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| 1 | +-- This file originates from this repository: https://github.com/iskolbin/lbase64 |
| 2 | +-- It was modified to translate between base64 strings and lists of bytes instead of base64 strings and strings. |
| 3 | + |
| 4 | +local base64 = {} |
| 5 | + |
| 6 | +local extract = _G.bit32 and _G.bit32.extract -- Lua 5.2/Lua 5.3 in compatibility mode |
| 7 | +if not extract then |
| 8 | + if _G._VERSION == "Lua 5.4" then |
| 9 | + extract = load[[return function( v, from, width ) |
| 10 | + return ( v >> from ) & ((1 << width) - 1) |
| 11 | + end]]() |
| 12 | + elseif _G.bit then -- LuaJIT |
| 13 | + local shl, shr, band = _G.bit.lshift, _G.bit.rshift, _G.bit.band |
| 14 | + extract = function( v, from, width ) |
| 15 | + return band( shr( v, from ), shl( 1, width ) - 1 ) |
| 16 | + end |
| 17 | + elseif _G._VERSION == "Lua 5.1" then |
| 18 | + extract = function( v, from, width ) |
| 19 | + local w = 0 |
| 20 | + local flag = 2^from |
| 21 | + for i = 0, width-1 do |
| 22 | + local flag2 = flag + flag |
| 23 | + if v % flag2 >= flag then |
| 24 | + w = w + 2^i |
| 25 | + end |
| 26 | + flag = flag2 |
| 27 | + end |
| 28 | + return w |
| 29 | + end |
| 30 | + end |
| 31 | +end |
| 32 | + |
| 33 | + |
| 34 | +function base64.makeencoder( s62, s63, spad ) |
| 35 | + local encoder = {} |
| 36 | + for b64code, char in pairs{[0]='A','B','C','D','E','F','G','H','I','J', |
| 37 | + 'K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y', |
| 38 | + 'Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n', |
| 39 | + 'o','p','q','r','s','t','u','v','w','x','y','z','0','1','2', |
| 40 | + '3','4','5','6','7','8','9',s62 or '+',s63 or'/',spad or'='} do |
| 41 | + encoder[b64code] = char:byte() |
| 42 | + end |
| 43 | + return encoder |
| 44 | +end |
| 45 | + |
| 46 | +function base64.makedecoder( s62, s63, spad ) |
| 47 | + local decoder = {} |
| 48 | + for b64code, charcode in pairs( base64.makeencoder( s62, s63, spad )) do |
| 49 | + decoder[charcode] = b64code |
| 50 | + end |
| 51 | + return decoder |
| 52 | +end |
| 53 | + |
| 54 | +local DEFAULT_ENCODER = base64.makeencoder() |
| 55 | +local DEFAULT_DECODER = base64.makedecoder() |
| 56 | + |
| 57 | +local char, concat = string.char, table.concat |
| 58 | + |
| 59 | +function base64.encode( arr, encoder ) |
| 60 | + encoder = encoder or DEFAULT_ENCODER |
| 61 | + local t, k, n = {}, 1, #arr |
| 62 | + local lastn = n % 3 |
| 63 | + for i = 1, n-lastn, 3 do |
| 64 | + local a, b, c = arr[i], arr[i + 1], arr[i + 2] |
| 65 | + local v = a*0x10000 + b*0x100 + c |
| 66 | + local s |
| 67 | + s = char(encoder[extract(v,18,6)], encoder[extract(v,12,6)], encoder[extract(v,6,6)], encoder[extract(v,0,6)]) |
| 68 | + t[k] = s |
| 69 | + k = k + 1 |
| 70 | + end |
| 71 | + if lastn == 2 then |
| 72 | + local a, b = arr[n-1], arr[n] |
| 73 | + local v = a*0x10000 + b*0x100 |
| 74 | + t[k] = char(encoder[extract(v,18,6)], encoder[extract(v,12,6)], encoder[extract(v,6,6)], encoder[64]) |
| 75 | + elseif lastn == 1 then |
| 76 | + local v = arr[n]*0x10000 |
| 77 | + t[k] = char(encoder[extract(v,18,6)], encoder[extract(v,12,6)], encoder[64], encoder[64]) |
| 78 | + end |
| 79 | + return concat( t ) |
| 80 | +end |
| 81 | + |
| 82 | +function base64.decode( b64, decoder ) |
| 83 | + decoder = decoder or DEFAULT_DECODER |
| 84 | + local pattern = '[^%w%+%/%=]' |
| 85 | + if decoder then |
| 86 | + local s62, s63 |
| 87 | + for charcode, b64code in pairs( decoder ) do |
| 88 | + if b64code == 62 then s62 = charcode |
| 89 | + elseif b64code == 63 then s63 = charcode |
| 90 | + end |
| 91 | + end |
| 92 | + pattern = ('[^%%w%%%s%%%s%%=]'):format( char(s62), char(s63) ) |
| 93 | + end |
| 94 | + b64 = b64:gsub( pattern, '' ) |
| 95 | + local t, k = {}, 1 |
| 96 | + local n = #b64 |
| 97 | + local padding = b64:sub(-2) == '==' and 2 or b64:sub(-1) == '=' and 1 or 0 |
| 98 | + for i = 1, padding > 0 and n-4 or n, 4 do |
| 99 | + local a, b, c, d = b64:byte( i, i+3 ) |
| 100 | + local s |
| 101 | + local v = decoder[a]*0x40000 + decoder[b]*0x1000 + decoder[c]*0x40 + decoder[d] |
| 102 | + table.insert(t,extract(v,16,8)) |
| 103 | + table.insert(t,extract(v,8,8)) |
| 104 | + table.insert(t,extract(v,0,8)) |
| 105 | + end |
| 106 | + if padding == 1 then |
| 107 | + local a, b, c = b64:byte( n-3, n-1 ) |
| 108 | + local v = decoder[a]*0x40000 + decoder[b]*0x1000 + decoder[c]*0x40 |
| 109 | + table.insert(t,extract(v,16,8)) |
| 110 | + table.insert(t,extract(v,8,8)) |
| 111 | + elseif padding == 2 then |
| 112 | + local a, b = b64:byte( n-3, n-2 ) |
| 113 | + local v = decoder[a]*0x40000 + decoder[b]*0x1000 |
| 114 | + table.insert(t,extract(v,16,8)) |
| 115 | + end |
| 116 | + return t |
| 117 | +end |
| 118 | + |
| 119 | +return base64 |
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