added readlink to Chef::Win32::File

2 files changed, 71 insertions, 1 deletions

diff --git a/chef/lib/chef/win32/api/file.rb b/chef/lib/chef/win32/api/file.rb
index f0ef9fba49..5f1c5fc901 100644
--- a/chef/lib/chef/win32/api/file.rb
+++ b/chef/lib/chef/win32/api/file.rb
@@ -49,6 +49,13 @@ class Chef
 
         SYMBOLIC_LINK_FLAG_DIRECTORY = 0x1
 
+        FILE_NAME_NORMALIZED = 0x0
+        FILE_NAME_OPENED = 0x8
+
+        # TODO add the rest of these CONSTS
+        FILE_SHARE_READ = 0x00000001
+        OPEN_EXISTING = 3
+
 =begin
 typedef struct _FILETIME {
   DWORD dwLowDateTime;
@@ -101,6 +108,19 @@ typedef struct _WIN32_FIND_DATA {
         end
 
 =begin
+HANDLE WINAPI CreateFile(
+  __in      LPCTSTR lpFileName,
+  __in      DWORD dwDesiredAccess,
+  __in      DWORD dwShareMode,
+  __in_opt  LPSECURITY_ATTRIBUTES lpSecurityAttributes,
+  __in      DWORD dwCreationDisposition,
+  __in      DWORD dwFlagsAndAttributes,
+  __in_opt  HANDLE hTemplateFile
+);
+=end
+        attach_function :CreateFileW, [:LPCTSTR, :DWORD, :DWORD, :LPSECURITY_ATTRIBUTES, :DWORD, :DWORD, :pointer], :HANDLE
+
+=begin
 BOOL WINAPI FindClose(
   __inout  HANDLE hFindFile
 );
@@ -113,6 +133,17 @@ DWORD WINAPI GetFileAttributes(
 );
 =end
         attach_function :GetFileAttributesW, [:LPCWSTR], :DWORD
+
+=begin
+DWORD WINAPI GetFinalPathNameByHandle(
+  __in   HANDLE hFile,
+  __out  LPTSTR lpszFilePath,
+  __in   DWORD cchFilePath,
+  __in   DWORD dwFlags
+);
+=end
+        attach_function :GetFinalPathNameByHandleW, [:HANDLE, :LPTSTR, :DWORD, :DWORD], :DWORD
+
 =begin
 HANDLE WINAPI FindFirstFile(
   __in   LPCTSTR lpFileName,
diff --git a/chef/lib/chef/win32/file.rb b/chef/lib/chef/win32/file.rb
index 86f8505931..b330a6bc95 100644
--- a/chef/lib/chef/win32/file.rb
+++ b/chef/lib/chef/win32/file.rb
@@ -18,6 +18,7 @@
 #
 
 require 'chef/win32/api/file'
+require 'chef/win32/api/security'
 require 'chef/win32/error'
 require 'chef/win32/unicode'
 
@@ -27,6 +28,7 @@ class Chef
 
       class << self
         include Chef::Win32::API::File
+        include Chef::Win32::API::Security
 
         # Creates a symbolic link called +new_name+ for the file or directory
         # +old_name+.
@@ -79,6 +81,24 @@ class Chef
           is_symlink
         end
 
+        # Returns the path of the of the symbolic link referred to by +file+.
+        #
+        # Requires Windows Vista or later. On older versions of Windows it
+        # will raise a NotImplementedError, as per MRI.
+        #
+        def readlink(link_name)
+          # TODO do a check for GetFinalPathNameByHandleW and
+          # raise NotImplemented exception on older Windows
+          open_file(link_name) do |handle|
+            buffer = FFI::MemoryPointer.new(0.chr * MAX_PATH)
+            num_chars = GetFinalPathNameByHandleW(handle, buffer, buffer.size, FILE_NAME_NORMALIZED)
+            if num_chars == 0
+              Chef::Win32::Error.raise! #could be misleading if problem is too small buffer size as GetLastError won't report failure
+            end
+            buffer.read_wstring(num_chars).sub(path_prepender, "")
+          end
+        end
+
         private
 
         # takes the given path pre-pends "\\?\" and
@@ -86,7 +106,11 @@ class Chef
         # to be passed to the *W vesion of WinAPI File
         # functions
         def encode_path(path)
-          ("\\\\?\\" << path).to_wstring
+          (path_prepender << path).to_wstring
+        end
+
+        def path_prepender
+          "\\\\?\\"
         end
 
         # retrieves a file search handle and passes it
@@ -106,6 +130,21 @@ class Chef
           end
         end
 
+        def open_file(path, &block)
+          begin
+            path = encode_path(path)
+            handle = CreateFileW(path, GENERIC_READ, FILE_SHARE_READ,
+                                  nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nil)
+
+            if handle == INVALID_HANDLE_VALUE
+              Chef::Win32::Error.raise!
+            end
+            block.call(handle)
+          ensure
+            FindClose(handle) if handle && handle != INVALID_HANDLE_VALUE
+          end
+        end
+
       end
 
     end