diff --git a/mercurial/mdiff.py b/mercurial/mdiff.py
new file mode 100644
--- /dev/null
+++ b/mercurial/mdiff.py
@@ -0,0 +1,76 @@
+#!/usr/bin/python
+import difflib, struct
+from cStringIO import StringIO
+
+def unidiff(a, b, fn):
+    a = a.splitlines(1)
+    b = b.splitlines(1)
+    l = difflib.unified_diff(a, b, fn, fn)
+    return "".join(l)
+
+def textdiff(a, b):
+    return diff(a.splitlines(1), b.splitlines(1))
+
+def sortdiff(a, b):
+    la = lb = 0
+
+    while 1:
+        if la >= len(a) or lb >= len(b): break
+        if b[lb] < a[la]:
+            si = lb
+            while lb < len(b) and b[lb] < a[la] : lb += 1
+            yield "insert", la, la, si, lb
+        elif a[la] < b[lb]:
+            si = la
+            while la < len(a) and a[la] < b[lb]: la += 1
+            yield "delete", si, la, lb, lb
+        else:
+            la += 1
+            lb += 1
+
+    si = lb
+    while lb < len(b):
+        lb += 1
+        yield "insert", la, la, si, lb
+
+    si = la
+    while la < len(a):
+        la += 1
+        yield "delete", si, la, lb, lb
+
+def diff(a, b, sorted=0):
+    bin = []
+    p = [0]
+    for i in a: p.append(p[-1] + len(i))
+
+    if sorted:
+        d = sortdiff(a, b)
+    else:
+        d = difflib.SequenceMatcher(None, a, b).get_opcodes()
+
+    for o, m, n, s, t in d:
+        if o == 'equal': continue
+        s = "".join(b[s:t])
+        bin.append(struct.pack(">lll", p[m], p[n], len(s)) + s)
+
+    return "".join(bin)
+
+def patch(a, bin):
+    last = pos = 0
+    r = []
+
+    while pos < len(bin):
+        p1, p2, l = struct.unpack(">lll", bin[pos:pos + 12])
+        pos += 12
+        r.append(a[last:p1])
+        r.append(bin[pos:pos + l])
+        pos += l
+        last = p2
+    r.append(a[last:])
+
+    return "".join(r)
+
+
+
+
+