Roll forward to cl/343785060

Signed-off-by: hai007 <hais@google.com>

cpp/platform/base/byte_utils.h

@@ -0,0 +1,24 @@
+#ifndef PLATFORM_BASE_BYTE_UTILS_H_
+#define PLATFORM_BASE_BYTE_UTILS_H_
+
+#include "platform/base/byte_array.h"
+
+namespace location {
+namespace nearby {
+
+class ByteUtils {
+ public:
+  static std::string ToFourDigitString(ByteArray& bytes);
+
+ private:
+  // The biggest prime number under 10000, used as a mod base to trim integers
+  // into 4 digits.
+  static constexpr int kHashBasePrime = 9973;
+  // The hash multiplier.
+  static constexpr int kHashBaseMultiplier = 31;
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_BASE_BYTE_UTILS_H_