one thing I forgot to mention. When checking the individual file chunks, it seems the downloader only does a size check.
I say this because I had a corrupt Gabriel Kinght 2 download, and everytime I added the game to the downloader, It would fail the checksum verify, but it would download instantly, as if everything was downloaded correctly. When I tried running the installer, the installer would fail because of the bad file integrity.
After I deleted the file, the downloader finally downloaded it correctly; but only because it had to dowload the WHOLE file again, not just a chunk.
I assume the downloader wasn't downloadind the chunk correctly because it wasn't verifying it's individual checksum, only its size, and the size of the chunk was allright. Look at the output of my log when trying to dowload "La Mulana", for example:
09:31:03 Instance_NewDownloadAdded called. Download: la_mulana (completed bytes 0/0)
09:31:03 Started downloading info: la_mulana
09:31:06 Worker -1 Requesting
https://api.gog.com/downloader2/game/la_mulana/installer_win_en 09:31:07 Worker -1 Request
https://api.gog.com/downloader2/game/la_mulana/installer_win_en successed?:True
09:31:07 La Mulana info fetched
09:31:07 ended downloading info
09:31:07 fetching download sizes and chunk info for La Mulana
09:31:07 Worker -1 Requesting
https://api.gog.com/downloader2/game/la_mulana/installer_win_en 09:31:08 Worker -1 Request
https://api.gog.com/downloader2/game/la_mulana/installer_win_en successed?:True
09:31:08 Worker -1 Requesting
https://api.gog.com/downloader2/file/la_mulana/en1installer0 09:31:09 Worker -1 Request
https://api.gog.com/downloader2/file/la_mulana/en1installer0 successed?:True
09:31:09 Worker -1 Requesting
https://api.gog.com/downloader2/installer/la_mulana/en1installer0/crc/
09:31:11 Worker -1 Request
https://api.gog.com/downloader2/installer/la_mulana/en1installer0/crc/ successed?:True
09:31:11 ended previous download verification - la_mulana
09:31:11 download for la_mulana is incomplete, resuming...
09:31:11 Instance_DownloadInfoRetrieved called. Download: la_mulana (completed bytes 0/195664616)
09:31:11 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.0)
09:31:11 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.3)
09:31:12 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.2)
09:31:12 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.4)
09:31:12 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.6)
09:31:12 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.5)
09:31:12 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.1)
09:31:12 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.7)
09:31:13 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.8)
09:31:13 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.9)
09:31:13 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.10)
09:31:13 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.11)
09:31:13 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.12)
09:31:14 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.13)
09:31:14 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.14)
09:31:14 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.15)
09:31:14 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.16)
09:31:14 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.17)
09:31:14 Chunk already downloaded. File: setup_la-mulana_2.0.0.7.exe.18)
09:31:14 Instance_DownloadEnded called. Download: la_mulana (completed bytes 195664616/195664616)
09:31:14 Resetting cache
09:31:14 Instance_DownloadCombined called. Download: la_mulana (completed bytes 195664616/195664616)
09:31:15 Cleaning completed download La Mulana
09:31:15 Cleaning ended
It says "chunk already downloaded", suggesting it only checked for the file size. And every time I add the game, it says that "download for la_mulana is incomplete, resuming..." message, even thought the file is complete.
Returning to the Gabriel Knight 2 case, I already had the compete file and it was corrupt, but when I readded the game to the downloader, the downloader was adding it to the queue, but it wasn't redownloading the corrupt chunk. It only returned that "Chunk already downloaded" message in the log.
If I didn't have the sensibility to erase the whole file manually, I'd still be trying to download the game unsuccessfuly through the downloader.