net/http/http_vary_data.h

   1 // Copyright (c) 2012 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
   8 #include "base/md5.h"
   9 #include "net/base/net_export.h"
  10
  11 namespace base {
  12 class Pickle;
  13 class PickleIterator;
  14 }
  15
  16 namespace net {
  17
  18 struct HttpRequestInfo;
  19 class HttpResponseHeaders;
  20
  21 // Used to implement the HTTP/1.1 Vary header.  This class contains a MD5 hash
  22 // over the request headers indicated by a Vary header.
  23 //
  24 // While RFC 2616 requires strict request header comparisons, it is much
  25 // cheaper to store a MD5 sum, which should be sufficient.  Storing a hash also
  26 // avoids messy privacy issues as some of the request headers could hold
  27 // sensitive data (e.g., cookies).
  28 //
  29 // NOTE: This class does not hold onto the contents of the Vary header.
  30 // Instead, it relies on the consumer to store that and to supply it again to
  31 // the MatchesRequest function for comparing against future HTTP requests.
  32 //
  33 class NET_EXPORT_PRIVATE HttpVaryData {
  34  public:
  35   HttpVaryData();
  36
  37   bool is_valid() const { return is_valid_; }
  38
  39   // Initialize from a request and its corresponding response headers.
  40   //
  41   // Returns true if a Vary header was found in the response headers and that
  42   // Vary header was not empty and did not contain the '*' value.  Upon
  43   // success, the object is also marked as valid such that is_valid() will
  44   // return true.  Otherwise, false is returned to indicate that this object
  45   // is marked as invalid.
  46   //
  47   bool Init(const HttpRequestInfo& request_info,
  48             const HttpResponseHeaders& response_headers);
  49
  50   // Initialize from a pickle that contains data generated by a call to the
  51   // vary data's Persist method.
  52   //
  53   // Upon success, true is returned and the object is marked as valid such that
  54   // is_valid() will return true.  Otherwise, false is returned to indicate
  55   // that this object is marked as invalid.
  56   //
  57   bool InitFromPickle(base::PickleIterator* pickle_iter);
  58
  59   // Call this method to persist the vary data. Illegal to call this on an
  60   // invalid object.
  61   void Persist(base::Pickle* pickle) const;
  62
  63   // Call this method to test if the given request matches the previous request
  64   // with which this vary data corresponds.  The |cached_response_headers| must
  65   // be the same response headers used to generate this vary data.
  66   bool MatchesRequest(const HttpRequestInfo& request_info,
  67                       const HttpResponseHeaders& cached_response_headers) const;
  68
  69  private:
  70   // Returns the corresponding request header value.
  71   static std::string GetRequestValue(const HttpRequestInfo& request_info,
  72                                      const std::string& request_header);
  73
  74   // Append to the MD5 context for the given request header.
  75   static void AddField(const HttpRequestInfo& request_info,
  76                        const std::string& request_header,
  77                        base::MD5Context* context);
  78
  79   // A digested version of the request headers corresponding to the Vary header.
  80   base::MD5Digest request_digest_;
  81
  82   // True when request_digest_ contains meaningful data.
  83   bool is_valid_;
  84 };
  85
  86 }  // namespace net
  87
  88 #endif  // NET_HTTP_HTTP_VARY_DATA_H_