zlua

--[[----------------------------------------------------------------------------
    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/>
--]]----------------------------------------------------------------------------
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local M = {}
local string, table = string, table

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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

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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

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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 {
    mode = "rb",
    loadfile = function(file, env)
        local hand = package.filesystem.open(file, "rb")
        local data = ""
        local lc = " "
        while lc and lc ~= "" do
            lc = hand:read(math.huge)
            data = data .. (lc or "")
        end
        hand:close()
        return load(M.decompress(data:sub(5)), "="..file, "t", env)
    end,
    load = function(hand, env)
        local data = ""
        local lc = " "
        while lc and lc ~= "" do
            lc = hand:read(math.huge)
            data = data .. (lc or "")
        end
        hand:close()
        return load(M.decompress(data:sub(5)), "="..os.getenv("_"), env)
    end,
    info = function()
        print("    Loads LZSS compressed Lua files.")
    end,
    version = "1.0"
}