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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CLOUD_PRINT_GCP20_PROTOTYPE_DNS_PACKET_PARSER_H_
      6 #define CLOUD_PRINT_GCP20_PROTOTYPE_DNS_PACKET_PARSER_H_
      7 
      8 #include <string>
      9 
     10 #include "net/dns/dns_protocol.h"
     11 #include "net/dns/dns_response.h"
     12 
     13 // Parsed response record.
     14 struct DnsQueryRecord {
     15   DnsQueryRecord() : qtype(0), qclass(0) {}
     16   ~DnsQueryRecord() {}
     17 
     18   std::string qname;  // in dotted form
     19   uint16 qtype;
     20   uint16 qclass;
     21 };
     22 
     23 // Iterator to walk over records of the DNS response packet. Encapsulates
     24 // |DnsRecordParser| object for using its functionality.
     25 class DnsPacketParser {
     26  public:
     27   // Constructs an iterator to process the |packet| of given |length|.
     28   DnsPacketParser(const char* packet, size_t length);
     29 
     30   // Destroys the object.
     31   ~DnsPacketParser() {}
     32 
     33   bool IsValid() const { return record_parser_.IsValid() && is_header_read_; }
     34 
     35   // Returns |true| if no more bytes remain in the packet.
     36   bool AtEnd() const { return record_parser_.AtEnd(); }
     37 
     38   // Returns header of DNS packet.
     39   const net::dns_protocol::Header& header() const { return header_; }
     40 
     41   // Parses the next query record into |record|. Returns true if succeeded.
     42   bool ReadRecord(DnsQueryRecord* record);
     43 
     44   // Parses the next resource record into |record|. Returns true if succeeded.
     45   bool ReadRecord(net::DnsResourceRecord* record) {
     46     return record_parser_.ReadRecord(record);
     47   }
     48 
     49  private:
     50   // Returns current offset into the packet.
     51   size_t GetOffset() const { return record_parser_.GetOffset(); }
     52 
     53   // Parses a (possibly compressed) DNS name from the packet starting at
     54   // |pos|. Stores output (even partial) in |out| unless |out| is NULL. |out|
     55   // is stored in the dotted form, e.g., "example.com". Returns number of bytes
     56   // consumed or 0 on failure.
     57   // This is exposed to allow parsing compressed names within RRDATA for TYPEs
     58   // such as NS, CNAME, PTR, MX, SOA.
     59   // See RFC 1035 section 4.1.4.
     60   unsigned ReadName(std::string* out) const {
     61     return record_parser_.ReadName(packet_ + GetOffset(), out);
     62   }
     63 
     64   const char* packet_;
     65   size_t length_;
     66 
     67   // Contents parsed header_;
     68   net::dns_protocol::Header header_;
     69   bool is_header_read_;
     70 
     71   // Encapsulated parser.
     72   net::DnsRecordParser record_parser_;
     73 
     74   DISALLOW_COPY_AND_ASSIGN(DnsPacketParser);
     75 };
     76 
     77 #endif  // CLOUD_PRINT_GCP20_PROTOTYPE_DNS_PACKET_PARSER_H_
     78 
     79