Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10' r/724

git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1adf74a3706efbcb0ea4625da106fb2
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10

1 files changed, 38 insertions, 0 deletions

diff --git a/third_party/nix/src/libstore/pathlocks.hh b/third_party/nix/src/libstore/pathlocks.hh
new file mode 100644
index 000000000000..411da022295d
--- /dev/null
+++ b/third_party/nix/src/libstore/pathlocks.hh
@@ -0,0 +1,38 @@
+#pragma once
+
+#include "util.hh"
+
+namespace nix {
+
+/* Open (possibly create) a lock file and return the file descriptor.
+   -1 is returned if create is false and the lock could not be opened
+   because it doesn't exist.  Any other error throws an exception. */
+AutoCloseFD openLockFile(const Path & path, bool create);
+
+/* Delete an open lock file. */
+void deleteLockFile(const Path & path, int fd);
+
+enum LockType { ltRead, ltWrite, ltNone };
+
+bool lockFile(int fd, LockType lockType, bool wait);
+
+class PathLocks
+{
+private:
+    typedef std::pair<int, Path> FDPair;
+    list<FDPair> fds;
+    bool deletePaths;
+
+public:
+    PathLocks();
+    PathLocks(const PathSet & paths,
+        const string & waitMsg = "");
+    bool lockPaths(const PathSet & _paths,
+        const string & waitMsg = "",
+        bool wait = true);
+    ~PathLocks();
+    void unlock();
+    void setDeletion(bool deletePaths);
+};
+
+}