Miscellaneous OpenComputers stuff.
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--[[----------------------------------------------------------------------------
LZSS - encoder / decoder
This is free and unencumbered software released into the public domain.
Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.
In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
For more information, please refer to <http://unlicense.org/>
--]]----------------------------------------------------------------------------
--------------------------------------------------------------------------------
local M = {}
local string, table = string, table
--------------------------------------------------------------------------------
local POS_BITS = 12
local LEN_BITS = 16 - POS_BITS
local POS_SIZE = 1 << POS_BITS
local LEN_SIZE = 1 << LEN_BITS
local LEN_MIN = 3
--------------------------------------------------------------------------------
function M.compress(input)
local offset, output = 1, {}
local window = ''
local function search()
for i = LEN_SIZE + LEN_MIN - 1, LEN_MIN, -1 do
local str = string.sub(input, offset, offset + i - 1)
local pos = string.find(window, str, 1, true)
if pos then
return pos, str
end
end
end
while offset <= #input do
local flags, buffer = 0, {}
for i = 0, 7 do
if offset <= #input then
local pos, str = search()
if pos and #str >= LEN_MIN then
local tmp = ((pos - 1) << LEN_BITS) | (#str - LEN_MIN)
buffer[#buffer + 1] = string.pack('>I2', tmp)
else
flags = flags | (1 << i)
str = string.sub(input, offset, offset)
buffer[#buffer + 1] = str
end
window = string.sub(window .. str, -POS_SIZE)
offset = offset + #str
else
break
end
end
if #buffer > 0 then
output[#output + 1] = string.char(flags)
output[#output + 1] = table.concat(buffer)
end
end
return table.concat(output)
end
--------------------------------------------------------------------------------
function M.decompress(input)
local offset, output = 1, {}
local window = ''
while offset <= #input do
local flags = string.byte(input, offset)
offset = offset + 1
for i = 1, 8 do
local str = nil
if (flags & 1) ~= 0 then
if offset <= #input then
str = string.sub(input, offset, offset)
offset = offset + 1
end
else
if offset + 1 <= #input then
local tmp = string.unpack('>I2', input, offset)
offset = offset + 2
local pos = (tmp >> LEN_BITS) + 1
local len = (tmp & (LEN_SIZE - 1)) + LEN_MIN
str = string.sub(window, pos, pos + len - 1)
end
end
flags = flags >> 1
if str then
output[#output + 1] = str
window = string.sub(window .. str, -POS_SIZE)
end
end
end
return table.concat(output)
end
return M