rework client using async api

webcc/parser.h

@@ -94,17 +94,35 @@ private:
 class Parser {
 public:
   Parser();
-  virtual ~Parser() = default;
 
   Parser(const Parser&) = delete;
   Parser& operator=(const Parser&) = delete;
 
+  virtual ~Parser() = default;
+
   void Init(Message* message);
 
   bool finished() const {
     return finished_;
   }
 
+  // If the headers part has been parsed or not.
+  bool header_ended() const {
+  return header_ended_;
+  }
+
+  // Get the length of the headers part.
+  // Available after the headers have been parsed (see header_ended()).
+  std::size_t header_length() const {
+    return header_length_;
+  }
+
+  // The content length parsed from `Content-Length` header.
+  // kInvalidLength if the content is chunked.
+  std::size_t content_length() const {
+    return content_length_;
+  }
+
   bool Parse(const char* data, std::size_t length);
 
 protected:
@@ -144,25 +162,28 @@ protected:
   bool Finish();
 
 protected:
-  Message* message_;
+  Message* message_ = nullptr;
 
   std::unique_ptr<BodyHandler> body_handler_;
 
   // Data streaming or not.
-  bool stream_;
+  bool stream_ = false;
 
   // Data waiting to be parsed.
   std::string pending_data_;
 
+  // The length of the headers part.
+  std::size_t header_length_ = 0;
+
   // Temporary data and helper flags for parsing.
-  std::size_t content_length_;
+  std::size_t content_length_ = kInvalidLength;
   ContentType content_type_;
-  bool start_line_parsed_;
-  bool content_length_parsed_;
-  bool header_ended_;
-  bool chunked_;
-  std::size_t chunk_size_;
-  bool finished_;
+  bool start_line_parsed_ = false;
+  bool content_length_parsed_ = false;
+  bool header_ended_ = false;
+  bool chunked_ = false;
+  std::size_t chunk_size_ = kInvalidLength;
+  bool finished_ = false;
 };
 
 }  // namespace webcc