Win API File abstraction calls

readlink.rb

require 'chef/win32/api/file'
require 'chef/win32/error'
require 'chef/win32/unicode'

class Chef
  module Win32
    class File
      class << self
        include Chef::Win32::API::File

        def symlink?(file_name)
          is_symlink = false
          if ((GetFileAttributesW(windows_encode_path(file_name)) & FILE_ATTRIBUTE_REPARSE_POINT) > 0)
            find_data = WIN32_FIND_DATA.new
            if FindFirstFileW(path, find_data) == INVALID_HANDLE_VALUE
              Chef::Win32::Error.raise!
            end
            if find_data[:dw_reserved_0] == IO_REPARSE_TAG_SYMLINK
              is_symlink = true
            end
          end
          is_symlink
        end

        def readlink(link_name)
          out = FFI::MemoryPointer.new MAX_PATH
          #returns 0 on failure, returns buffer size on success OR if buffer size is too small, returns needed buffer size
          #GetFilePathNameByHandle fails in interesting ways with remote paths, see:
          #http://stackoverflow.com/questions/221417/how-do-i-programmatically-access-the-target-path-of-a-windows-symbolic-link
          pointer = FFI::MemoryPointer.from_string(windows_encode_path(link_name))
          buffer_size = GetFinalPathNameByHandleW(pointer, out, out.size, FILE_NAME_NORMALIZED)
          if (buffer_size == 0 || buffer_size >= MAX_PATH)
            Chef::Win32::Error.raise! #could be misleading if problem is too small buffer size as GetLastError won't report failure
          end
          out.get_string
        end

        def windows_encode_path(path)
          ("\\\\?\\" << path).to_wstring
        end
      end
    end
  end
end