Reimplemented status() and symlink_status() in terms of handles on Windows.

Using handles allows to reduce the number of system calls and avoids requesting
reparse point info, if the file is one. This should improve performance.

Author: Lastique

src/operations.cpp

@@ -3521,25 +3521,13 @@ file_status status(path const& p, error_code* ec)
 
 #else // defined(BOOST_POSIX_API)
 
-    DWORD attrs = ::GetFileAttributesW(p.c_str());
-    if (attrs == INVALID_FILE_ATTRIBUTES)
+    // We should first test if the file is a symlink or a reparse point. Resolving some reparse
+    // points by opening the file may fail, and status() should return file_status(reparse_file) in this case.
+    // Which is what symlink_status() returns.
+    fs::file_status st(detail::symlink_status(p, ec));
+    if (st.type() == symlink_file)
     {
-        return process_status_failure(p, ec);
-    }
-
-    perms permissions = make_permissions(p, attrs);
-
-    //  reparse point handling;
-    //    since GetFileAttributesW does not resolve symlinks, try to open a file
-    //    handle to discover if the file exists
-    if (attrs & FILE_ATTRIBUTE_REPARSE_POINT)
-    {
-        if (!is_reparse_point_a_symlink(p))
-        {
-            return file_status(reparse_file, permissions);
-        }
-
-        // try to resolve symlink
+        // Resolve the symlink
         handle_wrapper h(
             create_file_handle(
                 p.c_str(),
@@ -3551,20 +3539,36 @@ file_status status(path const& p, error_code* ec)
 
         if (h.handle == INVALID_HANDLE_VALUE)
         {
+        return_status_failure:
             return process_status_failure(p, ec);
         }
 
-        // take attributes of target
-        BY_HANDLE_FILE_INFORMATION info;
-        if (!::GetFileInformationByHandle(h.handle, &info))
+        DWORD attrs;
+        GetFileInformationByHandleEx_t* get_file_information_by_handle_ex = filesystem::detail::atomic_load_relaxed(get_file_information_by_handle_ex_api);
+        if (BOOST_LIKELY(get_file_information_by_handle_ex != NULL))
         {
-            return process_status_failure(p, ec);
+            file_attribute_tag_info info;
+            BOOL res = get_file_information_by_handle_ex(h.handle, file_attribute_tag_info_class, &info, sizeof(info));
+            if (BOOST_UNLIKELY(!res))
+                goto return_status_failure;
+
+            attrs = info.FileAttributes;
         }
+        else
+        {
+            BY_HANDLE_FILE_INFORMATION info;
+            BOOL res = ::GetFileInformationByHandle(h.handle, &info);
+            if (BOOST_UNLIKELY(!res))
+                goto return_status_failure;
 
-        attrs = info.dwFileAttributes;
+            attrs = info.dwFileAttributes;
+        }
+
+        st.permissions(make_permissions(p, attrs));
+        st.type((attrs & FILE_ATTRIBUTE_DIRECTORY) ? fs::directory_file : fs::regular_file);
     }
 
-    return (attrs & FILE_ATTRIBUTE_DIRECTORY) ? file_status(directory_file, permissions) : file_status(regular_file, permissions);
+    return st;
 
 #endif // defined(BOOST_POSIX_API)
 }
@@ -3627,18 +3631,52 @@ file_status symlink_status(path const& p, error_code* ec)
 
 #else // defined(BOOST_POSIX_API)
 
-    DWORD attrs = ::GetFileAttributesW(p.c_str());
-    if (attrs == INVALID_FILE_ATTRIBUTES)
+    handle_wrapper h(
+        create_file_handle(
+            p.c_str(),
+            0u, // dwDesiredAccess; attributes only
+            FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE,
+            NULL, // lpSecurityAttributes
+            OPEN_EXISTING,
+            FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT));
+
+    if (h.handle == INVALID_HANDLE_VALUE)
     {
+    return_status_failure:
         return process_status_failure(p, ec);
     }
 
-    perms permissions = make_permissions(p, attrs);
+    DWORD attrs;
+    fs::perms permissions;
+    GetFileInformationByHandleEx_t* get_file_information_by_handle_ex = filesystem::detail::atomic_load_relaxed(get_file_information_by_handle_ex_api);
+    if (BOOST_LIKELY(get_file_information_by_handle_ex != NULL))
+    {
+        file_attribute_tag_info info;
+        BOOL res = get_file_information_by_handle_ex(h.handle, file_attribute_tag_info_class, &info, sizeof(info));
+        if (BOOST_UNLIKELY(!res))
+            goto return_status_failure;
+
+        attrs = info.FileAttributes;
+        permissions = make_permissions(p, attrs);
 
-    if (attrs & FILE_ATTRIBUTE_REPARSE_POINT)
-        return is_reparse_point_a_symlink(p) ? file_status(symlink_file, permissions) : file_status(reparse_file, permissions);
+        if (attrs & FILE_ATTRIBUTE_REPARSE_POINT)
+            return is_reparse_point_tag_a_symlink(info.ReparseTag) ? fs::file_status(fs::symlink_file, permissions) : fs::file_status(fs::reparse_file, permissions);
+    }
+    else
+    {
+        BY_HANDLE_FILE_INFORMATION info;
+        BOOL res = ::GetFileInformationByHandle(h.handle, &info);
+        if (BOOST_UNLIKELY(!res))
+            goto return_status_failure;
+
+        attrs = info.dwFileAttributes;
+        permissions = make_permissions(p, attrs);
+
+        if (attrs & FILE_ATTRIBUTE_REPARSE_POINT)
+            return is_reparse_point_a_symlink_ioctl(h.handle) ? fs::file_status(fs::symlink_file, permissions) : fs::file_status(fs::reparse_file, permissions);
+    }
 
-    return (attrs & FILE_ATTRIBUTE_DIRECTORY) ? file_status(directory_file, permissions) : file_status(regular_file, permissions);
+    return (attrs & FILE_ATTRIBUTE_DIRECTORY) ? fs::file_status(fs::directory_file, permissions) : fs::file_status(fs::regular_file, permissions);
 
 #endif // defined(BOOST_POSIX_API)
 }