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
|
"use strict";
var domain; // The domain module is executed on demand
var hasSetImmediate = typeof setImmediate === "function";
// Use the fastest means possible to execute a task in its own turn, with
// priority over other events including network IO events in Node.js.
//
// An exception thrown by a task will permanently interrupt the processing of
// subsequent tasks. The higher level `asap` function ensures that if an
// exception is thrown by a task, that the task queue will continue flushing as
// soon as possible, but if you use `rawAsap` directly, you are responsible to
// either ensure that no exceptions are thrown from your task, or to manually
// call `rawAsap.requestFlush` if an exception is thrown.
module.exports = rawAsap;
function rawAsap(task) {
if (!queue.length) {
requestFlush();
flushing = true;
}
// Avoids a function call
queue[queue.length] = task;
}
var queue = [];
// Once a flush has been requested, no further calls to `requestFlush` are
// necessary until the next `flush` completes.
var flushing = false;
// The position of the next task to execute in the task queue. This is
// preserved between calls to `flush` so that it can be resumed if
// a task throws an exception.
var index = 0;
// If a task schedules additional tasks recursively, the task queue can grow
// unbounded. To prevent memory excaustion, the task queue will periodically
// truncate already-completed tasks.
var capacity = 1024;
// The flush function processes all tasks that have been scheduled with
// `rawAsap` unless and until one of those tasks throws an exception.
// If a task throws an exception, `flush` ensures that its state will remain
// consistent and will resume where it left off when called again.
// However, `flush` does not make any arrangements to be called again if an
// exception is thrown.
function flush() {
while (index < queue.length) {
var currentIndex = index;
// Advance the index before calling the task. This ensures that we will
// begin flushing on the next task the task throws an error.
index = index + 1;
queue[currentIndex].call();
// Prevent leaking memory for long chains of recursive calls to `asap`.
// If we call `asap` within tasks scheduled by `asap`, the queue will
// grow, but to avoid an O(n) walk for every task we execute, we don't
// shift tasks off the queue after they have been executed.
// Instead, we periodically shift 1024 tasks off the queue.
if (index > capacity) {
// Manually shift all values starting at the index back to the
// beginning of the queue.
for (var scan = 0, newLength = queue.length - index; scan < newLength; scan++) {
queue[scan] = queue[scan + index];
}
queue.length -= index;
index = 0;
}
}
queue.length = 0;
index = 0;
flushing = false;
}
rawAsap.requestFlush = requestFlush;
function requestFlush() {
// Ensure flushing is not bound to any domain.
// It is not sufficient to exit the domain, because domains exist on a stack.
// To execute code outside of any domain, the following dance is necessary.
var parentDomain = process.domain;
if (parentDomain) {
if (!domain) {
// Lazy execute the domain module.
// Only employed if the user elects to use domains.
domain = require("domain");
}
domain.active = process.domain = null;
}
// `setImmediate` is slower that `process.nextTick`, but `process.nextTick`
// cannot handle recursion.
// `requestFlush` will only be called recursively from `asap.js`, to resume
// flushing after an error is thrown into a domain.
// Conveniently, `setImmediate` was introduced in the same version
// `process.nextTick` started throwing recursion errors.
if (flushing && hasSetImmediate) {
setImmediate(flush);
} else {
process.nextTick(flush);
}
if (parentDomain) {
domain.active = process.domain = parentDomain;
}
}
|
