Add mkntemp, atomic_symlink4

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

2 files changed, 45 insertions, 32 deletions

diff --git a/src/libunixonacid/atomic_symlink.c b/src/libunixonacid/atomic_symlink.c
index a4c7ecf..13e82e6 100644
--- a/src/libunixonacid/atomic_symlink.c
+++ b/src/libunixonacid/atomic_symlink.c
@@ -1,39 +1,9 @@
 /* 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_symlink (char const *target, char const *name, char const *suffix)
 {
-  {
-    int e = errno ;
-    if (symlink(target, name) == 0) return 1 ;
-    if (errno != EEXIST) return 0 ;
-    errno = e ;
-  }
-  {
-    size_t namelen = strlen(name) ;
-    size_t suffixlen = suffix ? strlen(suffix) + 1 : 0 ;
-    char tmp[namelen + suffixlen + 8] ;
-    memcpy(tmp, name, namelen) ;
-    if (suffix)
-    {
-      tmp[namelen] = ':' ;
-      memcpy(tmp + namelen + 1, suffix, suffixlen - 1) ;
-    }
-    memcpy(tmp + namelen + suffixlen, ":XXXXXX", 7) ;
-    tmp[namelen + suffixlen + 7] = 0 ;
-    if (mkltemp(target, tmp) == -1) return 0 ;
-    if (rename(tmp, name) < 0)
-    {
-      unlink_void(tmp) ;
-      return 0 ;
-    }
-  }
-  return 1 ;
+  (void)suffix ;
+  return atomic_symlink4(target, name, 0, 0) ;
 }
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 ;
+}