text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef NET_WEBSOCKETS_WEBSOCKET_FRAME_PARSER_H_
  #define NET_WEBSOCKETS_WEBSOCKET_FRAME_PARSER_H_
  
  #include <stddef.h>
  #include <stdint.h>
  
  #include <memory>
  #include <vector>
  
  #include "base/containers/span.h"
  #include "net/base/net_export.h"
  #include "net/websockets/websocket_errors.h"
  #include "net/websockets/websocket_frame.h"
  
  namespace net {
  
  // Parses WebSocket frames from byte stream.
  //
  // Specification of WebSocket frame format is available at
  // <http://tools.ietf.org/html/rfc6455#section-5>.
  // This class does *NOT* unmask frame payload.
  class NET_EXPORT WebSocketFrameParser {
   public:
    WebSocketFrameParser();
  
    WebSocketFrameParser(const WebSocketFrameParser&) = delete;
    WebSocketFrameParser& operator=(const WebSocketFrameParser&) = delete;
  
    ~WebSocketFrameParser();
  
    // Decodes the given byte stream and stores parsed WebSocket frames in
    // |frame_chunks|.
    // Each WebSocketFrameChunk's payload is a subspan of [data, data + length).
    // Thus callers must take care of its lifecycle.
    //
    // If the parser encounters invalid payload length format, Decode() fails
    // and returns false. Once Decode() has failed, the parser refuses to decode
    // any more data and future invocations of Decode() will simply return false.
    //
    // Payload data of parsed WebSocket frames may be incomplete; see comments in
    // websocket_frame.h for more details.
    bool Decode(const char* data,
                size_t length,
                std::vector<std::unique_ptr<WebSocketFrameChunk>>* frame_chunks);
  
    // Returns kWebSocketNormalClosure if the parser has not failed to decode
    // WebSocket frames. Otherwise returns WebSocketError which is defined in
    // websocket_errors.h. We can convert net::WebSocketError to net::Error by
    // using WebSocketErrorToNetError().
    WebSocketError websocket_error() const { return websocket_error_; }
  
   private:
    // Tries to decode a frame header from |data|.
    // If successful, this function updates
    // |current_frame_header_|, and |masking_key_| (if available) and returns
    // the number of consumed bytes in |data|.
    // If there is not enough data in the remaining buffer to parse a frame
    // header, this function returns 0 without doing anything.
    // This function may update |websocket_error_| if it observes a corrupt frame.
    size_t DecodeFrameHeader(base::span<const char> data);
  
    // Decodes frame payload and creates a WebSocketFrameChunk object.
    // This function updates |frame_offset_| after
    // parsing. This function returns a frame object even if no payload data is
    // available at this moment, so the receiver could make use of frame header
    // information. If the end of frame is reached, this function clears
    // |current_frame_header_|, |frame_offset_| and |masking_key_|.
    std::unique_ptr<WebSocketFrameChunk> DecodeFramePayload(
        bool first_chunk,
        base::span<const char>* data);
  
    // Internal buffer to store the data to parse header.
    std::vector<char> incomplete_header_buffer_;
  
    // Frame header and masking key of the current frame.
    // |masking_key_| is filled with zeros if the current frame is not masked.
    std::unique_ptr<WebSocketFrameHeader> current_frame_header_;
  
    // Amount of payload data read so far for the current frame.
    uint64_t frame_offset_;
  
    WebSocketError websocket_error_;
  };
  
  }  // namespace net
  
  #endif  // NET_WEBSOCKETS_WEBSOCKET_FRAME_PARSER_H_
  