Sunday, February 1, 2015

Loading HTML files in 128K

I spent most of yesterday trying to track down a nasty bug in the lwIP http server. Most of lwIP is very well coded, and other than the CRLF problem I had, very portable and bug-free. The lwIP http server is a bit of a hodgepodge of code though. Lucky me. Anyway, the callback to release the html file resources happens before the server has sent the TCP packet. As a result, I was free()ing memory before the server was done with it which caused corruption in the HTTP headers. I decided to just keep a file buffer up all of the time instead of malloc()ing and free()ing memory as needed. This was a constraint on the size of file that can be loaded though.

I spent the rest of the night moving more PPP code into a separate code segment that I can unload once the connection is up. It worked so well, I was shocked when I saw 9K of free RAM. This easily left me 4K of RAM to load HTML files. I can even open the menus without crashing. Unfortunately, it crashes on Quit on a 128K because it needs too much RAM to bring down the interface.

So, I will get an upload ready and get a video done in the morning!

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