In Adobe Flash and AIR development using ActionScript 3 (AS3), managing system resources is a critical task. A common challenge developers face is handling large binary data blocks. If you are working with external assets, manipulating pixels, or handling network streams, you will likely use the ByteArray class. However, failing to properly release this data can severely degrade performance.
How to Create and Allocate a ByteArray
Before addressing how to clear data, it is important to look at how a ByteArray is typically instantiated and populated in an application.
Instantiation: You create a new instance using the standard constructor syntax.
Data Population: Data is usually loaded into the object using built-in methods like writeBytes(), writeUTFBytes(), or by loading external files via URLLoader.
Here is a basic look at initializing a binary stream:
ActionScript
var myData:ByteArray = new ByteArray();
myData.writeUTFBytes("This is a sample string stored as binary data.");
The Problem: Memory Leakage and Persistent Footprints
Simply nullifying a reference to a ByteArray does not guarantee that the application immediately reclaims the allocated system memory.
Garbage Collection Delays: The Flash Player Garbage Collector (GC) operates on its own schedule. It does not immediately free memory just because a variable is set to null.
Persistent Ram Footprint: Large files like compressed images or video chunks can remain trapped in the system RAM, causing noticeable performance degradation or application crashes.
Sub-references: If other parts of the application retain a reference to the same data stream, the memory will never be cleared, leading to an application-wide memory leak.
The Solution: Explicit Clearing and Disposal
To solve the accumulation of unmanaged binary data, ActionScript 3 provides an explicit mechanism to release the underlying byte array layout instantly.
The clear() Method: Introduced to give developers direct control, calling myData.clear() immediately sets the internal array length to zero and overrides the allocated memory block.
Nullifying the Reference: After clearing the contents, setting the variable to null ensures that the Garbage Collector recognizes the object as ready for collection.
Forcing Garbage Collection (Optional): In testing environments or specific AIR desktop applications, developers sometimes invoke System.gc() to suggest an immediate sweep, though relying on clear() remains the primary best practice.
The optimized disposal routine looks like this:
ActionScript
// Safely disposing of the byte array
if (myData != null) {
myData.clear();
myData = null;
}
Sumita
Web Developer
