[nativert] Port string join and split to c10/util (#152873)

Summary:
Torch Native Runtime RFC: https://github.com/pytorch/rfcs/pull/72
Port string utils functions join and split to c10/util

Test Plan:
Added tests in `string_util_test.cpp`
buck2 run mode/opt caffe2/c10/test:util_base_tests

Differential Revision: D74202473

Pull Request resolved: https://github.com/pytorch/pytorch/pull/152873
Approved by: https://github.com/cyyever, https://github.com/Skylion007

c10/test/util/string_util_test.cpp

@@ -133,4 +133,34 @@ TEST(tryToTest, Double) {
   EXPECT_FALSE(c10::tryToNumber<double>(nullptr).has_value());
 }
 } // namespace test_try_to
+
+namespace test_split {
+TEST(SplitTest, NormalCase) {
+  std::string str = "torch.ops.aten.linear";
+  auto result = c10::split(str, '.');
+  ASSERT_EQ(4, result.size());
+  EXPECT_EQ("torch", result[0]);
+  EXPECT_EQ("ops", result[1]);
+  EXPECT_EQ("aten", result[2]);
+  EXPECT_EQ("linear", result[3]);
+}
+TEST(SplitTest, EmptyString) {
+  auto result = c10::split("", '.');
+  EXPECT_TRUE(result.empty());
+}
+TEST(SplitTest, NoDelimiter) {
+  std::string str = "single";
+  auto result = c10::split(str, '.');
+  ASSERT_EQ(1, result.size());
+  EXPECT_EQ("single", result[0]);
+}
+TEST(SplitTest, ConsecutiveDelimiters) {
+  std::string str = "atom1..atom2";
+  auto result = c10::split(str, '.');
+  ASSERT_EQ(3, result.size());
+  EXPECT_EQ("atom1", result[0]);
+  EXPECT_EQ("", result[1]);
+  EXPECT_EQ("atom2", result[2]);
+}
+} // namespace test_split
 } // namespace

c10/util/StringUtil.cpp

@@ -200,4 +200,19 @@ std::optional<double> tryToNumber<double>(const char* symbol) {
   return value;
 }
 
+std::vector<std::string_view> split(std::string_view target, char delimiter) {
+  std::vector<std::string_view> atoms;
+  std::string_view buffer = target;
+  while (!buffer.empty()) {
+    auto i = buffer.find(delimiter);
+    if (i == std::string_view::npos) {
+      atoms.push_back(buffer);
+      buffer.remove_prefix(buffer.size());
+    } else {
+      atoms.push_back(buffer.substr(0, i));
+      buffer.remove_prefix(i + 1);
+    }
+  }
+  return atoms;
+}
 } // namespace c10

c10/util/StringUtil.h

@@ -10,6 +10,7 @@
 #include <sstream>
 #include <string>
 #include <string_view>
+#include <vector>
 
 C10_CLANG_DIAGNOSTIC_PUSH()
 #if C10_CLANG_HAS_WARNING("-Wshorten-64-to-32")
@@ -238,6 +239,9 @@ C10_API std::optional<double> tryToNumber<double>(const char* symbol);
 template <>
 C10_API std::optional<double> tryToNumber<double>(const std::string& symbol);
 
+C10_API std::vector<std::string_view> split(
+    std::string_view target,
+    char delimiter);
 } // namespace c10
 
 C10_CLANG_DIAGNOSTIC_POP()