Updates to StringSplit implementation

base/strings/string_split.cc

Index: base/strings/string_split.cc
diff --git a/base/strings/string_split.cc b/base/strings/string_split.cc
index b01ca66dea7476ff331a0a111e86d18617e0e5ee..4253e2f8f86b7ed393dfdf66193b91b489176bf8 100644
--- a/base/strings/string_split.cc
+++ b/base/strings/string_split.cc
@@ -99,52 +99,57 @@ static std::vector<OutputStringType> SplitStringT(
   return result;
 }
 
-bool SplitStringIntoKeyValue(const std::string& line,
-                             char key_value_delimiter,
-                             std::string* key,
-                             std::string* value) {
-  key->clear();
-  value->clear();
+bool AppendStringKeyValue(StringPiece input,
+                          char delimiter,
+                          StringPairs* result) {
+  // Always append a new item regardless of success (it might be empty). The
+  // below code will copy the strings directly into the result pair.
+  result->resize(result->size() + 1);
+  auto& result_pair = result->back();
 
   // Find the delimiter.
-  size_t end_key_pos = line.find_first_of(key_value_delimiter);
+  size_t end_key_pos = input.find_first_of(delimiter);
   if (end_key_pos == std::string::npos) {
-    DVLOG(1) << "cannot find delimiter in: " << line;
-    return false;    // no delimiter
+    DVLOG(1) << "cannot find delimiter in: " << input;
+    return false;    // No delimiter.
   }
-  key->assign(line, 0, end_key_pos);
+  input.substr(0, end_key_pos).CopyToString(&result_pair.first);
 
   // Find the value string.
-  std::string remains(line, end_key_pos, line.size() - end_key_pos);
-  size_t begin_value_pos = remains.find_first_not_of(key_value_delimiter);
-  if (begin_value_pos == std::string::npos) {
-    DVLOG(1) << "cannot parse value from line: " << line;
-    return false;   // no value
+  StringPiece remains = input.substr(end_key_pos, input.size() - end_key_pos);
+  size_t begin_value_pos = remains.find_first_not_of(delimiter);
+  if (begin_value_pos == StringPiece::npos) {
+    DVLOG(1) << "cannot parse value from input: " << input;
+    return false;   // No value.
   }
-  value->assign(remains, begin_value_pos, remains.size() - begin_value_pos);
+  remains.substr(begin_value_pos, remains.size() - begin_value_pos)
+      .CopyToString(&result_pair.second);
+
   return true;
 }
 
-template <typename STR>
-void SplitStringUsingSubstrT(const STR& str,
-                             const STR& s,
-                             std::vector<STR>* r) {
-  r->clear();
-  typename STR::size_type begin_index = 0;
+template <typename Str>
+void SplitStringUsingSubstrT(BasicStringPiece<Str> input,
+                             BasicStringPiece<Str> delimiter,
+                             std::vector<Str>* result) {
+  using Piece = BasicStringPiece<Str>;
+  using size_type = typename Piece::size_type;
+
+  result->clear();
+  size_type begin_index = 0;
   while (true) {
-    const typename STR::size_type end_index = str.find(s, begin_index);
-    if (end_index == STR::npos) {
-      const STR term = str.substr(begin_index);
-      STR tmp;
-      TrimWhitespace(term, TRIM_ALL, &tmp);
-      r->push_back(tmp);
+    size_type end_index = input.find(delimiter, begin_index);
+    if (end_index == Piece::npos) {
+      // No delimiter, use the rest of the string.
+      Piece term = TrimString(input.substr(begin_index),
+                              WhitespaceForType<Str>(), TRIM_ALL);
+      result->push_back(term.as_string());
       return;
     }
-    const STR term = str.substr(begin_index, end_index - begin_index);
-    STR tmp;
-    TrimWhitespace(term, TRIM_ALL, &tmp);
-    r->push_back(tmp);
-    begin_index = end_index + s.size();
+    Piece term = TrimString(input.substr(begin_index, end_index - begin_index),
+                            WhitespaceForType<Str>(), TRIM_ALL);
+    result->push_back(term.as_string());
+    begin_index = end_index + delimiter.size();
   }
 }
 
@@ -198,77 +203,38 @@ std::vector<StringPiece16> SplitStringPiece(StringPiece16 input,
       input, separators, whitespace, result_type);
 }
 
-void SplitString(const string16& str,
-                 char16 c,
-                 std::vector<string16>* result) {
-  DCHECK(CBU16_IS_SINGLE(c));
-  *result = SplitStringT<string16, string16, char16>(
-      str, c, TRIM_WHITESPACE, SPLIT_WANT_ALL);
-
-  // Backward-compat hack: The old SplitString implementation would keep
-  // empty substrings, for example:
-  //    "a,,b" -> ["a", "", "b"]
-  //    "a, ,b" -> ["a", "", "b"]
-  // which the current code also does. But the old one would discard them when
-  // the only result was that empty string:
-  //    "  " -> []
-  // In the latter case, our new code will give [""]
-  if (result->size() == 1 && (*result)[0].empty())
-    result->clear();
-}
-
-void SplitString(const std::string& str,
-                 char c,
-                 std::vector<std::string>* result) {
-#if CHAR_MIN < 0
-  DCHECK_GE(c, 0);
-#endif
-  DCHECK_LT(c, 0x7F);
-  *result = SplitStringT<std::string, std::string, char>(
-      str, c, TRIM_WHITESPACE, SPLIT_WANT_ALL);
-
-  // Backward-compat hack, see above.
-  if (result->size() == 1 && (*result)[0].empty())
-    result->clear();
-}
-
-bool SplitStringIntoKeyValuePairs(const std::string& line,
+bool SplitStringIntoKeyValuePairs(StringPiece input,
                                   char key_value_delimiter,
                                   char key_value_pair_delimiter,
                                   StringPairs* key_value_pairs) {
   key_value_pairs->clear();
 
-  std::vector<std::string> pairs;
-  SplitString(line, key_value_pair_delimiter, &pairs);
+  std::vector<StringPiece> pairs = SplitStringPiece(
+      input, std::string(1, key_value_pair_delimiter),
+      TRIM_WHITESPACE, SPLIT_WANT_NONEMPTY);
+  key_value_pairs->reserve(pairs.size());
 
   bool success = true;
-  for (size_t i = 0; i < pairs.size(); ++i) {
-    // Don't add empty pairs into the result.
-    if (pairs[i].empty())
-      continue;
-
-    std::string key;
-    std::string value;
-    if (!SplitStringIntoKeyValue(pairs[i], key_value_delimiter, &key, &value)) {
+  for (const StringPiece& pair : pairs) {
+    if (!AppendStringKeyValue(pair, key_value_delimiter, key_value_pairs)) {
       // Don't return here, to allow for pairs without associated
       // value or key; just record that the split failed.
       success = false;
     }
-    key_value_pairs->push_back(make_pair(key, value));
   }
   return success;
 }
 
-void SplitStringUsingSubstr(const string16& str,
-                            const string16& s,
-                            std::vector<string16>* r) {
-  SplitStringUsingSubstrT(str, s, r);
+void SplitStringUsingSubstr(StringPiece16 input,
+                            StringPiece16 delimiter,
+                            std::vector<string16>* result) {
+  SplitStringUsingSubstrT(input, delimiter, result);
 }
 
-void SplitStringUsingSubstr(const std::string& str,
-                            const std::string& s,
-                            std::vector<std::string>* r) {
-  SplitStringUsingSubstrT(str, s, r);
+void SplitStringUsingSubstr(StringPiece input,
+                            StringPiece delimiter,
+                            std::vector<std::string>* result) {
+  SplitStringUsingSubstrT(input, delimiter, result);
 }
 
 }  // namespace base