Use string_view in address methods

When setting or getting the underlying string data used for an `Address`
object, avoid extra copying by using `string_view`. During
initialization a copy is performed into the `Address` object's local
stroage, which makes sense. Though the input to the function need not
copy to `string`. It can just be viewed while the data is copied into
the object's local memory. Further when converting the `Address` to a
string, a view can be used to avoid a copy during the return. If the
caller would like to persist the string longer than the lifetime of the
`Address` object, they can copy it at that point. Though we can save
them a copy before then. Especially if they will use the string while
the `Address` object is present.

Author: jakirkham

cpp/include/ucxx/address.h

@@ -5,7 +5,7 @@
 #pragma once
 
 #include <memory>
-#include <string>
+#include <string_view>
 
 #include <ucp/api/ucp.h>
 
@@ -75,7 +75,7 @@ class Address : public Component {
    *
    * @returns The `shared_ptr<ucxx::Address>` object.
    */
-  friend std::shared_ptr<Address> createAddressFromString(std::string addressString);
+  friend std::shared_ptr<Address> createAddressFromString(std::string_view addressString);
 
   /**
    * @brief Get the underlying `ucp_address_t*` handle.
@@ -112,7 +112,7 @@ class Address : public Component {
    *
    * @returns The underlying `ucp_address_t` handle.
    */
-  [[nodiscard]] std::string getString() const;
+  [[nodiscard]] std::string_view getString() const;
 };
 
 }  // namespace ucxx

cpp/src/address.cpp

@@ -3,7 +3,7 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 #include <memory>
-#include <string>
+#include <string_view>
 
 #include <ucxx/address.h>
 #include <ucxx/utils/ucx.h>
@@ -38,7 +38,7 @@ std::shared_ptr<Address> createAddressFromWorker(std::shared_ptr<Worker> worker)
   return std::shared_ptr<Address>(new Address(worker, address, length));
 }
 
-std::shared_ptr<Address> createAddressFromString(std::string addressString)
+std::shared_ptr<Address> createAddressFromString(std::string_view addressString)
 {
   ucp_address_t* address = reinterpret_cast<ucp_address_t*>(new char[addressString.length()]);
   size_t length          = addressString.length();
@@ -50,9 +50,9 @@ ucp_address_t* Address::getHandle() const { return _handle; }
 
 size_t Address::getLength() const { return _length; }
 
-std::string Address::getString() const
+std::string_view Address::getString() const
 {
-  return std::string{reinterpret_cast<char*>(_handle), _length};
+  return std::string_view{reinterpret_cast<const char*>(_handle), _length};
 }
 
 }  // namespace ucxx