<div dir="ltr">Hi David, Hi All,<div><br></div><div> here's an example of an occasional problem. I'm looking at the free tree in Spur and I have an unused field in each free chunk that is a remnant of an old attempt at a compaction algorithm I've long abandoned. I'd like to eliminate the field (2nd slot in a free chunk) but that means either breaking the loading of existing Spur images or some version marker in the image header to indicate whether the image contains old format free chunks or new format. This is the kind of internal micro-change that I don't think warrants taking a bit from the image version field.</div><div><br></div><div>However, it /would/ be nice to have a field there-in for a minor version number that the VM implementor could simply increment when they want to make such a minor change. What do you think? Currently the unused bits in the image format are</div><div><br></div><div>ImageFormat availableBits printStringBase: 2 '1111111,11111110,11100110,00000000'</div><div><br></div><div>(the top bit is reserved for an extension bit).</div><div><br></div><div>So we could use the top 7 bits for a 0-127 field that will probably last me for a long time, and it would be easy to mask it out of the version field.</div><div><br></div><div>An alternative is for me to use some other field in the Spur image header. I'm happy to do that if the above scheme smells to anyone. There's a 16-bit field in Cog image headers I can use (see the2ndUnknownShort in VMMaker.oscog).<br>-- <br><div class="gmail_signature">best,<div>Eliot</div></div>
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