Fix split to absl::StrSplit. (#98)

Fix split to absl::StrSplit.

Author: shuoyang2016

src/include/grpc_transcoding/path_matcher.h

@@ -25,6 +25,7 @@
 #include "http_template.h"
 #include "path_matcher_node.h"
 #include "percent_encoding.h"
+#include "absl/strings/str_split.h"
 
 namespace google {
 namespace grpc {
@@ -172,16 +173,6 @@ class PathMatcherBuilder {
 
 namespace {
 
-std::vector<std::string>& split(const std::string& s, char delim,
-                                std::vector<std::string>& elems) {
-  std::stringstream ss(s);
-  std::string item;
-  while (std::getline(ss, item, delim)) {
-    elems.push_back(item);
-  }
-  return elems;
-}
-
 template <class VariableBinding>
 void ExtractBindingsFromPath(const std::vector<HttpTemplate::Variable>& vars,
                              const std::vector<std::string>& parts,
@@ -229,8 +220,7 @@ void ExtractBindingsFromQueryParameters(
   // Query parameters may also contain system parameters such as `api_key`.
   // We'll need to ignore these. Example:
   //      book.id=123&book.author=Neal%20Stephenson&api_key=AIzaSyAz7fhBkC35D2M
-  std::vector<std::string> params;
-  split(query_params, '&', params);
+  std::vector<std::string> params = absl::StrSplit(query_params, '&');
   for (const auto& param : params) {
     size_t pos = param.find('=');
     if (pos != 0 && pos != std::string::npos) {
@@ -242,7 +232,7 @@ void ExtractBindingsFromQueryParameters(
         // sequence of field names that identify the (potentially deep) field
         // in the request, e.g. `book.author.name`.
         VariableBinding binding;
-        split(name, '.', binding.field_path);
+        binding.field_path = absl::StrSplit(name, '.');
         binding.value = UrlUnescapeString(param.substr(pos + 1),
                                           UrlUnescapeSpec::kAllCharacters,
                                           query_param_unescape_plus);
@@ -286,7 +276,7 @@ std::vector<std::string> ExtractRequestParts(
 
   std::vector<std::string> result;
   if (path.size() > 0) {
-    split(path.substr(1), '/', result);
+    result = absl::StrSplit(path.substr(1), '/');
   }
   // Removes all trailing empty parts caused by extra "/".
   while (!result.empty() && (*(--result.end())).empty()) {