1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_UPDATE_CLIENT_CRX_DOWNLOADER_H_
#define COMPONENTS_UPDATE_CLIENT_CRX_DOWNLOADER_H_
#include <stdint.h>
#include <memory>
#include <string>
#include <vector>
#include "base/callback.h"
#include "base/files/file_path.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/sequenced_task_runner.h"
#include "base/threading/thread_checker.h"
#include "url/gurl.h"
namespace net {
class URLRequestContextGetter;
}
namespace update_client {
// Defines a download interface for downloading components, with retrying on
// fallback urls in case of errors. This class implements a chain of
// responsibility design pattern. It can give successors in the chain a chance
// to handle a download request, until one of them succeeds, or there are no
// more urls or successors to try. A callback is always called at the end of
// the download, one time only.
// When multiple urls and downloaders exists, first all the urls are tried, in
// the order they are provided in the StartDownload function argument. After
// that, the download request is routed to the next downloader in the chain.
// The members of this class expect to be called from the main thread only.
class CrxDownloader {
public:
struct DownloadMetrics {
enum Downloader { kNone = 0, kUrlFetcher, kBits };
DownloadMetrics();
GURL url;
Downloader downloader;
int error;
int64_t downloaded_bytes; // -1 means that the byte count is unknown.
int64_t total_bytes;
uint64_t download_time_ms;
};
// Contains the progress or the outcome of the download.
struct Result {
Result();
// Download error: 0 indicates success.
int error;
// Path of the downloaded file if the download was successful.
base::FilePath response;
// Number of bytes actually downloaded, not including the bytes downloaded
// as a result of falling back on urls.
int64_t downloaded_bytes;
// Number of bytes expected to be downloaded.
int64_t total_bytes;
};
// The callback fires only once, regardless of how many urls are tried, and
// how many successors in the chain of downloaders have handled the
// download. The callback interface can be extended if needed to provide
// more visibility into how the download has been handled, including
// specific error codes and download metrics.
using DownloadCallback = base::Callback<void(const Result& result)>;
// The callback may fire 0 or many times during a download. Since this
// class implements a chain of responsibility, the callback can fire for
// different urls and different downloaders. The number of actual downloaded
// bytes is not guaranteed to monotonically increment over time.
using ProgressCallback = base::Callback<void(const Result& result)>;
using Factory = std::unique_ptr<CrxDownloader> (*)(
bool,
net::URLRequestContextGetter*,
const scoped_refptr<base::SequencedTaskRunner>&);
// Factory method to create an instance of this class and build the
// chain of responsibility. |is_background_download| specifies that a
// background downloader be used, if the platform supports it.
// |task_runner| should be a task runner able to run blocking
// code such as file IO operations.
static std::unique_ptr<CrxDownloader> Create(
bool is_background_download,
net::URLRequestContextGetter* context_getter,
const scoped_refptr<base::SequencedTaskRunner>& task_runner);
virtual ~CrxDownloader();
void set_progress_callback(const ProgressCallback& progress_callback);
// Starts the download. One instance of the class handles one download only.
// One instance of CrxDownloader can only be started once, otherwise the
// behavior is undefined. The callback gets invoked if the download can't
// be started. |expected_hash| represents the SHA256 cryptographic hash of
// the download payload, represented as a hexadecimal string.
void StartDownloadFromUrl(const GURL& url,
const std::string& expected_hash,
const DownloadCallback& download_callback);
void StartDownload(const std::vector<GURL>& urls,
const std::string& expected_hash,
const DownloadCallback& download_callback);
const std::vector<DownloadMetrics> download_metrics() const;
protected:
CrxDownloader(const scoped_refptr<base::SequencedTaskRunner>& task_runner,
std::unique_ptr<CrxDownloader> successor);
// Handles the fallback in the case of multiple urls and routing of the
// download to the following successor in the chain. Derived classes must call
// this function after each attempt at downloading the urls provided
// in the StartDownload function.
// In case of errors, |is_handled| indicates that a server side error has
// occured for the current url and the url should not be retried down
// the chain to avoid DDOS of the server. This url will be removed from the
// list of url and never tried again.
void OnDownloadComplete(bool is_handled,
const Result& result,
const DownloadMetrics& download_metrics);
// Calls the callback when progress is made.
void OnDownloadProgress(const Result& result);
// Returns the url which is currently being downloaded from.
GURL url() const;
scoped_refptr<base::SequencedTaskRunner> task_runner() const {
return task_runner_;
}
scoped_refptr<base::SequencedTaskRunner> main_task_runner() const {
return main_task_runner_;
}
private:
virtual void DoStartDownload(const GURL& url) = 0;
void VerifyResponse(bool is_handled,
Result result,
DownloadMetrics download_metrics);
void HandleDownloadError(bool is_handled,
const Result& result,
const DownloadMetrics& download_metrics);
base::ThreadChecker thread_checker_;
// Executes blocking operations such as file I/O.
scoped_refptr<base::SequencedTaskRunner> task_runner_;
// Used to post callbacks to the main thread.
scoped_refptr<base::SequencedTaskRunner> main_task_runner_;
std::vector<GURL> urls_;
// The SHA256 hash of the download payload in hexadecimal format.
std::string expected_hash_;
std::unique_ptr<CrxDownloader> successor_;
DownloadCallback download_callback_;
ProgressCallback progress_callback_;
std::vector<GURL>::iterator current_url_;
std::vector<DownloadMetrics> download_metrics_;
DISALLOW_COPY_AND_ASSIGN(CrxDownloader);
};
} // namespace update_client
#endif // COMPONENTS_UPDATE_CLIENT_CRX_DOWNLOADER_H_
|
