Apple provides sample code for compressing a single file here, but the "aa" command and Finder cannot decompress these files. I needed to write a custom decompresser using Apple's sample code here. Apple provides sample code for creating an "aar" file for directories here and a single string here, and the aa command and Finder can deal with these. However, I have struggled creating an ".aar" file for a single file. The file could be quite large, so reading it into memory and writing it as a blob is not an option. Does anyone have suggestions or can point me to Apple documentation that can create a ".aar" file for a single file?