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Re: [Discuss-gnuradio] Bug in digital::glfsr_source_b


From: Marcus Müller
Subject: Re: [Discuss-gnuradio] Bug in digital::glfsr_source_b
Date: Tue, 9 Aug 2016 09:18:45 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1

Hi Eugene,


that sounds like a bug, and a fix, indeed!

I'd immediately go ahead and just replace the int by uint32_t (which happens to be the thing we want to use here, considering the degree self-limits to 32).


But: I know this has been around 0.75 eterneties; Michael even fixed some compiler warning in glfsr.cc last year; I want to be sure we're not breaking anything hence I'm, hereby asking around:


was there a rationale behind having signed intage here?


Best regards,

Marcus



On 09.08.2016 02:29, Eugene Grayver wrote:

Note: It is, of course, possible to trick the blocks into working by passing in negative values (n - 2**32), but it is not elegant.


________________________

Eugene Grayver, Ph.D.
Aerospace Corp., Sr. Eng. Spec.
Tel: 310.336.1274
________________________




From: Eugene Grayver
Sent: Monday, August 8, 2016 5:22 PM
To: address@hidden
Subject: Re: Bug in digital::glfsr_source_b
 

Note: same issue with descrambler_bb and scrambler_bb.  The digital.lfsr block is correct.


________________________

Eugene Grayver, Ph.D.
Aerospace Corp., Sr. Eng. Spec.
Tel: 310.336.1274
________________________




From: Eugene Grayver
Sent: Monday, August 8, 2016 2:47 PM
To: address@hidden
Subject: Bug in digital::glfsr_source_b
 

I found a minor (?) bug in glfsr_source_b and _f, and in glfsr.h.  The input types for mask and seed should be 'unsigned int', not 'int'.  Currently it does not allow 32-bit values, only 31-bit values.  While somebody is fixing that, they should also make 'length' an optional input to have the LFSR restart after fewer than 2^degree outputs.


________________________

Eugene Grayver, Ph.D.
Aerospace Corp., Sr. Eng. Spec.
Tel: 310.336.1274
________________________




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