+/**
+ * Wrapper for the open(2) system call.
+ *
+ * \param path The filename.
+ * \param flags The usual open(2) flags.
+ * \param mode Specifies the permissions to use.
+ *
+ * The mode parameter must be specified when O_CREAT is in the flags, and is ignored
+ * otherwise.
+ *
+ * \return Positive on success, negative on errors.
+ *
+ * \sa open(2).
+ */
+int para_open(const char *path, int flags, mode_t mode)
+{
+ int ret = open(path, flags, mode);
+
+ if (ret >= 0)
+ return ret;
+ switch (errno) {
+ case EEXIST:
+ ret = -E_EXIST;
+ break;
+ case EISDIR:
+ ret = -E_ISDIR;
+ break;
+ case ENOENT:
+ ret = -E_NOENT;
+ break;
+ case EPERM:
+ ret = -E_OPEN_PERM;
+ break;
+ };
+ PARA_ERROR_LOG("failed to open %s: %s\n", path, strerror(errno));
+ return ret;
+}
+
+/**
+ * Save the cwd and open a given directory.
+ *
+ * \param dirname Path to the directory to open.
+ * \param dir Result pointer.
+ * \param cwd File descriptor of the current working directory.
+ *
+ * \return Positive on success, negative on errors.
+ *
+ * Opening the current directory (".") and calling fchdir() to return is
+ * usually faster and more reliable than saving cwd in some buffer and calling
+ * chdir() afterwards.
+ *
+ * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
+ * stored in \a cwd. If the function returns success, and \a cwd is not \p
+ * NULL, the caller must close this file descriptor (probably after calling
+ * fchdir(*cwd)).
+ *
+ * On errors, the function undos everything, so the caller needs neither close
+ * any files, nor change back to the original working directory.
+ *
+ * \sa getcwd(3).
+ *
+ */
+int para_opendir(const char *dirname, DIR **dir, int *cwd)
+{
+ int ret;
+
+ if (cwd) {
+ ret = para_open(".", O_RDONLY, 0);
+ if (ret < 0)
+ return ret;
+ *cwd = ret;
+ }
+ ret = -E_CHDIR;
+ if (chdir(dirname) < 0)
+ goto close_cwd;
+ ret = -E_OPENDIR;
+ *dir = opendir(".");
+ if (!*dir)
+ goto change_to_orig_dir;
+ return 1;
+/* Ignore return value of fchdir() and close(). We're busted anyway. */
+change_to_orig_dir:
+ if (cwd)
+ fchdir(*cwd);
+close_cwd:
+ if (cwd)
+ close(*cwd);
+ return ret;
+}
+
+/**
+ * A wrapper for fchdir().
+ *
+ * \param fd An open file descriptor
+ *
+ * \return Positive on success, negative on errors.
+ */
+int para_fchdir(int fd)
+{
+ if (fchdir(fd) < 0)
+ return -E_FCHDIR;
+ return 1;
+}
+
+/**
+ * A wrapper for mkdir(2).
+ *
+ * \param path Name of the directory to create.
+ * \param mode The permissions to use.
+ *
+ * \return positive on success, negative on errors.
+ */
+int para_mkdir(const char *path, mode_t mode)
+{
+ if (!mkdir(path, mode))
+ return 1;
+ if (errno == EEXIST)
+ return -E_EXIST;
+ if (errno == ENOSPC)
+ return -E_NOSPC;
+ if (errno == ENOTDIR)
+ return -E_NOTDIR;
+ if (errno == EPERM)
+ return -E_MKDIR_PERM;
+ return -E_MKDIR;
+}