jwz@teak.berkeley.edu (Jamie Zawinski) (11/16/89)
I have some code for reading sun raster files on the Explorer; Rather than reading the files a byte at a time, I make a 1d, 8-bit array displaced to the bitmap I want to store into, and then hand this to :string-in (thus bypassing a lot of method-calling overhead). This is reasonably fast, and I think about as good as I can expect to get. Now, 60% of the time in reading the file is spent opening the damn FTP connection, but 80% of the rest of the time is spent reversing the order of bits in the bytes read in (since Lispms and Suns store their bits in the opposite order). I'm doing this reversal by precomputing an array inwhich (aref array #b11110001) ==> #b10001111, and after reading in the array, zipping through the 8-bit version and flipping things around. Can anyone think of a better way? It seems like I ought to be able to do this with a series of blits, kind of like the SmallTalk Life and rotation algorithms. -- Jamie PS: I know the difference between big-endian and little-endian, but which is which? PPS: The code of which I speak is accessible by anon FTP from spice.cs.cmu.edu in the directory /usr/jwz/public/