Merge pull request #109 from d0c-s4vage/hotfix/100-implement_memcmp

Added Memcmp implementation and tests

pfp/native/compat_string.py

@@ -137,7 +137,25 @@ def IntToBinaryStr(params, ctxt, scope, stream, coord):
 # int Memcmp( const uchar s1[], const uchar s2[], int n )
 @native(name="Memcmp", ret=pfp.fields.Int)
 def Memcmp(params, ctxt, scope, stream, coord):
-    raise NotImplementedError()
+    """
+    int Memcmp( const uchar s1[], const uchar s2[], int n )
+
+    Compares the first n bytes of s1 and s2. Returns a value less than zero if
+    s1 is less than s2, zero if they are equal, or a value greater than zero if
+    s1 is greater than s2.
+    """
+    if len(params) < 3:
+        raise errors.InvalidArguments(
+            coord, "{} args".format(len(params)), "3 arguments",
+        )
+    s1 = PYSTR(params[0])
+    s2 = PYSTR(params[1])
+    n = PYVAL(params[2])
+
+    s1_sub = s1[:n]
+    s2_sub = s2[:n]
+
+    return _cmp(s1_sub, s2_sub)
 
 
 # void Memcpy( uchar dest[], const uchar src[], int n, int destOffset=0, int srcOffset=0 )

tests/test_compat.py

@@ -501,6 +501,23 @@ def test_strstr2(self):
             stdout="-1",
         )
 
+    def test_memcmp(self):
+        dom = self._test_parse_build(
+            "",
+            r"""
+            local string a = "hellothere";
+            local string b = "helloblah";
+            Printf("%d\n", Memcmp(a, b, 1));
+            Printf("%d\n", Memcmp(a, b, 2));
+            Printf("%d\n", Memcmp(a, b, 3));
+            Printf("%d\n", Memcmp(a, b, 4));
+            Printf("%d\n", Memcmp(a, b, 5));
+            Printf("%d\n", Memcmp(a, b, 6));
+            Printf("%d\n", Memcmp(b, a, 6));
+            """,
+            stdout="0\n0\n0\n0\n0\n1\n-1\n",
+        )
+
 
 class TestCompatTools(utils.PfpTestCase):
     def setUp(self):