summaryrefslogtreecommitdiff
path: root/absl/strings
diff options
context:
space:
mode:
authorGravatar Zie Weaver <zearen@google.com>2023-10-18 16:17:51 -0700
committerGravatar Copybara-Service <copybara-worker@google.com>2023-10-18 16:18:51 -0700
commit9687a8ea750bfcddf790372093245a1d041b21a3 (patch)
tree32c06ea4c2061d0212872cc37b73ce487b1af84c /absl/strings
parent7676c565eedd2581b66839c239f3825d8e381119 (diff)
Add a template gadget to detect whether a type supports the ostream operator.
I.e. for a type `Example`, if ``` std::ostream& operator<<(std::ostream&, const Example&); ``` is declared, `absl::HasOstreamOperator<Example>::value` is `true`. PiperOrigin-RevId: 574637891 Change-Id: I123d8f35a6e3ea894745133f7d81b1610fb475d5
Diffstat (limited to 'absl/strings')
-rw-r--r--absl/strings/BUILD.bazel25
-rw-r--r--absl/strings/CMakeLists.txt26
-rw-r--r--absl/strings/has_absl_stringify_test.cc3
-rw-r--r--absl/strings/has_ostream_operator.h42
-rw-r--r--absl/strings/has_ostream_operator_test.cc41
5 files changed, 137 insertions, 0 deletions
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 37273491..a3ef3ae8 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -194,6 +194,31 @@ cc_test(
visibility = ["//visibility:private"],
deps = [
":strings",
+ "//absl/types:optional",
+ "@com_google_googletest//:gtest",
+ "@com_google_googletest//:gtest_main",
+ ],
+)
+
+cc_library(
+ name = "has_ostream_operator",
+ hdrs = ["has_ostream_operator.h"],
+ copts = ABSL_DEFAULT_COPTS,
+ linkopts = ABSL_DEFAULT_LINKOPTS,
+ deps = [
+ "//absl/base:config",
+ ],
+)
+
+cc_test(
+ name = "has_ostream_operator_test",
+ size = "small",
+ srcs = ["has_ostream_operator_test.cc"],
+ copts = ABSL_TEST_COPTS,
+ visibility = ["//visibility:private"],
+ deps = [
+ ":has_ostream_operator",
+ "//absl/types:optional",
"@com_google_googletest//:gtest",
"@com_google_googletest//:gtest_main",
],
diff --git a/absl/strings/CMakeLists.txt b/absl/strings/CMakeLists.txt
index f470ff5a..b129096d 100644
--- a/absl/strings/CMakeLists.txt
+++ b/absl/strings/CMakeLists.txt
@@ -103,6 +103,18 @@ absl_cc_library(
PUBLIC
)
+absl_cc_library(
+ NAME
+ has_ostream_operator
+ HDRS
+ "has_ostream_operator.h"
+ COPTS
+ ${ABSL_DEFAULT_COPTS}
+ DEPS
+ absl::config
+ PUBLIC
+)
+
# Internal-only target, do not depend on directly.
absl_cc_library(
NAME
@@ -162,12 +174,26 @@ absl_cc_test(
COPTS
${ABSL_TEST_COPTS}
DEPS
+ absl::optional
absl::strings
GTest::gmock_main
)
absl_cc_test(
NAME
+ has_ostream_operator_test
+ SRCS
+ "has_ostream_operator_test.cc"
+ COPTS
+ ${ABSL_TEST_COPTS}
+ DEPS
+ absl::has_ostream_operator
+ absl::optional
+ GTest::gmock_main
+)
+
+absl_cc_test(
+ NAME
ascii_test
SRCS
"ascii_test.cc"
diff --git a/absl/strings/has_absl_stringify_test.cc b/absl/strings/has_absl_stringify_test.cc
index e9915c66..59e7e1d3 100644
--- a/absl/strings/has_absl_stringify_test.cc
+++ b/absl/strings/has_absl_stringify_test.cc
@@ -17,6 +17,7 @@
#include <string>
#include "gtest/gtest.h"
+#include "absl/types/optional.h"
namespace {
@@ -32,6 +33,8 @@ TEST(HasAbslStringifyTest, Works) {
EXPECT_FALSE(absl::HasAbslStringify<std::string>::value);
EXPECT_FALSE(absl::HasAbslStringify<TypeWithoutAbslStringify>::value);
EXPECT_TRUE(absl::HasAbslStringify<TypeWithAbslStringify>::value);
+ EXPECT_FALSE(
+ absl::HasAbslStringify<absl::optional<TypeWithAbslStringify>>::value);
}
} // namespace
diff --git a/absl/strings/has_ostream_operator.h b/absl/strings/has_ostream_operator.h
new file mode 100644
index 00000000..156ffc74
--- /dev/null
+++ b/absl/strings/has_ostream_operator.h
@@ -0,0 +1,42 @@
+// Copyright 2023 The Abseil Authors
+//
+// 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
+//
+// https://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.
+
+#ifndef ABSL_STRINGS_HAS_OSTREAM_OPERATOR_H_
+#define ABSL_STRINGS_HAS_OSTREAM_OPERATOR_H_
+
+#include <ostream>
+#include <type_traits>
+#include <utility>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// Detects if type `T` supports streaming to `std::ostream`s with `operator<<`.
+
+template <typename T, typename = void>
+struct HasOstreamOperator : std::false_type {};
+
+template <typename T>
+struct HasOstreamOperator<
+ T, std::enable_if_t<std::is_same<
+ std::ostream&, decltype(std::declval<std::ostream&>()
+ << std::declval<const T&>())>::value>>
+ : std::true_type {};
+
+ABSL_NAMESPACE_END
+} // namespace absl
+
+#endif // ABSL_STRINGS_HAS_OSTREAM_OPERATOR_H_
diff --git a/absl/strings/has_ostream_operator_test.cc b/absl/strings/has_ostream_operator_test.cc
new file mode 100644
index 00000000..9ef41366
--- /dev/null
+++ b/absl/strings/has_ostream_operator_test.cc
@@ -0,0 +1,41 @@
+// Copyright 2023 The Abseil Authors
+//
+// 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
+//
+// https://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.
+
+#include "absl/strings/has_ostream_operator.h"
+
+#include <ostream>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "absl/types/optional.h"
+
+namespace {
+
+struct TypeWithoutOstreamOp {};
+
+struct TypeWithOstreamOp {
+ friend std::ostream& operator<<(std::ostream& os, const TypeWithOstreamOp&) {
+ return os;
+ }
+};
+
+TEST(HasOstreamOperatorTest, Works) {
+ EXPECT_TRUE(absl::HasOstreamOperator<int>::value);
+ EXPECT_TRUE(absl::HasOstreamOperator<std::string>::value);
+ EXPECT_FALSE(absl::HasOstreamOperator<absl::optional<int>>::value);
+ EXPECT_FALSE(absl::HasOstreamOperator<TypeWithoutOstreamOp>::value);
+ EXPECT_TRUE(absl::HasOstreamOperator<TypeWithOstreamOp>::value);
+}
+
+} // namespace