[Truffle] Add Process.euid

Author: bjfish

spec/truffle/tags/core/process/egid_tags.txt

@@ -1,5 +1,3 @@
-fails:Process.euid also goes by Process::UID.eid
-fails:Process.euid also goes by Process::Sys.geteuid
 fails:Process.euid= raises TypeError if not passed an Integer
 fails:Process.euid= raises Errno::ERPERM if run by a non superuser trying to set the superuser id
 fails:Process.euid= raises Errno::ERPERM if run by a non superuser trying to set the superuser id from username

spec/truffle/tags/core/process/euid_tags.txt

@@ -400,6 +400,69 @@ def setresuid(rid, eid, sid)
     end
   end
 
+  module UID
+    class << self
+      def change_privilege(uid)
+        uid = Rubinius::Type.coerce_to uid, Integer, :to_int
+
+        ret = FFI::Platform::POSIX.setreuid(uid, uid)
+        Errno.handle if ret == -1
+        uid
+      end
+
+      def eid
+        ret = FFI::Platform::POSIX.geteuid
+        Errno.handle if ret == -1
+        ret
+      end
+
+      def eid=(uid)
+        uid = Rubinius::Type.coerce_to uid, Integer, :to_int
+
+        ret = FFI::Platform::POSIX.seteuid(uid)
+        Errno.handle if ret == -1
+        uid
+      end
+      alias_method :grant_privilege, :eid=
+
+      def re_exchange
+        real = FFI::Platform::POSIX.getuid
+        Errno.handle if real == -1
+        eff = FFI::Platform::POSIX.geteuid
+        Errno.handle if eff == -1
+        ret = FFI::Platform::POSIX.setreuid(eff, real)
+        Errno.handle if ret == -1
+        eff
+      end
+
+      def re_exchangeable?
+        true
+      end
+
+      def rid
+        ret = FFI::Platform::POSIX.getuid
+        Errno.handle if ret == -1
+        ret
+      end
+
+      def sid_available?
+        true
+      end
+
+      def switch
+        eff = re_exchange
+        if block_given?
+          ret = yield
+          re_exchange
+          return ret
+        else
+          return eff
+        end
+      end
+
+    end
+  end
+
   module GID
     class << self
       def change_privilege(gid)