Possibly dumb question: why doesn't the hash verification take place on the uncompressed contents, moving recompression from the updating-critical-path to the nice-to-have-later-to-save-disk-space category?
My dream updater would just be a bunch of stream processors, so the downloading / decompression / disassembly (a la courgette), patching / recompression happens all at once, as the data packets come in (thus utilizing both CPU and IO). If done right an update shouldn't take much longer to complete than the download step, no?
Many (most?) Android phones are chronically short of flash space, even in the status quo storage shortage often prevents applying app updates. There is really no room to make storage use more lax.
My dream updater would just be a bunch of stream processors, so the downloading / decompression / disassembly (a la courgette), patching / recompression happens all at once, as the data packets come in (thus utilizing both CPU and IO). If done right an update shouldn't take much longer to complete than the download step, no?