1 files changed, 48 insertions, 0 deletions
diff --git a/src/libs6rc/s6rc_lock.c b/src/libs6rc/s6rc_lock.c
new file mode 100644
index 0000000..69ec75b
--- /dev/null
+++ b/src/libs6rc/s6rc_lock.c
@@ -0,0 +1,48 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/diuint.h>
+#include <skalibs/djbunix.h>
+#include <s6-rc/s6rc-utils.h>
+
+int s6rc_lock (char const *live, int lwhat, int *llfd, char const *compiled, int cwhat, int *ccfd)
+{
+  int e ;
+  int lfd = -1, cfd = -1 ;
+
+  if (lwhat)
+  {
+    unsigned int llen = str_len(live) ;
+    char lfn[llen + 6] ;
+    byte_copy(lfn, llen, live) ;
+    byte_copy(lfn + llen, 6, "/lock") ;
+    lfd = open_create(lfn) ;
+    if (lfd < 0) return 0 ;
+    if ((lwhat > 1 ? lock_ex(lfd) : lock_sh(lfd)) < 0) { e = errno ; goto lerr ; }
+  }
+
+  if (cwhat)
+  {
+    unsigned int clen = str_len(compiled) ;
+    char cfn[clen + 6] ;
+    byte_copy(cfn, clen, compiled) ;
+    byte_copy(cfn + clen, 6, "/lock") ;
+    cfd = open_create(cfn) ;
+    if (cfd < 0)
+      if (cwhat == 1 || errno != EROFS) { e = errno ; goto lerr ; }
+      else cfd = -errno ;
+    else if ((cwhat > 1 ? lock_ex(cfd) : lock_sh(cfd)) < 0) { e = errno ; goto cerr ; }
+  }
+
+  if (lwhat) *llfd = lfd ;
+  if (cwhat) *ccfd = cfd ;
+  return 1 ;
+
+ cerr:
+  fd_close(cfd) ;
+ lerr:
+  if (lwhat) fd_close(lfd) ;
+  errno = e ;
+  return 0 ;
+}