Move SerializeToStringDeterministic to a header file

It is a useful function for computing hash values.

PiperOrigin-RevId: 170013135

2 files changed, 21 insertions, 0 deletions

diff --git a/tensorflow/core/lib/hash/hash.cc b/tensorflow/core/lib/hash/hash.cc
index dc9d300d00..ed9b4df37a 100644
--- a/tensorflow/core/lib/hash/hash.cc
+++ b/tensorflow/core/lib/hash/hash.cc
@@ -126,4 +126,15 @@ uint64 Hash64(const char* data, size_t n, uint64 seed) {
   return h;
 }
 
+bool SerializeToStringDeterministic(const protobuf::MessageLite& msg,
+                                    string* result) {
+  const size_t size = msg.ByteSizeLong();
+  *result = string(size, '\0');
+  protobuf::io::ArrayOutputStream array_stream(&(*result)[0], size);
+  protobuf::io::CodedOutputStream output_stream(&array_stream);
+  output_stream.SetSerializationDeterministic(true);
+  msg.SerializeWithCachedSizes(&output_stream);
+  return !output_stream.HadError() && size == output_stream.ByteCount();
+}
+
 }  // namespace tensorflow
diff --git a/tensorflow/core/lib/hash/hash.h b/tensorflow/core/lib/hash/hash.h
index 77b8031598..0fb12966af 100644
--- a/tensorflow/core/lib/hash/hash.h
+++ b/tensorflow/core/lib/hash/hash.h
@@ -24,6 +24,7 @@ limitations under the License.
 #include <string>
 
 #include "tensorflow/core/lib/core/stringpiece.h"
+#include "tensorflow/core/platform/protobuf.h"
 #include "tensorflow/core/platform/types.h"
 
 namespace tensorflow {
@@ -84,6 +85,15 @@ struct hash<std::pair<T, U>> {
   }
 };
 
+// Wrapper around protocol buffer serialization that requests deterministic
+// serialization, in particular for Map fields, which serialize in a random
+// order by default. Returns true on success.
+// Serialization is guaranteed to be deterministic for a given binary only.
+// See the following for more details:
+// https://github.com/google/protobuf/blob/a1bb147e96b6f74db6cdf3c3fcb00492472dbbfa/src/google/protobuf/io/coded_stream.h#L834
+bool SerializeToStringDeterministic(const protobuf::MessageLite& msg,
+                                    string* result);
+
 }  // namespace tensorflow
 
 #endif  // TENSORFLOW_LIB_HASH_HASH_H_