From 94c0297649d229113dea545eb6c4473c5fd669a4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=B5=96=E8=BF=8E=E6=98=A5?= <laiyingchun@sensorsdata.cn>
Date: Wed, 26 Apr 2023 14:05:11 +0800
Subject: [PATCH] [SKV-627] feat(utils): add an utility function to find string
 prefix by separator (#1338)

---
 src/rdsn/include/dsn/utility/strings.h |  4 ++++
 src/rdsn/src/utils/strings.cpp         |  9 +++++++++
 src/rdsn/src/utils/test/utils.cpp      | 22 ++++++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/src/rdsn/include/dsn/utility/strings.h b/src/rdsn/include/dsn/utility/strings.h
index 5fbb5af10d..2b6548b77c 100644
--- a/src/rdsn/include/dsn/utility/strings.h
+++ b/src/rdsn/include/dsn/utility/strings.h
@@ -81,5 +81,9 @@ char *trim_string(char *s);
 
 // calculate the md5 checksum of buffer
 std::string string_md5(const char *buffer, unsigned int length);
+
+// splits the "input" string by the only character "separator" to get the string prefix.
+// if there is no prefix or the first character is "separator", it will return "".
+std::string find_string_prefix(const std::string &input, char separator);
 } // namespace utils
 } // namespace dsn
diff --git a/src/rdsn/src/utils/strings.cpp b/src/rdsn/src/utils/strings.cpp
index 412d3e17d8..0ae8578b2c 100644
--- a/src/rdsn/src/utils/strings.cpp
+++ b/src/rdsn/src/utils/strings.cpp
@@ -219,5 +219,14 @@ std::string string_md5(const char *buffer, unsigned length)
 
     return result;
 }
+
+std::string find_string_prefix(const std::string &input, char separator)
+{
+    auto current = input.find(separator);
+    if (current == 0 || current == std::string::npos) {
+        return std::string();
+    }
+    return input.substr(0, current);
+}
 } // namespace utils
 } // namespace dsn
diff --git a/src/rdsn/src/utils/test/utils.cpp b/src/rdsn/src/utils/test/utils.cpp
index 7cf009aa73..a0940b115c 100644
--- a/src/rdsn/src/utils/test/utils.cpp
+++ b/src/rdsn/src/utils/test/utils.cpp
@@ -212,6 +212,28 @@ TEST(core, dlink)
     EXPECT_TRUE(count == 0);
 }
 
+TEST(core, find_string_prefix)
+{
+    struct test_case
+    {
+        std::string input;
+        char separator;
+        std::string expected_prefix;
+    } tests[] = {{"", ' ', ""},
+                 {"abc.def", ' ', ""},
+                 {"abc.def", '.', "abc"},
+                 {"ab.cd.ef", '.', "ab"},
+                 {"abc...def", '.', "abc"},
+                 {".abc.def", '.', ""},
+                 {" ", ' ', ""},
+                 {"..", '.', ""},
+                 {". ", ' ', "."}};
+    for (const auto &test : tests) {
+        auto actual_output = find_string_prefix(test.input, test.separator);
+        EXPECT_EQ(actual_output, test.expected_prefix);
+    }
+}
+
 class foo : public ::dsn::ref_counter
 {
 public: