File descriptor of the current working directory.
 206  *
 207  * \return Positive on success, negative on errors.
 208  *
 209  * Opening the current directory (".") and calling fchdir() to return is
 210  * usually faster and more reliable than saving cwd in some buffer and calling
 211  * chdir() afterwards.
 212  *
 213  * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
 214  * stored in \a cwd. If the function returns success, and \a cwd is not \p
 215  * NULL, the caller must close this file descriptor (probably after calling
 216  * fchdir(*cwd)).
 217  *
 218  * On errors, the function undos everything, so the caller needs neither close
 219  * any files, nor change back to the original working directory.
 220  *
 221  * \sa getcwd(3).
 222  *
 223  */
 224 int para_opendir(const char *dirname, DIR **dir, int *cwd)
 225 {
 226         int ret;
 227
 228         if (cwd) {
 229                 ret = para_open(".", O_RDONLY, 0);
 230                 if (ret < 0)
 231                         return ret;
 232                 *cwd = ret;
 233         }
 234         ret = -E_CHDIR;
 235         if (chdir(dirname) < 0)
 236                 goto close_cwd;
 237         ret = -E_OPENDIR;
 238         *dir = opendir(".");
 239         if (!*dir)
 240                 goto change_to_orig_dir;
 241         return 1;
 242 /* Ignore return value of fchdir() and close(). We're busted anyway. */
 243 change_to_orig_dir:
 244         if (cwd)
 245                 fchdir(*cwd);
 246 close_cwd:
 247         if (cwd)
 248                 close(*cwd);
 249         return ret;
 250 }
 251
 252 /**
 253  * A wrapper for fchdir().
 254  *
 255  * \param fd An open file descriptor
 256  *
 257  * \return Positive on success, negative on errors.
 258  */
 259 int para_fchdir(int fd)
 260 {
 261         if (fchdir(fd) < 0)
 262                 return -E_FCHDIR;
 263         return 1;
 264 }
 265
 266 /**
 267  * A wrapper for mkdir(2).
 268  *
 269  * \param path Name of the directory to create.
 270  * \param mode The permissions to use.
 271  *
 272  * \return positive on success, negative on errors.
 273  */
 274 int para_mkdir(const char *path, mode_t mode)
 275 {
 276         if (!mkdir(path, mode))
 277                 return 1;
 278         if (errno == EEXIST)
 279                 return -E_EXIST;
 280         if (errno == ENOSPC)
 281                 return -E_NOSPC;
 282         if (errno == ENOTDIR)
 283                 return -E_NOTDIR;
 284         if (errno == EPERM)
 285                 return -E_MKDIR_PERM;
 286         return -E_MKDIR;
 287 }