From efd154a6af61e80be1b0c46642cefd73cc83d7ed Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 29 Sep 2015 13:04:29 +0200
Subject: Add auto_rmfile and auto_rmdir

---
 butl/filesystem     | 48 ++++++++++++++++++++++++++++++++++++++++--------
 butl/filesystem.cxx |  8 ++++----
 butl/filesystem.ixx | 35 +++++++++++++++++++++++++++++++++--
 3 files changed, 77 insertions(+), 14 deletions(-)

diff --git a/butl/filesystem b/butl/filesystem
index 5b1c656..c3340d7 100644
--- a/butl/filesystem
+++ b/butl/filesystem
@@ -55,20 +55,20 @@ namespace butl
   mkdir_status
   try_mkdir_p (const dir_path&, mode_t = 0777);
 
-  // Try to remove the directory returning not_exist if it does not
-  // exist and not_empty if it is not empty. All other errors are
-  // reported by throwing std::system_error.
+  // Try to remove the directory returning not_exist if it does not exist
+  // and not_empty if it is not empty. Unless ignore_error is true, all
+  // other errors are reported by throwing std::system_error.
   //
   enum class rmdir_status {success, not_exist, not_empty};
 
   rmdir_status
-  try_rmdir (const dir_path&);
+  try_rmdir (const dir_path&, bool ignore_error = false);
 
   // The '-r' (recursive) version of the above. Note that it will
   // never return not_empty.
   //
   rmdir_status
-  try_rmdir_r (const dir_path&);
+  try_rmdir_r (const dir_path&, bool ignore_error = false);
 
   // As above but throws rather than returns not_exist if the directory
   // does not exist, so check before calling. If the second argument is
@@ -78,13 +78,45 @@ namespace butl
   rmdir_r (const dir_path&, bool dir = true);
 
   // Try to remove the file (or symlinks) returning not_exist if
-  // it does not exist. All other errors are reported by throwing
-  // std::system_error.
+  // it does not exist. Unless ignore_error is true, all other
+  // errors are reported by throwing std::system_error.
   //
   enum class rmfile_status {success, not_exist};
 
   rmfile_status
-  try_rmfile (const path&);
+  try_rmfile (const path&, bool ignore_error = false);
+
+  // Automatically try to remove the path on destruction unless cancelled.
+  // Since the non-cancelled destruction will normally happen as a result
+  // of an exception, the failure to remove the path is silently ignored.
+  //
+  template <typename P>
+  struct auto_rm
+  {
+    explicit
+    auto_rm (P p = P ()): path_ (std::move (p)) {}
+
+    void
+    cancel () {path_ = P ();}
+
+    const P&
+    path () {return path_;}
+
+    // Movable-only type. Move-assignment cancels the lhs object.
+    //
+    auto_rm (auto_rm&&);
+    auto_rm& operator= (auto_rm&&);
+    auto_rm (const auto_rm&) = delete;
+    auto_rm& operator= (const auto_rm&) = delete;
+
+    ~auto_rm ();
+
+  private:
+    P path_;
+  };
+
+  using auto_rmfile = auto_rm<path>;
+  using auto_rmdir = auto_rm<dir_path>; // Note: recursive (rm_r).
 
   // Return timestamp_nonexistent if the entry at the specified path
   // does not exist or is not a path. All other errors are reported
diff --git a/butl/filesystem.cxx b/butl/filesystem.cxx
index f1341ee..5a43cd2 100644
--- a/butl/filesystem.cxx
+++ b/butl/filesystem.cxx
@@ -81,7 +81,7 @@ namespace butl
   }
 
   rmdir_status
-  try_rmdir (const dir_path& p)
+  try_rmdir (const dir_path& p, bool ignore_error)
   {
     rmdir_status r (rmdir_status::success);
 
@@ -91,7 +91,7 @@ namespace butl
         r = rmdir_status::not_exist;
       else if (errno == ENOTEMPTY || errno == EEXIST)
         r = rmdir_status::not_empty;
-      else
+      else if (!ignore_error)
         throw system_error (errno, system_category ());
     }
 
@@ -125,7 +125,7 @@ namespace butl
   }
 
   rmfile_status
-  try_rmfile (const path& p)
+  try_rmfile (const path& p, bool ignore_error)
   {
     rmfile_status r (rmfile_status::success);
 
@@ -133,7 +133,7 @@ namespace butl
     {
       if (errno == ENOENT || errno == ENOTDIR)
         r = rmfile_status::not_exist;
-      else
+      else if (!ignore_error)
         throw system_error (errno, system_category ());
     }
 
diff --git a/butl/filesystem.ixx b/butl/filesystem.ixx
index 256cbba..3b72b4a 100644
--- a/butl/filesystem.ixx
+++ b/butl/filesystem.ixx
@@ -5,16 +5,47 @@
 namespace butl
 {
   inline rmdir_status
-  try_rmdir_r (const dir_path& p)
+  try_rmdir_r (const dir_path& p, bool ignore_error)
   {
     bool e (dir_exists (p)); //@@ What if it exists but is not a directory?
 
     if (e)
-      rmdir_r (p);
+      rmdir_r (p, ignore_error);
 
     return e ? rmdir_status::success : rmdir_status::not_exist;
   }
 
+  // auto_rm
+  //
+  template <typename P>
+  inline auto_rm<P>::
+  auto_rm (auto_rm&& x)
+      : path_ (std::move (x.path_))
+  {
+    x.cancel ();
+  }
+
+  template <typename P>
+  inline auto_rm<P>& auto_rm<P>::
+  operator= (auto_rm&& x)
+  {
+    if (this != &x)
+    {
+      path_ = std::move (x.path_);
+      x.cancel ();
+    }
+
+    return *this;
+  }
+
+  template <>
+  inline auto_rm<path>::
+  ~auto_rm () {if (!path_.empty ()) try_rmfile (path_, true);}
+
+  template <>
+  inline auto_rm<dir_path>::
+  ~auto_rm () {if (!path_.empty ()) try_rmdir_r (path_, true);}
+
   // permissions
   //
   inline permissions operator& (permissions x, permissions y) {return x &= y;}
-- 
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