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					102 lines
				
				4.0 KiB
			
		
		
			
		
	
	
					102 lines
				
				4.0 KiB
			| 
											3 years ago
										 | "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; | ||
|  |     } | ||
|  | } |