Add comments for in line methods

cpp/src/gandiva/hash_utils.cc

@@ -22,6 +22,7 @@
 #include "arrow/util/logging.h"
 
 namespace gandiva {
+  /// Hashes a generic message using the SHA256 algorithm
   const char* gdv_hash_using_sha256(int64_t context,
                                     const void* message,
                                     size_t message_length,
@@ -31,6 +32,8 @@ namespace gandiva {
                               sha256_result_length, out_length);
   }
 
+
+  /// Hashes a generic message using the SHA1 algorithm
   const char* gdv_hash_using_sha1(int64_t context,
                                   const void* message,
                                   size_t message_length,
@@ -40,6 +43,11 @@ namespace gandiva {
                               sha1_result_length, out_length);
   }
 
+  /// \brief Hashes a generic message using SHA algorithm.
+  ///
+  /// It uses the EVP API in the OpenSSL library to generate
+  /// the hash. The type of the hash is defined by the
+  /// \b hash_type \b parameter.
   const char* gdv_hash_using_sha(int64_t context,
                                  const void* message,
                                  size_t message_length,