Bring fbstring::operator+ to date with C++11

Summary: Some overloads, particularly with rvalue references, were missing. Also this fixes https://our.intern.facebook.com/intern/tasks/?t=5849579

Test Plan: unittests

Reviewed By: simpkins@fb.com

Subscribers: trunkagent, las, net-systems@, njormrod, folly-diffs@

FB internal diff: D1746319

Tasks: 5849579

Signature: t1:1746319:1418875228:febb965cf52710a5e76b7c1cce5aec601086ad90

folly/FBString.h

@@ -1969,11 +1969,18 @@ public:
     return find_last_not_of(&c, pos, 1);
   }
 
-  basic_fbstring substr(size_type pos = 0, size_type n = npos) const {
+  basic_fbstring substr(size_type pos = 0, size_type n = npos) const& {
     enforce(pos <= size(), std::__throw_out_of_range, "");
     return basic_fbstring(data() + pos, std::min(n, size() - pos));
   }
 
+  basic_fbstring substr(size_type pos = 0, size_type n = npos) && {
+    enforce(pos <= size(), std::__throw_out_of_range, "");
+    erase(0, pos);
+    if (n < size()) resize(n);
+    return std::move(*this);
+  }
+
   int compare(const basic_fbstring& str) const {
     // FIX due to Goncalo N M de Carvalho July 18, 2005
     return compare(0, size(), str);
@@ -2021,7 +2028,7 @@ private:
 };
 
 // non-member functions
-// C++11 21.4.8.1/2
+// C++11 21.4.8.1/1
 template <typename E, class T, class A, class S>
 inline
 basic_fbstring<E, T, A, S> operator+(const basic_fbstring<E, T, A, S>& lhs,
@@ -2063,24 +2070,44 @@ basic_fbstring<E, T, A, S> operator+(basic_fbstring<E, T, A, S>&& lhs,
   return std::move(lhs.append(rhs));
 }
 
+// C++11 21.4.8.1/5
 template <typename E, class T, class A, class S>
 inline
 basic_fbstring<E, T, A, S> operator+(
-  const typename basic_fbstring<E, T, A, S>::value_type* lhs,
+  const E* lhs,
   const basic_fbstring<E, T, A, S>& rhs) {
   //
   basic_fbstring<E, T, A, S> result;
-  const typename basic_fbstring<E, T, A, S>::size_type len =
-    basic_fbstring<E, T, A, S>::traits_type::length(lhs);
+  const auto len = basic_fbstring<E, T, A, S>::traits_type::length(lhs);
   result.reserve(len + rhs.size());
   result.append(lhs, len).append(rhs);
   return result;
 }
 
+// C++11 21.4.8.1/6
 template <typename E, class T, class A, class S>
 inline
 basic_fbstring<E, T, A, S> operator+(
-  typename basic_fbstring<E, T, A, S>::value_type lhs,
+  const E* lhs,
+  basic_fbstring<E, T, A, S>&& rhs) {
+  //
+  const auto len = basic_fbstring<E, T, A, S>::traits_type::length(lhs);
+  if (rhs.capacity() >= len + rhs.size()) {
+    // Good, at least we don't need to reallocate
+    return std::move(rhs.insert(rhs.begin(), lhs, lhs + len));
+  }
+  // Meh, no go. Do it by hand since we have len already.
+  basic_fbstring<E, T, A, S> result;
+  result.reserve(len + rhs.size());
+  result.append(lhs, len).append(rhs);
+  return result;
+}
+
+// C++11 21.4.8.1/7
+template <typename E, class T, class A, class S>
+inline
+basic_fbstring<E, T, A, S> operator+(
+  E lhs,
   const basic_fbstring<E, T, A, S>& rhs) {
 
   basic_fbstring<E, T, A, S> result;
@@ -2090,11 +2117,28 @@ basic_fbstring<E, T, A, S> operator+(
   return result;
 }
 
+// C++11 21.4.8.1/8
+template <typename E, class T, class A, class S>
+inline
+basic_fbstring<E, T, A, S> operator+(
+  E lhs,
+  basic_fbstring<E, T, A, S>&& rhs) {
+  //
+  if (rhs.capacity() > rhs.size()) {
+    // Good, at least we don't need to reallocate
+    return std::move(rhs.insert(rhs.begin(), lhs));
+  }
+  // Meh, no go. Forward to operator+(E, const&).
+  auto const& rhsC = rhs;
+  return lhs + rhsC;
+}
+
+// C++11 21.4.8.1/9
 template <typename E, class T, class A, class S>
 inline
 basic_fbstring<E, T, A, S> operator+(
   const basic_fbstring<E, T, A, S>& lhs,
-  const typename basic_fbstring<E, T, A, S>::value_type* rhs) {
+  const E* rhs) {
 
   typedef typename basic_fbstring<E, T, A, S>::size_type size_type;
   typedef typename basic_fbstring<E, T, A, S>::traits_type traits_type;
@@ -2106,11 +2150,22 @@ basic_fbstring<E, T, A, S> operator+(
   return result;
 }
 
+// C++11 21.4.8.1/10
+template <typename E, class T, class A, class S>
+inline
+basic_fbstring<E, T, A, S> operator+(
+  basic_fbstring<E, T, A, S>&& lhs,
+  const E* rhs) {
+  //
+  return std::move(lhs += rhs);
+}
+
+// C++11 21.4.8.1/11
 template <typename E, class T, class A, class S>
 inline
 basic_fbstring<E, T, A, S> operator+(
   const basic_fbstring<E, T, A, S>& lhs,
-  typename basic_fbstring<E, T, A, S>::value_type rhs) {
+  E rhs) {
 
   basic_fbstring<E, T, A, S> result;
   result.reserve(lhs.size() + 1);
@@ -2119,6 +2174,16 @@ basic_fbstring<E, T, A, S> operator+(
   return result;
 }
 
+// C++11 21.4.8.1/12
+template <typename E, class T, class A, class S>
+inline
+basic_fbstring<E, T, A, S> operator+(
+  basic_fbstring<E, T, A, S>&& lhs,
+  E rhs) {
+  //
+  return std::move(lhs += rhs);
+}
+
 template <typename E, class T, class A, class S>
 inline
 bool operator==(const basic_fbstring<E, T, A, S>& lhs,

folly/test/FBStringTest.cpp

@@ -603,6 +603,21 @@ template <class String> void clause11_21_4_7_2_a(String & test) {
   Num2String(test, test.find(str, random(0, test.size())));
 }
 
+template <class String> void clause11_21_4_7_2_a1(String & test) {
+  String str = String(test).substr(
+    random(0, test.size()),
+    random(0, test.size()));
+  Num2String(test, test.find(str, random(0, test.size())));
+}
+
+template <class String> void clause11_21_4_7_2_a2(String & test) {
+  auto const& cTest = test;
+  String str = cTest.substr(
+    random(0, test.size()),
+    random(0, test.size()));
+  Num2String(test, test.find(str, random(0, test.size())));
+}
+
 template <class String> void clause11_21_4_7_2_b(String & test) {
   auto from = random(0, test.size());
   auto length = random(0, test.size() - from);
@@ -612,6 +627,25 @@ template <class String> void clause11_21_4_7_2_b(String & test) {
                              random(0, str.size())));
 }
 
+template <class String> void clause11_21_4_7_2_b1(String & test) {
+  auto from = random(0, test.size());
+  auto length = random(0, test.size() - from);
+  String str = String(test).substr(from, length);
+  Num2String(test, test.find(str.c_str(),
+                             random(0, test.size()),
+                             random(0, str.size())));
+}
+
+template <class String> void clause11_21_4_7_2_b2(String & test) {
+  auto from = random(0, test.size());
+  auto length = random(0, test.size() - from);
+  const auto& cTest = test;
+  String str = cTest.substr(from, length);
+  Num2String(test, test.find(str.c_str(),
+                             random(0, test.size()),
+                             random(0, str.size())));
+}
+
 template <class String> void clause11_21_4_7_2_c(String & test) {
   String str = test.substr(
     random(0, test.size()),
@@ -620,6 +654,23 @@ template <class String> void clause11_21_4_7_2_c(String & test) {
                              random(0, test.size())));
 }
 
+template <class String> void clause11_21_4_7_2_c1(String & test) {
+  String str = String(test).substr(
+    random(0, test.size()),
+    random(0, test.size()));
+  Num2String(test, test.find(str.c_str(),
+                             random(0, test.size())));
+}
+
+template <class String> void clause11_21_4_7_2_c2(String & test) {
+  const auto& cTest = test;
+  String str = cTest.substr(
+    random(0, test.size()),
+    random(0, test.size()));
+  Num2String(test, test.find(str.c_str(),
+                             random(0, test.size())));
+}
+
 template <class String> void clause11_21_4_7_2_d(String & test) {
   Num2String(test, test.find(
                random('a', 'z'),
@@ -838,6 +889,30 @@ template <class String> void clause11_21_4_8_1_a(String & test) {
 }
 
 template <class String> void clause11_21_4_8_1_b(String & test) {
+  String s1;
+  randomString(&s1, maxString);
+  String s2;
+  randomString(&s2, maxString);
+  test = move(s1) + s2;
+}
+
+template <class String> void clause11_21_4_8_1_c(String & test) {
+  String s1;
+  randomString(&s1, maxString);
+  String s2;
+  randomString(&s2, maxString);
+  test = s1 + move(s2);
+}
+
+template <class String> void clause11_21_4_8_1_d(String & test) {
+  String s1;
+  randomString(&s1, maxString);
+  String s2;
+  randomString(&s2, maxString);
+  test = move(s1) + move(s2);
+}
+
+template <class String> void clause11_21_4_8_1_e(String & test) {
   String s;
   randomString(&s, maxString);
   String s1;
@@ -845,13 +920,27 @@ template <class String> void clause11_21_4_8_1_b(String & test) {
   test = s.c_str() + s1;
 }
 
-template <class String> void clause11_21_4_8_1_c(String & test) {
+template <class String> void clause11_21_4_8_1_f(String & test) {
+  String s;
+  randomString(&s, maxString);
+  String s1;
+  randomString(&s1, maxString);
+  test = s.c_str() + move(s1);
+}
+
+template <class String> void clause11_21_4_8_1_g(String & test) {
   String s;
   randomString(&s, maxString);
   test = typename String::value_type(random('a', 'z')) + s;
 }
 
-template <class String> void clause11_21_4_8_1_d(String & test) {
+template <class String> void clause11_21_4_8_1_h(String & test) {
+  String s;
+  randomString(&s, maxString);
+  test = typename String::value_type(random('a', 'z')) + move(s);
+}
+
+template <class String> void clause11_21_4_8_1_i(String & test) {
   String s;
   randomString(&s, maxString);
   String s1;
@@ -859,20 +948,28 @@ template <class String> void clause11_21_4_8_1_d(String & test) {
   test = s + s1.c_str();
 }
 
-template <class String> void clause11_21_4_8_1_e(String & test) {
+template <class String> void clause11_21_4_8_1_j(String & test) {
   String s;
   randomString(&s, maxString);
   String s1;
   randomString(&s1, maxString);
-  test = s + s1.c_str();
+  test = move(s) + s1.c_str();
 }
 
-template <class String> void clause11_21_4_8_1_f(String & test) {
+template <class String> void clause11_21_4_8_1_k(String & test) {
   String s;
   randomString(&s, maxString);
   test = s + typename String::value_type(random('a', 'z'));
 }
 
+template <class String> void clause11_21_4_8_1_l(String & test) {
+  String s;
+  randomString(&s, maxString);
+  String s1;
+  randomString(&s1, maxString);
+  test = move(s) + s1.c_str();
+}
+
 // Numbering here is from C++11
 template <class String> void clause11_21_4_8_9_a(String & test) {
   basic_stringstream<typename String::value_type> stst(test.c_str());
@@ -969,8 +1066,14 @@ TEST(FBString, testAllClauses) {
   TEST_CLAUSE(21_4_7_1);
 
   TEST_CLAUSE(21_4_7_2_a);
+  TEST_CLAUSE(21_4_7_2_a1);
+  TEST_CLAUSE(21_4_7_2_a2);
   TEST_CLAUSE(21_4_7_2_b);
+  TEST_CLAUSE(21_4_7_2_b1);
+  TEST_CLAUSE(21_4_7_2_b2);
   TEST_CLAUSE(21_4_7_2_c);
+  TEST_CLAUSE(21_4_7_2_c1);
+  TEST_CLAUSE(21_4_7_2_c2);
   TEST_CLAUSE(21_4_7_2_d);
   TEST_CLAUSE(21_4_7_3_a);
   TEST_CLAUSE(21_4_7_3_b);
@@ -1004,6 +1107,12 @@ TEST(FBString, testAllClauses) {
   TEST_CLAUSE(21_4_8_1_d);
   TEST_CLAUSE(21_4_8_1_e);
   TEST_CLAUSE(21_4_8_1_f);
+  TEST_CLAUSE(21_4_8_1_g);
+  TEST_CLAUSE(21_4_8_1_h);
+  TEST_CLAUSE(21_4_8_1_i);
+  TEST_CLAUSE(21_4_8_1_j);
+  TEST_CLAUSE(21_4_8_1_k);
+  TEST_CLAUSE(21_4_8_1_l);
   TEST_CLAUSE(21_4_8_9_a);
 }