OOH.. nice one. I had missed that in my template implementation. I'm a big fan of using C++ templating to do type-safe versions of this kind of stuff... This is my template version:

/** Sign extend an unsigned to a signed integer of the same size.
*/
template<typename UINT, typename INT, uint8_t SIGNBIT>
INT sign_extend( UINT uvalue)
{
typedef typename std::make_unsigned<INT>::type uint_t;
uint_t newuvalue = uvalue;
if ( newuvalue & ( UINT(1U) << SIGNBIT) ) {
newuvalue |= ~((uint_t(1U) << SIGNBIT) - 1);
}
return reinterpret_cast<INT &>(uvalue);
}
It could probably be converted into a version that would infer some of the types.. but this should work pretty well and should compile down to close to the same code.

Usage from my code: Where BYTES is a templated integer value parameter.

res = sign_extend < uint32_t, int32_t, BYTES * 8 - 1 > (ures);

I also have a templated buffer extractor that allows for checking available space!

For example this code (which extracts 2 bytes as a signed integer), which should now work with sign extension thanks to your bugfix and the above templated version of sign extension:

int32_t signedValue;
if (!can_buff_int<2>(data, 10, signedValue )) {
ESP_LOGE(TAG, "IoniqISOTP.BMC: BMS Current: Bad Buffer");
} else {
StdMetrics.ms_v_bat_current->SetValue((float)signedValue / 10.0, Amps);

}

//.ichael

On Fri, 14 Oct 2022 at 05:35, Ludovic LANGE <ll-ovmsdev@lange.nom.fr> wrote:

Dear list,

I've come across an issue with the DBC parser where a non-32-bit negative number was incorrectly decoded.

I've traced this to an issue with sign-extension ; and I've proposed a fix here https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/pull/736

Before having it merged, I'd like to gather some feedback from users of the DBC module.

Please have a look, and comment directly on the GitHub PR.

Thanks in advance !

Regards,

Ludovic

_______________________________________________
OvmsDev mailing list
OvmsDev@lists.openvehicles.com
http://lists.openvehicles.com/mailman/listinfo/ovmsdev