Diff functions

src/util/Diff.py

@@ -0,0 +1,44 @@
+import cStringIO as StringIO
+
+import difflib
+
+
+def sumLen(lines):
+    return sum(map(len, lines))
+
+
+def diff(old, new, limit=False):
+    matcher = difflib.SequenceMatcher(None, old, new)
+    actions = []
+    size = 0
+    for tag, old_from, old_to, new_from, new_to in matcher.get_opcodes():
+        if tag == "insert":
+            new_line = new[new_from:new_to]
+            actions.append(("+", new_line))
+            size += sum(map(len, new_line))
+        elif tag == "equal":
+            actions.append(("=", sumLen(old[old_from:old_to])))
+        elif tag == "delete":
+            actions.append(("-", sumLen(old[old_from:old_to])))
+        elif tag == "replace":
+            actions.append(("-", sumLen(old[old_from:old_to])))
+            new_lines = new[new_from:new_to]
+            actions.append(("+", new_lines))
+            size += sumLen(new_lines)
+        if limit and size > limit:
+            return False
+    return actions
+
+
+def patch(old_f, actions):
+    new_f = StringIO.StringIO()
+    for action, param in actions:
+        if action == "=":  # Same lines
+            new_f.write(old_f.read(param))
+        elif action == "-":  # Delete lines
+            old_f.seek(param, 1)  # Seek from current position
+            continue
+        elif action == "+":  # Add lines
+            for add_line in param:
+                new_f.write(add_line)
+    return new_f