forked from izaya/OC-PsychOS2
124 lines
3.6 KiB
Lua
124 lines
3.6 KiB
Lua
--[[----------------------------------------------------------------------------
|
|
|
|
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
|