1 files changed, 25 insertions, 0 deletions
diff --git a/src/libstddjb/fd_lock.c b/src/libstddjb/fd_lock.c
new file mode 100644
index 0000000..422e667
--- /dev/null
+++ b/src/libstddjb/fd_lock.c
@@ -0,0 +1,25 @@
+/* ISC license. */
+
+#include <fcntl.h>
+#include <errno.h>
+
+#include <skalibs/error.h>
+#include <skalibs/djbunix.h>
+
+int fd_lock (int fd, int w, int nb)
+{
+  struct flock fl =
+  {
+    .l_type = w ? F_WRLCK : F_RDLCK,
+    .l_whence = SEEK_SET,
+    .l_start = 0,
+    .l_len = 0
+  } ;
+  int e = errno ;
+  int r ;
+  do r = fcntl(fd, nb ? F_SETLK : F_SETLKW, &fl) ;
+  while (r < 0 && errno == EINTR) ;
+  return r >= 0 ? 1 :
+    errno == EACCES || error_isagain(errno) ? (errno = e, 0) :
+    -1 ;
+}