Fix a crash when parsing empty HTTP headers

changelog.md

@@ -25,6 +25,7 @@ HEAD
 - Bug: Fix handler allocation crash with multithreaded io_service.
 - Bug: Fixes incorrect whitespace handling in header parsing. #301 Thank you
   Wolfram Schroers for reporting
+- Bug: Fix a crash when parsing empty HTTP headers. Thank you Thingol for reporting.
 
 0.3.0-alpha4 - 2013-10-11
 - HTTP requests ending normally are no longer logged as errors. Thank you Banaan

test/http/parser.cpp

@@ -363,6 +363,7 @@ BOOST_AUTO_TEST_CASE( strip_lws ) {
     std::string test5 = "    foo     ";
     std::string test6 = "  \r\n  foo     ";
     std::string test7 = "  \t  foo     ";
+    std::string test8 = "  \t       ";
 
     BOOST_CHECK_EQUAL( websocketpp::http::parser::strip_lws(test1), "foo" );
     BOOST_CHECK_EQUAL( websocketpp::http::parser::strip_lws(test2), "foo" );
@@ -371,6 +372,7 @@ BOOST_AUTO_TEST_CASE( strip_lws ) {
     BOOST_CHECK_EQUAL( websocketpp::http::parser::strip_lws(test5), "foo" );
     BOOST_CHECK_EQUAL( websocketpp::http::parser::strip_lws(test6), "foo" );
     BOOST_CHECK_EQUAL( websocketpp::http::parser::strip_lws(test7), "foo" );
+    BOOST_CHECK_EQUAL( websocketpp::http::parser::strip_lws(test8), "" );
 }
 
 BOOST_AUTO_TEST_CASE( case_insensitive_headers ) {

websocketpp/http/parser.hpp

@@ -369,6 +369,9 @@ InputIterator extract_parameters(InputIterator begin, InputIterator end,
 
 inline std::string strip_lws(std::string const & input) {
     std::string::const_iterator begin = extract_all_lws(input.begin(),input.end());
+    if (begin == input.end()) {
+        return std::string();
+    }
     std::string::const_reverse_iterator end = extract_all_lws(input.rbegin(),input.rend());
 
     return std::string(begin,end.base());