Enable AsciiStrToLower and AsciiStrToUpper overloads for rvalue refer…

…ences.

PiperOrigin-RevId: 657719871
Change-Id: If0f16b1d8cfae79f31427a804a5b838599154895

absl/strings/ascii.h

@@ -55,6 +55,7 @@
 #include <algorithm>
 #include <cstddef>
 #include <string>
+#include <utility>
 
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
@@ -184,6 +185,16 @@ ABSL_MUST_USE_RESULT inline std::string AsciiStrToLower(absl::string_view s) {
   return result;
 }
 
+// Creates a lowercase string from a given std::string&&.
+//
+// (Template is used to lower priority of this overload.)
+template <int&... DoNotSpecify>
+ABSL_MUST_USE_RESULT inline std::string AsciiStrToLower(std::string&& s) {
+  std::string result = std::move(s);
+  absl::AsciiStrToLower(&result);
+  return result;
+}
+
 // ascii_toupper()
 //
 // Returns the ASCII character, converting to upper-case if lower-case is
@@ -203,6 +214,16 @@ ABSL_MUST_USE_RESULT inline std::string AsciiStrToUpper(absl::string_view s) {
   return result;
 }
 
+// Creates an uppercase string from a given std::string&&.
+//
+// (Template is used to lower priority of this overload.)
+template <int&... DoNotSpecify>
+ABSL_MUST_USE_RESULT inline std::string AsciiStrToUpper(std::string&& s) {
+  std::string result = std::move(s);
+  absl::AsciiStrToUpper(&result);
+  return result;
+}
+
 // Returns absl::string_view with whitespace stripped from the beginning of the
 // given string_view.
 ABSL_MUST_USE_RESULT inline absl::string_view StripLeadingAsciiWhitespace(

absl/strings/ascii_benchmark.cc

@@ -129,4 +129,32 @@ BENCHMARK(BM_StrToUpper)
     ->RangeMultiplier(2)
     ->Range(64, 1 << 26);
 
+static void BM_StrToUpperFromRvalref(benchmark::State& state) {
+  const size_t size = static_cast<size_t>(state.range(0));
+  std::string s(size, 'X');
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(s);
+    std::string res = absl::AsciiStrToUpper(std::string(s));
+    benchmark::DoNotOptimize(res);
+  }
+}
+BENCHMARK(BM_StrToUpperFromRvalref)
+    ->DenseRange(0, 32)
+    ->RangeMultiplier(2)
+    ->Range(64, 1 << 26);
+
+static void BM_StrToLowerFromRvalref(benchmark::State& state) {
+  const size_t size = static_cast<size_t>(state.range(0));
+  std::string s(size, 'x');
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(s);
+    std::string res = absl::AsciiStrToLower(std::string(s));
+    benchmark::DoNotOptimize(res);
+  }
+}
+BENCHMARK(BM_StrToLowerFromRvalref)
+    ->DenseRange(0, 32)
+    ->RangeMultiplier(2)
+    ->Range(64, 1 << 26);
+
 }  // namespace

absl/strings/ascii_test.cc

@@ -192,11 +192,13 @@ TEST(AsciiStrTo, Lower) {
   const absl::string_view sp(str2);
   const std::string long_str("ABCDEFGHIJKLMNOPQRSTUVWXYZ1!a");
   std::string mutable_str("_`?@[{AMNOPQRSTUVWXYZ");
+  auto fun = []() -> std::string { return "PQRSTU"; };
 
   EXPECT_EQ("abcdef", absl::AsciiStrToLower(buf));
   EXPECT_EQ("ghijkl", absl::AsciiStrToLower(str));
   EXPECT_EQ("mnopqr", absl::AsciiStrToLower(sp));
   EXPECT_EQ("abcdefghijklmnopqrstuvwxyz1!a", absl::AsciiStrToLower(long_str));
+  EXPECT_EQ("pqrstu", absl::AsciiStrToLower(fun()));
 
   absl::AsciiStrToLower(&mutable_str);
   EXPECT_EQ("_`?@[{amnopqrstuvwxyz", mutable_str);
@@ -213,11 +215,13 @@ TEST(AsciiStrTo, Upper) {
   const std::string str2("_`?@[{amnopqrstuvwxyz");
   const absl::string_view sp(str2);
   const std::string long_str("abcdefghijklmnopqrstuvwxyz1!A");
+  auto fun = []() -> std::string { return "pqrstu"; };
 
   EXPECT_EQ("ABCDEF", absl::AsciiStrToUpper(buf));
   EXPECT_EQ("GHIJKL", absl::AsciiStrToUpper(str));
   EXPECT_EQ("_`?@[{AMNOPQRSTUVWXYZ", absl::AsciiStrToUpper(sp));
   EXPECT_EQ("ABCDEFGHIJKLMNOPQRSTUVWXYZ1!A", absl::AsciiStrToUpper(long_str));
+  EXPECT_EQ("PQRSTU", absl::AsciiStrToUpper(fun()));
 
   char mutable_buf[] = "Mutable";
   std::transform(mutable_buf, mutable_buf + strlen(mutable_buf),