Base Sixty Four
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The following implementation provides some samples of Base64 encoder/decoder functions (for background see [Wikipedia: Base64]). Since the last implementation, I had a small competition for the smallest Base64 codec in JavaScript? - converting the new results to lua gave the following, very small as fast codec: !Lua Base64 is also implemented in the b64/unb64 methods in LuaSocket? ([1]), but you may still want to use this snippet for its few requirements -- and it is a nice example with educational value for how to perform logical operations without actual bit-shift or OR operators.I want to apologize if somebody encountered a serious error with the former version of base64 - Not all logical functions can be easily replaced with mathematical ones, so I had to find a way around. The following code is not as fast as the mime C-Module - yet on smaller values the loading time can make a program slower, too. Find the newest (and corrected) version here: !Lua See also the same version but compatible with lua 5.0. !Lua On a further notice, I received a mail from someone using my code without acknowledgement of my copyright and license. If you need another license as explicitly stated in the code, feel free to contact me on my email address. === See Also === * [ee5_base64] faster natural Lua 5.2 base64 encoding/decoding * [lbase64] lhf's lbase64 library (Lua library implemented in C) * [luasocket/mime.html#b64] base64 in LuaSocket? (Lua library implemented in C) * http://libb64.sourceforge.net/ is a fast, public domain base64 encoder/decoder. It's implemented in a coroutine-like style in C. Something similar might be done in Lua, perhaps using real coroutines, or you could bind directly to this library (or just use the base64 routines in luasocket mentioned above). * Lua/APR provides [base64 encoding and decoding functions] (wraps APR functions in C). |
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The following implementation provides some samples of Base64 encoder/decoder functions (for background see [Wikipedia: Base64]). Since the last implementation, I had a small competition for the smallest Base64 codec in JavaScript? - converting the new results to lua gave the following, very small as fast codec:
Base64 is also implemented in the b64/unb64 methods in LuaSocket? ([1]), but you may still want to use this snippet for its few requirements -- and it is a nice example with educational value for how to perform logical operations without actual bit-shift or OR operators.I want to apologize if somebody encountered a serious error with the former version of base64 - Not all logical functions can be easily replaced with mathematical ones, so I had to find a way around. The following code is not as fast as the mime C-Module - yet on smaller values the loading time can make a program slower, too. Find the newest (and corrected) version here:
See also the same version but compatible with lua 5.0.
On a further notice, I received a mail from someone using my code without acknowledgement of my copyright and license. If you need another license as explicitly stated in the code, feel free to contact me on my email address. == Using binary operators in Lua 5.3 == I wrote the snippet below today to speed up the base64 encoding in my application using the new binary operators in Lua5.3, it might be of use for others. I think the algorithm is pretty much optimal, but I'm open to any suggestions and improvements. Every three input bytes are mapped to four output bytes using the binary operations below:
The input is padded to always be a multiple of three bytes, the output padding with '='s is fixed up after calculating the base64 of the padded input string.
=== See Also === * [ee5_base64] faster natural Lua 5.2 base64 encoding/decoding * [lbase64] lhf's lbase64 library (Lua library implemented in C) * [luasocket/mime.html#b64] base64 in LuaSocket? (Lua library implemented in C) * http://libb64.sourceforge.net/ is a fast, public domain base64 encoder/decoder. It's implemented in a coroutine-like style in C. Something similar might be done in Lua, perhaps using real coroutines, or you could bind directly to this library (or just use the base64 routines in luasocket mentioned above). * Lua/APR provides [base64 encoding and decoding functions] (wraps APR functions in C). |
Since the last implementation, I had a small competition for the smallest Base64 codec in JavaScript? - converting the new results to lua gave the following, very small as fast codec:
#!/usr/bin/env lua -- Lua 5.1+ base64 v3.0 (c) 2009 by Alex Kloss <alexthkloss@web.de> -- licensed under the terms of the LGPL2 -- character table string local b='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/' -- encoding function enc(data) return ((data:gsub('.', function(x) local r,b='',x:byte() for i=8,1,-1 do r=r..(b%2^i-b%2^(i-1)>0 and '1' or '0') end return r; end)..'0000'):gsub('%d%d%d?%d?%d?%d?', function(x) if (#x < 6) then return '' end local c=0 for i=1,6 do c=c+(x:sub(i,i)=='1' and 2^(6-i) or 0) end return b:sub(c+1,c+1) end)..({ '', '==', '=' })[#data%3+1]) end -- decoding function dec(data) data = string.gsub(data, '[^'..b..'=]', '') return (data:gsub('.', function(x) if (x == '=') then return '' end local r,f='',(b:find(x)-1) for i=6,1,-1 do r=r..(f%2^i-f%2^(i-1)>0 and '1' or '0') end return r; end):gsub('%d%d%d?%d?%d?%d?%d?%d?', function(x) if (#x ~= 8) then return '' end local c=0 for i=1,8 do c=c+(x:sub(i,i)=='1' and 2^(8-i) or 0) end return string.char(c) end)) end -- command line if not called as library if (arg ~= nil) then local func = 'enc' for n,v in ipairs(arg) do if (n > 0) then if (v == "-h") then print "base64.lua [-e] [-d] text/data" break elseif (v == "-e") then func = 'enc' elseif (v == "-d") then func = 'dec' else print(_G[func](v)) end end end else module('base64',package.seeall) end
Base64 is also implemented in the b64/unb64 methods in LuaSocket? ([1]), but you may still want to use this snippet for its few requirements -- and it is a nice example with educational value for how to perform logical operations without actual bit-shift or OR operators.
I want to apologize if somebody encountered a serious error with the former version of base64 - Not all logical functions can be easily replaced with mathematical ones, so I had to find a way around. The following code is not as fast as the mime C-Module - yet on smaller values the loading time can make a program slower, too. Find the newest (and corrected) version here:
#!/usr/bin/env lua -- working lua base64 codec (c) 2006-2008 by Alex Kloss -- compatible with lua 5.1 -- http://www.it-rfc.de -- licensed under the terms of the LGPL2 -- bitshift functions (<<, >> equivalent) -- shift left function lsh(value,shift) return (value*(2^shift)) % 256 end -- shift right function rsh(value,shift) return math.floor(value/2^shift) % 256 end -- return single bit (for OR) function bit(x,b) return (x % 2^b - x % 2^(b-1) > 0) end -- logic OR for number values function lor(x,y) result = 0 for p=1,8 do result = result + (((bit(x,p) or bit(y,p)) == true) and 2^(p-1) or 0) end return result end -- encryption table local base64chars = {[0]='A',[1]='B',[2]='C',[3]='D',[4]='E',[5]='F',[6]='G',[7]='H',[8]='I',[9]='J',[10]='K',[11]='L',[12]='M',[13]='N',[14]='O',[15]='P',[16]='Q',[17]='R',[18]='S',[19]='T',[20]='U',[21]='V',[22]='W',[23]='X',[24]='Y',[25]='Z',[26]='a',[27]='b',[28]='c',[29]='d',[30]='e',[31]='f',[32]='g',[33]='h',[34]='i',[35]='j',[36]='k',[37]='l',[38]='m',[39]='n',[40]='o',[41]='p',[42]='q',[43]='r',[44]='s',[45]='t',[46]='u',[47]='v',[48]='w',[49]='x',[50]='y',[51]='z',[52]='0',[53]='1',[54]='2',[55]='3',[56]='4',[57]='5',[58]='6',[59]='7',[60]='8',[61]='9',[62]='-',[63]='_'} -- function encode -- encodes input string to base64. function enc(data) local bytes = {} local result = "" for spos=0,string.len(data)-1,3 do for byte=1,3 do bytes[byte] = string.byte(string.sub(data,(spos+byte))) or 0 end result = string.format('%s%s%s%s%s',result,base64chars[rsh(bytes[1],2)],base64chars[lor(lsh((bytes[1] % 4),4), rsh(bytes[2],4))] or "=",((#data-spos) > 1) and base64chars[lor(lsh(bytes[2] % 16,2), rsh(bytes[3],6))] or "=",((#data-spos) > 2) and base64chars[(bytes[3] % 64)] or "=") end return result end -- decryption table local base64bytes = {['A']=0,['B']=1,['C']=2,['D']=3,['E']=4,['F']=5,['G']=6,['H']=7,['I']=8,['J']=9,['K']=10,['L']=11,['M']=12,['N']=13,['O']=14,['P']=15,['Q']=16,['R']=17,['S']=18,['T']=19,['U']=20,['V']=21,['W']=22,['X']=23,['Y']=24,['Z']=25,['a']=26,['b']=27,['c']=28,['d']=29,['e']=30,['f']=31,['g']=32,['h']=33,['i']=34,['j']=35,['k']=36,['l']=37,['m']=38,['n']=39,['o']=40,['p']=41,['q']=42,['r']=43,['s']=44,['t']=45,['u']=46,['v']=47,['w']=48,['x']=49,['y']=50,['z']=51,['0']=52,['1']=53,['2']=54,['3']=55,['4']=56,['5']=57,['6']=58,['7']=59,['8']=60,['9']=61,['-']=62,['_']=63,['=']=nil} -- function decode -- decode base64 input to string function dec(data) local chars = {} local result="" for dpos=0,string.len(data)-1,4 do for char=1,4 do chars[char] = base64bytes[(string.sub(data,(dpos+char),(dpos+char)) or "=")] end result = string.format('%s%s%s%s',result,string.char(lor(lsh(chars[1],2), rsh(chars[2],4))),(chars[3] ~= nil) and string.char(lor(lsh(chars[2],4), rsh(chars[3],2))) or "",(chars[4] ~= nil) and string.char(lor(lsh(chars[3],6) % 192, (chars[4]))) or "") end return result end -- command line if not called as library if (arg ~= nil) then local func = 'enc' for n,v in ipairs(arg) do if (n > 0) then if (v == "-h") then print "base64.lua [-e] [-d] text/data" break elseif (v == "-e") then func = 'enc' elseif (v == "-d") then func = 'dec' else print(_G[func](v)) end end end else module('base64',package.seeall) end
See also the same version but compatible with lua 5.0.
-- working lua base64 codec (c) 2006-2008 by Alex Kloss -- compatible with lua 5.0 -- http://www.it-rfc.de -- licensed under the terms of the LGPL2 -- bitshift functions (<<, >> equivalent) -- shift left function lsh(value,shift) return math.mod((value*(2^shift)), 256) end -- shift right function rsh(value,shift) return math.mod(math.floor(value/2^shift), 256) end -- return single bit (for OR) function bit(x,b) return (math.mod(x, 2^b) - math.mod(x, 2^(b-1)) > 0) end -- logic OR for number values function lor(x,y) result = 0 for p=1,8 do result = result + (((bit(x,p) or bit(y,p)) == true) and 2^(p-1) or 0) end return result end -- encryption table local base64chars = {[0]='A',[1]='B',[2]='C',[3]='D',[4]='E',[5]='F',[6]='G',[7]='H',[8]='I',[9]='J',[10]='K',[11]='L',[12]='M',[13]='N',[14]='O',[15]='P',[16]='Q',[17]='R',[18]='S',[19]='T',[20]='U',[21]='V',[22]='W',[23]='X',[24]='Y',[25]='Z',[26]='a',[27]='b',[28]='c',[29]='d',[30]='e',[31]='f',[32]='g',[33]='h',[34]='i',[35]='j',[36]='k',[37]='l',[38]='m',[39]='n',[40]='o',[41]='p',[42]='q',[43]='r',[44]='s',[45]='t',[46]='u',[47]='v',[48]='w',[49]='x',[50]='y',[51]='z',[52]='0',[53]='1',[54]='2',[55]='3',[56]='4',[57]='5',[58]='6',[59]='7',[60]='8',[61]='9',[62]='-',[63]='_'} -- function encode -- encodes input string to base64. function enc(data) local bytes = {} local result = "" for spos=0,string.len(data)-1,3 do for byte=1,3 do bytes[byte] = string.byte(string.sub(data,(spos+byte))) or 0 end result = string.format('%s%s%s%s%s', result, base64chars[rsh(bytes[1],2)], base64chars[lor(lsh((math.mod(bytes[1], 4)),4), rsh(bytes[2],4))] or "=", ((string.len(data)-spos) > 1) and base64chars[lor(lsh( math.mod(bytes[2], 16) ,2), rsh(bytes[3],6))] or "=", ((string.len(data)-spos) > 2) and base64chars[(math.mod(bytes[3], 64))] or "=" ) end return result end -- decryption table local base64bytes = {['A']=0,['B']=1,['C']=2,['D']=3,['E']=4,['F']=5,['G']=6,['H']=7,['I']=8,['J']=9,['K']=10,['L']=11,['M']=12,['N']=13,['O']=14,['P']=15,['Q']=16,['R']=17,['S']=18,['T']=19,['U']=20,['V']=21,['W']=22,['X']=23,['Y']=24,['Z']=25,['a']=26,['b']=27,['c']=28,['d']=29,['e']=30,['f']=31,['g']=32,['h']=33,['i']=34,['j']=35,['k']=36,['l']=37,['m']=38,['n']=39,['o']=40,['p']=41,['q']=42,['r']=43,['s']=44,['t']=45,['u']=46,['v']=47,['w']=48,['x']=49,['y']=50,['z']=51,['0']=52,['1']=53,['2']=54,['3']=55,['4']=56,['5']=57,['6']=58,['7']=59,['8']=60,['9']=61,['-']=62,['_']=63,['=']=nil} -- function decode -- decode base64 input to string function dec(data) local chars = {} local result="" for dpos=0,string.len(data)-1,4 do for char=1,4 do chars[char] = base64bytes[(string.sub(data,(dpos+char),(dpos+char)) or "=")] end result = string.format('%s%s%s%s', result, string.char(lor(lsh(chars[1],2), rsh(chars[2],4))), (chars[3] ~= nil) and string.char(lor(lsh(chars[2],4), rsh(chars[3],2))) or "", (chars[4] ~= nil) and string.char(lor(math.mod(lsh(chars[3],6), 192), (chars[4]))) or "" ) end return result end -- command line if not called as library if (arg ~= nil) then local func = 'enc' for n,v in ipairs(arg) do if (n > 0) then if (v == "-h") then print "base64.lua [-e] [-d] text/data" break elseif (v == "-e") then func = 'enc' elseif (v == "-d") then func = 'dec' else print(_G[func](v)) end end end else module('base64',package.seeall) end
On a further notice, I received a mail from someone using my code without acknowledgement of my copyright and license. If you need another license as explicitly stated in the code, feel free to contact me on my email address.
I wrote the snippet below today to speed up the base64 encoding in my application using the new binary operators in Lua5.3, it might be of use for others. I think the algorithm is pretty much optimal, but I'm open to any suggestions and improvements.
Every three input bytes are mapped to four output bytes using the binary operations below:
a b c
+-----------------+-----------------+-----------------+
| 0 0 0 0 0 0 1 1 | 1 1 1 1 2 2 2 2 | 2 2 3 3 3 3 3 3 |
+|- - - - - -|- - + - - - -|- - - - + - -|- - - - - -|+
/ / | \ \
/ / | \ \
a>>2 (a&3)<<4|b>>4 (b&15)<<2|c>>6 c&63
The input is padded to always be a multiple of three bytes, the output padding with '='s is fixed up after calculating the base64 of the padded input string.
local bs = { [0] = 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P', 'Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f', 'g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v', 'w','x','y','z','0','1','2','3','4','5','6','7','8','9','+','/', } local function base64(s) local byte, rep = string.byte, string.rep local pad = 2 - ((#s-1) % 3) s = (s..rep('\0', pad)):gsub("...", function(cs) local a, b, c = byte(cs, 1, 3) return bs[a>>2] .. bs[(a&3)<<4|b>>4] .. bs[(b&15)<<2|c>>6] .. bs[c&63] end) return s:sub(1, #s-pad) .. rep('=', pad) end assert(base64("") == "") assert(base64("f") == "Zg==") assert(base64("fo") == "Zm8=") assert(base64("foo") == "Zm9v") assert(base64("foob") == "Zm9vYg==") assert(base64("fooba") == "Zm9vYmE=") assert(base64("foobar") == "Zm9vYmFy")
\ and => are alternatives for function and return.