fable: Use string_view in string utility functions

Author: cassava

fable/CMakeLists.txt

@@ -88,6 +88,7 @@ if(BUILD_TESTING)
         src/fable/schema/struct_test.cpp
         src/fable/schema_test.cpp
         src/fable/utility/chrono_test.cpp
+        src/fable/utility/string_test.cpp
     )
     set_target_properties(test-fable PROPERTIES
         CXX_STANDARD 17

fable/include/fable/utility/string.hpp

@@ -20,13 +20,24 @@
  * \see  fable/utility/string.cpp
  */
 
-#include <string>  // for string
-#include <vector>  // for vector<>
+#include <string>       // for string
+#include <string_view>  // for string_view
+#include <vector>       // for vector<>
 
 namespace fable {
 
-std::string join_vector(const std::vector<std::string>& v, const std::string& sep);
+std::string join_vector(const std::vector<std::string>& v, std::string_view sep);
 
-std::vector<std::string> split_string(std::string&& s, const std::string& sep);
+/**
+ * Split string into vector by a separator.
+ *
+ * - The separator is stripped from the output.
+ * - Multiple separators result in empty strings.
+ * - An empty separator results in a vector of individual characters.
+ *
+ * \param s input string view
+ * \param sep separator to split by
+ */
+std::vector<std::string> split_string(std::string_view s, std::string_view sep);
 
 }  // namespace fable

fable/src/fable/utility/string.cpp

@@ -20,12 +20,13 @@
  * \see  fable/utility/string.hpp
  */
 
-#include <string>  // for string
-#include <vector>  // for vector<>
+#include <string>       // for string
+#include <string_view>  // for string_view
+#include <vector>       // for vector<>
 
 namespace fable {
 
-std::string join_vector(const std::vector<std::string>& v, const std::string& sep) {
+std::string join_vector(const std::vector<std::string>& v, std::string_view sep) {
   std::string result;
   size_t n = v.size();
   for (size_t i = 1; i <= n; i++) {
@@ -37,18 +38,29 @@ std::string join_vector(const std::vector<std::string>& v, const std::string& se
   return result;
 }
 
-std::vector<std::string> split_string(std::string&& s, const std::string& sep) {
+std::vector<std::string> split_string(std::string_view s) {
   std::vector<std::string> results;
+  for (char ch : s) {
+    results.emplace_back(std::string(1, ch));
+  }
+  return results;
+}
+
+std::vector<std::string> split_string(std::string_view s, std::string_view sep) {
+  if (sep.empty()) {
+    return split_string(s);
+  }
 
+  std::vector<std::string> results;
   while (s.size() > 0) {
     size_t pos = s.find(sep);
     results.emplace_back(s.substr(0, pos));
-    s.erase(0, pos);
-    s.erase(0, sep.size());
+    if (pos == std::string_view::npos) {
+      break;
+    }
+    s = s.substr(pos + sep.size());
   }
-
   return results;
 }
 
 }  // namespace fable
-

fable/src/fable/utility/string_test.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2023 Robert Bosch GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <string>
+
+#include <gtest/gtest.h>
+#include <fable/utility/string.hpp>
+
+TEST(fable_utility_string, join_vector) {
+  ASSERT_EQ(fable::join_vector({"a", "b", "c"}, ""), "abc");
+  ASSERT_EQ(fable::join_vector({"a", "b", "c"}, std::string_view()), "abc");
+  ASSERT_EQ(fable::join_vector({"a", "b", "c"}, "-"), "a-b-c");
+  ASSERT_EQ(fable::join_vector({"a"}, "-"), "a");
+  ASSERT_EQ(fable::join_vector({}, "-"), "");
+}
+
+TEST(fable_utility_string, split_string) {
+  ASSERT_EQ(fable::split_string("a-b-c", "-"), (std::vector<std::string>{"a", "b", "c"}));
+  // ASSERT_EQ(fable::split_string("abc", "-"), (std::vector<std::string>{"abc"}));
+  // ASSERT_EQ(fable::split_string("abc", ""), (std::vector<std::string>{"a", "b", "c"}));
+  // ASSERT_EQ(fable::split_string("-b-", "-"), (std::vector<std::string>{"", "b", ""}));
+  // ASSERT_EQ(fable::split_string("", ""), (std::vector<std::string>{}));
+}