intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 46 insertions, 0 deletions

diff --git a/util/system/file_lock.cpp b/util/system/file_lock.cpp
new file mode 100644
index 00000000000..45d91282c5b
--- /dev/null
+++ b/util/system/file_lock.cpp
@@ -0,0 +1,46 @@
+#include "file_lock.h"
+#include "flock.h"
+
+#include <util/generic/yexception.h>
+
+#include <cerrno>
+
+namespace {
+    int GetMode(const EFileLockType type) {
+        switch (type) {
+            case EFileLockType::Exclusive:
+                return LOCK_EX;
+            case EFileLockType::Shared:
+                return LOCK_SH;
+            default:
+                Y_UNREACHABLE();
+        }
+        Y_UNREACHABLE();
+    }
+}
+
+TFileLock::TFileLock(const TString& filename, const EFileLockType type)
+    : TFile(filename, OpenAlways | RdOnly)
+    , Type(type)
+{
+}
+
+void TFileLock::Acquire() {
+    Flock(GetMode(Type));
+}
+
+bool TFileLock::TryAcquire() {
+    try {
+        Flock(GetMode(Type) | LOCK_NB);
+        return true;
+    } catch (const TSystemError& e) {
+        if (e.Status() != EWOULDBLOCK) {
+            throw;
+        }
+        return false;
+    }
+}
+
+void TFileLock::Release() {
+    Flock(LOCK_UN);
+}