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magnusja / libaums

Open source library to access USB Mass Storage devices on Android without rooting your device
Apache License 2.0
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Why does mass storage send a 16k data packet into multiple data packets? #406

Open junxiaojun opened 9 months ago

junxiaojun commented 9 months ago

Problem

private fun transferOneCommand(command: CommandBlockWrapper, inBuffer: ByteBuffer): Int

I have a 16k data packet. Why is it divided into 5 reads? Can I read 16k data packets at once? Instead of subcontracting to read

Expected behavior

Actual behavior

Stacktrace of Excpetion

(if exists)

Code where problem occurs

junxiaojun commented 9 months ago

@magnusja

magnusja commented 9 months ago

Depends on the flash drive. Oftentimes, some support larger ones, some do not.

But anyways, the ScsiWrite and Read commands currently only support some smaller chunk sizes. See here, https://github.com/magnusja/libaums/blob/develop/libaum

Screenshot 2023-11-24 at 21 37 49

s/src/main/java/me/jahnen/libaums/core/driver/scsi/commands/ScsiRead10.kt

Currently, there is a read command 32, which probably speeds up transfer by a lot if usb drive supports it. See here: https://www.seagate.com/files/staticfiles/support/docs/manual/Interface%20manuals/100293068j.pdf

Screenshot 2023-11-24 at 21 39 03

I am happy to take a PR. But as the USB spec is complex, it is hard to support each of these flawlessly.

junxiaojun commented 9 months ago

@magnusja Thank you. I am very happy to see your reply. The problem has been solved. Thank you very much.