CloudStorage (FTP): Do not buffer entire download in memory (#7597)

frontend/apps/cloudstorage/ftp.lua

@@ -22,18 +22,16 @@ end
 function Ftp:downloadFile(item, address, user, pass, path, close)
     local url = FtpApi:generateUrl(address, util.urlEncode(user), util.urlEncode(pass)) .. item.url
     logger.dbg("downloadFile url", url)
-    local response = FtpApi:ftpGet(url, "retr")
+    path = util.fixUtf8(path, "_")
+    local file, err = io.open(path, "w")
+    if not file then
+        UIManager:show(InfoMessage:new{
+            text = T(_("Could not save file to %1:\n%2"), BD.filepath(path), err),
+        })
+        return
+    end
+    local response = FtpApi:ftpGet(url, "retr", ltn12.sink.file(file))
     if response ~= nil then
-        path = util.fixUtf8(path, "_")
-        local file, err = io.open(path, "w")
-        if not file then
-            UIManager:show(InfoMessage:new{
-                text = T(_("Could not save file to %1:\n%2"), BD.filepath(path), err),
-            })
-            return
-        end
-        file:write(response)
-        file:close()
         local __, filename = util.splitFilePathName(path)
         if G_reader_settings:isTrue("show_unsupported") and not DocumentRegistry:hasProvider(filename) then
             UIManager:show(InfoMessage:new{

frontend/apps/cloudstorage/ftpapi.lua

@@ -20,16 +20,15 @@ function FtpApi:generateUrl(address, user, pass)
     return generated_url
 end
 
-function FtpApi:ftpGet(u, command)
-    local t = {}
+function FtpApi:ftpGet(u, command, sink)
     local p = url.parse(u)
     p.user = util.urlDecode(p.user)
     p.password = util.urlDecode(p.password)
     p.command = command
-    p.sink = ltn12.sink.table(t)
+    p.sink = sink
     p.type = "i"  -- binary
     local r, e = ftp.get(p)
-    return r and table.concat(t), e
+    return r, e
 end
 
 function FtpApi:listFolder(address_path, folder_path)
@@ -38,12 +37,14 @@ function FtpApi:listFolder(address_path, folder_path)
     local type
     local extension
     local file_name
-    local ls_ftp = self:ftpGet(address_path, "nlst")
+    local tbl = {}
+    local sink = ltn12.sink.table(tbl)
+    local ls_ftp = self:ftpGet(address_path, "nlst", sink)
     if ls_ftp == nil then return false end
     if folder_path == "/" then
         folder_path = ""
     end
-    for item in (ls_ftp..'\n'):gmatch'(.-)\r?\n' do
+    for item in (table.concat(tbl)..'\n'):gmatch'(.-)\r?\n' do
         if item ~= '' then
             file_name = item:match("([^/]+)$")
             extension = item:match("^.+(%..+)$")