Add mkntemp, atomic_symlink4

Signed-off-by: Laurent Bercot <ska@appnovation.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/src/libunixonacid/atomic_symlink4.c b/src/libunixonacid/atomic_symlink4.c
new file mode 100644
index 0000000..7b18a5e
--- /dev/null
+++ b/src/libunixonacid/atomic_symlink4.c
@@ -0,0 +1,43 @@
+/* ISC license. */
+
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
+
+#include <skalibs/posixplz.h>
+#include <skalibs/unix-transactional.h>
+
+int atomic_symlink4 (char const *target, char const *name, char *oldbuf, size_t oldlen)
+{
+  {
+    int e = errno ;
+    if (symlink(target, name) == 0)
+    {
+      if (oldbuf && oldlen) *oldbuf = 0 ;
+      return 1 ;
+    }
+    if (errno != EEXIST) return 0 ;
+    errno = e ;
+  }
+  {
+    size_t namelen = strlen(name) ;
+    char tmp[namelen + 32] ;
+    if (oldbuf && oldlen)
+    {
+      ssize_t r = readlink(name, oldbuf, oldlen) ;
+      if (r == -1) return 0 ;
+      if (r >= oldlen) return (errno = ENAMETOOLONG, 0) ;
+      oldbuf[r] = 0 ;
+    }
+    memcpy(tmp, name, namelen) ;
+    memcpy(tmp + namelen, ":skalibs-atomic_symlink4:XXXXXX", 32) ;
+    if (mkltemp(target, tmp) == -1) return 0 ;
+    if (rename(tmp, name) == -1)
+    {
+      unlink_void(tmp) ;
+      return 0 ;
+    }
+  }
+  return 1 ;
+}