1-byte Reports do not get written correctly

gary-rowe / hid4java

A cross-platform Java Native Access (JNA) wrapper for the libusb/hidapi library. Works out of the box on Windows/Mac/Linux.

MIT License

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1-byte Reports do not get written correctly #41

Closed StefanKrupop closed 7 years ago

StefanKrupop commented 8 years ago

I think there is an off-by-one error in the "write" method of org.hid4java.jna.HidApi:

The JavaDoc says the Report data should not include the Report ID. It will get prepended to the data automatically. However, both the Windows- and regular code path execute the arraycopy only if the data length is larger than 1. Thus, a 1-byte Report gets written out, but not including the supplied data... I think it should be "if (len >= 1) {".

Kind regards, Stefan

gary-rowe commented 8 years ago

Can you verify that this still occurs with the develop branch version of hid4java?

StefanKrupop commented 8 years ago

I did not (yet) check it with a compiled version of the branch, but the section I meant is also in the development version: https://github.com/gary-rowe/hid4java/blob/c08536c43bd3ea9e32e82941c36ebc02324df985/src/main/java/org/hid4java/jna/HidApi.java#L432-L439

When len=1 the arraycopy in both paths will not get executed.

marek-trmac commented 8 years ago

I found the same problem, and I verified that fixed condition if (len >= 1) works.

gary-rowe commented 7 years ago

Fixed in pull request.