Motivation and Context

Follow up to #6348

More optimizations in ByteArrayAsyncResponseTransformer to avoid unnecessary copying of data

Modifications

• Replace future return type of byte[] to ByteBuffer in ByteArrayAsyncResponseTransformer
• New subclass DirectAccessByteArrayOutputStream that extends ByteArrayOutputStream, with method toByteBuffer() to access the internal buffer directly without copying
• New method ResponseBytes.fromByteBufferUnsafe() to create ResponseBytes from ByteBuffer without copying

ByteArrayAsyncResponseTransformer.BaosSubscriber

• in onNext(), if byteBuffer.hasArray() is true, then we can safely invoke byteBuffer.array() and directly write the content to ByteArrayOutputStream instead of copying the bytes with BinaryUtils.copyBytesFrom()
• in onComplete(), get the internal buffer from DirectAccessByteArrayOutputStream without copying, using toByteBuffer() instead of toByteArray()

Testing

Added unit tests
Existing tests passing
Performance tests showed increased throughput and decrease in latency

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)