add folly::FixedString, a constexpr-usable string with a fixed-size internal buffer

Summary: Inspired by http://wg21.link/p0259, folly::BasicFixedString is a std::string replacement that is usable in constexpr contexts. It uses an internal fixed-size buffer to store up to N characters, where N is a template parameter.

Reviewed By: luciang

Differential Revision: D4249529

fbshipit-source-id: 10f12ea2510a8d21ec60a07a8f15ecc3e35c5431

folly/Makefile.am

@@ -144,6 +144,7 @@ nobase_follyinclude_HEADERS = \
 	File.h \
 	FileUtil.h \
 	Fingerprint.h \
+	FixedString.h \
 	folly-config.h \
 	Foreach.h \
 	FormatArg.h \

folly/test/FixedStringTest.cpp

+/*
+ * Copyright 2016 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Author: eniebler@fb.com
+
+#include <folly/FixedString.h>
+#include <folly/portability/GTest.h>
+
+#define FS(x) ::folly::makeFixedString(x)
+using namespace folly::StringLiterals;
+
+TEST(FixedStringExamples, Examples) {
+  // Example from the docs:
+  using namespace folly;
+  constexpr auto hello = makeFixedString("hello"); // a FixedString<5>
+  constexpr auto world = makeFixedString("world"); // another FixedString<5>
+  constexpr auto hello_world = hello + ' ' + world + '!';
+  static_assert(hello_world == "hello world!", "w00t");
+  EXPECT_STREQ("hello world!", hello_world.c_str());
+
+  FixedString<10> test{"****"};
+  test.replace(1, 2, "!!!!");
+  EXPECT_STREQ("*!!!!*", test.c_str());
+  static_assert(makeFixedString("****").creplace(1, 2, "!!!!") == "*!!!!*", "");
+}
+
+TEST(FixedStringCtorTest, Default) {
+  constexpr folly::FixedString<42> s{};
+  static_assert(s[0] == '\0', "");
+  static_assert(s.size() == 0u, "");
+
+  constexpr auto s2 = s;
+  static_assert(s2[0] == '\0', "");
+  static_assert(s2.size() == 0u, "");
+}
+
+TEST(FixedStringCtorTest, FromLiterals) {
+  constexpr folly::FixedString<42> s{"hello world"};
+  constexpr folly::FixedString<11> s2{"hello world"};
+  static_assert(s2[0] == 'h', "");
+  static_assert(s2[10] == 'd', "");
+  static_assert(s2[11] == '\0', "");
+
+  // Does not compile, hurray! :-)
+  // constexpr char a[1] = {'a'};
+  // constexpr folly::FixedString<10> s3(a);
+}
+
+TEST(FixedStringCtorTest, FromPtrAndLength) {
+  constexpr folly::FixedString<11> s{"hello world", 11};
+  static_assert(s[0] == 'h', "");
+  static_assert(s[10] == 'd', "");
+  static_assert(s[11] == '\0', "");
+  static_assert(s.size() == 11u, "");
+
+  constexpr folly::FixedString<5> s2{"hello world", 5};
+  static_assert(s2[0] == 'h', "");
+  static_assert(s2[4] == 'o', "");
+  static_assert(s2[5] == '\0', "");
+  static_assert(s2.size() == 5u, "");
+
+  constexpr folly::FixedString<20> s3{"hello world", 5};
+  static_assert(s2[0] == 'h', "");
+  static_assert(s2[4] == 'o', "");
+  static_assert(s2[5] == '\0', "");
+  static_assert(s2.size() == 5u, "");
+
+  static_assert("hello" == s3, "");
+  static_assert(s3 == "hello", "");
+  static_assert(s3 == s2, "");
+  static_assert("hell" != s3, "");
+  static_assert(s3 != "helloooo", "");
+  static_assert(!(s3 != s2), "");
+}
+
+TEST(FixedStringCtorTest, FromStringAndOffset) {
+  constexpr folly::FixedString<11> s{"hello world"};
+  constexpr folly::FixedString<5> s2{s, 6u, npos};
+  static_assert(s2 == "world", "");
+  constexpr folly::FixedString<0> s3{s, 11u, npos};
+  static_assert(s3 == "", "");
+  // Out of bounds offset, does not compile
+  // constexpr folly::FixedString<0> s4{s, 12};
+}
+
+TEST(FixedStringCtorTest, FromStringOffsetAndCount) {
+  constexpr folly::FixedString<11> s{"hello world"};
+  constexpr folly::FixedString<4> s2{s, 6u, 4u};
+  static_assert(s2 == "worl", "");
+  constexpr folly::FixedString<5> s3{s, 6u, 5u};
+  static_assert(s3 == "world", "");
+  // Out of bounds count, does not compile:
+  // constexpr folly::FixedString<5> s4{s, 6, 6};
+}
+
+TEST(FixedStringCtorTest, FromInitializerList) {
+  constexpr folly::FixedString<11> s{
+      'h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd'};
+  static_assert(s == "hello world", "");
+  // Out of bounds count, does not compile:
+  // constexpr folly::FixedString<10> s{
+  //     {'h','e','l','l','o',' ','w','o','r','l','d'}};
+}
+
+TEST(FixedStringCtorTest, FromUDL) {
+  using namespace folly::Literals;
+#if defined(__GNUC__)
+  constexpr auto x = "hello"_fs;
+  static_assert(
+      std::is_same<decltype(x), const folly::FixedString<5>>::value, "");
+  static_assert(x[0] == 'h', "");
+  static_assert(x[1] == 'e', "");
+  static_assert(x[2] == 'l', "");
+  static_assert(x[3] == 'l', "");
+  static_assert(x[4] == 'o', "");
+  static_assert(x[5] == '\0', "");
+  static_assert(x.size() == 5u, "");
+#endif
+
+  constexpr auto y = "goodbye"_fs8;
+  static_assert(
+      std::is_same<decltype(y), const folly::FixedString<8>>::value, "");
+  static_assert(y.size() == 7u, "");
+  static_assert(y == "goodbye", "");
+
+  constexpr auto z = "now is the time for all good llamas"_fs64;
+  static_assert(
+      std::is_same<decltype(z), const folly::FixedString<64>>::value, "");
+  static_assert(z.size() == 35u, "");
+  static_assert(z == "now is the time for all good llamas", "");
+}
+
+TEST(FixedStringConcatTest, FromStringAndLiteral) {
+  constexpr folly::FixedString<42> s{"hello world"};
+  constexpr auto res = s + "!!!";
+  static_assert(res.size() == 14u, "");
+  static_assert(res == "hello world!!!", "");
+}
+
+TEST(FixedStringConcatTest, FromTwoStrings) {
+  constexpr folly::FixedString<42> s{"hello world"};
+  constexpr auto res = s + "!!!";
+  static_assert(res.size() == 14u, "");
+  static_assert(res == "hello world!!!", "");
+}
+
+#if FOLLY_USE_CPP14_CONSTEXPR
+constexpr folly::FixedString<20> constexpr_swap_test() {
+  folly::FixedString<10> tmp1{"hello"}, tmp2{"world!"};
+  tmp2.swap(tmp1);
+  return tmp1 + tmp2;
+}
+
+TEST(FixedStringSwapTest, ConstexprSwap) {
+  static_assert(constexpr_swap_test() == "world!hello", "");
+}
+#endif
+
+TEST(FixedStringSwapTest, RuntimeSwap) {
+  folly::FixedString<10> tmp1{"hello"}, tmp2{"world!"};
+  tmp2.swap(tmp1);
+  EXPECT_STREQ((tmp1 + tmp2).c_str(), "world!hello");
+}
+
+#if FOLLY_USE_CPP14_CONSTEXPR
+constexpr folly::FixedString<10> constexpr_assign_string_test_1() {
+  folly::FixedString<10> tmp1, tmp2{"world!"};
+  tmp1 = tmp2;
+  return tmp1;
+}
+constexpr folly::FixedString<10> constexpr_assign_string_test_2() {
+  folly::FixedString<10> tmp{"aaaaaaaaaa"};
+  tmp.assign("hello"_fs8);
+  return tmp;
+}
+constexpr folly::FixedString<10> constexpr_assign_string_test_3() {
+  folly::FixedString<10> tmp{"aaaaaaaaaa"};
+  tmp.assign("goodbye"_fs8, 3u, 2u);
+  return tmp;
+}
+constexpr folly::FixedString<10> constexpr_assign_string_test_4() {
+  folly::FixedString<10> tmp{"aaaaaaaaaa"};
+  tmp.assign("goodbye"_fs8, 3u, npos);
+  return tmp;
+}
+
+TEST(FixedStringAssignTest, ConstexprAssignString) {
+  static_assert(constexpr_assign_string_test_1() == "world!", "");
+  static_assert(constexpr_assign_string_test_2() == "hello", "");
+  static_assert(constexpr_assign_string_test_3() == "db", "");
+  static_assert(constexpr_assign_string_test_4() == "dbye", "");
+}
+#endif
+
+TEST(FixedStringAssignTest, RuntimeAssignString) {
+  folly::FixedString<10> tmp1, tmp2{"world!"};
+  tmp1 = tmp2;
+  EXPECT_STREQ(tmp1.c_str(), "world!");
+  tmp1.assign("goodbye"_fs8);
+  EXPECT_STREQ("goodbye", tmp1.c_str());
+  tmp1.assign("goodbye"_fs8, 3u, npos);
+  EXPECT_STREQ("dbye", tmp1.c_str());
+  tmp1.assign("goodbye"_fs8, 3u, 3u);
+  EXPECT_STREQ("dby", tmp1.c_str());
+}
+
+#if FOLLY_USE_CPP14_CONSTEXPR
+constexpr folly::FixedString<10> constexpr_assign_literal_test_1() {
+  folly::FixedString<10> tmp{"aaaaaaaaaa"};
+  tmp = "hello";
+  // Not null-terminated, does not compile:
+  // using C = const char[1];
+  // tmp = C{'a'};
+  return tmp;
+}
+constexpr folly::FixedString<10> constexpr_assign_literal_test_2() {
+  folly::FixedString<10> tmp{"aaaaaaaaaa"};
+  tmp.assign("hello");
+  return tmp;
+}
+constexpr folly::FixedString<10> constexpr_assign_literal_test_3() {
+  folly::FixedString<10> tmp{"aaaaaaaaaa"};
+  tmp.assign("goodbye", 4u);
+  return tmp;
+}
+
+TEST(FixedStringAssignTest, ConstexprAssignLiteral) {
+  static_assert(constexpr_assign_literal_test_1() == "hello", "");
+  static_assert(constexpr_assign_literal_test_2() == "hello", "");
+  static_assert(constexpr_assign_literal_test_3() == "good", "");
+}
+#endif
+
+TEST(FixedStringAssignTest, RuntimeAssignLiteral) {
+  folly::FixedString<10> tmp{"aaaaaaaaaa"};
+  tmp = "hello";
+  EXPECT_STREQ("hello", tmp.c_str());
+  tmp.assign("goodbye");
+  EXPECT_STREQ("goodbye", tmp.c_str());
+  tmp.assign("goodbye", 4u);
+  EXPECT_STREQ("good", tmp.c_str());
+}
+
+TEST(FixedStringIndexTest, Index) {
+  constexpr folly::FixedString<11> digits{"0123456789"};
+  static_assert(digits[0] == '0', "");
+  static_assert(digits[1] == '1', "");
+  static_assert(digits[2] == '2', "");
+  static_assert(digits[9] == '9', "");
+  static_assert(digits[10] == '\0', "");
+  #ifdef NDEBUG
+  // This should be allowed and work in constexpr mode since the internal array
+  // is actually big enough and op[] does no parameter validation:
+  static_assert(digits[11] == '\0', "");
+  #endif
+
+  static_assert(digits.at(0) == '0', "");
+  static_assert(digits.at(1) == '1', "");
+  static_assert(digits.at(2) == '2', "");
+  static_assert(digits.at(9) == '9', "");
+  static_assert(digits.at(10) == '\0', "");
+  EXPECT_THROW(digits.at(11), std::out_of_range);
+}
+
+TEST(FixedStringCompareTest, Compare) {
+  constexpr folly::FixedString<10> tmp1{"aaaaaaaaaa"};
+  constexpr folly::FixedString<12> tmp2{"aaaaaaaaaba"};
+  static_assert(-1 == tmp1.compare(tmp2), "");
+  static_assert(1 == tmp2.compare(tmp1), "");
+  static_assert(0 == tmp2.compare(tmp2), "");
+  static_assert(tmp1 < tmp2, "");
+  static_assert(tmp1 <= tmp2, "");
+  static_assert(tmp2 > tmp1, "");
+  static_assert(tmp2 >= tmp1, "");
+  static_assert(tmp2 == tmp2, ""); // @nolint
+  static_assert(tmp2 <= tmp2, ""); // @nolint
+  static_assert(tmp2 >= tmp2, ""); // @nolint
+  static_assert(!(tmp2 < tmp2), "");
+  static_assert(!(tmp2 > tmp2), "");
+
+  constexpr folly::FixedString<10> tmp3{"aaa"};
+  constexpr folly::FixedString<12> tmp4{"aaaa"};
+  static_assert(-1 == tmp3.compare(tmp4), "");
+  static_assert(1 == tmp4.compare(tmp3), "");
+  static_assert(tmp3 < tmp4, "");
+  static_assert(tmp3 <= tmp4, "");
+  static_assert(tmp4 > tmp3, "");
+  static_assert(tmp4 >= tmp3, "");
+  static_assert(tmp3 < "aaaa", "");
+  static_assert(tmp3 <= "aaaa", "");
+  static_assert(!(tmp3 == tmp4), "");
+  static_assert(tmp3 != tmp4, "");
+  static_assert("aaaa" > tmp3, "");
+  static_assert("aaaa" >= tmp3, "");
+  static_assert("aaaa" != tmp3, "");
+  static_assert("aaa" == tmp3, "");
+  static_assert(tmp3 != "aaaa", "");
+  static_assert(tmp3 == "aaa", "");
+}
+
+#if FOLLY_USE_CPP14_CONSTEXPR
+constexpr folly::FixedString<20> constexpr_append_string_test() {
+  folly::FixedString<20> a{"hello"}, b{"X world!"};
+  a.append(1u, ' ');
+  a.append(b, 2u, 5u);
+  a.append(b, 7u, 1u);
+  return a;
+}
+
+TEST(FixedStringAssignTest, ConstexprAppendString) {
+  static_assert(constexpr_append_string_test() == "hello world!", "");
+}
+#endif
+
+TEST(FixedStringAssignTest, RuntimeAppendString) {
+  folly::FixedString<20> a{"hello"}, b{"X world!"};
+  a.append(1u, ' ');
+  a.append(b, 2u, 5u);
+  a.append(b, 7u, 1u);
+  EXPECT_STREQ("hello world!", a.c_str());
+}
+
+#if FOLLY_USE_CPP14_CONSTEXPR
+constexpr folly::FixedString<20> constexpr_append_literal_test() {
+  folly::FixedString<20> a{"hello"};
+  a.append(1u, ' ');
+  a.append("X world!" + 2u, 5u);
+  a.append("X world!" + 7u);
+  return a;
+}
+
+TEST(FixedStringAssignTest, ConstexprAppendLiteral) {
+  static_assert(constexpr_append_literal_test() == "hello world!", "");
+}
+#endif
+
+TEST(FixedStringAssignTest, RuntimeAppendLiteral) {
+  folly::FixedString<20> a{"hello"};
+  a.append(1u, ' ');
+  a.append("X world!" + 2u, 5u);
+  a.append("X world!" + 7u);
+  EXPECT_STREQ("hello world!", a.c_str());
+}
+
+TEST(FixedStringCAppendTest, CAppendString) {
+  constexpr folly::FixedString<10> a{"hello"}, b{"X world!"};
+  constexpr auto tmp1 = a.cappend(' ');
+  constexpr auto tmp2 = tmp1.cappend(b, 2u, 5u);
+  constexpr auto tmp3 = tmp2.cappend(b, 7u, 1u);
+  static_assert(tmp3 == "hello world!", "");
+}
+
+TEST(FixedStringCAppendTest, CAppendLiteral) {
+  constexpr folly::FixedString<10> a{"hello"};
+  constexpr auto tmp1 = a.cappend(' ');
+  constexpr auto tmp2 = tmp1.cappend("X world!", 2u, 5u);
+  constexpr auto tmp3 = tmp2.cappend("X world!", 7u, 1u);
+  static_assert(tmp3 == "hello world!", "");
+}
+
+#if FOLLY_USE_CPP14_CONSTEXPR
+constexpr folly::FixedString<10> constexpr_replace_string_test() {
+  folly::FixedString<10> tmp{"abcdefghij"};
+  tmp.replace(1, 5, FS("XX"));
+  return tmp;
+}
+
+TEST(FixedStringReplaceTest, ConstexprReplaceString) {
+  static_assert(constexpr_replace_string_test().size() == 7u, "");
+  static_assert(constexpr_replace_string_test() == "aXXghij", "");
+}
+#endif
+
+TEST(FixedStringReplaceTest, RuntimeReplaceString) {
+  folly::FixedString<10> tmp{"abcdefghij"};
+  tmp.replace(1, 5, FS("XX"));
+  EXPECT_EQ(7u, tmp.size());
+  EXPECT_STREQ("aXXghij", tmp.c_str());
+}
+
+TEST(FixedStringEraseTest, RuntimeEraseTest) {
+  auto x = FS("abcdefghijklmnopqrstuvwxyz"), y = x;
+  x.erase(x.size());
+  EXPECT_EQ(26u, x.size());
+  EXPECT_STREQ(y.c_str(), x.c_str());
+  x.erase(25u).erase(24u);
+  EXPECT_EQ(24u, x.size());
+  EXPECT_STREQ("abcdefghijklmnopqrstuvwx", x.c_str());
+  x.erase(1u, x.size() - 2u);
+  EXPECT_EQ(2u, x.size());
+  EXPECT_STREQ("ax", x.c_str());
+}
+
+TEST(FixedStringEraseTest, CEraseTest) {
+  constexpr auto x = FS("abcdefghijklmnopqrstuvwxyz"), y = x;
+  constexpr auto tmp0 = x.cerase(x.size());
+  static_assert(26u == tmp0.size(), "");
+  static_assert(y == tmp0, "");
+  constexpr auto tmp1 = tmp0.cerase(25u).cerase(24u);
+  static_assert(24u == tmp1.size(), "");
+  static_assert("abcdefghijklmnopqrstuvwx" == tmp1, "");
+  constexpr auto tmp2 = tmp1.cerase(1u, tmp1.size() - 2u);
+  static_assert(2u == tmp2.size(), "");
+  static_assert("ax" == tmp2, "");
+  constexpr auto tmp3 = tmp2.cerase();
+  static_assert("" == tmp3, "");
+}
+
+TEST(FixedStringFindTest, FindString) {
+  constexpr folly::FixedString<10> tmp{"hijdefghij"};
+  static_assert(tmp.find(FS("hij")) == 0u, "");
+  static_assert(tmp.find(FS("hij"), 1u) == 7u, "");
+  static_assert(tmp.find(FS("hijdefghij")) == 0u, "");
+  static_assert(tmp.find(FS("")) == 0u, "");
+}
+
+TEST(FixedStringFindTest, FindLiteral) {
+  constexpr folly::FixedString<10> tmp{"hijdefghij"};
+  static_assert(tmp.find("hij") == 0u, "");
+  static_assert(tmp.find("hij", 1u) == 7u, "");
+  static_assert(tmp.find("hijdefghij") == 0u, "");
+}
+
+TEST(FixedStringReverseFindTest, FindChar) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find('s') == 3u, "");
+  static_assert(tmp.find('s', 9u) == 10u, "");
+  static_assert(tmp.find('s', 10u) == 10u, "");
+  static_assert(tmp.find('s', 11u) == tmp.npos, "");
+}
+
+TEST(FixedStringReverseFindTest, ReverseFindString) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.rfind(FS("is")) == 5u, "");
+  static_assert(tmp.rfind(FS("is"), 4u) == 2u, "");
+  static_assert(tmp.rfind(FS("This is a string")) == 0u, "");
+  static_assert(tmp.rfind(FS("This is a string!")) == tmp.npos, "");
+  static_assert(tmp.rfind(FS("")) == 16u, "");
+}
+
+TEST(FixedStringReverseFindTest, ReverseFindLiteral) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.rfind("is") == 5u, "");
+  static_assert(tmp.rfind("is", 4u) == 2u, "");
+  static_assert(tmp.rfind("This is a string") == 0u, "");
+  static_assert(tmp.rfind("This is a string!") == tmp.npos, "");
+  static_assert(tmp.rfind("") == 16u, "");
+}
+
+TEST(FixedStringReverseFindTest, ReverseFindChar) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.rfind('s') == 10u, "");
+  static_assert(tmp.rfind('s', 5u) == 3u, "");
+  static_assert(tmp.rfind('s', 3u) == 3u, "");
+  static_assert(tmp.rfind('s', 2u) == tmp.npos, "");
+}
+
+TEST(FixedStringFindFirstOfTest, FindFirstOfString) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_first_of(FS("hi")) == 1u, "");
+  static_assert(tmp.find_first_of(FS("xi")) == 2u, "");
+  static_assert(tmp.find_first_of(FS("xi"), 6u) == 13u, "");
+  static_assert(tmp.find_first_of(FS("xz")) == tmp.npos, "");
+  static_assert(FS("a").find_first_of(FS("cba")) == 0u, "");
+  static_assert(FS("").find_first_of(FS("cba")) == tmp.npos, "");
+  static_assert(FS("a").find_first_of(FS("")) == tmp.npos, "");
+  static_assert(FS("").find_first_of(FS("")) == tmp.npos, "");
+}
+
+TEST(FixedStringFindFirstOfTest, FindFirstOfLiteral) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_first_of("hi") == 1u, "");
+  static_assert(tmp.find_first_of("xi") == 2u, "");
+  static_assert(tmp.find_first_of("xi", 6u) == 13u, "");
+  static_assert(tmp.find_first_of("xis", 6u, 2u) == 13u, "");
+  static_assert(tmp.find_first_of("xz") == tmp.npos, "");
+  static_assert(FS("a").find_first_of("cba") == 0u, "");
+  static_assert(FS("").find_first_of("cba") == tmp.npos, "");
+  static_assert(FS("a").find_first_of("") == tmp.npos, "");
+  static_assert(FS("").find_first_of("") == tmp.npos, "");
+}
+
+TEST(FixedStringFindFirstOfTest, FindFirstOfChar) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_first_of('h') == 1u, "");
+  static_assert(tmp.find_first_of('i') == 2u, "");
+  static_assert(tmp.find_first_of('i', 6u) == 13u, "");
+  static_assert(tmp.find_first_of('x') == tmp.npos, "");
+  static_assert(FS("a").find_first_of('a') == 0u, "");
+  static_assert(FS("").find_first_of('a') == tmp.npos, "");
+}
+
+TEST(FixedStringFindFirstNotOfTest, FindFirstNotOfString) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_first_not_of(FS("Ti")) == 1u, "");
+  static_assert(tmp.find_first_not_of(FS("hT")) == 2u, "");
+  static_assert(tmp.find_first_not_of(FS("s atr"), 6u) == 13u, "");
+  static_assert(tmp.find_first_not_of(FS("This atrng")) == tmp.npos, "");
+  static_assert(FS("a").find_first_not_of(FS("X")) == 0u, "");
+  static_assert(FS("").find_first_not_of(FS("cba")) == tmp.npos, "");
+  static_assert(FS("a").find_first_not_of(FS("")) == 0u, "");
+  static_assert(FS("").find_first_not_of(FS("")) == tmp.npos, "");
+}
+
+TEST(FixedStringFindFirstNotOfTest, FindFirstNotOfLiteral) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_first_not_of("Ti") == 1u, "");
+  static_assert(tmp.find_first_not_of("hT") == 2u, "");
+  static_assert(tmp.find_first_not_of("s atr", 6u) == 13u, "");
+  static_assert(tmp.find_first_not_of("This atrng") == tmp.npos, "");
+  static_assert(FS("a").find_first_not_of("X") == 0u, "");
+  static_assert(FS("").find_first_not_of("cba") == tmp.npos, "");
+  static_assert(FS("a").find_first_not_of("") == 0u, "");
+  static_assert(FS("").find_first_not_of("") == tmp.npos, "");
+}
+
+TEST(FixedStringFindFirstNotOfTest, FindFirstNotOfChar) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_first_not_of('T') == 1u, "");
+  static_assert(tmp.find_first_not_of('i') == 0u, "");
+  static_assert(tmp.find_first_not_of('x', 6u) == 6u, "");
+  static_assert(tmp.find_first_not_of('s', 6u) == 7u, "");
+  static_assert(FS("a").find_first_not_of('a') == tmp.npos, "");
+  static_assert(FS("").find_first_not_of('a') == tmp.npos, "");
+}
+
+TEST(FixedStringFindLastOfTest, FindLastOfString) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_last_of(FS("hi")) == 13u, "");
+  static_assert(tmp.find_last_of(FS("xh")) == 1u, "");
+  static_assert(tmp.find_last_of(FS("xi"), 6u) == 5u, "");
+  static_assert(tmp.find_last_of(FS("xz")) == tmp.npos, "");
+  static_assert(FS("a").find_last_of(FS("cba")) == 0u, "");
+  static_assert(FS("").find_last_of(FS("cba")) == tmp.npos, "");
+  static_assert(FS("a").find_last_of(FS("")) == tmp.npos, "");
+  static_assert(FS("").find_last_of(FS("")) == tmp.npos, "");
+}
+
+TEST(FixedStringFindLastOfTest, FindLastOfLiteral) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_last_of("hi") == 13u, "");
+  static_assert(tmp.find_last_of("xh") == 1u, "");
+  static_assert(tmp.find_last_of("xi", 6u) == 5u, "");
+  static_assert(tmp.find_last_of("xis", 6u, 2u) == 5u, "");
+  static_assert(tmp.find_last_of("xz") == tmp.npos, "");
+  static_assert(FS("a").find_last_of("cba") == 0u, "");
+  static_assert(FS("").find_last_of("cba") == tmp.npos, "");
+  static_assert(FS("a").find_last_of("") == tmp.npos, "");
+  static_assert(FS("").find_last_of("") == tmp.npos, "");
+}
+
+TEST(FixedStringFindLastOfTest, FindLastOfChar) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_last_of('h') == 1u, "");
+  static_assert(tmp.find_last_of('i') == 13u, "");
+  static_assert(tmp.find_last_of('i', 6u) == 5u, "");
+  static_assert(tmp.find_last_of('x') == tmp.npos, "");
+  static_assert(FS("a").find_last_of('a') == 0u, "");
+  static_assert(FS("").find_last_of('a') == tmp.npos, "");
+}
+
+TEST(FixedStringFindLastNotOfTest, FindLastNotOfString) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_last_not_of(FS("gstrin")) == 9u, "");
+  static_assert(tmp.find_last_not_of(FS("hT")) == 15u, "");
+  static_assert(tmp.find_last_not_of(FS("s atr"), 6u) == 5u, "");
+  static_assert(tmp.find_last_not_of(FS("This atrng")) == tmp.npos, "");
+  static_assert(FS("a").find_last_not_of(FS("X")) == 0u, "");
+  static_assert(FS("").find_last_not_of(FS("cba")) == tmp.npos, "");
+  static_assert(FS("a").find_last_not_of(FS("")) == 0u, "");
+  static_assert(FS("").find_last_not_of(FS("")) == tmp.npos, "");
+}
+
+TEST(FixedStringFindLastNotOfTest, FindLastNotOfLiteral) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_last_not_of("gstrin") == 9u, "");
+  static_assert(tmp.find_last_not_of("hT") == 15u, "");
+  static_assert(tmp.find_last_not_of("s atr", 6u) == 5u, "");
+  static_assert(tmp.find_last_not_of(" atrs", 6u, 4u) == 6u, "");
+  static_assert(tmp.find_last_not_of("This atrng") == tmp.npos, "");
+  static_assert(FS("a").find_last_not_of("X") == 0u, "");
+  static_assert(FS("").find_last_not_of("cba") == tmp.npos, "");
+  static_assert(FS("a").find_last_not_of("") == 0u, "");
+  static_assert(FS("").find_last_not_of("") == tmp.npos, "");
+}
+
+TEST(FixedStringFindLastNotOfTest, FindLastNotOfChar) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  static_assert(tmp.find_last_not_of('g') == 14u, "");
+  static_assert(tmp.find_last_not_of('i') == 15u, "");
+  static_assert(tmp.find_last_not_of('x', 6u) == 6u, "");
+  static_assert(tmp.find_last_not_of('s', 6u) == 5u, "");
+  static_assert(FS("a").find_last_not_of('a') == tmp.npos, "");
+  static_assert(FS("").find_last_not_of('a') == tmp.npos, "");
+}
+
+TEST(FixedStringConversionTest, ConversionToStdString) {
+  constexpr folly::FixedString<16> tmp{"This is a string"};
+  std::string str = tmp;
+  EXPECT_STREQ("This is a string", str.c_str());
+  str = "another string"_fs16;
+  EXPECT_STREQ("another string", str.c_str());
+}
+
+#if FOLLY_USE_CPP14_CONSTEXPR
+constexpr std::size_t countSpacesReverse(folly::FixedString<50> s) {
+  std::size_t count = 0u;
+  auto i = s.rbegin();
+  for( ; i != s.rend(); ++i, --i, i++, i--, i+=1, i-=1, i+=1 ) {
+    if (' ' == *i)
+      ++count;
+  }
+  return count;
+}
+
+TEST(FixedStringReverseIteratorTest, Cpp14ConstexprReverseIteration) {
+  static_assert(3 == countSpacesReverse("This is a string"), "");
+}
+#endif
+
+TEST(FixedStringReverseIteratorTest, ConstexprReverseIteration) {
+  static constexpr auto alpha = FS("abcdefghijklmnopqrstuvwxyz");
+  static_assert('a' == alpha.rbegin()[25], "");
+  static_assert('a' == *(alpha.rbegin() + 25), "");
+  static_assert('c' == *(alpha.rbegin() + 25 - 2), "");
+  static_assert((alpha.rend() - 2) == (alpha.rbegin() + 24), "");
+}
+
+#include <folly/Range.h>
+
+TEST(FixedStringConversionTest, ConversionToFollyRange) {
+  // The following declaraction is static for compilers that haven't implemented
+  // the resolution of:
+  // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1454
+  static constexpr folly::FixedString<16> tmp{"This is a string"};
+  constexpr folly::StringPiece piece = tmp;
+  static_assert(tmp.begin() == piece.begin(), "");
+  static_assert(tmp.end() == piece.end(), "");
+}