base::MD5Clone() clones MD5Context.

base/md5.h

Index: base/md5.h
diff --git a/base/md5.h b/base/md5.h
index fba02bd11635d63ac2057e25cf150bc25d84f012..ea81f531bd3925b44ba40eabbcfe64b5bc2e5d78 100644
--- a/base/md5.h
+++ b/base/md5.h
@@ -55,6 +55,11 @@ BASE_EXPORT void MD5Init(MD5Context* context);
 // during the computation, except that MD5Init() must have been called first.
 BASE_EXPORT void MD5Update(MD5Context* context, const StringPiece& data);
 
+// Clone the state of the given context.  This can be used to generate an
+// intermediate digest without affecting the original context.

[awong, 2014/03/25 20:00:41]

This comment is a little bit confusing. Can you motivate with an example of how
to use and how it differs?

Also, what about adding a MD5IncrementalFinal() or something? That seems more
friendly than cloning, finalizing, and discarding cloned version...

+BASE_EXPORT void MD5Clone(MD5Context* clone_context,
+                          MD5Context* original_context);
+
 // Finalizes the MD5 operation and fills the buffer with the digest.
 BASE_EXPORT void MD5Final(MD5Digest* digest, MD5Context* context);