base::MD5IntermediateFinal() generates digest non-destructively.

base/md5.cc

Index: base/md5.cc
diff --git a/base/md5.cc b/base/md5.cc
index 754994c0e562b45b2bc4b90cc2a7c612d14ec5a7..4e26febda0f1c0db25514a39bb00834de7da100f 100644
--- a/base/md5.cc
+++ b/base/md5.cc
@@ -260,6 +260,15 @@ void MD5Final(MD5Digest* digest, MD5Context* context) {
         memset(ctx, 0, sizeof(*ctx));    /* In case it's sensitive */
 }
 
+/*
+ * Clone the context and use the clone to generate the digest.
+ */
+void MD5IntermediateFinal(MD5Digest* digest, MD5Context* context) {
+  MD5Context context_copy;
+  memcpy(&context_copy, context, sizeof(context_copy));
+  MD5Final(digest, &context_copy);
+}
+
 std::string MD5DigestToBase16(const MD5Digest& digest) {
   static char const zEncode[] = "0123456789abcdef";