fix sstring.find(): make find("") compatible with std::string

- scylladb#1001
longqimin · Jan 18, 2022 · 7bb0754 · 7bb0754
1 parent 777e4b3
commit 7bb0754
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diff --git a/include/seastar/core/sstring.hh b/include/seastar/core/sstring.hh
@@ -245,6 +245,13 @@ public:
  const char_type* c_str = s.str();
  const char_type* c_str_end = s.str() + s.size();
 
+ if (c_str == c_str_end) {
+ /* see https://en.cppreference.com/w/cpp/string/basic_string/find
+ * - an empty substring is found at pos if and only if pos <= size()
+ */
+ return (pos <= size()) ? pos : npos;
+ }
+
  while (it < end) {
  auto i = it;
  auto j = c_str;

diff --git a/tests/unit/sstring_test.cc b/tests/unit/sstring_test.cc
@@ -54,6 +54,12 @@ BOOST_AUTO_TEST_CASE(test_add_literal_to_sstring) {
 BOOST_AUTO_TEST_CASE(test_find_sstring) {
  BOOST_REQUIRE_EQUAL(sstring("abcde").find('b'), 1u);
  BOOST_REQUIRE_EQUAL(sstring("babcde").find('b',1), 2u);
+ BOOST_REQUIRE_EQUAL(sstring("").find("", 0), 0u);
+ BOOST_REQUIRE_EQUAL(sstring("").find("", 1), sstring::npos);
+ BOOST_REQUIRE_EQUAL(sstring("abcde").find("", 0), 0u);
+ BOOST_REQUIRE_EQUAL(sstring("abcde").find("", 1), 1u);
+ BOOST_REQUIRE_EQUAL(sstring("abcde").find("", 5), 5u);
+ BOOST_REQUIRE_EQUAL(sstring("abcde").find("", 6), sstring::npos);
 }
 
 BOOST_AUTO_TEST_CASE(test_not_find_sstring) {