1. Michael Bolin's GIF Loader
Hey all,
I'm porting Michael's GIF loader to C++, and as my
Euphoria knowledge is not as comprehensive as I would
like, I'm having a little trouble divining the meaning
of certain parts of the meat of his decompression
code. Below is the code snippet I'm dealing w/,
commented here and there with my guess as to the
meaning of particular parts. For any parties familiar
w/ his code, any wisdom you could impart would be most
appreciated.
if code=end_of_info then
exit
elsif code=clear_code then
-- this part just recalcs the 'strings'
-- table?
strings=repeat({},n_colors+2)
for t=1 to n_colors do
strings[t]={t-1}
end for
num_bits=code_size+1
work_bits=bits[1..num_bits]
code=bits_to_int(work_bits)+1
-- this is very confusing for me...
-- 'strings' is basically a sequence of
-- sequences, yes? and if this is true,
-- then up above when we recalculated
-- the table, every sequence in the
-- table is further comprised of a one-
-- element sequence. and so, following
-- that line of reasoning, it would
-- appear as if this loop is effectively
-- equivalent to
-- 'output=output & strings[code][1]'
-- atleast, that's all i've figured on
-- so far. how hot/cold am i? 
for t=1 to length(strings[code]) do
output=append(output,strings[code][t])
end for
old=code
bits=bits[num_bits+1..length(bits)]
else
if code<=length(strings) then
-- 'string' points to 'strings[code]'
string=strings[code]
-- add all elements in sequence
-- 'string' to sequence 'output'
-- basically the same as adding all
-- elements from 'strings[code]'?
for t=1 to length(string) do
output=append(output,string[t])
end for
-- same as
-- 'work=strings[old] & strings[code][1]'?
work=strings[old] & string[1]
-- attach sequence 'work' to the
-- end of 'strings'
strings=append(strings,work)
-- so the entire point of this if-block
-- is to build a sequence, which gets
-- tacked onto the end of 'strings'?
old=code
else
-- tack a copy of the first element onto
-- the end of its own sequence?
work=strings[old] & strings[old][1]
-- add all elements in sequence 'work' to
-- sequences 'output'
for t=1 to length(work) do
output=append(output,work[t])
end for
-- and attach the sequence 'work' to
-- the end of 'strings' just like in the
-- if-block
strings=append(strings,work)
-- so this else-block seems like a
-- variation on the if-block
old=code
end if
end if
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