Item_Cache_Helper.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE muclient>

<muclient>
<plugin
   name="Item_Cache_Helper"
   author="Nick Gammon"
   id="928dc37b201539cd14239ff0"
   language="Lua"
   purpose="Manages cached item information for various plugins"
   date_written="2010-03-02"
   requires="4.50"
   version="1.0"
   >
<description trim="y">
<![CDATA[
Install required for new telnet negotiation plugins.
]]>
</description>

</plugin>


<!--  Script  -->


<script>
<![CDATA[

local PPI = require("ppi")

item_not_in_database = {}
requested_items = {}

count_items_found_in_db = 0
count_items_not_found_in_db = 0
count_items_requested_from_server = 0
count_items_received_from_server = 0
time_to_receive_items = 0
time_to_read_from_db = 0
time_to_write_to_db = 0

function dbcheck (code)

 if code ~= sqlite3.OK and    -- no error
    code ~= sqlite3.ROW and   -- completed OK with another row of data
    code ~= sqlite3.DONE then -- completed OK, no more rows
    local err = db:errmsg ()  -- the rollback will change the error message
    db:exec ("ROLLBACK")      -- rollback any transaction to unlock the database
    error (err, 2)            -- show error in caller's context
  end -- if

end -- dbcheck 

function fixsql (s)
  if s then
    return "'" .. (string.gsub (s, "'", "''")) .. "'" -- replace single quotes with two lots of single quotes
  else
    return "NULL"
  end -- if
end -- fixsql

function load_item_from_database (hash)

  local item
 
  assert (hash, "hash is nil in load_item_from_database")
  
  -- if not in database, don't look again
  if item_not_in_database [hash] then
    return nil
  end -- no point looking
  
  local start_time = GetInfo (232)
  
  for row in db:nrows(string.format ("SELECT item FROM items WHERE hash = %s", fixsql (hash))) do
     item = row.item
  end   -- finding item

  time_to_read_from_db = time_to_read_from_db + (GetInfo (232) - start_time)
  
  if item then
    count_items_found_in_db = count_items_found_in_db + 1
    return item
  end -- if found
  
  count_items_not_found_in_db = count_items_not_found_in_db + 1
  item_not_in_database [hash] = true
  return nil
    
end -- load_item_from_database


local IAC, SB, SE = 0xFF, 0xFA, 0xF0

-- check if single item cached
function get_item (hash)

  -- see if in database
  local item = load_item_from_database (hash)
  
  -- yes? just return it then
  if item then
    -- print ("found item for", hash, "hash of it is", utils.tohex (utils.md5 (item)))
    local t = {}  
    setfenv (assert (loadstring (item)), t) () -- compile and load into t
    return t  
  end -- if found
  
  if requested_items [hash] then
    return nil
  end -- if already asked for it

  SendPkt (string.char (IAC, SB, 102) .. "hash_info = \"" .. hash .. "\"" .. string.char (IAC, SE)) 
  -- Note ("Requested cache ID: ", hash)
  
  -- DEBUG
  CallPlugin ("b9cfe98d6a35dd98cd8ceacc", "LogIt", "Requested cache ID: " .. hash)
  
  requested_items [hash] = GetInfo (232)  -- don't request twice
  count_items_requested_from_server = count_items_requested_from_server + 1
  return nil
end -- get_item

function save_item_to_database (hash, item)

  dbcheck (db:execute (string.format ("INSERT INTO items (hash, item, date_added) VALUES (%s, %s, DATETIME('NOW'));", 
            fixsql (hash), fixsql (item)
         )))
  
  item_not_in_database [hash] = false
    
end -- function 

function OnPluginInstall ()

 -- open database on disk (uses world address, that is which MUD we are playing)
  db = assert (sqlite3.open( GetInfo (66) .. Trim (WorldAddress ()) .. "_" .. WorldPort () .. ".db"))
  
  -- create items table
  dbcheck (db:execute[[
  
    CREATE TABLE IF NOT EXISTS 
      items(
      itemid        INTEGER PRIMARY KEY AUTOINCREMENT,
      hash          STRING NOT NULL,  -- hash of contents
      item          TEXT,             -- item contents
      date_added    DATE,             -- date added to database
      UNIQUE (hash)
    );
    
  
  ]])

 
  PPI.Expose "get_item"

end -- function OnPluginInstall

function OnPluginClose ()
  -- close database
  db:close()
end -- OnPluginClose

function OnPluginTelnetOption (option)

  local t = {}  -- incoming server variables will go into table t
  setfenv (assert (loadstring (option)), t) () -- compile and load into t
  
  
  -- cache incoming item information
  if t.hash_info then
    
    local received_hashes = {}
  
    local start_time = GetInfo (232)
    
    if next (t.hash_info) then
      dbcheck (db:execute "BEGIN TRANSACTION;")
    end -- if at least one item
    
    for k, v in pairs (t.hash_info) do
      local time_now = GetInfo (232)
      local time_elapsed = 0
      if requested_items [k] then
        time_elapsed = GetInfo (232) - requested_items [k]
        time_to_receive_items = time_to_receive_items + time_elapsed
        count_items_received_from_server = count_items_received_from_server + 1
      end -- if
      
      -- Note (string.format ("RECEIVED item ID: %s in %.2f seconds.", k, time_elapsed))
      requested_items [k] = nil
      if v then
        save_item_to_database (k, v)
        table.insert (received_hashes, k)
      end -- if item data found
    end -- for
    
    if next (t.hash_info) then
       dbcheck (db:execute "COMMIT;")
    end -- if at least one item

    time_to_write_to_db = time_to_write_to_db + (GetInfo (232) - start_time)
    
    for _, v in ipairs (received_hashes) do
      BroadcastPlugin (1, v)
    end -- for
    
  end -- if t.hash_info
 
  if (count_items_found_in_db + count_items_not_found_in_db) > 0 and
      count_items_received_from_server > 0 then
        
    SetStatus (string.format ("%i db reads, %i db fails: %0.5f sec avg, %i sent, %i received in %0.3f sec avg, writes: %0.5f sec avg",
                count_items_found_in_db,
                count_items_not_found_in_db,
                time_to_read_from_db / (count_items_found_in_db + count_items_not_found_in_db),
                count_items_requested_from_server,
                count_items_received_from_server,
                time_to_receive_items / count_items_received_from_server,
                time_to_write_to_db / count_items_received_from_server))
  end -- if
    
end -- function OnPluginTelnetOption

function OnPluginTelnetRequest (type, data)

  if type == 102 and data == "WILL" then
    return true
  end -- if

end -- function OnPluginTelnetRequest

]]>
</script>


</muclient>