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authorLaurent Bercot <ska-skaware@skarnet.org>2014-09-18 18:55:44 +0000
committerLaurent Bercot <ska-skaware@skarnet.org>2014-09-18 18:55:44 +0000
commit3534b428629be185e096be99e3bd5fdfe32d5544 (patch)
tree210ef3198ed66bc7f7b7bf6a85e4579f455e5a36 /src/libunixonacid/dd_commit.c
downloadskalibs-3534b428629be185e096be99e3bd5fdfe32d5544.tar.xz
initial commit with rc for skalibs-2.0.0.0
Diffstat (limited to 'src/libunixonacid/dd_commit.c')
-rw-r--r--src/libunixonacid/dd_commit.c68
1 files changed, 68 insertions, 0 deletions
diff --git a/src/libunixonacid/dd_commit.c b/src/libunixonacid/dd_commit.c
new file mode 100644
index 0000000..b55addb
--- /dev/null
+++ b/src/libunixonacid/dd_commit.c
@@ -0,0 +1,68 @@
+/* ISC license. */
+
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h> /* for rename() */
+#include <skalibs/bytestr.h>
+#include <skalibs/stralloc.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/random.h>
+#include <skalibs/unix-transactional.h>
+
+static char const *mybasename (char const *s, unsigned int len)
+{
+ register unsigned int i = len ;
+ while (i--) if (s[i] == '/') return s + i + 1 ;
+ return s ;
+}
+
+int dd_commit (dirdescriptor_t_ref dd)
+{
+ dirdescriptor_t zero = DIRDESCRIPTOR_ZERO ;
+ unsigned int len = str_len(dd->lnkfn) ;
+ unsigned int oldbase = dd->new.len ;
+ unsigned int newlnkbase ;
+ char const *lnkbn = mybasename(dd->lnkfn, len) ;
+ if (!sadirname(&dd->new, dd->lnkfn, len)) return 0 ;
+ if (!stralloc_catb(&dd->new, "/", 1)) goto fail ;
+ if (sareadlink(&dd->new, dd->lnkfn) < 0)
+ {
+ unsigned int lnkbnbase = dd->new.len ;
+ if (errno != EINVAL) goto fail ;
+ if (!stralloc_cats(&dd->new, lnkbn)) goto fail ;
+ if (random_sauniquename(&dd->new, 8) < 0) goto fail ;
+ if (!stralloc_0(&dd->new)) goto fail ;
+ if (rename(dd->lnkfn, dd->new.s + oldbase) < 0) goto fail ;
+ /* /!\ race condition right here: there's no lnkfn in the fs */
+ if (symlink(dd->new.s + lnkbnbase, dd->lnkfn) < 0) /* now that's VERY BAD if it fails */
+ {
+ register int e = errno ;
+ rename(dd->new.s + oldbase, dd->lnkfn) ; /* attempt to revert to initial situation */
+ errno = e ;
+ goto fail ; /* and hope for the best */
+ }
+ }
+ if (!stralloc_0(&dd->new)) goto fail ;
+ newlnkbase = dd->new.len ;
+ if (!stralloc_catb(&dd->new, dd->lnkfn, len)) goto fail ;
+ if (random_sauniquename(&dd->new, 8) < 0) goto fail ;
+ if (!stralloc_0(&dd->new)) goto fail ;
+ if (symlink(dd->new.s, dd->new.s + newlnkbase) < 0) goto fail ;
+ if (rename(dd->new.s + newlnkbase, dd->lnkfn) < 0)
+ {
+ register int e = errno ;
+ unlink(dd->new.s + newlnkbase) ;
+ errno = e ;
+ goto fail ;
+ }
+ fd_close(dd->fd) ;
+ dd->new.len = newlnkbase ;
+ rm_rf_in_tmp(&dd->new, oldbase) ;
+ stralloc_free(&dd->new) ;
+ *dd = zero ;
+ return 1 ;
+
+ fail:
+ dd->new.len = oldbase ;
+ return 0 ;
+}