From de9ad62412ecf8071d2ba7e09a9cbb0bdbe2f82b Mon Sep 17 00:00:00 2001
From: Mike Auty <mike.auty@gmail.com>
Date: Thu, 8 Mar 2018 00:26:25 +0000
Subject: [PATCH] Add in support for AbsentValues.

---
 volatility/framework/interfaces/renderers.py | 10 +++++++-
 volatility/framework/renderers/__init__.py   | 14 ++++++++++-
 volatility/framework/renderers/text.py       | 26 +++++++++++++++-----
 3 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/volatility/framework/interfaces/renderers.py b/volatility/framework/interfaces/renderers.py
index b3c40e54b..cb9ec1407 100644
--- a/volatility/framework/interfaces/renderers.py
+++ b/volatility/framework/interfaces/renderers.py
@@ -73,9 +73,17 @@ class TreeNode(collections.Sequence, metaclass = ABCMeta):
         """
 
 
+class BaseAbsentValue(object):
+    """Class that represents values which are not present for some reason"""
+
+
 _Type = typing.TypeVar("_Type")
 ColumnsType = typing.List[typing.Tuple[str, typing.Type]]
-SimpleTypes = typing.Union[typing.Type[int], typing.Type[str], typing.Type[float], typing.Type[bytes]]
+SimpleTypes = typing.Union[typing.Type[int],
+                           typing.Type[str],
+                           typing.Type[float],
+                           typing.Type[bytes],
+                           typing.Type[BaseAbsentValue]]
 VisitorSignature = typing.Callable[[TreeNode, _Type], _Type]
 
 
diff --git a/volatility/framework/renderers/__init__.py b/volatility/framework/renderers/__init__.py
index c6ca3ac1b..aabb141d7 100644
--- a/volatility/framework/renderers/__init__.py
+++ b/volatility/framework/renderers/__init__.py
@@ -8,6 +8,18 @@ import typing
 from volatility.framework import interfaces
 
 
+class UnreadableValue(interfaces.renderers.BaseAbsentValue):
+    """Class that represents values which are empty because the data cannot be read"""
+
+
+class UnparsableValue(interfaces.renderers.BaseAbsentValue):
+    """Class that represents values which are empty because the data cannot be interpreted correctly"""
+
+
+class NotApplicableValue(interfaces.renderers.BaseAbsentValue):
+    """Class that represents values which are empty because they don't make sense for this node"""
+
+
 class TreeNode(interfaces.renderers.TreeNode):
     """Class representing a particular node in a tree grid"""
 
@@ -40,7 +52,7 @@ class TreeNode(interfaces.renderers.TreeNode):
                 "Values must be a list of objects made up of simple types and number the same as the columns")
         for index in range(len(self._treegrid.columns)):
             column = self._treegrid.columns[index]
-            if not isinstance(values[index], column.type):
+            if not isinstance(values[index], (column.type, interfaces.renderers.BaseAbsentValue)):
                 raise TypeError(
                     "Values item with index {} is the wrong type for column {} (got {} but expected {})".format(
                         index,
diff --git a/volatility/framework/renderers/text.py b/volatility/framework/renderers/text.py
index b4dd6e299..59a6ce203 100644
--- a/volatility/framework/renderers/text.py
+++ b/volatility/framework/renderers/text.py
@@ -1,6 +1,7 @@
 import sys
+import typing
 
-from volatility.framework import interfaces
+from volatility.framework import interfaces, renderers
 from volatility.framework.renderers import format_hints
 
 
@@ -24,12 +25,25 @@ def hex_bytes_as_text(value: bytes) -> str:
     return output
 
 
+class Optional(object):
+    def __init__(self, func: typing.Callable[[typing.Any], str]) -> None:
+        self._func = func
+
+    def __call__(self, x: typing.Any) -> str:
+        if isinstance(x, interfaces.renderers.BaseAbsentValue):
+            if isinstance(x, renderers.NotApplicableValue):
+                return "N/A"
+            else:
+                return "-"
+        return self._func(x)
+
+
 class QuickTextRenderer(interfaces.renderers.Renderer):
-    type_renderers = {format_hints.Bin: lambda x: "0b{:b}".format(x),
-                      format_hints.Hex: lambda x: "0x{:x}".format(x),
-                      format_hints.HexBytes: hex_bytes_as_text,
-                      bytes: lambda x: x.decode("utf-8"),
-                      'default': lambda x: "{}".format(x)}
+    type_renderers = {format_hints.Bin: Optional(lambda x: "0b{:b}".format(x)),
+                      format_hints.Hex: Optional(lambda x: "0x{:x}".format(x)),
+                      format_hints.HexBytes: Optional(hex_bytes_as_text),
+                      bytes: Optional(lambda x: x.decode("utf-8")),
+                      'default': Optional(lambda x: "{}".format(x))}
 
     def __init__(self, options = None) -> None:
         super().__init__(options)