Fix handling of empty strings in ToHex().

2 files changed, 14 insertions, 2 deletions

diff --git a/coding/coding_tests/hex_test.cpp b/coding/coding_tests/hex_test.cpp
index a0686e3dc0..2ba539687e 100644
--- a/coding/coding_tests/hex_test.cpp
+++ b/coding/coding_tests/hex_test.cpp
@@ -18,7 +18,7 @@ static string GenString()
 {
   static PseudoRNG32 rng;
   string result;
-  // By VNG: avoid empty string, else TeHex function failed.
+  // Avoid empty string, since we test it seperately.
   size_t size = rng.Generate() % 20 + 1;
   for (size_t i = 0; i < size; ++i)
   {
@@ -47,3 +47,13 @@ UNIT_TEST(DecodeLowerCaseHex)
 {
   TEST_EQUAL(FromHex("fe"), "\xfe", ());
 }
+
+UNIT_TEST(EncodeEmptyString)
+{
+  TEST_EQUAL(ToHex(string()), "", ());
+}
+
+UNIT_TEST(DecodeEmptyString)
+{
+  TEST_EQUAL(FromHex(""), "", ());
+}
diff --git a/coding/hex.hpp b/coding/hex.hpp
index 22a82af389..86ebe4dda6 100644
--- a/coding/hex.hpp
+++ b/coding/hex.hpp
@@ -27,7 +27,9 @@ template <typename ContainerT>
 inline string ToHex(ContainerT const & container)
 {
   STATIC_ASSERT(sizeof(*container.begin()) == 1);
-  ASSERT ( !container.empty(), ("Dereference of container::end() is illegal") );
+
+  if (container.empty())
+    return string();
 
   return ToHex(&*container.begin(), container.end() - container.begin());
 }