Add some utilities for working with camelCase names.

Swift SVN r15802

unittests/Basic/StringExtrasTest.cpp

@@ -0,0 +1,56 @@
+#include "swift/Basic/StringExtras.h"
+#include "gtest/gtest.h"
+#include <algorithm>
+
+using namespace swift;
+
+TEST(CamelCaseWordsTest, Iteration) {
+  auto words = camel_case::getWords("URLByPrependingHTTPToURL");
+
+  // Forward iteration count.
+  EXPECT_EQ(6, std::distance(words.begin(), words.end()));
+
+  // Reverse iteration count.
+  EXPECT_EQ(6, std::distance(words.rbegin(), words.rend()));
+
+  // Iteration contents.
+  auto iter = words.begin();
+  EXPECT_EQ(*iter, "URL");
+  
+  // Stepping forward.
+  ++iter;
+  EXPECT_EQ(*iter, "By");  
+
+  // Immediately stepping back (fast path).
+  --iter;
+  EXPECT_EQ(*iter, "URL");  
+
+  // Immediately stepping forward (fast path).
+  ++iter;
+  EXPECT_EQ(*iter, "By");
+
+  // Stepping forward.
+  ++iter;
+  EXPECT_EQ(*iter, "Prepending");  
+
+  // Stepping back twice (slow path).
+  --iter;
+  --iter;
+  EXPECT_EQ(*iter, "URL");
+
+  // Stepping forward to visit the remaining elements.
+  ++iter;
+  EXPECT_EQ(*iter, "By");
+  ++iter;
+  EXPECT_EQ(*iter, "Prepending");
+  ++iter;
+  EXPECT_EQ(*iter, "HTTP");
+  ++iter;
+  EXPECT_EQ(*iter, "To");
+  ++iter;
+  EXPECT_EQ(*iter, "URL");
+
+  // We're done.
+  ++iter;
+  EXPECT_EQ(iter, words.end());
+}