--- a/mercurial/pure/mpatch.py	Fri Jul 22 17:28:05 2016 +0200
+++ b/mercurial/pure/mpatch.py	Mon Jul 25 15:10:52 2016 +0200
@@ -9,8 +9,10 @@
 
 import struct
 
-from . import pycompat
+from . import policy, pycompat
 stringio = pycompat.stringio
+modulepolicy = policy.policy
+policynocffi = policy.policynocffi
 
 class mpatchError(Exception):
     """error raised when a delta cannot be decoded
@@ -125,3 +127,44 @@
 
     outlen += orig - last
     return outlen
+
+if modulepolicy not in policynocffi:
+    try:
+        from _mpatch_cffi import ffi, lib
+    except ImportError:
+        if modulepolicy == 'cffi': # strict cffi import
+            raise
+    else:
+        @ffi.def_extern()
+        def cffi_get_next_item(arg, pos):
+            all, bins = ffi.from_handle(arg)
+            container = ffi.new("struct mpatch_flist*[1]")
+            to_pass = ffi.new("char[]", str(bins[pos]))
+            all.append(to_pass)
+            r = lib.mpatch_decode(to_pass, len(to_pass) - 1, container)
+            if r < 0:
+                return ffi.NULL
+            return container[0]
+
+        def patches(text, bins):
+            lgt = len(bins)
+            all = []
+            if not lgt:
+                return text
+            arg = (all, bins)
+            patch = lib.mpatch_fold(ffi.new_handle(arg),
+                                    lib.cffi_get_next_item, 0, lgt)
+            if not patch:
+                raise mpatchError("cannot decode chunk")
+            outlen = lib.mpatch_calcsize(len(text), patch)
+            if outlen < 0:
+                lib.mpatch_lfree(patch)
+                raise mpatchError("inconsistency detected")
+            buf = ffi.new("char[]", outlen)
+            if lib.mpatch_apply(buf, text, len(text), patch) < 0:
+                lib.mpatch_lfree(patch)
+                raise mpatchError("error applying patches")
+            res = ffi.buffer(buf, outlen)[:]
+            lib.mpatch_lfree(patch)
+            return res
+

--- a/setup.py	Fri Jul 22 17:28:05 2016 +0200
+++ b/setup.py	Mon Jul 25 15:10:52 2016 +0200
@@ -318,7 +318,8 @@
         if self.distribution.pure:
             self.distribution.ext_modules = []
         elif self.distribution.cffi:
-            exts = []
+            import setup_mpatch_cffi
+            exts = [setup_mpatch_cffi.ffi.distutils_extension()]
             # cffi modules go here
             if sys.platform == 'darwin':
                 import setup_osutil_cffi