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Diffstat (limited to 'lib/replace/repdir_getdents.c')
| -rw-r--r-- | lib/replace/repdir_getdents.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/lib/replace/repdir_getdents.c b/lib/replace/repdir_getdents.c new file mode 100644 index 0000000000..afc634a796 --- /dev/null +++ b/lib/replace/repdir_getdents.c @@ -0,0 +1,166 @@ +/* + Unix SMB/CIFS implementation. + + Copyright (C) Andrew Tridgell 2005 + + ** NOTE! The following LGPL license applies to the replace + ** library. This does NOT imply that all of Samba is released + ** under the LGPL + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 3 of the License, or (at your option) any later version. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with this library; if not, see <http://www.gnu.org/licenses/>. +*/ +/* + a replacement for opendir/readdir/telldir/seekdir/closedir for BSD systems + + This is needed because the existing directory handling in FreeBSD + and OpenBSD (and possibly NetBSD) doesn't correctly handle unlink() + on files in a directory where telldir() has been used. On a block + boundary it will occasionally miss a file when seekdir() is used to + return to a position previously recorded with telldir(). + + This also fixes a severe performance and memory usage problem with + telldir() on BSD systems. Each call to telldir() in BSD adds an + entry to a linked list, and those entries are cleaned up on + closedir(). This means with a large directory closedir() can take an + arbitrary amount of time, causing network timeouts as millions of + telldir() entries are freed + + Note! This replacement code is not portable. It relies on getdents() + always leaving the file descriptor at a seek offset that is a + multiple of DIR_BUF_SIZE. If the code detects that this doesn't + happen then it will abort(). It also does not handle directories + with offsets larger than can be stored in a long, + + This code is available under other free software licenses as + well. Contact the author. +*/ + +#include <stdlib.h> +#include <sys/stat.h> +#include <unistd.h> +#include <sys/types.h> +#include <errno.h> +#include <fcntl.h> +#include <dirent.h> + +#define DIR_BUF_BITS 9 +#define DIR_BUF_SIZE (1<<DIR_BUF_BITS) + +struct dir_buf { + int fd; + int nbytes, ofs; + off_t seekpos; + char buf[DIR_BUF_SIZE]; +}; + +DIR *opendir(const char *dname) +{ + struct dir_buf *d; + struct stat sb; + d = malloc(sizeof(*d)); + if (d == NULL) { + errno = ENOMEM; + return NULL; + } + d->fd = open(dname, O_RDONLY); + if (d->fd == -1) { + free(d); + return NULL; + } + if (fstat(d->fd, &sb) < 0) { + close(d->fd); + free(d); + return NULL; + } + if (!S_ISDIR(sb.st_mode)) { + close(d->fd); + free(d); + errno = ENOTDIR; + return NULL; + } + d->ofs = 0; + d->seekpos = 0; + d->nbytes = 0; + return (DIR *)d; +} + +struct dirent *readdir(DIR *dir) +{ + struct dir_buf *d = (struct dir_buf *)dir; + struct dirent *de; + + if (d->ofs >= d->nbytes) { + d->seekpos = lseek(d->fd, 0, SEEK_CUR); + d->nbytes = getdents(d->fd, d->buf, DIR_BUF_SIZE); + d->ofs = 0; + } + if (d->ofs >= d->nbytes) { + return NULL; + } + de = (struct dirent *)&d->buf[d->ofs]; + d->ofs += de->d_reclen; + return de; +} + +long telldir(DIR *dir) +{ + struct dir_buf *d = (struct dir_buf *)dir; + if (d->ofs >= d->nbytes) { + d->seekpos = lseek(d->fd, 0, SEEK_CUR); + d->ofs = 0; + d->nbytes = 0; + } + /* this relies on seekpos always being a multiple of + DIR_BUF_SIZE. Is that always true on BSD systems? */ + if (d->seekpos & (DIR_BUF_SIZE-1)) { + abort(); + } + return d->seekpos + d->ofs; +} + +void seekdir(DIR *dir, long ofs) +{ + struct dir_buf *d = (struct dir_buf *)dir; + d->seekpos = lseek(d->fd, ofs & ~(DIR_BUF_SIZE-1), SEEK_SET); + d->nbytes = getdents(d->fd, d->buf, DIR_BUF_SIZE); + d->ofs = 0; + while (d->ofs < (ofs & (DIR_BUF_SIZE-1))) { + if (readdir(dir) == NULL) break; + } +} + +void rewinddir(DIR *dir) +{ + seekdir(dir, 0); +} + +int closedir(DIR *dir) +{ + struct dir_buf *d = (struct dir_buf *)dir; + int r = close(d->fd); + if (r != 0) { + return r; + } + free(d); + return 0; +} + +#ifndef dirfd +/* darn, this is a macro on some systems. */ +int dirfd(DIR *dir) +{ + struct dir_buf *d = (struct dir_buf *)dir; + return d->fd; +} +#endif |