net/http/partial_data.h

   1 // Copyright (c) 2011 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_PARTIAL_DATA_H_
   6 #define NET_HTTP_PARTIAL_DATA_H_
   7
   8 #include "base/basictypes.h"
   9 #include "net/base/completion_callback.h"
  10 #include "net/http/http_byte_range.h"
  11 #include "net/http/http_request_headers.h"
  12
  13 namespace disk_cache {
  14 class Entry;
  15 }
  16
  17 namespace net {
  18
  19 class HttpResponseHeaders;
  20 class IOBuffer;
  21
  22 // This class provides support for dealing with range requests and the
  23 // subsequent partial-content responses. We use sparse cache entries to store
  24 // these requests. This class is tightly integrated with HttpCache::Transaction
  25 // and it is intended to allow a cleaner implementation of that class.
  26 //
  27 // In order to fulfill range requests, we may have to perform a sequence of
  28 // reads from the cache, interleaved with reads from the network / writes to the
  29 // cache. This class basically keeps track of the data required to perform each
  30 // of those individual network / cache requests.
  31 class PartialData {
  32  public:
  33   PartialData();
  34   ~PartialData();
  35
  36   // Performs initialization of the object by examining the request |headers|
  37   // and verifying that we can process the requested range. Returns true if
  38   // we can process the requested range, and false otherwise.
  39   bool Init(const HttpRequestHeaders& headers);
  40
  41   // Sets the headers that we should use to make byte range requests. This is a
  42   // subset of the request extra headers, with byte-range related headers
  43   // removed.
  44   void SetHeaders(const HttpRequestHeaders& headers);
  45
  46   // Restores the byte-range headers, by appending the byte range to the headers
  47   // provided to SetHeaders().
  48   void RestoreHeaders(HttpRequestHeaders* headers) const;
  49
  50   // Starts the checks to perform a cache validation. Returns 0 when there is no
  51   // need to perform more operations because we reached the end of the request
  52   // (so 0 bytes should be actually returned to the user), a positive number to
  53   // indicate that PrepareCacheValidation should be called, or an appropriate
  54   // error code. If this method returns ERR_IO_PENDING, the |callback| will be
  55   // notified when the result is ready.
  56   int ShouldValidateCache(disk_cache::Entry* entry,
  57                           const CompletionCallback& callback);
  58
  59   // Builds the required |headers| to perform the proper cache validation for
  60   // the next range to be fetched.
  61   void PrepareCacheValidation(disk_cache::Entry* entry,
  62                               HttpRequestHeaders* headers);
  63
  64   // Returns true if the current range is stored in the cache.
  65   bool IsCurrentRangeCached() const;
  66
  67   // Returns true if the current range is the last one needed to fulfill the
  68   // user's request.
  69   bool IsLastRange() const;
  70
  71   // Extracts info from headers already stored in the cache. Returns false if
  72   // there is any problem with the headers. |truncated| should be true if we
  73   // have an incomplete 200 entry.
  74   bool UpdateFromStoredHeaders(const HttpResponseHeaders* headers,
  75                                disk_cache::Entry* entry, bool truncated);
  76
  77   // Sets the byte current range to start again at zero (for a truncated entry).
  78   void SetRangeToStartDownload();
  79
  80   // Returns true if the requested range is valid given the stored data.
  81   bool IsRequestedRangeOK();
  82
  83   // Returns true if the response headers match what we expect, false otherwise.
  84   bool ResponseHeadersOK(const HttpResponseHeaders* headers);
  85
  86   // Fixes the response headers to include the right content length and range.
  87   // |success| is the result of the whole request so if it's false, we'll change
  88   // the result code to be 416.
  89   void FixResponseHeaders(HttpResponseHeaders* headers, bool success);
  90
  91   // Fixes the content length that we want to store in the cache.
  92   void FixContentLength(HttpResponseHeaders* headers);
  93
  94   // Reads up to |data_len| bytes from the cache and stores them in the provided
  95   // buffer (|data|). Basically, this is just a wrapper around the API of the
  96   // cache that provides the right arguments for the current range. When the IO
  97   // operation completes, OnCacheReadCompleted() must be called with the result
  98   // of the operation.
  99   int CacheRead(disk_cache::Entry* entry, IOBuffer* data, int data_len,
 100                 const net::CompletionCallback& callback);
 101
 102   // Writes |data_len| bytes to cache. This is basically a wrapper around the
 103   // API of the cache that provides the right arguments for the current range.
 104   int CacheWrite(disk_cache::Entry* entry, IOBuffer* data, int data_len,
 105                  const net::CompletionCallback& callback);
 106
 107   // This method should be called when CacheRead() finishes the read, to update
 108   // the internal state about the current range.
 109   void OnCacheReadCompleted(int result);
 110
 111   // This method should be called after receiving data from the network, to
 112   // update the internal state about the current range.
 113   void OnNetworkReadCompleted(int result);
 114
 115   bool initial_validation() const { return initial_validation_; }
 116
 117  private:
 118   class Core;
 119   // Returns the length to use when scanning the cache.
 120   int GetNextRangeLen();
 121
 122   // Completion routine for our callback.
 123   void GetAvailableRangeCompleted(int result, int64 start);
 124
 125   int64 current_range_start_;
 126   int64 cached_start_;
 127   int64 resource_size_;
 128   int cached_min_len_;
 129   HttpByteRange byte_range_;  // The range requested by the user.
 130   // The clean set of extra headers (no ranges).
 131   HttpRequestHeaders extra_headers_;
 132   bool range_present_;  // True if next range entry is already stored.
 133   bool final_range_;
 134   bool sparse_entry_;
 135   bool truncated_;  // We have an incomplete 200 stored.
 136   bool initial_validation_;  // Only used for truncated entries.
 137   Core* core_;
 138   CompletionCallback callback_;
 139
 140   DISALLOW_COPY_AND_ASSIGN(PartialData);
 141 };
 142
 143 }  // namespace net
 144
 145 #endif  // NET_HTTP_PARTIAL_DATA_H_