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      1 // Copyright (c) 2006-2008 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 NET_HTTP_HTTP_VARY_DATA_H__
      6 #define NET_HTTP_HTTP_VARY_DATA_H__
      7 #pragma once
      8 
      9 #include "base/md5.h"
     10 
     11 class Pickle;
     12 
     13 namespace net {
     14 
     15 struct HttpRequestInfo;
     16 class HttpResponseHeaders;
     17 
     18 // Used to implement the HTTP/1.1 Vary header.  This class contains a MD5 hash
     19 // over the request headers indicated by a Vary header.
     20 //
     21 // While RFC 2616 requires strict request header comparisons, it is much
     22 // cheaper to store a MD5 sum, which should be sufficient.  Storing a hash also
     23 // avoids messy privacy issues as some of the request headers could hold
     24 // sensitive data (e.g., cookies).
     25 //
     26 // NOTE: This class does not hold onto the contents of the Vary header.
     27 // Instead, it relies on the consumer to store that and to supply it again to
     28 // the MatchesRequest function for comparing against future HTTP requests.
     29 //
     30 class HttpVaryData {
     31  public:
     32   HttpVaryData();
     33 
     34   bool is_valid() const { return is_valid_; }
     35 
     36   // Initialize from a request and its corresponding response headers.
     37   //
     38   // Returns true if a Vary header was found in the response headers and that
     39   // Vary header was not empty and did not contain the '*' value.  Upon
     40   // success, the object is also marked as valid such that is_valid() will
     41   // return true.  Otherwise, false is returned to indicate that this object
     42   // is marked as invalid.
     43   //
     44   bool Init(const HttpRequestInfo& request_info,
     45             const HttpResponseHeaders& response_headers);
     46 
     47   // Initialize from a pickle that contains data generated by a call to the
     48   // vary data's Persist method.
     49   //
     50   // Upon success, true is returned and the object is marked as valid such that
     51   // is_valid() will return true.  Otherwise, false is returned to indicate
     52   // that this object is marked as invalid.
     53   //
     54   bool InitFromPickle(const Pickle& pickle, void** pickle_iter);
     55 
     56   // Call this method to persist the vary data. Illegal to call this on an
     57   // invalid object.
     58   void Persist(Pickle* pickle) const;
     59 
     60   // Call this method to test if the given request matches the previous request
     61   // with which this vary data corresponds.  The |cached_response_headers| must
     62   // be the same response headers used to generate this vary data.
     63   bool MatchesRequest(const HttpRequestInfo& request_info,
     64                       const HttpResponseHeaders& cached_response_headers) const;
     65 
     66  private:
     67   // Returns the corresponding request header value.
     68   static std::string GetRequestValue(const HttpRequestInfo& request_info,
     69                                      const std::string& request_header);
     70 
     71   // Append to the MD5 context for the given request header.
     72   static void AddField(const HttpRequestInfo& request_info,
     73                        const std::string& request_header,
     74                        MD5Context* context);
     75 
     76   // A digested version of the request headers corresponding to the Vary header.
     77   MD5Digest request_digest_;
     78 
     79   // True when request_digest_ contains meaningful data.
     80   bool is_valid_;
     81 };
     82 
     83 }  // namespace net
     84 
     85 #endif  // NET_HTTP_HTTP_VARY_DATA_H__
     86