From dcccba655fe848564e961b3f285ce3a82d3ac73a Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Sat, 7 Mar 2020 14:07:28 +0300
Subject: Add more support for symlinks on Windows

See mksymlink() for details of the symlinks support on Windows.
---
 libbutl/win32-utility.hxx | 81 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

(limited to 'libbutl/win32-utility.hxx')

diff --git a/libbutl/win32-utility.hxx b/libbutl/win32-utility.hxx
index 70aafc4..b71eb1a 100644
--- a/libbutl/win32-utility.hxx
+++ b/libbutl/win32-utility.hxx
@@ -43,6 +43,86 @@ namespace butl
 {
   namespace win32
   {
+    // RAII type for handles. Note that failure to close the handle is
+    // silently ignored by both the destructor and reset().
+    //
+    // The handle can be INVALID_HANDLE_VALUE. Such a handle is treated as
+    // unopened and is not closed.
+    //
+    struct nullhandle_t
+    {
+      constexpr explicit nullhandle_t (HANDLE) {}
+      operator HANDLE () const {return INVALID_HANDLE_VALUE;}
+    };
+
+    LIBBUTL_SYMEXPORT extern const nullhandle_t nullhandle;
+
+    class LIBBUTL_SYMEXPORT auto_handle
+    {
+    public:
+      auto_handle (nullhandle_t = nullhandle) noexcept
+        : handle_ (INVALID_HANDLE_VALUE) {}
+
+      explicit
+      auto_handle (HANDLE h) noexcept: handle_ (h) {}
+
+      auto_handle (auto_handle&& h) noexcept: handle_ (h.release ()) {}
+      auto_handle& operator= (auto_handle&&) noexcept;
+
+      auto_handle (const auto_handle&) = delete;
+      auto_handle& operator= (const auto_handle&) = delete;
+
+      ~auto_handle () noexcept;
+
+      HANDLE
+      get () const noexcept {return handle_;}
+
+      void
+      reset (HANDLE h = INVALID_HANDLE_VALUE) noexcept;
+
+      HANDLE
+      release () noexcept
+      {
+        HANDLE r (handle_);
+        handle_ = INVALID_HANDLE_VALUE;
+        return r;
+      }
+
+      // Close an open handle. Throw std::system_error on the underlying OS
+      // error. Reset the descriptor to INVALID_HANDLE_VALUE whether the
+      // exception is thrown or not.
+      //
+      void
+      close ();
+
+    private:
+      HANDLE handle_;
+    };
+
+    inline bool
+    operator== (const auto_handle& x, const auto_handle& y)
+    {
+      return x.get () == y.get ();
+    }
+
+    inline bool
+    operator!= (const auto_handle& x, const auto_handle& y)
+    {
+      return !(x == y);
+    }
+
+    inline bool
+    operator== (const auto_handle& x, nullhandle_t)
+    {
+      return x.get () == INVALID_HANDLE_VALUE;
+    }
+
+    inline bool
+    operator!= (const auto_handle& x, nullhandle_t y)
+    {
+      return !(x == y);
+    }
+
     LIBBUTL_SYMEXPORT std::string
     error_msg (DWORD code);
 
@@ -51,4 +131,5 @@ namespace butl
   }
 };
 
+#include <libbutl/win32-utility.ixx>
 #endif // _WIN32
-- 
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