use iterators for split (#14)

* use iterators for split

Signed-off-by: Karsten Knese <karsten@openrobotics.org>

* address review comments

Signed-off-by: Karsten Knese <karsten@openrobotics.org>

include/rcpputils/split.hpp

@@ -36,34 +36,57 @@
 #ifndef RCPPUTILS__SPLIT_HPP_
 #define RCPPUTILS__SPLIT_HPP_
 
+#include <iterator>
 #include <sstream>
 #include <string>
 #include <vector>
 
 namespace rcpputils
 {
 
-/// Split a specified input into tokens using a delimiter.
+/// Split a specified input into tokens using a delimiter and a type erased insert iterator.
 /**
  * The returned vector will contain the tokens split from the input
  *
  * \param[in] input the input string to be split
  * \param[in] delim the dlelimiter used to split the input string
- * \return A vector of tokens.
+ * \param[in] insert iterator pointing to a storage container
  */
-inline std::vector<std::string>
-split(const std::string & input, char delim, bool skip_empty = false)
+template<
+  class InsertIterator,
+  typename std::enable_if<
+    std::is_same<
+      InsertIterator &,
+      decltype(std::declval<InsertIterator>().operator=(std::declval<std::string>()))>::value
+  >::type * = nullptr>
+void
+split(const std::string & input, char delim, InsertIterator & it, bool skip_empty = false)
 {
-  std::vector<std::string> result;
   std::stringstream ss;
   ss.str(input);
   std::string item;
   while (std::getline(ss, item, delim)) {
     if (skip_empty && item == "") {
       continue;
     }
-    result.push_back(item);
+    it = item;
   }
+}
+
+/// Split a specified input into tokens using a delimiter.
+/**
+ * The returned vector will contain the tokens split from the input
+ *
+ * \param[in] input the input string to be split
+ * \param[in] delim the dlelimiter used to split the input string
+ * \return A vector of tokens.
+ */
+inline std::vector<std::string>
+split(const std::string & input, char delim, bool skip_empty = false)
+{
+  std::vector<std::string> result;
+  auto it = std::back_inserter(result);
+  split(input, delim, it, skip_empty);
   return result;
 }
 }  // namespace rcpputils

test/test_split.cpp

@@ -14,6 +14,13 @@
 
 #include <gtest/gtest.h>
 
+#include <exception>
+#include <list>
+#include <set>
+#include <string>
+#include <tuple>
+#include <vector>
+
 #include "rcpputils/split.hpp"
 
 TEST(test_split, split) {
@@ -221,3 +228,89 @@ TEST(test_split, split_backslash) {
     EXPECT_EQ("world", ret[5]);
   }
 }
+
+TEST(test_split, vector_iterator)
+{
+  std::string s = "my/hello/world";
+
+  std::vector<std::string> vec = {};
+  auto vec_it = std::back_inserter(vec);
+  rcpputils::split(s, '/', vec_it);
+  EXPECT_EQ("my", vec[0]);
+  EXPECT_EQ("hello", vec[1]);
+  EXPECT_EQ("world", vec[2]);
+}
+
+TEST(test_split, list_iterator)
+{
+  std::string s = "my/hello/world";
+
+  std::list<std::string> ll = {};
+  auto ll_it = std::back_inserter(ll);
+  rcpputils::split(s, '/', ll_it);
+  EXPECT_EQ("my", ll.front());
+  EXPECT_EQ("world", ll.back());
+}
+
+TEST(test_split, set_iterator)
+{
+  std::string s = "wonderful string with wonderful duplicates duplicates";
+
+  std::set<std::string> set = {};
+  auto set_it = std::inserter(set, std::begin(set));
+  rcpputils::split(s, ' ', set_it);
+  EXPECT_EQ(4u, set.size());
+}
+
+class TripleExtractor
+{
+  size_t counter = 0;
+
+public:
+  std::string package_name;
+  std::string middle_element;
+  std::string message_name;
+
+  TripleExtractor & operator=(const std::string & s)
+  {
+    if (counter >= 3) {
+      throw std::out_of_range("triple extractor only can hold three parts");
+    }
+
+    if (counter == 0) {
+      package_name = s;
+    } else if (counter == 1) {
+      middle_element = s;
+    } else {
+      message_name = s;
+    }
+
+    counter++;
+
+    return *this;
+  }
+
+  std::tuple<std::string, std::string, std::string> get() const
+  {
+    return std::tie(package_name, middle_element, message_name);
+  }
+};
+
+TEST(test_split, custom_iterator)
+{
+  std::string s = "my_pkg/msg/MyMessage";
+  TripleExtractor triple_it;
+  rcpputils::split(s, '/', triple_it);
+  EXPECT_STREQ("my_pkg", triple_it.package_name.c_str());
+  EXPECT_STREQ("msg", triple_it.middle_element.c_str());
+  EXPECT_STREQ("MyMessage", triple_it.message_name.c_str());
+
+  EXPECT_EQ(std::make_tuple("my_pkg", "msg", "MyMessage"), triple_it.get());
+}
+
+TEST(test_split, custom_iterator_exception)
+{
+  std::string s = "my_pkg/msg/MyMessage/Wrong";
+  TripleExtractor triple_it;
+  ASSERT_THROW(rcpputils::split(s, '/', triple_it), std::out_of_range);
+}