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
|
// Copyright (c) 2010 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.
// Illustrates how to use worker threads that issue completion callbacks
#include "base/threading/worker_pool.h"
#include "net/base/completion_callback.h"
#include "net/base/test_completion_callback.h"
#include "testing/gtest/include/gtest/gtest.h"
#include "testing/platform_test.h"
typedef PlatformTest TestCompletionCallbackTest;
using net::CompletionCallback;
const int kMagicResult = 8888;
// ExampleEmployer is a toy version of HostResolver
// TODO: restore damage done in extracting example from real code
// (e.g. bring back real destructor, bring back comments)
class ExampleEmployer {
public:
ExampleEmployer();
~ExampleEmployer();
// Do some imaginary work on a worker thread;
// when done, worker posts callback on the original thread.
// Returns true on success
bool DoSomething(CompletionCallback* callback);
private:
class ExampleWorker;
friend class ExampleWorker;
scoped_refptr<ExampleWorker> request_;
DISALLOW_COPY_AND_ASSIGN(ExampleEmployer);
};
// Helper class; this is how ExampleEmployer puts work on a different thread
class ExampleEmployer::ExampleWorker
: public base::RefCountedThreadSafe<ExampleWorker> {
public:
ExampleWorker(ExampleEmployer* employer, CompletionCallback* callback)
: employer_(employer), callback_(callback),
origin_loop_(MessageLoop::current()) {
}
void DoWork();
void DoCallback();
private:
friend class base::RefCountedThreadSafe<ExampleWorker>;
~ExampleWorker() {}
// Only used on the origin thread (where DoSomething was called).
ExampleEmployer* employer_;
CompletionCallback* callback_;
// Used to post ourselves onto the origin thread.
Lock origin_loop_lock_;
MessageLoop* origin_loop_;
};
void ExampleEmployer::ExampleWorker::DoWork() {
// Running on the worker thread
// In a real worker thread, some work would be done here.
// Pretend it is, and send the completion callback.
Task* reply = NewRunnableMethod(this, &ExampleWorker::DoCallback);
// The origin loop could go away while we are trying to post to it, so we
// need to call its PostTask method inside a lock. See ~ExampleEmployer.
{
AutoLock locked(origin_loop_lock_);
if (origin_loop_) {
origin_loop_->PostTask(FROM_HERE, reply);
reply = NULL;
}
}
// Does nothing if it got posted.
delete reply;
}
void ExampleEmployer::ExampleWorker::DoCallback() {
// Running on the origin thread.
// Drop the employer_'s reference to us. Do this before running the
// callback since the callback might result in the employer being
// destroyed.
employer_->request_ = NULL;
callback_->Run(kMagicResult);
}
ExampleEmployer::ExampleEmployer() {
}
ExampleEmployer::~ExampleEmployer() {
}
bool ExampleEmployer::DoSomething(CompletionCallback* callback) {
DCHECK(!request_) << "already in use";
request_ = new ExampleWorker(this, callback);
// Dispatch to worker thread...
if (!base::WorkerPool::PostTask(FROM_HERE,
NewRunnableMethod(request_.get(), &ExampleWorker::DoWork), true)) {
NOTREACHED();
request_ = NULL;
return false;
}
return true;
}
TEST_F(TestCompletionCallbackTest, Simple) {
ExampleEmployer boss;
TestCompletionCallback callback;
bool queued = boss.DoSomething(&callback);
EXPECT_EQ(queued, true);
int result = callback.WaitForResult();
EXPECT_EQ(result, kMagicResult);
}
// TODO: test deleting ExampleEmployer while work outstanding
|
