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-- based on http://zerosoft.zophar.net/ips.php (note the data is big endian - this isn't clear from the text)
local function read_some_bytes(fin, siz)
local ret = 0
for _ = 1, siz do
ret = ret * 256 + fin:readU8()
end
return ret
end
function ips_patch(buffer, ips)
local header, offset, size, b = "", 0, 0
for _ = 1, 5 do
header = header .. string.char(ips:readU8())
end
if header ~= "PATCH" then error "Wrong IPS file format - bad header" end
while true do
offset = read_some_bytes(ips, 3)
-- that's one of the most stupid thing ever... you can NOT patch the offset
-- 0x454F46 since this is the end of the ips file marker... whomever came
-- with this brillant design needs a smack in the face.
if offset == 0x454F46 then
break
end
buffer:seek(offset)
if buffer.wseek then buffer:wseek(offset) end
size = read_some_bytes(ips, 2)
if size == 0 then
size = read_some_bytes(ips, 2)
b = ips:readU8()
for _ = 1, size do buffer:writeU8(b) end
else
ips:copyto(buffer, size)
end
end
buffer:seek(0)
if buffer.wseek then buffer:wseek(0) end
end
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