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
13namespace disk_cache {
14class Entry;
15}
16
17namespace net {
18
19class HttpResponseHeaders;
20class 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.
31class 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_
146