198 lines
6.1 KiB
Lua
198 lines
6.1 KiB
Lua
--[[
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* Copyright (c) 2015-2017 Iryont <https://github.com/iryont/lua-struct>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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]]
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struct = {}
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function struct.pack(format, ...)
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local stream = {}
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local vars = {...}
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local endianness = true
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for i = 1, format:len() do
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local opt = format:sub(i, i)
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if opt == '<' then
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endianness = true
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elseif opt == '>' then
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endianness = false
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elseif opt:find('[bBhHiIlL]') then
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local n = opt:find('[hH]') and 2 or opt:find('[iI]') and 4 or opt:find('[lL]') and 8 or 1
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local val = tonumber(table.remove(vars, 1))
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local bytes = {}
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for j = 1, n do
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table.insert(bytes, string.char(val % (2 ^ 8)))
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val = math.floor(val / (2 ^ 8))
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end
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if not endianness then
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table.insert(stream, string.reverse(table.concat(bytes)))
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else
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table.insert(stream, table.concat(bytes))
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end
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elseif opt:find('[fd]') then
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local val = tonumber(table.remove(vars, 1))
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local sign = 0
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if val < 0 then
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sign = 1
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val = -val
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end
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local mantissa, exponent = math.frexp(val)
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if val == 0 then
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mantissa = 0
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exponent = 0
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else
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mantissa = (mantissa * 2 - 1) * math.ldexp(0.5, (opt == 'd') and 53 or 24)
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exponent = exponent + ((opt == 'd') and 1022 or 126)
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end
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local bytes = {}
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if opt == 'd' then
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val = mantissa
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for i = 1, 6 do
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table.insert(bytes, string.char(math.floor(val) % (2 ^ 8)))
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val = math.floor(val / (2 ^ 8))
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end
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else
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table.insert(bytes, string.char(math.floor(mantissa) % (2 ^ 8)))
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val = math.floor(mantissa / (2 ^ 8))
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table.insert(bytes, string.char(math.floor(val) % (2 ^ 8)))
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val = math.floor(val / (2 ^ 8))
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end
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table.insert(bytes, string.char(math.floor(exponent * ((opt == 'd') and 16 or 128) + val) % (2 ^ 8)))
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val = math.floor((exponent * ((opt == 'd') and 16 or 128) + val) / (2 ^ 8))
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table.insert(bytes, string.char(math.floor(sign * 128 + val) % (2 ^ 8)))
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val = math.floor((sign * 128 + val) / (2 ^ 8))
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if not endianness then
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table.insert(stream, string.reverse(table.concat(bytes)))
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else
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table.insert(stream, table.concat(bytes))
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end
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elseif opt == 's' then
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table.insert(stream, tostring(table.remove(vars, 1)))
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table.insert(stream, string.char(0))
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elseif opt == 'c' then
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local n = format:sub(i + 1):match('%d+')
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local length = tonumber(n)
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if length > 0 then
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local str = tostring(table.remove(vars, 1))
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if length - str:len() > 0 then
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str = str .. string.rep(' ', length - str:len())
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end
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table.insert(stream, str:sub(1, length))
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end
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i = i + n:len()
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end
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end
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return table.concat(stream)
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end
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function struct.unpack(format, stream)
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local vars = {}
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local iterator = 1
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local endianness = true
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for i = 1, format:len() do
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local opt = format:sub(i, i)
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if opt == '<' then
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endianness = true
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elseif opt == '>' then
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endianness = false
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elseif opt:find('[bBhHiIlL]') then
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local n = opt:find('[hH]') and 2 or opt:find('[iI]') and 4 or opt:find('[lL]') and 8 or 1
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local signed = opt:lower() == opt
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local val = 0
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for j = 1, n do
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local byte = string.byte(stream:sub(iterator, iterator))
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if endianness then
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val = val + byte * (2 ^ ((j - 1) * 8))
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else
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val = val + byte * (2 ^ ((n - j) * 8))
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end
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iterator = iterator + 1
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end
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if signed and val >= 2 ^ (n * 8 - 1) then
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val = val - 2 ^ (n * 8)
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end
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table.insert(vars, val)
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elseif opt:find('[fd]') then
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local n = (opt == 'd') and 8 or 4
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local x = stream:sub(iterator, iterator + n - 1)
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iterator = iterator + n
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if not endianness then
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x = string.reverse(x)
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end
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local sign = 1
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local mantissa = string.byte(x, (opt == 'd') and 7 or 3) % ((opt == 'd') and 16 or 128)
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for i = n - 2, 1, -1 do
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mantissa = mantissa * (2 ^ 8) + string.byte(x, i)
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end
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if string.byte(x, n) > 127 then
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sign = -1
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end
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local exponent = (string.byte(x, n) % 128) * ((opt == 'd') and 16 or 2) + math.floor(string.byte(x, n - 1) / ((opt == 'd') and 16 or 128))
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if exponent == 0 then
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table.insert(vars, 0.0)
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else
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mantissa = (math.ldexp(mantissa, (opt == 'd') and -52 or -23) + 1) * sign
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table.insert(vars, math.ldexp(mantissa, exponent - ((opt == 'd') and 1023 or 127)))
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end
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elseif opt == 's' then
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local bytes = {}
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for j = iterator, stream:len() do
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if stream:sub(j, j) == string.char(0) then
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break
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end
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table.insert(bytes, stream:sub(j, j))
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end
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local str = table.concat(bytes)
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iterator = iterator + str:len() + 1
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table.insert(vars, str)
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elseif opt == 'c' then
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local n = format:sub(i + 1):match('%d+')
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table.insert(vars, stream:sub(iterator, iterator + tonumber(n)-1))
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iterator = iterator + tonumber(n)
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i = i + n:len()
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end
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end
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return unpack(vars)
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end
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return struct
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