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 ;
+}