fd.c

   1 /*
   2  * Copyright (C) 2006-2008 Andre Noll <maan@tuebingen.mpg.de>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file fd.c \brief Helper functions for file descriptor handling. */
   8
   9 #include <sys/types.h>
  10 #include <dirent.h>
  11 #include <sys/mman.h>
  12 #include <string.h>
  13
  14 #include "adu.h"
  15 #include "error.h"
  16 #include "string.h"
  17
  18 /**
  19  * Wrapper for the write system call.
  20  *
  21  * \param fd The file descriptor to write to.
  22  * \param buf The buffer to write.
  23  * \param size The length of \a buf in bytes.
  24  *
  25  * This function writes out the given buffer and retries if an interrupt
  26  * occurred during the write.
  27  *
  28  * \return Standard.
  29  *
  30  * \sa write(2).
  31  */
  32 ssize_t __write(int fd, const void *buf, size_t size)
  33 {
  34         ssize_t ret;
  35
  36         for (;;) {
  37                 ret = write(fd, buf, size);
  38                 if ((ret < 0) && (errno == EAGAIN || errno == EINTR))
  39                         continue;
  40                 return ret >= 0? ret : -ERRNO_TO_ERROR(errno);
  41         }
  42 }
  43
  44 /**
  45  * Write the whole buffer to a file descriptor.
  46  *
  47  * \param fd The file descriptor to write to.
  48  * \param buf The buffer to write.
  49  * \param size The length of \a buf in bytes.
  50  *
  51  * This function writes the given buffer and continues on short writes and
  52  * when interrupted by a signal.
  53  *
  54  * \return Standard.
  55  */
  56 static ssize_t write_all(int fd, const void *buf, size_t size)
  57 {
  58 //      DEBUG_LOG("writing %zu bytes\n", size);
  59         const char *b = buf;
  60         while (size) {
  61                 ssize_t ret = __write(fd, b, size);
  62 //              DEBUG_LOG("ret: %zd\n", ret);
  63                 if (ret < 0)
  64                         return ret;
  65                 b += ret;
  66                 size -= ret;
  67         }
  68         return 1;
  69 }
  70
  71 /**
  72  * Wrapper for the open(2) system call.
  73  *
  74  * \param path The filename.
  75  * \param flags The usual open(2) flags.
  76  * \param mode Specifies the permissions to use.
  77  *
  78  * The mode parameter must be specified when O_CREAT is in the flags, and is
  79  * ignored otherwise.
  80  *
  81  * \return The file descriptor on success, negative on errors.
  82  *
  83  * \sa open(2).
  84  */
  85 static int __open(const char *path, int flags, mode_t mode)
  86 {
  87         int ret = open(path, flags, mode);
  88
  89         if (ret >= 0)
  90                 return ret;
  91         return -ERRNO_TO_ERROR(errno);
  92 }
  93
  94 /**
  95  * Open a file, write the given buffer and close the file.
  96  *
  97  * \param filename Full path to the file to open.
  98  * \param buf The buffer to write to the file.
  99  * \param size The size of \a buf.
 100  *
 101  * \return Standard.
 102  */
 103 int adu_write_file(const char *filename, const void *buf, size_t size)
 104 {
 105         int ret, fd;
 106
 107         ret = __open(filename, O_WRONLY | O_CREAT | O_EXCL, 0644);
 108         if (ret < 0)
 109                 return ret;
 110         fd = ret;
 111         ret = write_all(fd, buf, size);
 112         if (ret < 0)
 113                 goto out;
 114         ret = 1;
 115 out:
 116         close(fd);
 117         return ret;
 118 }
 119
 120 /**
 121  * Wrapper for chdir(2).
 122  *
 123  * \param path The specified directory.
 124  *
 125  * \return Standard.
 126  */
 127 static int __chdir(const char *path)
 128 {
 129         int ret = chdir(path);
 130
 131         if (ret >= 0)
 132                 return 1;
 133         return -ERRNO_TO_ERROR(errno);
 134 }
 135
 136 /**
 137  * Save the cwd and open a given directory.
 138  *
 139  * \param dirname Path to the directory to open.
 140  * \param dir Result pointer.
 141  * \param cwd File descriptor of the current working directory.
 142  *
 143  * \return Standard.
 144  *
 145  * Opening the current directory (".") and calling fchdir() to return is
 146  * usually faster and more reliable than saving cwd in some buffer and calling
 147  * chdir() afterwards.
 148  *
 149  * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
 150  * stored in \a cwd. If the function returns success, and \a cwd is not \p
 151  * NULL, the caller must close this file descriptor (probably after calling
 152  * fchdir(*cwd)).
 153  *
 154  * On errors, the function undos everything, so the caller needs neither close
 155  * any files, nor change back to the original working directory.
 156  *
 157  * \sa getcwd(3).
 158  *
 159  */
 160 int adu_opendir(const char *dirname, DIR **dir, int *cwd)
 161 {
 162         int ret;
 163
 164         if (cwd) {
 165                 ret = __open(".", O_RDONLY, 0);
 166                 if (ret < 0)
 167                         return ret;
 168                 *cwd = ret;
 169         }
 170         ret = __chdir(dirname);
 171         if (ret < 0)
 172                 goto close_cwd;
 173         *dir = opendir(".");
 174         if (*dir)
 175                 return 1;
 176         ret = -ERRNO_TO_ERROR(errno);
 177 /* Ignore return value of fchdir() and close(). We're busted anyway. */
 178         if (cwd)
 179                 fchdir(*cwd);
 180 close_cwd:
 181         if (cwd)
 182                 close(*cwd);
 183         return ret;
 184 }
 185
 186 /**
 187  * A wrapper for fchdir().
 188  *
 189  * \param fd An open file descriptor.
 190  *
 191  * \return Standard.
 192  */
 193 int adu_fchdir(int fd)
 194 {
 195         if (fchdir(fd) < 0)
 196                 return -ERRNO_TO_ERROR(errno);
 197         return 1;
 198 }
 199
 200 /**
 201  * Open a file and map it into memory.
 202  *
 203  * \param path Name of the regular file to map.
 204  * \param open_mode Either \p O_RDONLY or \p O_RDWR.
 205  * \param map On success, the mapping is returned here.
 206  * \param size size of the mapping.
 207  * \param fd_ptr The file descriptor of the mapping.
 208  *
 209  * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
 210  * open call is closed after mmap().  Otherwise the file is kept open and the
 211  * file descriptor is returned in \a fd_ptr.
 212  *
 213  * \return Standard.
 214  *
 215  * \sa mmap(2).
 216  */
 217 int mmap_full_file(const char *path, int open_mode, void **map,
 218                 size_t *size, int *fd_ptr)
 219 {
 220         int fd, ret, mmap_prot, mmap_flags;
 221         struct stat file_status;
 222
 223         if (open_mode == O_RDONLY) {
 224                 mmap_prot = PROT_READ;
 225                 mmap_flags = MAP_PRIVATE;
 226         } else {
 227                 mmap_prot = PROT_READ | PROT_WRITE;
 228                 mmap_flags = MAP_SHARED;
 229         }
 230         ret = __open(path, open_mode, 0);
 231         if (ret < 0)
 232                 return ret;
 233         fd = ret;
 234         if (fstat(fd, &file_status) < 0) {
 235                 ret = -ERRNO_TO_ERROR(errno);
 236                 goto out;
 237         }
 238         *size = file_status.st_size;
 239         ret = -E_EMPTY;
 240         DEBUG_LOG("%s: size %zu\n", path, *size);
 241         if (!*size)
 242                 goto out;
 243         *map = mmap(NULL, *size, mmap_prot, mmap_flags, fd, 0);
 244         if (*map == MAP_FAILED) {
 245                 *map = NULL;
 246                 ret = -E_MMAP;
 247                 goto out;
 248         }
 249         ret = 1;
 250 out:
 251         if (ret < 0 || !fd_ptr)
 252                 close(fd);
 253         else
 254                 *fd_ptr = fd;
 255         return ret;
 256 }
 257
 258 /**
 259  * A wrapper for munmap(2).
 260  *
 261  * \param start The start address of the memory mapping.
 262  * \param length The size of the mapping.
 263  *
 264  * \return Positive on success, \p -E_MUNMAP on errors.
 265  *
 266  * \sa munmap(2), mmap_full_file().
 267  */
 268 int adu_munmap(void *start, size_t length)
 269 {
 270         int err;
 271         if (munmap(start, length) >= 0)
 272                 return 1;
 273         err = errno;
 274         ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
 275                 strerror(err));
 276         return -ERRNO_TO_ERROR(err);
 277 }
 278
 279 __must_check __malloc static char *adu_dirname(const char *name)
 280 {
 281         char *p, *ret;
 282
 283         if (!name || !*name)
 284                 return NULL;
 285         ret = adu_strdup(name);
 286         p = strrchr(ret, '/');
 287         if (!p)
 288                 *ret = '\0';
 289         else
 290                 *p = '\0';
 291         return ret;
 292 }
 293
 294 /**
 295  * Recursive mkdir
 296  *
 297  * \param p Full path that should be created.
 298  *
 299  * \param mode Use this mode when creating directories.
 300  *
 301  * \return 0 if successful, -E_MKDIR on errors.
 302  */
 303 int mkpath(const char *p, mode_t mode)
 304 {
 305         char *parent, *path;
 306         int ret = -E_MKDIR;
 307
 308         DEBUG_LOG("%s\n", p);
 309         if (strcmp(p, ".") == 0 || strcmp(p, "/") == 0 || strcmp(p, "") == 0) {
 310                 DEBUG_LOG("reached beginning of path\n");
 311                 return 0;
 312         }
 313         path = adu_strdup(p);
 314         parent = adu_dirname(p);
 315         if (!parent)
 316                 goto out;
 317         ret = mkpath(parent, mode);
 318         if (ret < 0)
 319                 goto out;
 320         INFO_LOG("making dir %s\n", path);
 321         ret = 0;
 322         if ((mkdir(path, mode) == -1) && (errno != EEXIST))
 323                 ret = -E_MKDIR;
 324 out:
 325         free(parent);
 326         free(path);
 327         return ret;
 328 }