Initial implementation of BASE64.LUA script.

Author: Lethja

util/BASE64.LUA

@@ -0,0 +1,158 @@
+
+-- b64c = base64 characters
+--   dt = decode table
+local b64c, dt = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/', {}
+for i = 1, #b64c do dt[b64c:sub(i,i)] = i - 1 end
+
+---Encode a file into base64
+---@param file file The file to turn into base64
+---@return string The base64 string
+function base64_encode_file(file)
+
+    -- r = result
+    -- l = length
+    local r, l = {}, 0
+    
+    while true do
+
+        -- c = chunk of 3 bytes
+        local c = file:read(3)
+        if not c or #c == 0 then break end
+        
+        -- Pad chunk to 3 bytes if needed
+        -- pa = padded
+        -- p  = pad length
+        local p = 3 - #c
+        for _ = 1, p do
+            c = c .. '\0'
+        end
+        
+        -- Convert 3 bytes to 4 base64 characters
+        local b1, b2, b3, c1, c2, c3, c4 = c:byte(1, 3)
+        local n = (b1 << 16) + (b2 << 8) + b3
+        
+        c1 = b64c:sub(((n >> 18) & 63) + 1, ((n >> 18) & 63) + 1)
+        c2 = b64c:sub(((n >> 12) & 63) + 1, ((n >> 12) & 63) + 1)
+        c3 = b64c:sub(((n >> 6) & 63) + 1, ((n >> 6) & 63) + 1)
+        c4 = b64c:sub((n & 63) + 1, (n & 63) + 1)
+        
+        -- Apply padding
+        if p == 1 then
+            c4 = '='
+        elseif p == 2 then
+            c3 = '='
+            c4 = '='
+        end
+        
+        local en = c1 .. c2 .. c3 .. c4
+        table.insert(r, en)
+        
+        l = l + 4
+        if l >= 76 then -- Standard base64 line length
+            table.insert(r, '\n')
+            l = 0
+        end
+    end
+    
+    return table.concat(r)
+end
+
+---Decode a file from base64
+---@param file file The file containing the base64 string to decode
+---@return string The decoded raw data
+function base64_decode_file(file)
+
+    -- r = result
+    -- b = buffer
+    local r, b = {}, ""
+    
+    -- Read all data and remove whitespace/newlines
+    while true do
+
+        -- l = line
+        local l = file:read("l")
+
+        if not l then break end
+        b = b .. l:gsub("[^" .. b64c .. "=]", "")
+    end
+    
+    -- Process 4 characters at a time
+    for i = 1, #b, 4 do
+
+        -- c = chunk of 3 bytes
+        --b1 = byte 1
+        --b2 = byte 2
+        --b3 = byte 3
+        --b4 = byte 4
+        --c1 = chunk 1
+        --c2 = chunk 2
+        --c3 = chunk 3
+        local c, b1, b2, b3, b4, n, c1, c2, c3 = b:sub(i, i + 3)
+        if #c < 4 then break end
+        
+        b1, b2, b3, b4 = dt[c:sub(1,1)] or 0, dt[c:sub(2,2)] or 0, dt[c:sub(3,3)] or 0, dt[c:sub(4,4)] or 0
+        n = (b1 << 18) + (b2 << 12) + (b3 << 6) + b4
+        c1, c2, c3 = string.char((n >> 16) & 255), string.char((n >> 8) & 255), string.char(n & 255)
+        
+        -- Handle padding
+        if c:sub(4,4) == '=' then
+            if c:sub(3,3) == '=' then
+                table.insert(r, c1) -- Only first byte
+            else
+                table.insert(r, c1 .. c2) -- First two bytes
+            end
+        else
+            table.insert(r, c1 .. c2 .. c3) -- All three bytes
+        end
+    end
+    
+    return table.concat(r)
+end
+
+if #arg < 1 or #arg > 2 then
+    print([[Usage: lua base64.lua [-e|-d] [file]
+  -e: encode (default)
+  -d: decode")
+  file: input file (default: stdin)]])
+    os.exit(1)
+end
+
+-- em = encode mode
+-- fn = file name
+--  f = file pointer
+local em, fn, f = 1
+
+for _, v in ipairs(arg) do
+    if v == "-d" then
+        em = nil
+    else
+        fn = v
+    end
+end
+
+if fn then
+    f, e = io.open(fn, "rb")
+    if not f then
+        print(e)
+        os.exit(1)
+    end
+else
+    f, e = io.stdin
+end
+
+if not f then print(e) exit(1) end
+
+if em then
+    local encoded = base64_encode_file(f)
+    io.write(encoded)
+    if not encoded:sub(-1):match('\n') then
+        io.write('\n')
+    end
+else
+    io.write(base64_decode_file(f))
+end
+
+-- Close file if it was opened
+if fn then
+    f:close()
+end