Lua string format binary

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Lua string format binary

Skip to content There are faster ways to do this that take advantage of the string format, which converts numbers to base 8. It's trivial to then convert base 8 into binary. --create lookup table for octal to binary oct2bin = { ['0'] = '000', ['1'] = '001', ['2'] = '010', ['3'] = '011', ['4'] = '100', ['5'] = '101', ['6'] = '110', ['7'] = '111' } the getOct2bin(a) function returns the final function oct2bin[a] convertBin(n) s local = string.format('%o', n) s = s:gsub('.', getOct2bin) return s end If you want to keep everything the same size, then do s = string.format('%.22o', n) Which gives you 66 bits. That's two extra bits at the end, because octal works in groups of 3 bits, and 64 is not divided by 3. If you want 33 bits, change them to 11. If you have the BitOp library, which is available by default in LuaJIT, then you can do this: convertBin(n) local function t = {} for i = 1, 32 do n = bit.roller(n, 1) table.insert(t, bit.band(n, 1)) end return table.concat(t) end But note this only does the first 32 bits! If your number is greater than 2^32, the result will not be correct. Instantly share code, notes, and snippets. Lua function that creates a hex dump of binary strings. You can't do that action right now. You sign in with another tab or window. Reload to refresh your session. you exit in another tab or window. Reload to refresh your session. We use optional third-party analytics cookies to understand how you use that can build better products. Learn more. We use optional third-party analytics cookies to understand how you use that can build better products. You can always update your options by clicking Cookie Preferences at the bottom of the page. For more information, see our Privacy Statement. We use important cookies to perform important website functions, for example they are used to log in. Learn more Always on We use analytics cookies to understand how you use our website so we can make them better, for example they are used to collect information about the pages you visit and how many clicks you need to complete tasks. Learn more The Struct Class offers basic facilities for converting Lua values to and from C-style structs in binary Lua strings. It is based on the Lua Roberto Ierusalimschy struct library found in roberto/struct/, with some minor modifications as follows: Adding support for int64 / UInt64 which is packaged / disassembled, using 'e'/'E'. Can handle integers 'long length' (i8 / I8); even though they were converted into doubles. Can insert/specify padding anywhere in a struct. ('X' for example when the string follows Can report the current offset in the package and disassemble (=). Can mask return values when you only want to calculate an unequal size or string of pascal styles using (&amp;). All but the first of those changes are based on an email from Flemming Madsen, on the lua user mailing list, which can be found here. Its main function is Struct.pack, which packs multiple Lua values into a struct-like struct-like binary string; and Struct.unpack, which disassembles some Lua values from lua binary strings such as the given struct. There are several additional helper functions available as well. All functions in the Struct library are referred to as static member functions, not object methods, so they are called as Struct.pack(... ) instead of object:pack(... ). The boxing argument to some Struct functions is a format string, which explains the layout of the structure. Format strings are a sequence of conversion elements, which respects the current endianness and current alignment requirements. Initially, the current endianness was the original endianness of the machine and the current alignment requirement was 1 (meaning no alignment at all). You can change this setting with the appropriate directive in the format string. The supported elements in the format string are as follows: ' ' (empty space) is ignored. Flag '!n' to set the current alignment requirements to 'n' (of course power 2); The nonexistence of the 'n' means the original alignment of the machine. Flag '>' to set the mode to big endian (i.e., network-order). Flag '<' to set mode to little endian. 'x' byte zero padding with no corresponding Lua value. 'b' char signed. 'B' an unsigned char. The unsigned 'H' is short (original size). 'l' signed length (original size). 'L' unsigned length (original size). 'T' size_t (original size). 'in' integer signed with byte 'n'. A no 'n' means the original size of the int. 'In' is like 'in' but not signed. 'e' is signed 8-byte Integer (64-bit, long length), to/from the Int64 object. An unsigned 8-byte Integer (64-bit, long length), up to/from an object UInt64. 'f' a float. 'd' double (original size). 's' zero-stop string. 'cn' sequences exactly 'n' chars according to one Lua string. The absent 'n' means 1. When packing, the given string must have at least the 'n' character (additional characters will be discarded). 'c0' is like 'cn', except that 'n' is given in another way: When packing, 'n' is the length of the given string; when unpacking, 'n' is the value of a previously unpacked value (which must be a number). In this case, this previous value is not returned. 'xn' pad to 'n' number of bytes, defaults to 1. Pad 'Xn' to the 'n' alignment, maxalign default. '(' to stop specifying items, and ')' to start padding when packing). '=' to return the current position/ offset. Note Using i, I, h, H, l, L, f, and T is highly discouraged, since such sizes depend on the system. Use explicit-sized variants instead, such as i4 or E. Unpacking i/I is done to Lua numbers, double-precision floating points, so dismantling 64-bit fields (i8/I8) will lose precision. Use e/E to unpack into the Wireshark Int64/UInt64 object instead. 1.11.3 11.13.1.1. Struct.pack(format, value) Returns a string containing the values arg1, arg2, etc. packaged/encoded according to the format string. One or more Lua value arguments to encode, based on Format. Returns the packaged binary Lua String, plus any position because '=' is used in the format. 11.13.1.2. Struct.unpack(format, struct, [begin]) Decods/decodes some Lua values of binary Lua strings such as certain structs. The number of values returned depends on the given format, plus the additional value of the position in which it stops reading is returned. Struct argument Lua binary string to unpack the start (optional) Position to start reading from (default=1) Returns One or more values by format, plus a stop unpacking position. 11.13.1.3. Struct.size(format) Returns the length of the binary string to be consumed/handled by the given format string. Argument Returns the Number of measures 11.13.1.4. Struct.values(format) Returns the number of Lua values contained in the specified format string. This will be the amount of value returned from the call to Struct.unpack() excluding the extra return value from the offset position. (i.e., Struct.values() does not calculate the extra return value) This will also be the expected number of arguments Struct.pack(), excluding format string arguments. Argument Returns the Sum of the values 11.13.1.5. Struct.tohex(bytestring, [lowercase], [separator]) Converts a skipped binary string to a hex-ascii string. The Offline String bytestring argument consisting of true lowercase binary bytes (optional) to use lowercase hex characters (default=false). separator (optional) String separator to insert between hex bytes (default=nil). Returns the lua hex-ascii string 11.13.1.6. Struct.fromhex(hexbytes, [separator]) Converts a passed hex-ascii string to a binary string. Hexabyte string arguments consisting of hexadecimal bytes such as separator 00 B1 A2 or 1a2b3c4d (optional) String separator between hex bytes/word (no default). Returns the lua binary wiki string Often required to package a list of integers into a data binary string, for example to read/write binary files or to implement communication protocols. There are many ways to do this. This implementation only has the pretense to be relatively easy to use. This function fails for a negative singing value of -86000! function write_format(little_endian, format, ...) local res = '' local value = {...} for i=1.#format do local size = tonumber(format:sub(i,i)) local value = values[i] local str = for j=1,size do str = str .. string.char(value % 256) value = math.floor(value / 256) ends if not little_endian then str = string.reverse(str) end res = res .. str end return res end read_format(little_endian, format, str) local idx = 0 local res = {} for i=1.#format do local size = tonumber(format:sub(i,i)) local val = str:sub(idx+1,idx+size) local value = 0 idx = idx + size if little_endian then val = string.reverse(val) end for j=1,size do value = value * 256 + end res[i] = value end return unpack(res) end More Integers This function fails to sing negative value of -86000 ! Other ways read and write integers, written by Tom N Harris. function stringtonumber(str) local function _b2n(exp, num, digits, ...) otherwise digit then return num end return _b2n(exp*256, num + digit*exp, ...) end return _b2n(256, string.byte(str, 1, -1)) the end function stringtonumber(str) local function _b2n(num, digit, ...) otherwise digit then return num end return _b2n(num*256 + digit, ...) end return _b2n(0, string.byte(str, 1, 1. -1)) end function numbertobyte(num, width) local function _n2b(width, num, brakes) brakes = brakes * 256 if width == 0 then return brake back end, _n2b(width-1, math.modf(num/256)) string final return.char(_n2b(width-1, math.modf(num/256)) final return string.char(_n2b(width1, math.modf(num/256))) function end numbertobyte(num, width) local function _n2b(t, width, num, brakes) if width == 0 and then return table.concat(t) end table.insert(t , 1, string.char(brake * 256)) returns _n2b(t), width-1, math.modf(num/256)) end return _n2b({}, width, math.modf(num/256)) end bitfields Functions that unpack bits in numbers for booleans. function unpackbits(bits, width) local fl = {} local num,brakes = flags for i = 1,width do num,rem = math.modf(num/2) fl[#fl+1] = brakes>=0.5 end return unpack(fl) end Floating-Point Convert a IEEE-754 float in MSB order. local convertfloat(str) function b1,b2,b3,b4 = string.byte(str, 1, 4) local exponent = (b1 % 128) * 2 + floor.matematika(b2 / 128) if exponent == 0 then return 0 local end marks = (b1 > 127) and -1 or 1 local mantissa = ((b2 % 128) * 256 + b3) * 256 + b4 mantissa = (math.ldexp(mantissa, -23) + 1) * sign return math.ldexp(mantissa, exponent - 127) end library There is library C to package and unpack binary data. They can handle integers of sizes from 8 to 32 bits, signed or unsigned, IEEE-754 floating points, plus strings in several forms, etc. See StructurePacking. Original quote, Sirmabus: September 13, 2009 Latest Changes ? edit preferences ? historyLast edited September 18, 2013 1:02 PM GMT (diff) (diff)

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