Move JoinString to the base namespace.

Change "Separator" from string to StringPIece (most are constants). Remove char versions for symmetry with SplitString.

Update callers who pass empty separators to use a base::StringPiece()

Change chromecast/base/metrics/cast_metrics_helper.cc to not use JoinString at all and just append to the output (code is simpler and faster).

TBR=zelidrag@chromium.org for chromeos

Review URL: https://codereview.chromium.org/1223153003

Cr-Commit-Position: refs/heads/master@{#338762}

3 files changed, 15 insertions, 52 deletions

diff --git a/base/strings/string_util.cc b/base/strings/string_util.cc
index ae5fb80..a0c95ec 100644
--- a/base/strings/string_util.cc
+++ b/base/strings/string_util.cc
@@ -884,43 +884,36 @@ char16* WriteInto(base::string16* str, size_t length_with_null) {
   return WriteIntoT(str, length_with_null);
 }
 
-}  // namespace base
-
 template<typename STR>
-static STR JoinStringT(const std::vector<STR>& parts, const STR& sep) {
+static STR JoinStringT(const std::vector<STR>& parts,
+                       BasicStringPiece<STR> sep) {
   if (parts.empty())
     return STR();
 
   STR result(parts[0]);
-  typename std::vector<STR>::const_iterator iter = parts.begin();
+  auto iter = parts.begin();
   ++iter;
 
   for (; iter != parts.end(); ++iter) {
-    result += sep;
+    sep.AppendToString(&result);
     result += *iter;
   }
 
   return result;
 }
 
-std::string JoinString(const std::vector<std::string>& parts, char sep) {
-  return JoinStringT(parts, std::string(1, sep));
-}
-
-string16 JoinString(const std::vector<string16>& parts, char16 sep) {
-  return JoinStringT(parts, string16(1, sep));
-}
-
 std::string JoinString(const std::vector<std::string>& parts,
-                       const std::string& separator) {
+                       StringPiece separator) {
   return JoinStringT(parts, separator);
 }
 
 string16 JoinString(const std::vector<string16>& parts,
-                    const string16& separator) {
+                    StringPiece16 separator) {
   return JoinStringT(parts, separator);
 }
 
+}  // namespace base
+
 template<class FormatStringType, class OutStringType>
 OutStringType DoReplaceStringPlaceholders(const FormatStringType& format_string,
     const std::vector<OutStringType>& subst, std::vector<size_t>* offsets) {
diff --git a/base/strings/string_util.h b/base/strings/string_util.h
index e4abce2..b75a9f88 100644
--- a/base/strings/string_util.h
+++ b/base/strings/string_util.h
@@ -491,6 +491,12 @@ BASE_EXPORT char16* WriteInto(base::string16* str, size_t length_with_null);
 BASE_EXPORT wchar_t* WriteInto(std::wstring* str, size_t length_with_null);
 #endif
 
+// Does the opposite of SplitString().
+BASE_EXPORT std::string JoinString(const std::vector<std::string>& parts,
+                                   StringPiece separator);
+BASE_EXPORT string16 JoinString(const std::vector<string16>& parts,
+                                StringPiece16 separator);
+
 }  // namespace base
 
 #if defined(OS_WIN)
@@ -501,22 +507,6 @@ BASE_EXPORT wchar_t* WriteInto(std::wstring* str, size_t length_with_null);
 #error Define string operations appropriately for your platform
 #endif
 
-//-----------------------------------------------------------------------------
-
-// Does the opposite of SplitString().
-BASE_EXPORT base::string16 JoinString(const std::vector<base::string16>& parts,
-                                      base::char16 s);
-BASE_EXPORT std::string JoinString(
-    const std::vector<std::string>& parts, char s);
-
-// Join |parts| using |separator|.
-BASE_EXPORT std::string JoinString(
-    const std::vector<std::string>& parts,
-    const std::string& separator);
-BASE_EXPORT base::string16 JoinString(
-    const std::vector<base::string16>& parts,
-    const base::string16& separator);
-
 // Replace $1-$2-$3..$9 in the format string with |a|-|b|-|c|..|i| respectively.
 // Additionally, any number of consecutive '$' characters is replaced by that
 // number less one. Eg $$->$, $$$->$$, etc. The offsets parameter here can be
diff --git a/base/strings/string_util_unittest.cc b/base/strings/string_util_unittest.cc
index 1593f81..5d5ba8b 100644
--- a/base/strings/string_util_unittest.cc
+++ b/base/strings/string_util_unittest.cc
@@ -669,26 +669,7 @@ TEST(StringUtilTest, HexDigitToInt) {
   EXPECT_EQ(15, HexDigitToInt('f'));
 }
 
-// Test for JoinString
 TEST(StringUtilTest, JoinString) {
-  std::vector<std::string> in;
-  EXPECT_EQ("", JoinString(in, ','));
-
-  in.push_back("a");
-  EXPECT_EQ("a", JoinString(in, ','));
-
-  in.push_back("b");
-  in.push_back("c");
-  EXPECT_EQ("a,b,c", JoinString(in, ','));
-
-  in.push_back(std::string());
-  EXPECT_EQ("a,b,c,", JoinString(in, ','));
-  in.push_back(" ");
-  EXPECT_EQ("a|b|c|| ", JoinString(in, '|'));
-}
-
-// Test for JoinString overloaded with std::string separator
-TEST(StringUtilTest, JoinStringWithString) {
   std::string separator(", ");
   std::vector<std::string> parts;
   EXPECT_EQ(std::string(), JoinString(parts, separator));
@@ -706,8 +687,7 @@ TEST(StringUtilTest, JoinStringWithString) {
   EXPECT_EQ("a|b|c|| ", JoinString(parts, "|"));
 }
 
-// Test for JoinString overloaded with string16 separator
-TEST(StringUtilTest, JoinStringWithString16) {
+TEST(StringUtilTest, JoinString16) {
   string16 separator = ASCIIToUTF16(", ");
   std::vector<string16> parts;
   EXPECT_EQ(string16(), JoinString(parts, separator));