[mkgmap-dev] [mkgmap-svn] Commit r4848: catch some special cases which caused infinite loop in mkgmap or wrong data in MDR16 if there is not much data

Thu Jan 6 09:37:01 GMT 2022

Hi Ticker,

I looked again at the code in GPXSee and that seems to indicate that Garmin may drop the lookup table for small trees.
In that case 0 is written instead of 5 or 6. I already tried values like 4 and that always caused crashes.

Working on this ..
Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
Gesendet: Donnerstag, 6. Januar 2022 10:34
An: mkgmap-dev at lists.mkgmap.org.uk; mkgmap-svn at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] [mkgmap-svn] Commit r4848: catch some special cases which caused infinite loop in mkgmap or wrong data in MDR16 if there is not much data

Hi Gerd

Did the '5' nibble in byte 2 indicate the size of lookup table? if so,
could reduce the table size so it overflows. I assume that setting byte
3 to <= table size didn't work

Ticker

On Thu, 2022-01-06 at 09:25 +0000, svn commit wrote:
> Version mkgmap-r4848 was committed by gerd on Thu, 06 Jan 2022
> BRANCH: mdr2
> catch some special cases which caused infinite loop in mkgmap or
> wrong data in MDR16 if there is not much data
> in the index
> - I don't know yet what Garmin expects when there are very few
> characters in the Huffman tree so that all fit into the lookup table.
> Maybe this is what the unknown flag in the initial bits field is
> about
> - don't try to encode with invalid data in mdr16
>
> http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4848
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